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Dead battery fix & off season maintenance.

Old 07-08-19, 02:18 PM
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chas58
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Dead battery fix & off season maintenance.

Tried riding my bike this spring on a 4 year old battery. It went about a mile. UGH. I'm adding up the dollar signs in my mind...

This happened to me before, and I disposed of the battery (partially because LiFePo4 was a boat anchor). But this battery is too nice to throw out.

I looked into purchasing a new one and test procedures to find out what cells were bad, but...

I managed to bring it back to life by charging it for a month (not sure how long it took). My thought that by leaving it charging for a long time, that it would eventually balance out the cells as the weak cells would continuously get topped off until they were out of the red zone.

That of course brings to mind the question of what to do with a battery in the off season? If a cell gets too far into a state of discharge, it may never come back.

What do you do to keep your battery healthy when not using it for an extended time?
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Old 07-08-19, 03:48 PM
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I reside in socal so this is theoretical, but I think that as long as the battery SOC is 20% - 80% at the proper temperature (50 - 80 degrees F or so), it should deteriorate minimally. ebikesca seems to test everything; did you check to see if they've done any studies?
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Old 07-09-19, 11:57 AM
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If I let a battery sit long enough, it will lose charge. If one or more of the cells get too low, they will not revive. I consider myself lucky that it did eventually balance out and revive. Not a problem on a new battery but this one is getting old.

The proper ebike.ca answer is to use their trickle charger to keep it at 50%. But that charger costs more than my battery...
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Old 07-09-19, 04:17 PM
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I assume you are referring to an L-ion battery pack. They can be permanently damaged by overcharging, deep discharge, and temperature extremes. Most sources I have referenced recommend storage at 50-60% SOC at "room temperature" Most new packs are stored and shipped at about 50% SOC with instructions to charge before using.

If your garage/storage space gets up into the 90s in summer and down in the 30s in winter, pull the battery and bring in inside the house. In the MN winter I charge mine to about 50% and put it on the floor of the coat closet until I think it's warm enough to ride again. It is a three year old LiFe-Po4 pack that shows no signs of degradation.

If you ride in winter, store and charge inside until you ride and bring it back in when finished. The mass of the pack should resist cold-sink for the duration of the ride.

Cell balancing should be handled by the pack's management system while charging. A severely unbalanced pack may take several charge cycles to re-balance completely.
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Old 07-09-19, 07:43 PM
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Originally Posted by chas58 View Post
If I let a battery sit long enough, it will lose charge. If one or more of the cells get too low, they will not revive. I consider myself lucky that it did eventually balance out and revive. Not a problem on a new battery but this one is getting old.

The proper ebike.ca answer is to use their trickle charger to keep it at 50%. But that charger costs more than my battery...
For batteries that are used sporadically I just check the voltage occasionally, then charge as necessary.
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Old 07-10-19, 07:09 PM
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As far as balancing goes. Your BMS determines at what point in the charging process the cells are balanced. On many batteries you need to put a full charge on them so the BMS will balance the cells. You can charge no higher than 80% and discharge no lower than 20% to extremely lengthen the life of the battery but put a full charge on once a month or every two months so the cells will balance. The BMS in the batteries That ebikesca sell will balance at any point in the charge. If you are going to store it for a long time put a full charge on before you quit using it and the BMS should use minimal voltage to protect it. I sporadically use my cordless power tools so I charge them 3 times a year.
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