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, has a new email address. It is 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…

Author: grouchyfarmer

Yes, I'm a former farmer. Sort of. I'm also an amateur radio operator, amateur astronomer, gardener, maker of furniture, photographer.

8 thoughts on “New Email, Solar Panels, Last Bluetti Article”

  1. I think the “solar generators” are nice for camping and such, but for reference I have 29 390W panels on my garage roof, for a total of just over 11KW of power, and that basically just barely or slightly underproduces my annual electricity needs. Although my house is not very energy efficient, at 135 years old. Still, if I did all the upgrades to windows and A/C, I could be on the net producer side of the equation, but remember over 11KW. I think that’s a more reasonable home system figure, off grid or not.

    Great article as always!


    1. You’re right, of course. Systems like the Bluetti are fine for RVs, camping and to provide power during a blackout, but these plug ‘n play “solar generators” are just not suited for use as a primary power system for off-grid applications. Storage capacity is too low and you simply can’t pump enough solar energy into them because of their relatively wimpy charging systems to get ahead of the game.

      11KW is a lot of power, but from the stats I’ve seen the average house in the US uses about 30KWh of energy per day. Renewable energy is fantastic, but I think we need to also include more efficient use of energy or we’re never going to get ahead.

      Liked by 1 person

  2. The way your panels are just leaned against the wall, I believe, is hindering your maximum charge potential.

    IMO, you need to build a frame to hold them at the best angle you can get to the sun. I might even stagger the horizontal angles a smidge so when panel one gets past maximum exposure, panel two is getting maximum exposure, and so on. That I doubt would be as important as altitude, as the sun does not follow the same path through the year. Some altitude adjustment mechanism would be key. I suppose the simplest thing would be to shim one side of the frame as the sun cycle does its figure eight. That would be the easiest way to get the altitude.

    It sure is easy to spend other peoples money 😉 And take up their time… It’s also quite possible I’m overthinking this. But that is my tendency when it comes to things like this.

    Great follow up, you did good rewiring the system.


  3. The Bluetti thing is very interesting but way above my technical capabilities. I do find it fascinating though… and maybe I am learning something.


    1. You don’t really need to know much to use systems like the Bluetti. At its basic level it’s really a plug ‘n play system intended to provide power during a power failure, and that’s what most people will use it for. A lot of these will never be plugged into a solar panel system, people will just recharge them using the AC charger.

      Liked by 1 person

      1. I have always been fascinated by the idea of solar panels too … but in an urban setting in a well populated area, does it really save a significant amount of money on electric bills when compared to the cost and maintenance of the installation? If the answer to that is yes, then I might consider them but I am such a novice at these kinds of things …


        1. Cost effectiveness is what it all boils down to. You’re absolutely right about that. Is the savings on electricity worth the cost of installing the system? The answer to that is a definite maybe? A lot is going to depend on how expensive electricity is in your area and whether or not the price of electricity service is going to go up significantly in the relatively near future, the price of components to build the system, labor costs if you can’t do it yourself, etc.

          My wife and I were discussing that very question the other day, would it pay for us to try to build a solar power system that would take over at least some of our electric needs. And it would seem that it makes sense for us to at least explore the idea further. Prices of batteries, inverters, chargers and solar panels have come down to the point where it’s starting to look like it might make sense even from a purely financial point of view. We did a bit of rough estimating of costs and came up with some interesting numbers. If I put together a system that could take up about 1/3 of our normal electrical usage we figured it would pay for itself within about 5 years. That surprised me because I hadn’t thought we’d see a payback that quickly. Of course there are a lot of variables in there. Weather is the biggest problem, of course. Solar systems will still produce some power during cloudy days, but energy production drops by 80% – 90%, and we get a lot of cloudy days here, especially in winter. Still the numbers look interesting enough that we might actually try something in the future.

          Liked by 1 person

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