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Old 01-11-20, 09:38 PM
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yippee
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Back to the battery

So in another thread, I mentioned that the 36V 10Ah LIPO battery on my bought used Xtreme Baja folding wasn't taking a charge. Charger goes red for about 15 minutes and then shows green again.

Total battery voltage after charging reads 39.4v. So I took the battery out of the metal slide-in case, removed the blue shrink wrap and found 40 cells LS LR1865SZ which aren't LIPO, they're lithium ion.

After testing the cells, I found various voltages, some cells read 3.8V, some cells read 4.0 or 4.1V and four cells read 3.2V. Am I right to think that I should change out the 4 cells that are at 3.2V and see if

the BMS will balance and charge all the cells to 4.2. I would just cut the nickel strips and solder new ones in since I don't have a spot welder. Finding 4 similar speced batteries for $10-15 (maybe less) total shouldn't be a problem.

I'm thinking this might get the battery back up to 42 volts when charged. Any thoughts?
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Old 01-11-20, 10:46 PM
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Doc_Wui
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Your battery is well out of balance. Normally, cells should be within 0.100 volt of each other. The good news is that your worst looking cells are only at 3.20 volts.THese may be the cells that power the BMS and ran down while the battery was in storage.

Here's what happens when charging. The BMS watches the voltage on all ten cell groups As soon as the groups that are at 4.10 volt hit 4.2 volts (max full charge) , it stops charging leaving those low cells at 3.2V yelling for more power, but sorry, the bar is closed. Meanwhile, if you try to use the battery, it shuts off as soon as any cells reach 3.0 volts, The lowest cells get there fast, so even though the battery is at 39 volts, it is useless.

If you leave the charger connected, some BMS will try to balance the cells. It will discharge the highest cells a little and start the recharge again. Slowly the cells at 3.2V will catch up. This could take several days. The charger will stay green, but if you had an ammeter on it, you would see it pull about .05 amp. However, not all BMS have this balance function. Give it a try anyway. Watch those cells with a voltmeter. See if they are coming up.

If the above doesn't work, you can try charging the 4 cells individually. Disclaimer. Do this at your own risk, You need a 4 volt charger, and you should not exceed 4.1 volts. Suggest you go to the endless sphere forum and ask for directions. There's risk of cell damage and fire if you make a mistake.Let's hope your battery can rebalance itself.

Even if you could stitch in four new cells, they start at 3.6V when new, so the pack is still unbalalanced,

Last edited by Doc_Wui; 01-12-20 at 08:11 AM.
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Old 01-12-20, 04:42 PM
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yippee
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Ok, Doc Wui, thanks.
I got the battery and charger in my barbecue outside and will leave it there, charging on green, for a few days.
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