Wrapping It All Up. The Last Solar Power Article Ever.

Yeah, that title is probably a lie. I’ll probably talk more about it in the future as I gain experience with this. I’ll certainly let you know if I run into problems. And you’re probably getting tired of reading about as I am of writing about it so let me wrap this all up.

The good news is that the damned thing actually works. I got tired of waiting for some miscellaneous parts to arrive to do the final installation and cobbled together a messy looking but safe wiring configuration so I could get on with testing the inverters. That may look like a mess down there, but it is, frankly, a lot better looking than some of the wiring I’ve seen people turn out on Youtube and other places.

But it is a mess that works and, believe it or not, is safe. And the battery cabinet is here now so today this whole thing is going to get torn down and put back together the right way and will meet building codes, etc.

I fired the sucker up. I went through the “commissioning” procedures in the manuals to set the two inverters up to run in 240V split phase, rebooted everything and it all started up and, well, damn. It actually worked! I had the entire house was running off-grid, running from the inverters, batteries and solar panels. Everything in the house was working just as it did running off the grid. Lights, microwave, coffee maker, even the 240V appliances like the stove and clothes dryer. Just for the heck of it I fired up my big table saw in the wood shop. The lights flickered a bit when it first kicked in, but they do that even when I’m running off grid power. End result is I ran the house for the rest of the afternoon off the two inverters with no problems at all before shutting it down and pulling the plug, so to speak, so I could start prepping to put in the battery cabinet.

So, it works! I actually put together something that works? Wow…

So for those of you who are interested in all the technical stuff and some observations about the equipment, let me get on with us. Some of this I’ve mentioned before but I want to make sure I covered everything for those of you who are interested in putting together a solar power system yourselves. And yes, I’m going to include the actual retail cost of all of this as well along the way. So so be warned this could get long.

So let’s start with the inverters.

What I have are two EG4 6500EX all in one inverters. Each one can handle a sustained load of 6,500 watts with a surge capacity of 13,000W for up to 5 seconds. When some equipment (like my table saw or sump pumps) first start up they can demand huge amounts of power for a brief time, so that’s why that surge capacity is important. Both of them together give me 13KW load capacity, more than enough to run the entire house.

Each inverter has two MPPT solar charge controllers. Each of the two chargers can handle up to 4,000 watts of solar panels at 80 to 500 volts. And I can tell you that they absolutely have to have at least that 80V before they’ll start charging the batteries. Anyway that’s some pretty hefty solar charging capacity. If I’d max out the capacity of both inverters I could feed about 16KW of solar power into these things.

If the inverter is connected to grid power it can charge the batteries off the grid, or off solar, or off both, or prioritize one source over another. And I’m told these things, if hooked to the grid, will pass through grid power to your house, and switch to battery/solar power in case of a blackout, and do it in 10 ms. I don’t have mine hooked to the grid and don’t plan to so I’m not going to be able to test that.

The battery chargers, both solar powered and grid powered, can be configured to deal with just about any kind of 48V battery system you might have, ranging from old fashioned lead acid batteries up to state of the art LiFePo batteries like the EG4LLs I have. You can set maximum and minimum voltages, rate of charge, you name it. In my case I just told it I was using EG4LL batteries and it automatically sets itself up properly. It also has battery communications as well to talk to the battery management systems most LiFePo batteries have these days. And I should add that the inverters are UL listed as well so they should be able to pass inspection.

And, of course, two of these units can be paralleled together so that when combined they work as a single 240V split phase system, which is how I have mine configured at the moment. One inverter is set as the master and the other as the slave, and a setting in the menu has to be changed to make sure that the slave’s sine wave is 180 degrees out of phase with the other inverter. That took maybe all of a minute to configure.

And if the 13KW that two of these together make isn’t enough for you, you can connect up to six of the things if you need more power.

There are lots more options and settings and other things that I’m not going to get into because it would take forever and I don’t really care about a lot of them. If you’re interested in all of that you can download the manual from Signature Solar.

So, let’s talk cost. Personally I think that considering the capacity of these inverters and the things they can do they’re pretty inexpensive, $1,299 each. Since I wanted 240V I needed two of them. Signature Solar had a combo deal that included two EG 6500EX inverters, two PV cutoff switches, two battery disconnect switches (which you need to meet code) and some cables and a few other goodies for a bit less than $3,000, so that’s what I ended up buying.

I am not urging you to buy EG4 equipment by any means. These are just the ones I ended up getting because they suited my needs. There are a lot of different inverters on the market and most of them work pretty well. Some are better than others. But as you go shopping around you will find that a lot of different brands seem to have remarkably similar specifications, and even seem to look quite a bit alike except for the case. That’s because they are basically the same inverter, just packaged differently. I know of at least two other inverters, sold under different brand names, that are exactly the same as the EG4 6500 that I have. There are some minor differences, like the EG4 can handle higher PV voltages, but other than that they’re identical except for the case and graphics and they all come out of the same factories in Taiwan and Singapore.


Batteries are the most expensive part of a system like this. 48V LiFePo batteries are expensive. But when the sheer energy storage capacity of these things is taken into consideration, along with their life span, they actually are very cost effective.

What I ended up getting were EG4LL, 48V, 5,120 Wh capacity server rack style LiFePo batteries. These are “smart” batteries with built in battery management systems and both RS485 and CAN communications capability and fancy full color LCD screens. They have a 10 year warranty and it’s claimed that after 7,000 charge/discharge cycles they’ll still have 80% of their original capacity left.

