Battery question

DdMIXk

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May 21, 2022
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For my ebike, my setup has been 3 Mighty Max ML 10-12 12V 10Amp Hr. batteries, serially connected, giving me 36Volts.

A weeks back, I found a Hi Boy Escooter by the dumpster, missing its battery. Thinking I could get it working, I ordered the battery from their website and a charger from Amazon. It's a36V 7500mAh.
It has two sets of cables, one hooks up to the charging port on the scooter, the other to the controller.

After using the scooter for a day, I left it charging overnight. The next day, it wouldn't start at all. Not even any lights. The multimeter was still showing 42V, too.

Long story short, not having been able to figure it out, the scooter is now really in the dumpster in pieces, but I still have the battery. I hooked it up to my ebike and the regular controller outlet on the battery did not power anything. I decided to try the charging port, spliced the wires and the ebike throttle lights came on. It even spun the wheel a few turns, then I noticed the battery level on the ebike display went all the way down, now it's showing it almost empty.

Do you think this is a faulty battery, perhaps gone bad with that one time charge, or is it my complete ignorance on batteries?

HiBoy battery: https://drive.google.com/file/d/1k2135AczsK7_fR6lj_nQOEEE8TCzZgvo/view?usp=sharing
MightMax battery: https://drive.google.com/file/d/1dZxkQrQJ-FnEPQdwv3UxlCnos5MWaF1z/view?usp=sharing
 

Nelson37

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Mar 15, 2022
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Multiple possible problems, worked once, charged once, then failed. check ALL battery connectors and cables, meter everywhere, take notes, charge a bit, meter some more, etc.

See if both sets of battery connectors read the same, change the same after charging, etc. you SHOULD be able to charge thru the "output" connectors, as well.

Something has gone seriously wrong, likely with the battery itself. Test the charger.

How long between the single, only charge and the connection to the ebike? Hours or days, or weeks and months?

Chinese QC puts everything in question. Bad internal connection, may need to cut off all that protective shrink wrap.
 

DdMIXk

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May 21, 2022
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When I was still contemplating on whether it would even work with the bike, I also charged it from the other connectors from my bike battery charger. I did my testing with the bare wires, then soldered T60 connectors on each end. Still same result.
I'm thinking that charger I bought when I bought the battery may have done a number to it, as the problem started immediately after using it overnight. It was also a little shady as when the charger arrived, the tip didn't fit.
When I contacted the seller on Amazon, he sent me another one. Same issue. He sent me the charger with the correct plug on the 3rd try.

I just wanted to confirm that this battery (when working properly) is comparable to my MightyMax battery. I was hoping it would work, as the MightyMax makes the bike heavy at 7lbs each..
 
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