diy solar

diy solar

LFP from Docan failed + the warranty experience

That's still not the the ceiling or top balanced. It takes a long time to get through the 3.2-3.4 range.

You've got 6 - 180 Ah (?) cells in parallel, that's 1080 Ah in total. At 10 amps, that is 108 hours of charging. That would be 4.5 days if the charger held 10 amps without dropping at all.

Edit: they might be 280Ah cells. Similar math makes it 7 full days.
 
Thank you Bud Martin, et al. for the feedback :)

We have considered all the points. We have no short circuit concerns – I know you cannot see the situation clearly from 2D photos.

1) As I said earlier, we have 8S + 2 x 4S, we are in a transition to 2 x 8S. That’s why we were using 3 BMSs.

2) Wow, thank you for noticing this. We didn’t. I double-checked my BMS order and confirmed that we ordered the LiFePO4 version correctly, but JBD sent us the wrong version -- model # and part # are the same -- that’s crazy! We did try to configure some parameters differently using Overkill app because the BMS manual says the BMS was made for ternary (Li-ion) cells. We are not aware if a separate manual exists for two versions. We made parameter changes before starting to use the BMS. We may or may not have changed everything we needed to change for LiFePO4. Looking from the outside, the LiFePO4 and Li-ion versions are identical. May attach a photo when I get a chance later. We will be busy dismantling the battery, etc.
Will contact JBD, and see what they say.

4) It’s actually 250A MRBF.

We will now turn our attention to learning how to top balance as it would be our first time. Then seeing how many cells we can salvage.
1) Looking at the pictures, I cannot tell how all the 16 cells are connected and you only have one BMS. I do not see any cells connected in parallel to get 8s2p. I see top row cells are connected in series, same for the bottom row so I cannot see how you use one BMS for two 8s-cell configuration.
2) The BMS (21s) is rated at 3.7V for Li-ion, not for 3.2V LiFePO4. Can it be configured for LiFePO4? And are you wiring the BMS as 8s?
3) The way you are using the battery busbar for connections, it does not look good, not much clearance.
4) What are those 50A fuses on the cell terminals for?
5) You you draw out the wiring diagram of your battery?
In particular Item #2, If the JBD BMS is in fact NOT configurable to LiFe then most likely these cells have been being overcharged for a while, AKA, damaged. Most here know, but for those that don't, The peak/max voltage for LiFe is around 3.6v per cell and Li-Ion is 4.1v to 4.2v, considerably higher even if configured to a lower SOC for "safety" would equate to say 3.9v or so (I charge my Li-Ions to 3.95v to lengthen the lifespan).
We did try to configure some parameters differently using Overkill app because the BMS manual says the BMS was made for ternary (Li-ion) cells. We are not aware if a separate manual exists for two versions. We made parameter changes before starting to use the BMS. We may or may not have changed everything we needed to change for LiFePO4
If the Overkill app did not actually configure the peak charge voltages to 3.65v or lower, this is possibly what killed these cells

Great day to all
-Chuck
 
Well I'd hope that his charge controller was set to LFP so that regardless of what the BMS peak cell voltage was, his charger wasn't actually pumping it that high.
 
Well I'd hope that his charge controller was set to LFP so that regardless of what the BMS peak cell voltage was, his charger wasn't actually pumping it that high.
Yes, but that could mean an individual cell could go as high as 4 volts if the BMS setting was wrong. Long term that would destroy a LFP cell or two.
 
screenshot_20230219-183040-png.136712

If you can press the parameter button and/or control buttons and take screen shots there is likely a screen with the voltage cutoff parameters in there, someone here can further help guide you through this terrible situation. There's some information still needed to help you solve and possibly prevent this from happening again. (The BMS setting information)
 
"1) As I said earlier, we have 8S + 2 x 4S, we are in a transition to 2 x 8S. That’s why we were using 3 BMSs."

Are the 2 x 4S in series creating an 8S (24V) or are they isolated as 2 x 4s (12v) seperately? This may mean nothing but some BMS units do not function properly when series connected, I will have to say I cannot speak to what brands work or don't but I do know its not preferred for sure. Some serious experts here can speak to that I'm sure.
 
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