A word about battery safety. You’ve probably heard all kinds of stories about lithium batteries exploding, starting unquenchable fires and all of that. These are not those types of batteries. These are lithium iron phosphate, LiFePo, and they use a different chemistry. They do not explode, do not turn into raging infernos, etc. And just for the extra paranoid people out there (like me), these particular model batteries have their own fire suppression systems built in. I saw a demonstration where they took one of these batteries, piled a bunch of flammable material on it and started the sucker on fire. After burning for a few minutes, the suppression system triggered and the battery put the fire out. Cool, I said. I’ll take those, please.

The LCD screens let you monitor all kinds of stuff that I’m sure will interest someone. The only thing I really care about is if they work or not, and they do. But if there are problems you can even monitor the state of health of individual cells in the battery if you need to. If you want to save a few bucks EG4 also sells batteries that have the same capacity as these, but without the fancy displays.

The batteries have communications ports which allows them to be connected to the EG4 inverter which directly monitors the battery conditions so it doesn’t over charge them, charge them too fast, discharge the too fast, etc. If you have more than one, one battery is set up as the “master” which connects to the inverter, and the other batteries comm ports are daisy chained to the master battery. There are DIP switches on the front of each battery that you need to set so the communications system can figure out which one is which. Don’t worry, it’s easy. The batteries come with a booklet that has a chart showing exactly how to set the switches.

The batteries come with short (very short) battery cables designed to to connect them to the busbars in a battery cabinet. If you aren’t going to use a battery cabinet you’re going to have to buy or make your own cables to connect them to your own busbars. If you need to go down that route you need to remember that the cables connecting multiple batteries to a busbar need to be the same length and gauge. If the cables aren’t matched in length and gauge it means they aren’t going to have the same resistance. You want the load on each individual battery to be as evenly distributed as possible. That’s why you need to use busbars rather than just daisy chaining the batteries together. It helps to distribute the load more evenly.

And if you’re going to make your own, go get yourself a decent hydraulic crimping tool! I do not recommend one of those cheap crimpers that you whack with a big hammer. I don’t trust those things. You risk damaging the cable, damaging the lug, and not making a very good connection inside of the lug. A decent hydraulic crimper will set you back about $100 or so, which seems like a lot. but if you’re making cables for a power system that’s costing $10,000 or more, do you really want to cheap out on a crimping tool and risk making bad connections?

If you haven’t had to buy heavy gauge copper wire recently you’re in for a shock. Two 10 foot pieces of 4 gauge copper battery cable costs about $170 off Amazon. And while it is very nice cable and it comes with a bag of copper connecting lugs that’s still a heck of a lot of money. That’s another reason to go with a battery rack like the one I got. That big steel box may cost $500 but making or buying cables to hook the individual batteries to a wall mounted busbar is going to cost you several hundred dollars by itself.

The EG4LL batteries sell for $1,750 each. I have three of then for a total cost of $5,250. You can save a few bucks by going with batteries that don’t have all of the bells and whistles that these do,. The cheapest 48V server rack style LiFepo batteries that I’ve seen for sale are are around $1,500, so you could save yourself about $250 per battery by doing some shopping around.

So the running total right now for the system is about $3,000 for the inverters and $5,250 for the batteries, a total of $8,250.

But we’re not done yet.

Miscellaneous stuff

To put together a system like this a lot of other misc. parts are needed, and perhaps also some specialty tools like that crimper I talked about. I strongly recommend you get a decent torque wrench to make sure all of those electrical connections are torqued to the proper specifications. You don’t want to end up having to ship an inverter or battery back to the manufacturer, at your cost, because you snapped off a bolt or stripped out the threads on a connector trying to hook something up.

You also need some test equipment like a decent voltmeter and an amp meter. If you don’t already have all of that, you need to add that cost into the total price. Test equipment isn’t expensive and if you’re fiddling around with electrical equipment you need to have it anyway.

Let’s talk battery cabinet. The one in that photo came from Signature Solar and cost me about $500. It’s big enough to hold 6 batteries, has the busbars to connect to the batteries already installed, and it’s built like a freaking tank. It’s made of heavy gauge steel with a locking door, and has heavy duty wheels that can handle the weight because it can hold something like a quarter of a ton of batteries. And as I said it can save you enough money in cables to pay for itself.

Feel free to make your own if you’re handy that way. Just make sure it has adequate ventilation (batteries do get warm under normal operation) and that it can be secured somehow to keep people from fiddling around with it.

There are some safety items you absolutely are going to need. First you need battery cutoff switches between the inverters and the batteries so you can kill power to the inverters quickly in case of an emergency. Look at the photo up there. The two small gray boxes under the first inverter are first a PV cutoff switch and to the right of that the battery cutoff/circuit breaker. I only just got those mounted when I took the photo so they aren’t hooked up yet. The batteries have their own circuit breakers and I have a PV cutoff already in the system that you can’t see in this photo so I don’t have these hooked up yet. The final wiring job will have a PV switch and battery breaker for both inverters.

A decent PV cutoff switch is about $90. The breaker is about $70. I got two of each in the package deal I bought from signature solar. Total cost about $320 if you have to buy them separately.

Oh, and did I mention your solar panels need to be grounded? Yeah, they do. Almost all solar panels, at least the ones I’ve seen, will already have holes, often marked with a special grounding symbol, on the frames. Generally you daisy chain a grounding wire to every panel, then that wire goes to a grounding rod near the panels.

I should add that I already had a lot of the stuff I needed like spare wire, connectors, conduit, etc. laying around because I’m an amateur radio person and I’m constantly tinkering with antennas and fun stuff like that so I already had ground wire, grounding rods and other misc. bits on the shelf.

