Bluetti AC200P - Reverse Engineering

Product Discussion BLUETTI Apex & AC Series
1

I am the proud owner of a Bluetti AC200P. It’s a nice unit, but it won’t power on or charge.

When I pressed the power button, the green light surrounding it would flash 3 times - then go right back off. When I plugged in the charger, its indicator light did not turn red. The unit showed no response.

I contacted Bluetti support, but they were not much help diagnosing it. They said it needs a new charger, for $150. I had already tested the charger - 56V coming out of it. I opted not to waste $150 and began diagnostics. A lot of you guys probably already know all this stuff, but this was a fun journey so I thought I would post my findings for anyone else trying to figure this out.

I disassembled the unit down to the battery and BMS. I plugged everything back in, but in a way where I could peek in to see the BMS. I hit the power button, I saw the green LED on the BMS. Then I heard a click, and the BMS shut back off.

From what I can see, this is a 16S10P (16 series, 10 parallel) battery. This means there are 160 batteries, split into 10 groups of 16 cells each. Each 16 cell group is wired in series, producing 48V nominal. And then all 10 groups were wired in parallel.

I checked the raw battery voltage at these terminals, it showed 53V. That ruled out over-discharge:

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Next I checked the individual cell series using these pins. All were within 0.02V of one another, so that ruled out unbalanced cells:
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Next I checked the voltage on the BMS output for the few seconds it was powered on, it showed 0V:
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The click before shutdown made me think a component is shutting this BMS down, probably for safety reasons. I figured this could be the thermal sensors or a shorted output. Thermal sensors are here:
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I opted to check the BMS output for a shirt first. The cables ends themselves didn’t show continuity. Then I checked the battery input on the power inverter board. Bingo! 0 ohm resistance:
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I carefully looked over the inverter board, considering a DIY repair. I would probably have to desolder all the MOSFETS, gates and other things and check them individually. Even if I find the bad ones, they might just burn out again if I miss the actual root problem. Plus I’d have to fight through all this funky glue that’s holding it together. I opted not to go this route.

Armed (proudly) with my diagnosis, I contacted Bluetti support again. Lois was very nice, but knew nothing technical. She again insisted the charger was bad. I pushed back on this with my findings, and she brought someone else into the email chain - I assume a technician.

He tried to sell me a new charger again, I said no thank you. He informed me that I was welcome to ship the unit in for repair, at my expense. I said I already have it apart, and I know the part I need - and asked him to sell me the part. He said they don’t sell repair parts, they’d have to service it themselves. I asked how much it would cost to replace this board, he said he didn’t know - they’d have to diagnose it when it arrives and then give me a price.

Bluetti’s solution to this problem is to have me spend $100 or so on shipping costs just to find out how much it would cost me to fix this unit. Since the charger alone is $150, I have to assume the repair would have cost a minimum of $300 plus shipping.

This is my reason for refusing to do so: I can spend upwards of $400 (just my guesstimate) for a repair on this unit that has a limited lifespan remaining on the battery. Once the battery goes bad, all of this expensive, proprietary, one-off circuitry (that I’m paying to replace) is now worthless to me.

I looked at this box of parts and took inventory:

  • Box itself - battery fits nicely, has a nice set of AC/DC/USB plugs and boards that may be reusable, nice fan slots up top
  • Battery - still putting out voltage and still in balance
  • BMS - I think it communicates via some kind of CAN bus design that I have no interest in reverse engineering, but it may still be reusable for the safe charge/discharge of the battery pack
  • Power inverter - proprietary, and burned out anyway
  • LCD & mainboard - proprietary and reliant on CAN bus, likely not reusable

I opted to rebuild the box with my own parts - non-proprietary parts that belong to me and can be reused on the next build or project. I will detail my progress on that journey in my next post.

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2

I wonder if the extended warranty might apply if you fill in the form:

Is your AC200P less than 4 years old?

I just got an Elite 100v2. The 5 year warranty was a significant attraction.

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Thanks for the info on this. I wasn’t aware of the extended warranty. However, I purchased this unit second-hand and have no information or documentation of the original purchase date - so customer support never suggested this route.

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To confirm my theory, my next step was to unplug the inverter board from the BMS and jumper the BMS power-on pins. The BMS powered on and stayed on, confirming that the inverter board was the source of the problem.

