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diy solar

Dead Duck Battery?

jesfl

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Joined
May 17, 2020
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104
From what I've found and read on this Forum, the only solution to attempt to make this battery functional again is to charge/discharge the two low/high cells independently? Is that correct? Any other possible tricks or techniques?

Please see screenshots below of the BMS app's main screen: (1) while charging, and (2) after BMS/charger shutoff after hitting the max 3.65 volts point on cell #4. Also shots of the battery with part of the case and shrinkwrap cover removed from top and BMS side.

This is the third of three batteries that died last year. With incredibly patient guidance for this newbie here at the Forum, I learned the BMS failed, not the cells. Three new (JD?) BMS are now connected on all three sets of cells. The first two recharged and balanced fine, seemingly. The last pack (#3 shown here) will only charge cell #3 to about 2.6 volts because then cell #4 hits the max 3.65 volts and the BMS shuts off the charger.

I have no idea what type of cells are in these (cheap) Chinese cell packs? I got brave enough to open up the outer shrinkwrap cover to find the failed BMS, clean up the connections, and connect the new BMS. (See photo below.) From there, whatever is inside the bolted-together covering is unknown to me. And, at my low skill level, I have no desire to unbolt and open it further . . . in order to figure out what is what and attempt to charge/balance different cell packs manually.

So, if there is a trick or two for evenly charging these cells as is -- without breaking apart the case further -- I'll give those a try.

Otherwise, this cell pack is going into the trash. Exactly how does one properly dispose of a 46-pound LiFePO4 cell pack?

Thanks for any ideas.

jesfl
 

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Without breaking the pack apart, you can load cell #4 and draw is down. I used a car headlamp connected to the one cell to pull mine down. When that cell is down, you can start another charge cycle.
 
I would start with carefully removing the tie plates 1 at a time and cleaning the bars and terminals thoroughly, including the bms leads. If you have an adjustable bench charger you can try charging the low cell without taking it apart.
For disposal you can send it to me-I'll look after it!
 
Thanks to both of you. I wondered about "how to" charge one cell only without breaking apart the entire bolted-together pack? But with my limited knowledge, that doesn't get me very far.

I guessed the cell(s) below each of the plates I numbered are the cells showing as pack #1, #2, and #3 on the app? I identified those by checking voltage with my multimeter and the voltage adds consecutively in that 1-2-3 order. But, cell pack #4 (with the total voltage) is measured by connecting the main +/- connections directly. And, that always reads whatever the total voltage for the set of 4 cells/packs is at that time.

I've had all the plates off previously, as I removed unused cut-off wires and solder points. See the photo below.

My guess was/is that there are other connections within the case because regardless of whether I check the bolt connectors or the bars connecting each two of the bolts, I get the same voltage readings, i.e. #1 = 3.3 volts, #2 = 6.6 volts, #3 = 9.9 volts and the total for cell group four testing the main positive and negative connections is always the total for the four sets, about 13.2 volts. (These are example voltages only.)eee

But, here's an oddity. When just checking the voltage on each of the sections, I got a 0.005 reading for # 2C? With the plate on connecting all 3 bars w/ 6 bolt connections, the #2 cells together read the normal 6.6 volts. I guess that means 1/3 of either a 3-cell pack (3 bars) or a 6-cell pack (6 bolts) is not working at all?

But, I still don't know how to connect my 12-volt headlight bulb to drain cell pack #4?

Is it plausible to drain all cells to zero and then slowly recharge?

Thanks for any further thoughts.

jesfl
 

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