Now we come to the house side of things. You somehow need to get the power produced by those inverters into your house’s electrical system.

First you need to run suitably sized wiring from the inverters to your service panel. The EG4 manual recommends 6 gauge wire which is going to be sufficient to carry the amperage the inverters can produce. In my case I used 6/2 (6 gauge wire, 1 hot, one neutral, and one ground). That stuff ain’t cheap either. It runs about $3.50 per foot here. That’s why ideally your inverters will be reasonably close to your service panel. Depending on regulations in your area that cable may need to be run through conduit. Even the relatively short run I had to make ended up costing me close to $300 in wire for that, not including the cost of the conduit.

Now I am going to give the usual disclaimer here about using a licensed electrician to make any modifications necessary to the service panel that feeds electricity to your house. In a lot of jurisdictions it may even be illegal for you to make any modifications to your house’s electrical service.

It’s Money Time

Bob the Electrician

So here’s the total cost of this whole house off grid (sort of) alternative energy system, not including solar panels. This number includes the two inverters, three batteries, all of the cables, connectors, switches, electrical wiring, etc. It includes the crimping tool, a cable cutter, torque wrench, wiring to the house panel, circuit breakers, screws, bolts, etc. Prices are rounded. It does not include the cost of Bob the electrician who makes sure I don’t blow things up and keeps the inspectors happy.

Inverter combo deal including 2 EG4 6500EX inverters, two battery breaker boxes, 2 PV disconnect switches and some misc. bits and pieces: $3,000.

Three EG4LL 48V server rack style batteries at $1,750 each: $5,250

Battery cabinet: $500

Equipment total from Signature Solar: $8750.

Shipping: $250

Taxes: $450

total: $9,450

Wait, we’re not quite done yet.

Now we need to add in the misc. costs for wire, cables, connectors, a few speciality tools I had to buy. I won’t itemize all of that. That all added up to about $2,500 rounded to the nearest hundred bucks. Wire is crazy expensive right now, a transfer switch that is eventually going to be hooked into the system set me back almost $500, some circuit breakers for the electrical panel, conduit, fittings. Oh, and lunch for Bob is in there somewhere too I think.

Grand total, not including solar panels: $11,950.

My original cost estimates for this project, minus solar panels, was around $12K to $13K so estimates were spot on.

Now let’s talk solar panels. Solar panel prices are currently sitting at a bit more than $1 to $1.50 per watt. And a system this size is going to need a lot of watts to charge the batteries in a reasonable amount of time even without trying to run your house off solar as well. It’s going to take quite a bit of solar power to keep this system fed. There are 15 KWh of batteries to keep charged plus one would want to get as much solar power as possible to feed through the inverters directly into the house to use solar power directly, not just charge batteries.

I only have my original 800W of solar out there right now, but I just got in 1,320W of solar panels last week and if the budget permits I’ll be adding another 1,320W by the end of June and I’ll have more than 3KW of solar sitting out there.

To make a long story a bit shorter, total cost for this whole project, including solar panels, is going to be right around $15K

Now let’s talk about taxes. There is a federal tax credit for up to 30% of the cost of alternative energy projects, including solar. I’m not exactly sure of all of the details because that’s what I pay my accountant for (Hi, Eric, how you doing? Recover from tax season yet?) Theoretically I could get up to $4,500 in federal tax credits. I doubt if I will. Considering what the tax system is like in the US I’ll be surprised if I get anything at all. But let’s say I do. That would bring the cost of this down to $10,500. Ooo, nice. Personally I think that getting a solar power system that can run my entire house for ten grand sounds like a pretty good deal.

Is it really worth it though? Even if I get the tax breaks that is a hell of a lot of money and a hell of a lot of work. I talked about pay back times and other factors involved before so I won’t go into that here. All I can say at this point is that only time will tell. If nothing else we’ll have a whole house emergency power system we can fall back on during a blackout even if we don’t save a lot of money on the utility bill.

Oh, and I just heard that all of the electric utilities in the state are pushing for yet another rate increase of anywhere from 4% to 8%. So there’s that. And I have friends in the electric utility industry and from what I hear from them we could be looking at wide spread rolling blackouts if we get above average temperatures, so there’s that too… Hmm, maybe this was a good idea after all.

Final Thoughts

A few things struck me as we were proceeding with this project.

First is the cost. $15K is a lot of money but if you think about for a moment, is it really all that much? We’re talking about a system that can handle all of the electrical needs of an entire modern household, at least part of the time, for less than the cost of a decent used car. If you can snag the 30% tax credit it makes it look even more attractive.

Second thing that struck me was how ridiculously easy it was to put this system in. If I’d had all of the parts and bits I needed right off the bat I could have installed this whole system in an afternoon and still have had time to go play with the neighbor’s dog before supper. The inverters have become so sophisticated these days that it’s almost a plug-n-play system. You don’t need separate solar charge controllers, separate AC battery chargers, separate battery management systems, etc. Everything is built right in. If you can read a manual, are qualified to do basic electrical wiring, have some basic tools and test equipment, etc. just about any reasonably intelligent person can set this up. Of course there are a lot of, if you’ll excuse the term, idiots out there. Some of them are on Youtube. Start scrounging around on Youtube sometime searching for solar power systems and you’ll see what I mean. And that’s why cities, towns and counties have to have building codes and inspectors and permitting processes.

The third thing that struck me was that I’ve been going on and on and on about this system for this long when I should be going on and on and on and on about biking, nature, photography, gardening, amateur radio and the other stuff I normally bore you with.