Once properly powered on, the BMS delivered 53V to its output terminals.

Next, I wanted to confirm that the BMS could act independently to properly charge/discharge the batteries without interaction from the inverter or main board. A typical “safe” range for these batteries is 40V → 54.4V. I was hoping the BMS would keep the minimum above 48V, as I’ve read that this extends the life of the batteries.

I connected a 48V inverter to the BMS power output and ran a small load (box fan + lamp) for around 24 hours total (I sat it beside me during my workday so I could monitor for safe voltage). The voltage dropped down to 46.7V then the BMS shut it down. Not 48V, but not bad either.

Next I wired the OEM charger directly to the BMS output for charging. The red light turned on and charging began. While plugged in, the voltage can show ~59V but I unplugged the charger periodically to check the BMS voltage. It charged to 54.2V and then stopped charging.

This confirms some good news, and something I do like about the bluetti design - the battery and BMS are able to operate independent of the rest of the circuitry. Now I don’t have to worry about purchasing another BMS to manage the cells.

This is as far as I have taken the project so far:

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Next steps:

  • Install a bus bar/distribution block for the 48V DC output
  • Install an 80A ANL fuse for the 48V DC output
  • Wire the 120V AC output from the inverter to the input terminals on the 120V plug board
  • Install a 48V → 12V step-down converter, and wire it to the input terminals on the 12V plug
  • Consider a relay and control-board to disconnect output voltage at 48V
  • Figure out how to wire up the USB charging board

This is the USB charging board:

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I’m hoping it accepts 12V and steps it down to the needed 5V, but I need to research that further. The yellow plug is the input power, the two white plugs go out to the wireless chargers on top of the unit.

Question for the pros: Where is a good place to buy this sort of hardware? Bus bars, ring terminals, etc. Amazon seems high. AliExpress is around half the price of amazon, but long shipping window. I can’t find much local.

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5

I’m not a pro but NAZ Solar Electric immediately comes to mind, if you’re in the US. Diysolarforum.com is a good place to ask this type of question too.

If the board has a blown mosfet maybe you can find it with a multimeter, without having to unsolder all of them?

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Thank you for the tip. That forum looks fascinating, I’m already deep into several interesting topics.

And yeah, that might work - but it’s tough to figure out when the entire output is shorted. I’m not entirely sure what to look for. Plus, a bad MOSFET might be causing the short, but there’s a decent chance something else caused it to fail. And it will just fail again.

Have you ever done this level of troubleshooting on a board? It does sound like an interesting challenge.

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Hi @steveh_131, In general, we do not recommend customers disassemble the unit themselves, as non-professional handling may cause damage to the power station.
However, based on your description, we believe you are a very professional person in the industry. Please operate under the premise of ensuring safety.
It seems you have already contacted our customer service team. Could you please inform us of your service ticket number? We will check whether the local repair warehouse can provide additional assistance according to your situation.
Thank you, @paulr, for your attention and explanation.

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@BLUETTI_CARE thank you for the response. My service ticket # is 309414.

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I’ve done component level troubleshooting on boards though not these power things. But, MOSFETS burn out sometimes. A good electronics forum is EEVblog Electronics Community Forum - Index where you could ask for troubleshooting help. They are better than I am about it. I dabble in electronics but am mostly a software guy.

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If anything, I see an overqualified customer and clueless Bluetti here. All Bluetti had to do was refer to the service manual, identify the part number, then confirm payment and shipping with the customer, and that’s it.

local repair warehouse can provide additional assistance according to your situation.

This is indeed very sound advice. However, the acknowledgment that any local repair shop has better expertise and deeper access to Bluetti’s internal documentation than the manufacturer’s official representative seems paradoxical.

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Hi @steveh_131, Out of responsibility for your order, we have to decline your request for purchasing spare parts separately.

This is because we are concerned that the problem may not be solved simply by replacing parts. It requires our professional engineers to get hold of the machine and conduct a thorough inspection to truly identify the root cause.

Secondly, the repair needs to be completed by our engineers, and only we can guarantee the quality of the repair and subsequent services.

After the repair is done, we will also conduct a series of quality tests until all of them are passed before sending the machine back to the customer. We will ensure the maintenance of your machine now and in the future, as well as protect all your rights and interests. We hope you can understand.

