diy solar

diy solar

Charging a lifepo4 battery and BMS with Bench Supply?

bigbluefan

New Member
Joined
Nov 22, 2021
Messages
5
Hey all, long time lurker first time poster.

I got my hands on a used Bluetti that has a BMS defect i believe. The device will not take a charge via the Inputs (tried both). (error 43 Low BMS voltage)

My plan is to totally disassemble it and but the battery on a bench supply to charge it. (After checking cell voltages)

I don't want to deconstruct the entire battery pack, so my question is

1. Do you foresee any issues with charging the battery in series with 48V on a bench supply? Was thinking slow and long, 2-3 amps

2. If the load portion is disconnected should i still disconnect all BMS components from the battery just in case?


Thanks for any feedback!
 
Hey all, long time lurker first time poster.

I got my hands on a used Bluetti that has a BMS defect i believe. The device will not take a charge via the Inputs (tried both). (error 43 Low BMS voltage)

Does that Bluetti allow you to see the individual cell voltages?

My plan is to totally disassemble it and but the battery on a bench supply to charge it. (After checking cell voltages)

I don't want to deconstruct the entire battery pack, so my question is

1. Do you foresee any issues with charging the battery in series with 48V on a bench supply? Was thinking slow and long, 2-3 amps

Yes. Most bench supplies discussed here aren't 48V capable. Unless the cells show conditions of concern (swelling, very low resting voltage, etc.), I wouldn't be concerned by charging at higher current.

2. If the load portion is disconnected should i still disconnect all BMS components from the battery just in case?

If it's needed to make it work, yes. If not, no.

If you can access the individual cells, you don't need to charge them in series. You can simply attach your PS to a single cell and charge it directly. This may be tedious, but it works. If you're just dealing with a low cell or two, this might be the fastest way to get the unit functioning again.... just charge the lowest cell(s).
 
Does that Bluetti allow you to see the individual cell voltages?


Only The indigo model (ac200) i believe, new BMS in the production wont allow it

Yes. Most bench supplies discussed here aren't 48V capable. Unless the cells show conditions of concern (swelling, very low resting voltage, etc.), I wouldn't be concerned by charging at higher current.
Yea i had to amazon a CC CV - 60V 5A Bench Supply to use just for this

But no foreseeable issues with the 48V charging?I believe the cells are PCB welded, havent broke into it yet just going off 1 video online.

ac200p.PNG

If it's needed to make it work, yes. If not, no.

If you can access the individual cells, you don't need to charge them in series. You can simply attach your PS to a single cell and charge it directly. This may be tedious, but it works. If you're just dealing with a low cell or two, this might be the fastest way to get the unit functioning again.... just charge the lowest cell(s).


Sorry not quite sure if i understand this portion. Should i remove the BMS Balance leads as well as main voltage leads? before charging? Any particular order (I'll admit i haven't done research here so may be a dumb question i can find easy enough)
 
Sorry for the confusion. If you charge through the main leads, the BMS may prevent you from charging. That would necessitate you to go directly to the terminals.

I'd wait until you can check the cell voltages and then develop a plan.
 
Sorry for the confusion. If you charge through the main leads, the BMS may prevent you from charging. That would necessitate you to go directly to the terminals.

I'd wait until you can check the cell voltages and then develop a plan.
Gotcha,
100% agree. Going to take lots of video and photos for anyone that might be in a similar situation once these warranties expire.

Thanks for your input!
 
If you are charging in series you need to be watching for overcharged cells. (The job of the bms). One idea might be to get another bms and attach it and charge through that.
 
If you are charging in series you need to be watching for overcharged cells. (The job of the bms). One idea might be to get another bms and attach it and charge through that.

Thanks for Sharing. Good point!
I'm going to check all the cells first.

Since the unit is so solid, if I do find a low voltage cell and i disconnect everything from the BMS, i wonder if i could charge by using the specific balance leads of the bms as a way to shortcut taking the entire unit apart? If nothing in the BMS is connected, in theory would it be similar to just charging the cell directly?

Or would it just take the path of least resistance (i don't know what that would be in a 16S battery pack that's all welded. The most full cell or least full cell?)

Edit: Just thinking again, if they are 16 series, i feel like me theory would be correct. If i were to set a constant voltage of 3.6 (or whatever the mean average for the pack is) would it not effectively be top balancing that cell? Current should only be able to travel from the entry point on that cell to the exit point (1 over) on that same cell using the BMS balance wires. And if voltage never exceeds 3.6 should be able to charge all individuals cells in that series to 3.6?

Edit2: Found a guy doing something similar, makes me feel a bit more confident about the approach, Mind you he's using a Regulated charger, but i don't think that should be an issue with a Bench supply from what i've read


 
Last edited:
Updating on Bluetti Forum as well. But Voltage reads 53.1!

Going to check what they might offer for diagnostics, but good to know battery wasn't actually 36V!

Some how thers a component on here that is sending mixed signals to the head unit :(

I hope i can get a replacement! The teardown wasn't too bad, But the Grey bevel around the edge is made to be a disposable component IMHO (Barbed hook clips that lock after insertion. i broke 8/8 of that type and 0 / 16 of the other ones.

20211123_233816.jpg
 
Back
Top