So that’s it. It’s time to get back to our regularly scheduled programming. I’ll keep you up to date about the system but unless something major happens it will be more of a sidenote than anything else while I get back to the more important things in life, like screwing around out in the gardens, bothering people on amateur radio, etc.

New Email, Solar Panels, Last Bluetti Article

My AC200Max with a B300, 3,000Wh expansion battery

I want to do one last article about the Bluetti AC200Max before I move on to other things. I’ve been doing a lot of research into solar power systems, have my own solar power system up now, well, sort of, and I wanted to talk about trying to use one of these in an off-grid situation.

First, though, grouchyfarmer.com has a new email address. It is theoldgrouch@grouchyfarmer.com. If you have questions or comments about any of the stuff you see here or even suggestions for future articles you can reach me at that address.

Now let’s get on with what I hope will be the last Bluetti article for a while. I’ve tested this thing with one B300 3KWh expansion battery (you can add two of them) and it’s handled everything I’ve thrown at it. It is working exactly as advertised and I’m very pleased with it. With the extra cost B300 ($2,300) battery it now has 5KWh of power. Preliminary testing indicates that it could keep the furnace going for at least 24 hours, maybe as long as 36 hours. And it will keep our sump pumps going for 2 – 4 hours in heavy spring rains depending on weather conditions.

But one thing I didn’t talk about much was recharging this beast. 5 KWh is a hell of a lot of energy to pump into a battery pack and eventually this thing has to be recharged. That’s where I start to run into what could be potential bottlenecks for some people, especially someone trying to use this as their primary power supply in an off-grid situation.

It comes standard with a big AC charging brick that will put 450W into this unit to recharge it. That’s a lot, but this is also a massive battery which means it’s going to take a considerable amount of time to fill it up from empty. With my system it would take the AC charger alone more than 11 hours to fully recharge it. If I had the 2nd battery pack for a total of 8KWh it would take almost 18 hours to do a full charge. Frankly I think that’s woefully inadequate.

Now I could fudge and fiddle around. The B300 battery has its own AC charging port.I could get a second AC charger and dump another 450W into the battery independently of the AC200Max to get a total 0f 900W AC charging. That would bring the charge time for my 5KWh system down to about five and a half hours.

But they call these things “solar generators”. Where the hell is the solar part of all of this?

Well you generally don’t get the part that actually makes it a solar generator, the solar panels. Those are an extra cost option. Companies like Jackery and Bluetti will gladly sell you their own branded portable folding solar panels. For a price. A really, really big price. Generally two or three times what it would cost you to get the same wattage in generic panels you bought off Amazon or somewhere. Here’s an example.

Bluetti will sell you this:

That’s the PV350. It’s a folding panel intended for temporary use. It folds up into a nice neat package, gives you up to 350 watts of power to dump into your Bluetti, and from all the reviews I’ve seen of it, it is very, very nice.

But dear lord, that price!!! $850 for only 350 watts of power? Seriously? And I’d need two of these things because with just one of them it would take 15 hours to recharge my system. It’s winter here in Wisconsin. The days are short, the sun is low in the sky. We often have clouds. With just one of these panels it would take something like three days to fully charge my system in the winter. And that’s if I wasn’t using the system to power something. Even with two of these panels it would take me more than a day to recharge because I only get about 5-6 hours of usable sunlight a day this time of year.

So I did some shopping around and a great deal of research and finally came up with these:

That’s a set of 4, 100W panels from a company called HQST. So I could get two four panel sets for a total of 800 watts for $550, or I could get two PV350 for a total of 700W for $1,700.

Guess what I bought? Damn right. I may be crazy but I’m not stupid.

Yes, I know that’s only six. There’s a reason why I could only hook up six at first. Read on to find out what I ran into.

And the panels themselves are actually really nice. They’re well made, sturdy, small enough and light enough to be easy to handle. And best of all, they work pretty much exactly as the company claims they do. And I now have all 8 of them outside leaning up against the south side of my garage all hooked up and feeding power into the basement.

Hooking up solar panels is about as easy as it gets. Most of them come equipped with MP4 connectors that just snap together. It’s pretty much impossible to wire them wrong. They just daisy chain together in series, plug in the cable to go to the basement. The AC200Max comes with a pigtail that has MP4 connectors on one end to go to the solar panels, and a T90 connector on the other that plugs into the AC2ooMax. And that’s all there was to it. It took me less than half an hour to set up six panels, hook them together, run a cable into the basement, plug it into the Bluetti and start sucking up all that yummy free solar power.

Well, sort of. I ran into some limitations which kept me from using all 8 panels, but let me tell you about the realities of solar power first of all.

The first thing I learned is that I will almost never get the maximum rated power out of those solar panels. Oh, they don’t lie when they give you those numbers. But you need to remember that those ratings are done in a laboratory under ideal conditions. Conditions that you will almost never see out in the real world. Especially not in Wisconsin. In February. I had 600W of panels out there but the maximum I was getting out of them was about 400W, and that was only for a couple of hours around midday.

Still, the system was working. I tried running my office/radio shack/mad scientist’s lab in the basement off the Bluetti and feeding it power from the solar panels and it worked quite well. By about 9:30 in the morning those six panels were producing enough power to run my little office, about 240W, that would gradually go up during the day, peaking at midday around 400+ watts in perfect weather, then dwindle until about 3 when power production shrank to under 100W. I was running my office entirely off those panels alone for about 3 or four hours in good weather.

Why Only Six Panels

Okay, let’s deal with that situation. The AC200Max has a built in solar charge controller. It is rated at up to 900W, 145V, 15A. Those are the maximum numbers it can handle. If you exceed those inputs by more than a small amount either the system just won’t use the extra or, even worse, the charger will just shut down to protect itself.

