AC200Max battery drain overnight?

EDIT 2: A couple of weeks later and it seems we do indeed have a fault in one of our AC200Max units. I’ve tried the recommended fully discharge / full charge routine and whilst at first that seemed to do the trick it’s continued to fully discharge overnight - first intermittently but now the unit is just unusable.

EDIT: It’s now a few days later and it LOOKS as if all that was needed was a complete discharge/recharge to reset the system (which had got confused about how much energy was in the battery). Read the thread for full details.

I’m not yet certain whether I’m dealing with user error or a fault - so any ideas of what could have gone wrong welcome!

We have 2 x AC200Max and they’ve been working brilliantly without issue for 6 weeks or so.

Yesterday one of them was showing battery at around 40% full at sunset and I decided not to use that energy until the next day. AC / DC was never switched on (99% certain - but it is possible that I switched it on without noticing) so the unit should have switched itself off completely, waking up when the sun came up this morning.

I’ve just checked to see how much power is being generated this morning and the battery is showing 0%. I tried switching on AC and running a small device to establish whether it’s just a reporting error, but sure enough, it failed to run the device and AC switched itself back off.

We’re only getting about 40watts from the panels right now, and the battery is now showing 1%. So it seems to be charging OK.

But what happened to the 40% that was in the battery last night?? Even if AC was left running all night (22w) that wouldn’t be enough to drain the battery completely. (and I’m 99% certain that that didn’t happen).

Has anyone seen this kind of problem before? Any tests etc that you can suggest?

It is possible that the state of charge meter is out of calibration and did not actually contain 40% as indicated. I would fully charge the unit followed by a full discharge and recharge again to see if the problem goes away.


Thank you. I will do as you suggest to ensure that we’re back to a known starting point.

However, this alone doesn’t explain the problem.

Yesterday morning the display was saying (from memory) 20%
We didn’t use the generator to power any devices yesterday
We had some sun trickling in yesterday and we ended the day with 40%.
I’m 99.9% certain that everything was shut down (including the unit) shortly after sunset, with a 40% charge in the battery.

So even if the display was wrong, what happened to the energy that was stored in the battery yesterday? I guess it’s within the realms of possibility that AC was left on, but almost certainly that wasn’t the case.

So if you have any other ideas to help us trouble shoot? What could cause a battery to completely discharge when nothing (even the unit) isn’t switched on? Is it even possible?

It’s now at 8% so is charging as you’d expect via solar. (We have two units and both are charging at the same rate).

When something unusual happens I like to try and understand why. Even if it never happens again.

Thanks for your help!

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The most likely things would be that the battery was actually discharged even though the display stated otherwise. Second most likely would be a combination of the first thing plus something left on.

It ended the day at 14% (which matches with our other unit) - so all seems well. I think I’ll just let it charge to 100% over the coming days via solar. I’ll get up before the sun in the mornings and switch on manually. That’ll give me a chance to make sure all the numbers are adding up each day.

If there’s no fault that fits what happened then chances are I had some kind of brain fart and left it switched on last night.

I’ll report back in a few days to confirm.

Thank you!

Hi, I’m exepriencing the same issue after a couple of months of correct working.
At the end of the day the battery is fully charged, I switch off the AC and also the AC200Max. In the morning the display shows a very low charge: 0% or 4%. I’m pretty sure the battery are still charged but the display show the wrong charge. After few hours of weak sunlight I can see again the full real charge of the battery.


It’s only been a few days since I reported this issue, so too soon to say for certain. However, it LOOKS as if @Scott-Benson was right.

I think it’s now been three full days and I’ve had no further problems. I haven’t actually run anything from the AC200Max - but I am letting it steadily charge to 100% from solar. There’s not much sun at this time of year in Scotland so it’ll take a few days longer.

I BELIEVE (and @Scott-Benson will hopefully correct me if I’m wrong) that the battery technology has a weakness in the sense that it’s not possible to get an accurate reading of charge state. Presumably the generator uses some kind of algorithmic method of estimating available power. If, for some reason, things have got into an inconsistent state the algorithm comes up with the wrong answer and misleads you with regards to how much power you have.

So - chances are that your mind is playing tricks. You blindly believe what the display tells you is available. However, it could be much less. Your unit probably (like mine) switches itself on in the morning when the sun comes up and if it’s cloudy it will use more to run than it’s actually getting from the sun. That’s enough to empty the battery and finally the display reports the true charge. So it could be the season and lack of sun that causes the problem to reveal itself suddenly. Earlier in the season there will be enough sun in the mornings to prevent the battery from draining completely.

Scott’s recommendation was to fully empty (which is where you are) then fully charge the battery. This will reset the algorithm to display the battery state more accurately. You could do it from the mains, or like me - just don’t use it again until solar has had time to recharge it to 100%.

If anything changes for me I’ll report back, but it LOOKS as if Scott was right.

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@bluetti @Scott-Benson

It seems we have something more serious going on here - I’ve tried the recommendation to fully charge and discharge the unit a couple of times but to no avail.

Yesterday I fully charged the unit from the mains. I used it to power some devices in the afternoon leaving 58% remaining charge when it was all switched off last night. This morning it’s showing zero and won’t let me switch on the AC.

I tried the fully charge/discharge remedy a couple of times - at first it would intermittently discharge, but it seems to be getting worse rather than better. The unit is now unusable.

We have two AC200Max (the other is working perfectly) - we swapped them around to rule out something being wrong with the solar array or even temperatures in the room it’s situated in. But it’s definitely the unit.

I guess the next stage is to contact by mail for an exchange under guarantee? Or is there anything else I should try before escalating to that level?

Hi @Poppy , I am very sorry to have heard this news.
Yes, you need to contact customer support to resolve this matter further and they will provide you with a more detailed solution.

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It seems I have exactly the same issue again on my second AC200max replacing the first one having battery drain…the last week I have been charging on solar up to 30-40-50% and every morning It’s gone 0% so I tried not to switch off at night, eco mode is off, AC-DC off, 8 AM: device off, batt 0%. last night I added screen on always but in the morning AC200max is off and upon starting : 82% !!
I always put eco mode off but it doesn’t keep the device awake anyway…
So I guess I have to make a full charge/discharge or what would chatgpt advice…?:

"Yes, there is a way to balance the battery modules in the Bluetti AC200 Max to ensure that you get accurate charge indication. Here are the steps:

Turn off the Bluetti AC200 Max and unplug all the devices connected to it.
Open the battery compartment cover and locate the balance charging port. It should be labeled "Balance Charging" or "Balancing Port".
Connect a balance charging cable to the balance charging port. You can use a balance charging cable that comes with a LiPo battery charger or purchase one separately.
Connect the other end of the balance charging cable to a balance charger. Make sure the balance charger is set to the correct voltage for your Bluetti AC200 Max battery.
Turn on the balance charger and let it run until all the battery modules are balanced. The balance charger will automatically detect the voltage of each battery module and charge them to the same voltage.
Once the balance charger is finished, disconnect the balance charging cable from the Bluetti AC200 Max and the balance charger.
Close the battery compartment cover and turn on the Bluetti AC200 Max. You should now get accurate charge indication. "

for me with a little bit of knowledge on battery systems this does make sense indeed.
What do you think about it?

It may make some sense if you are an electronic technician and are comfortable with the level of product tear down and reassembly not to mention you will have voided your warranty by disassembling your unit. I would contact Bluetti service and support for assistance and advice.

Having this issue as well. Need to drain to 0% and charge to 100% every few weeks. Any real fix for this would be great.

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