Battery Help!

Tortellini

New Member
Ok, so I have just gotten this e-bike. I could not find out the name of it anywhere. It runs 3 12v battery's for a total of 36v. They are all near dead. (can power lights, bike will move but die out rather quick, not be able to support the weight of person.) They all read 12v or above. So I could only afford to buy 2/3 new ones, so will the 2 new batteries be able to power the bike with the older one? Even if the battery life is shortened by a 1/3. Thanks :)
 

AguassissiM

Well-Known Member
@Tortellini it would be best if you can purchase a full new pack @ 36volts, your solution will only kill the 2 new batteries rather quickly because they will try to charge the old one. I'm no expert in this field and may be totally wrong, someone like @Ann M. may give you a proper answer.
 

Ann M.

Well-Known Member
@AguassissiM, you are totally correct. Replacing 2 of 3 dead SLA (lead acid) batteries will not solve the problem. If the 3rd battery is totally in the dirt amps wise, the two new batteries will be damaged in a very short time. @Tortellini, if you do this you may lose the warranty on the 2 new batteries. Better to wait a little longer and buy all 3 new batteries. Any auto supply shop or battery shop and many ebike repair shops will have a load test tool and can tell you exactly how weak those original batteries are. This will help you understand why it's not recommended to only replace a portion of a pack.

If the battery pack was truly new, then you might have an issue where one battery had a manufacturing issue that damaged it; however, it doesn't sound like this is the case here.