So now we need to do some math. Don’t worry. It won’t hurt. Much.

My panels were hooked in series, like in this diagram below.

It’s quick, it’s simple, and it works well. But as you can see from the diagram when panels are hooked together in series the voltage of each panel you add to the string is added to the voltage previous panels, and eventually you get to a voltage that the charge controller can’t handle.

My HQST panels have an open circuit voltage of 21.6. Six panels in series gives me a voltage of 129.6. The AC200max can handle 145V so that’s just fine. But if I add a seventh panel? 129.6+21.6=151.2. And 151V is over the 145V limit. So I can’t have more than 6 of these panels in series without going over the limit.

So how can I stuff more watts into this beastie without going over that limit? This is where parallel wiring comes along. Here’s another diagram for you to look at.

When connected in parallel, the amperage of each panel adds up, while the voltage stays the same. My panels have an amp rating of 5.5. So I could put two panels in parallel and remain under the 15A max rating of the Bluetti. In effect I’d have a single 200W panel producing just 21.6V at 11A, well within the Bluetti’s limitations.

So I started doodling and came up with this.

I’d create 4 banks of two panels each connected in parallel. Each bank would have 21.6V and 11A. Then I’d connect all 4 banks in series. That would give me all 800 watts they could produce, I’d have a voltage of 86.4, and my amperage would be 11. Of course I didn’t have the right connectors to do that and I’d need some extra cable so it was off to Amazon and a few more bucks and a couple of days later that stuff arrived and I spent a half hour or so switching from series wiring to my parallel/series sketch, hooked everything up this morning.

Then the moment of truth came. I crossed my fingers, held my breath and plugged it into the Bluetti and… And it worked? Wait, it actually worked???

Yeah. It worked. I was getting about 80V, the amperage looked good and the watts coming in… Well okay I was only getting 80W but it was 7:30 in the morning and the panels were still mostly in shadow. By 9:30 they were making 300W and by noon I was getting between 650 – 700 watts! Damn, it works!

As I said before my conditions here for solar are far from ideal, so seeing those 800W of panels peaking at 700 watts at midday was very satisfying.

And on the charging side of things? If I were drawing no power at all from the Bluetti and could get a consistent 700W solar input I could charge my 5Kwh system in a bit over 7 hours, which isn’t … Well I was going to say it isn’t bad, and I suppose it isn’t absolutely horrible but I only get useable sunlight here for about 5 – 6 hours a day this time of year, so it would take me more than a day to recharge this thing.

The Problems With Going Off Grid

Now let’s talk about going off grid. If you start scrounging around on YouTube and places like that you’ll run into videos from people who claim you can use the AC200Max like mine to go off-grid, using it as your primary source of power to run a small house or cabin or whatever, and replenishing the power you use entirely with solar. I have the Bluetti with 5KWh of power stored in it. I have all those solar panels. Why not try to run part of the house off grid and see what happens? So I’ve been experimenting with running my office/radio shack/mad scientist’s lab off the AC200Max and keeping it charged with just solar. And I’ll tell you right up front that it ain’t gonna work. I’m sorry, but it isn’t. At least not in the real world. Not without having to resort to some kind of additional power inputs from either the traditional grid or a backup generator of some sort. The numbers just don’t work. I knew that even before I started the experiment but I decided to try it anyway just to get some real world experience with the system.

My office uses about 270W of power as long as I’m not using my laser engraver or other energy hog piece of equipment. Just to keep things simple let’s round that up to 300W. That means that if I run my office for 10 hours I’d use 3,000Wh, with 2,000Wh remaining in the Bluetti.

So it’s the morning of the next day. I need to recover that 3KWh of energy I used the previous day. I have 800W of solar power but that only peaks at about 700W. But that’s not too bad. 7ooW of solar going into the system would recover that 3KWh in a bit over 4 hours. Great.

Well, no, not so great. First of all I only get those 700 watts for an hour or maybe two, during midday. The rest of the time I’m getting much less than that.

Second, I’m still running my office off that system. I’m not going to shut down for 4 hours to recharge the batteries. So even as I’m trying to recharge it, I’m drawing 270W. Even if I were getting 700W of power out of the panels, I only have a net gain of 430W. Recovering 3,000Wh with an input of only 430W gives a time of about 7 hours.

And I only get about 5 hours of usable sunlight a day this time of year.

And that’s with a load of only 270W. If you’re trying to use this system as your primary source of power running a furnace, refrigerator, some lights, etc. you’re going to be drawing considerably more than that.

So as I said, the numbers just don’t add up. This time of year, with the conditions I have here, with the amount of daylight I have here, I am never, ever, going to be able to get ahead with the amount of energy my solar system puts out. Even if I could max out my solar and put together a system that would pump the 900W maximum into the Bluetti it wouldn’t work. That would give me a net gain of 630W, and I’d get 3KWh out of the system in about 5 hours. But that’s assuming I’d get all 900W for that entire 5 hour period. And I won’t. Not even close. Not in Wisconsin, in February. With the standard solar charging system in the Bluetti I simply cannot dump enough power into it, fast enough, to get ahead.

Is there a way I can fudge things? Well, yeah. Sort of. The B300 expansion battery has its own solar charger built into it. Granted it is a pathetically wimpy one, only able to handle 200W. Trying to charge a 3KWh battery with 20oW is sort of like trying to fill a bathtub with a teacup, but it’s better than nothing. And if I’d add that into the 900W theoretical max I could dump into the AC200Max: 900 + 200 = 1,100W. 1,100 – 270 = 830. I’d now have a net gain of 830W. That gets us down to a bit less than 4 hours to recharge my system.