We understand that the repair fee is indeed relatively high, as it involves labor and material costs. We care a lot about your service experience. In this regard, we have applied for a reduction or exemption of the repair fee, and we will communicate about this matter via email. Please keep an eye out for the new email, and we will continue to follow up on this issue.

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By far one of my favorite posts I have ever seen on this forum. One thing to understand about Bluetti is they are an extremely sales centric/marketing first company. In my opinion pro level consumer grade hardware should come with upgrades like modularity for simplifying repair, easier direct access, and better diagnostics capabilities. I should be able to bypass the BMS if the SOC reaches zero, know the voltage of the battery from a manual display, or have access to replace limited consumer replaceable parts. The AC200P was designed to become obsolete and eventually into a landfill.

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I appreciate the offer, but I will have to decline. I already got this working myself and it probably cost less than what it would cost just to ship the unit. And instead of buying a likely expensive and certainly proprietary inverter board, I now have one that I can use on the next build.

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Unfortunately, you seem to be correct. I have another Bluetti unit that has served me well, they seem to have decent build-quality overall - I’m sad to find out that the support is so lacking. I do appreciate that they offered a discounted service rate, but they didn’t offer it until I made this thread. I imagine the typical customer would find it very difficult to justify the cost of shipping and repairing these units - especially since you don’t know the cost until you pay for shipping.

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Hi @steveh_131, We regret that we couldn’t be of more help.
Our service process has many rules, and our staff need to follow these rules when providing services.
If you have any other questions, please feel free to contact us at any time.

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@BLUETTI_CARE May I ask why it is a rule that you will not sell replacement components for your products? This is not a standard practice for other home appliances - many of which are also dangerous and difficult to repair. When my washer quits working, I don’t have to ship it back to Maytag for repair. I can hire a local expert or I can do it myself.

I would urge you to reconsider. As these larger units begin to age out, I think your customer-base will start to think that they “invested” in a very expensive device from a company that never intended it to last much longer than its warranty period.

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I have the exact problem you describe. I got my unit for free and am not going to “mail it in” for repair. At some point I was going to take the thing apart and see what I could find. Y ou’ve given me a path to follow. Thank you…

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This seems to me like a basic repair typical of what TV repair shops did all the time back when they had those. I would say the smaller Bluetti units like the 30v2 are basically glorified USB power banks, 5 year warranty and reasonably shippable if something goes wrong within the warranty period, and not a big loss if something happens afterwards. The bigger ones though are quite hard to ship and localized repair seems important. Plus there is the whole right to repair movement that may come into play. I’d say publish some service manuals. This stuff isn’t magic. The product and the repairs aren’t more complex for this stuff than they are for cars, and those do have manuals avaiable.

I think at this point I’d imagine buying an AC300 and B300 in preference to an Apex 300 just because of the AC300’s lighter weight if it has to be shipped. I understand people like having a single box but maybe it could somehow disassemble if necessary. That would still beat two boxes and a cable.

If I were doing a fulll sized home solar install (say 5KW) I’d use separate components and not consider Bluetti even with the new Solar 4K. But, the smaller portable stuff still seems viable even with these drawbacks.

I’d be interested to hear how the AC200L repair goes. If it were me I’d attempt component level diagnosis but if you’ve got an alternate inverter that’s cool too. I’d like to know what you ended up using.

1 Like
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Hi @steveh_131, Thank you for sharing your opinions. We believe they are put forward to help us develop better.

We do not sell replacement components, first of all, to protect ordinary customers and prevent them from getting injured during the repair process.
In addition, we are worried that the problem may not be as the customer observes, and simply replacing a part may not solve it, so as to avoid the situation where the customer buys the part but still fails to fix the problem.
Finally, we are also concerned that unprofessional operations may cause greater damage to the power station.

We fully understand the feelings of customers, especially professionals, who are willing to try to repair by themselves. This can not only save maintenance fees and freight but also a lot of time. We have conveyed your opinions to the technical maintenance department, hoping that they can provide more support to customers with relevant technical backgrounds.

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I’m glad to hear that this is helpful to someone - I hoped that it would be. I’d be interested to hear about your progress moving forward. What model is yours?