Now I’m finally seeing some numbers that almost make sense. Well, in July. In February I only have 5 hours of usable sun and I’m not going to get anywhere near peak production so I’m still going to be running at a net loss most of the day.

Bluetti will sell you a gadget they call a DC charge enhancer for $200. That would let me dump up to another 500W of solar into the AC200Max through its AC charging port. I build myself a third solar panel system, this one with 500W. I plug that into the charge enhancer, and that plugs into the AC charging port of the AC200Max giving me another 500W. 900 into the AC200 +200 going into the B300 battery +500 going into the charge enhancer = 1,600. 1600 minus my power consumption, 270W gives me a net gain of 1,330W. Now I’m looking at recovering those 3,000W in about two and a half hours.

Now, finally, I’m seeing numbers that would let me get ahead of the game. Peak solar production is only for around 2 hours at midday. But that, together with producing a bit more solar than I’m consuming the rest of the 5-6 hours of useable daylight I have, might get me to the break even point or even a bit better.

But only at the cost of building two additional solar panel systems, that $200 DC charge enhancer, cables, connectors, etc. But it should work.

Well until you get a day like today where we have solid cloud cover and my 800 watts of solar panels are putting out a whopping 80 watts of power.

So could you go off grid with the AC200Max and a couple of the expansion batteries? Uh, well, maybe? If your total power consumption was less than about 5KWh or so per day, and if you max out solar production by building extra solar arrays and adding in the DC charge enhancer and if you had perfect weather conditions to max out solar production.

But out here in the real world? No. Not without having to resort to some kind of alternative power source like a gas generator to help along in bad weather or help to cover unexpected power demands.

This particular system is great at what it is intended for, which is being a relatively short term power replacement during grid failures or to provide power for an RV or camper. It is not intended for use as an off grid system, long term, primary power system.

One more bit about solar power systems before I shut down this discussion and get back to more important things like fiddling around with gardens and photography and plants or wood and stuff.

Bluetti, Ecoflow and a few other companies make absolutely massive power systems that are intended to provide power for almost an entire home for lengthy periods of time. Some of them offer up to 18KWh. Eighteen thousand watt hours of power. If you really want to go off grid should you consider one of those?

Frankly, no. Those massive beasts look tempting, even will give you true 240V split phase systems. But the prices are just as massive as the battery packs. We’re getting up into price ranges and amounts of power where you should be seriously considering contacting a professional solar system contractor. A fully loaded AC500 system from Bluetti is going to be pushing $15,000, and that’s without a solar system to keep it fed.

And here’s another thing to consider. There’s no reason why you couldn’t save yourself a lot of money and build your own. LiFePo batteries have really come down in price. You can get a 2KWh or larger LiFePo battery for less than $700. You can get inverters that will handle a heck of a lot more than the 2,000W version in my AC200Max. You can get solar charge controllers to handle just about any configuration of solar panels and batteries you can build. And you can put it together with all off the shelf parts. And you can do it for a heck of a lot less than these plug ‘n play systems from Ecoflow, Bluetti and the others.

I’m seriously considering doing just that, covering the south facing garage roof with a couple of kilowatts of solar panels, putting a bank of LiFePo batteries in, getting a big inverter, and setting up a separate power panel in the basement to feed selected circuits in the house.

Well, maybe. I keep forgetting how lazy I am…

A Look At The Bluetti AC200MAX Portable Power Station

I want to talk about how to keep the lights on when the grid fails, something a lot of people were thinking about when that major winter storm rolled over much of the United States during the holidays and then when another hammered California and the southern part of the country, leaving millions of people without power, and sometimes even trapped in their homes.

This is going to be a two part series. I’m going to talk about the AC200MAX first because there are several people waiting for the review of this device. The second part is going to talk about these portable power systems in general, why you might want one, and most importantly how to determine how to properly size it to suit your needs without wasting money and, even worse, getting mislead by the advertising.

These things are often mislabeled “solar generators”, but they are neither solar nor generators. If you buy the almost always optional solar panels to recharge these devices you could make the argument they’re solar generators I suppose. But these devices by themselves are really energy storage devices. Basically they’re a big box of batteries.

Bluetti has been around for a few years now and its PPSs (portable power stations) are generally rated well in reviews and so far my experience with the one in the photo above has been completely positive.

The model I picked, the AC200MAX has a capacity of 2048 watt hours, and it can handle a maximum sustained load of 2,000 watts, and can handle brief surges in demand of up to 4,000 watts. It has a built in inverter that converts the batteries DC power to 120VAC. There are four standard 120 VAC plugs on the front. It also has a 30 Amp 120V NEMA TT-30 connector typically seen in RVs that would let it power an entire RV.

If you have a device that needs power, AC or DC, the Bluetti has enough plug ins of various types to handle just about anything you might need.

It also has a variety of DC power ports including USB-A 5V 3A, two USB A 18W ports, a 100W USB-C port, a DC 12V 10A cigarette lighter type plug in port, a DC 12V 30 Amp port, and as if that wasn’t enough, there are two wireless 15W charging pads for cellphones on the top of the box.

Basically this thing has just about every kind of power plug I’ve ever heard of. All of the outputs have overload and short circuit protection. And no, I did not test that. I’m not about to deliberately short circuit a device that cost me almost two grand just to see if the protection actually works.

The two top connector are for the optional additional battery packs that can be added to give the unit a capacity of up to about 8,500 Wh. The blue cap covers the plug for optional solar panels. The lower right is the connector for the 500 watt AC charger that comes with the unit.

On the lower left side of the unit are there are two connectors to hook up optional external battery packs. Up to two optional battery modules, either a 2048Wh ($1,300) or 3072Wh ($2,200) battery packs can be added to the unit to that can give it a total capacity of more than 8,000 Wh. And that, folks, is a hell of a lot of energy to be packed into that small of a space.

Also on the left side of the unit are the charging ports. You have several options here too for charging. The unit can be charged by, well, just about anything. It comes with a 500 watt charger for topping off the AC200 from the grid and it will charge up the unit reasonably quickly. The single AC charger will replenish the AC200MAX in about 5 – 6 hours.

There is also a DC input port intended for use with an optional solar charging system. There is a solar charge controller built into the AC200. That port can also be used to recharge the unit from a car with an optional cable (I’m not sure how long that would take but at least it’s an available option).

If that’s not enough options for you and you need to recharge the AC200 even faster, you can pick up a second 500 watt charger and with an optional cable charge the unit with two chargers at once, one plugged into the solar charging port. Or you can charge it at the same time from a solar panel system and the AC charger.

If you plan on getting solar panels for recharging the device it can handle up to 145V and 15.2 Amps maximum without the need for an external charge controller.

The manual claims you can recharge this thing by plugging a cable into a car’s cigarette lighter. Considering those things only put out about 120 watts, be prepared to wait a while to do a recharge. But still it’s an interesting feature that might be useful.

Physically, this thing is a beast. It is as large and heavy as my Yamaha 2KW gasoline powered inverter. It weighs in at about 60lbs, and the physical dimensions are around 17″ X 11″ X 15″. At 60 pounds you aren’t going to be casually carrying this thing around. If you end up getting the optional expansion battery packs this thing is going to be seriously heavy. But the weight and size is typical for portable power stations with this capacity.

Oh, and I should talk about the batteries. This unit uses LiFePO4 batteries. The manufacturer claims that after 3,500 charge cycles the batteries should still retain about 80% of their original capacity. That means you could recharge this thing every day for 10 years and still have 80% capacity left.

The touch screen is easy to read. In the “home” screen it shows the basic status of the unit. Here you can see that the AC outlets are turned on and that something is drawing 368 watts of energy, and it has 99% capacity left in the battery. It was running the house’s natural gas furnace when this photo was taken.

Now we come to the control systems. Just left of the screen is a big ON button. Push that and after a moment it will boot up and the color touch screen turns on. The screen not only displays all of the information you need, it is the primary control system for the unit.

Before you can use it you have to specifically turn on the DC and/or AC power systems to make the plugs “live”. But once you do that it’s ready to go and all you need to do is plug in whatever devices or appliances you need to power.

Other information is also available on various screens including load statistics, the ability to switch the system to handle European or Japanese electrical devices which use a different power system, and a few other goodies.

And there is a free app you can get for your phone that allows you to monitor what the Bluetti is doing. It is Bluetooth only, the device has no WiFi capabilities, so the range is limited. I was able to keep in touch with the Bluetti with my phone anywhere I was in the house, garage and even much of my backyard.

How well does it work?

If you thought all of the above was boring, you’re going to find the actual in-use evaluation of the Bluetti even more dull. It just works exactly as specified by the manufacturer. No drama, no problems, no issues, nothing. It just did everything it was supposed to do without any problems at all.

The primary use for mine is to provide backup power for two essential systems in the house, our gas furnace and our sump pumps. So that’s what I’ve been testing it on.

A gas furnace doesn’t use a lot of electricity, just enough to keep the thermostat system operating, which is minimal, and, of course, the blower fans. The actual heating is done by the combustion of natural gas. A natural gas furnace doesn’t use a great deal of electricity, generally in the 350 – 700 watt range. The electronic igniter that actually lights the gas uses some electricity of course. Rather a lot, in fact, but it works for such a short period of time that it isn’t that important.

My furnace was already set up to be used with our backup generator so I didn’t have to do any additional electrical work to make it possible to power the furnace alone. All I have to do was turn off the furnace, plug in a single electrical cable to switch from grid power to the Bluetti, and turn the furnace back on again.

Sidenote: I am going to give the usual disclaimer here. Consult with a licensed electrician before trying to make any modifications to your house’s electrical systems. Yes, I know house wiring isn’t that difficult to deal with, but unless you know what you’re doing you can end up in serious trouble or even dead if you screw something up. Then there is the legal issues to consider. A lot of jurisdictions require a licensed electrician to make any significant changes to a home’s electrical systems. There are also issues when it comes to your home owner’s insurance. If there is a fire in your home and subsequent investigation reveals that the home had electrical modifications that did not meet building codes or that were not performed by a licensed electrician the insurance company may refuse to cover the damage.

So, how did the Bluetti work while powering the furnace? Exactly as I expected it would. It handled the furnace easily with no issues at all. As my research indicated, the furnace required about 350 – 550 watts during operation. The wide range there is because this model furnace has a variable speed blower fan.

After 3 hours running the furnace the Bluetti still had 78% capacity left.

Once you know how much power a device draws, figuring out how long a battery system will run that device is pretty simple. The Bluetti has a bit more than 2,000 watt hour capacity so it should be able to run a device that needs, on average, about 400 watts, for about 5 hours. But that’s assuming that the device will be running all the time, and the furnace isn’t running constantly. The fans only run when the furnace’s burner is actually in use. On the day I did this test after 3 hours of operating the furnace the Bluetti still had 78% capacity, far better than I had anticipated.

So in actual testing, with those particular weather conditions, with the thermostat set at 67F degrees, the Bluetti should have been able to keep the furnace operating for around 12 hours.

Those numbers are under a specific set of conditions that could change quickly, of course. The weather was relatively mild with outdoor temperatures about 30F and very little wind. During colder weather and higher winds the furnace would run more often and for longer periods of time in order to maintain the temperature in the house. That, of course, would deplete the Bluetti more quickly.

The other intended use for the Bluetti is to keep the sump pumps going. We had part of the basement flood because of a sump pump failure here some years ago and we do not want to go through that again. I now have a backup pump on the shelf along with all of the tools and plumbing parts I need, and I changed the whole system so I can swap out a pump in just a few minutes. But in case of a power failure that isn’t going to do me any good. And since power failures often happen during storms when we’re getting heavy rain, they can happen at the worst possible time when we need the pumps the most.

Sump pumps require considerably more power than the furnace. The pumps I have require about 700 watts to run, but they run only intermittently. In addition to that load, there is a significant surge current when the pump first starts up, with can hit 1,300 watts for a few seconds.

I picked the capacity of the Bluetti specifically so it could, hopefully, handle both sump pumps at the same time. It can handle a current demand of up to 2,000 watts, sustained and the pumps together would take about 1,400. The PPS can handle a surge demand of over 4,000 watts. In a worst case scenario the two pumps might start at exactly the same time so there would be a momentary surge demand of about 2,600 watts. So it should be able to handle both pumps, at the same time, even if both pumps start at the same time.

I did test the Bluetti running the pumps. I already knew that because of the surge load and increased power requirements I would get much less actual runtime on the pumps than I would with the furnace. And I was a bit anxious about it being to able to run both pumps at the same time, especially if both started at exactly the same time. I’m pleased to report that it was able to handle both pumps with no problems. The Bluetti’s internal cooling fans did come on while running the pumps, but that was expected and normal.

During an actual rainstorm situation the Bluetti wouldn’t be able to keep both pumps running for more than an hour or so I estimate, but that’s all I need from it. I want it to give me some breathing room, carry the load for a while until I have a chance to get one of the gasoline generators running. My big Generac is cranky and hard to start sometimes, and even my little 2KW Yamaha inverter takes a while to get set up in a good location outside and run a cable down to the basement.

Could it run both of the pumps and the furnace at the same time? Well, maybe? That would be pushing the Bluetti to its full capacity, though. Theoretically it could. Total sustained demand running all three at the same time would be about 1,900 watts, maybe a bit more, really close to it’s top limit of 2,000 watts sustained load, and in a worst case scenario where both pumps and the furnace would start up at exactly the same time the surge load would be pushing the theoretical limits of the device’s maximum surge capacity.

Hopefully that won’t be necessary to deal with. Usually during the heating season the pumps don’t run at all. They’re generally only needed in the spring, summer and fall, and then only when we have a significant rain event.

Now, what about recharging this thing? At the moment I’m using the grid powered 500 watt charger that came with the unit. Bluetti will sell you solar panels that are capable of recharging this unit in a reasonable amount of time, but there are problems with that system. First it’s expensive, Buetti’s system will cost you $800+ for enough capacity. And even worse, these are portable, non-weather proof and not intended to be left outside. They can’t be left up in rain or snow. That’s not what I’m looking for. I want to set up a solar charging system that will be more or less a permanent installation that I don’t need to worry about. I’m still looking into that. I’ll probably set something up this spring when I can get outside to work.

So let’s sum everything up. The Bluetti AC200MAX is a very well made piece of equipment, it works exactly as advertised. I’ve encountered no problems at all with it during testing. It has met and even exceeded my expectations all the way around and I am very pleased with it. Yes, it’s heavy and awkward to lug around but so is any PPS with this capacity. It just plain works, and works well.


This thing ain’t cheap, and this may be a deal breaker for a lot of people. The Bluetti model I’ve been talking about cost me, including taxes, $2,000. That’s a heck of a lot of money, especially when you can get a gasoline powered generator with the same capacity or even more for a quarter of that price. So before you buy one of these you need to consider all of your options and what your needs are.

In our case here, we feel it was worth the money even though we have gasoline powered generators. The Bluetti takes some of the panic out of the situation. If necessary it could keep the essentials, the furnace and pumps, running long enough to give me a chance to get one of the gas generators set up and running. And I was also thinking of MrsGF if I didn’t happen to be home when there was a power failure. There’s no way she could get the big Generac set up and running by herself and there’s a good chance she couldn’t get the little 2KW Yamaha running either. With the Bluetti all she has to do is turn it on and plug in some electrical cords and she has some time to figure out what to do. And she would have some, oh, buffer time, let’s call it, to possibly get out the little Yamaha generator and get it running to take over if the outage lasts more than a couple of hours.

Long Term Plans

I’m looking into a solar panel system to keep it charged but at this point I don’t know what that is going to be. I want something that can be semi-permanently mounted on the roof of the garage where it is out of the way and I don’t need to worry about it. I’m looking for a system that would give me a minimum of 800 – 1,000 watts and that would be easily expandable because I’m seriously considering trying to make at least some of the household independent of the grid, not for any particular reason but just because I want to.

I’m considering getting another PPS, not necessarily another Bluetti, and using that as the primary power source to run my entire combined office, radio shack, electronics work area, charged by solar panels on the roof and/or on the south facing wall of the garage. How far that project will go depends on how ambitious I get and what my budget looks like.

Comments and questions are always welcome.