Duff charger or battery?

alistair1537

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Apr 14, 2022
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Hi all,

I bought a battery and charger - 48V 20Ahr for a Bafang mid-mount conversion I'm busy building for my wife. I bought the kit back in September, but due to circumstances have only got around to it now. I plugged the charger into the battery to charge it fully, but I shut it down after a few hours (2) as it didn't seem to be gaining any lights on the battery state. I checked the voltage of the battery charger - 2.34V??? Then I checked the battery voltage and this was also 2.34V?? So, what is the prognosis? Is the charger broke? Did the charger break the battery? I have contacted the supplier - E-bay but, I haven't heard back yet?
 
D

Deleted member 4845

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Letting a battery sit uncharged for 4-6 months is bad. Some chargers do not output full voltage without a load. Could get a bit tricky to test. Put a new battery in your voltmeter, common cause of flakey readings. Double check limit settings on voltmeter, should be over 50. 50.4V is fully charged for your battery.

If you are waiting for answers from Ebay, then you do not know how this works.

Check the voltmeter, verify correct readings, new chargers are fairly cheap, you may need to partially disassemble the battery and take readings directly from the BMS.

How many lights are there in total, and how many lit, on the battery itself?

This will be expensive to replace, and good odds you need a new battery or some extensive repair, likely not covered under warranty, assuming anybody is there to honor one, anyway.
 

alistair1537

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Ok, Thanks for your reply - I got it sorted. This battery sits in a rear rack mount - it has a different locking key to my bike's battery that is frame mounted - this key also functions as an "On" switch for the battery - it also has an "on" switch which really only lights the power remaining bar's leds. So after switching the key on fully - slight depress past a lock position - it now shows the true battery voltage - 48.6V and the charger is also pulling the full 56.5V. I had a Duh! moment...
 

HumanPerson

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Ok, Thanks for your reply - I got it sorted. This battery sits in a rear rack mount - it has a different locking key to my bike's battery that is frame mounted - this key also functions as an "On" switch for the battery - it also has an "on" switch which really only lights the power remaining bar's leds. So after switching the key on fully - slight depress past a lock position - it now shows the true battery voltage - 48.6V and the charger is also pulling the full 56.5V. I had a Duh! moment...
Good job and Welcome! :)
 
D

Deleted member 4845

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Something is very wrong with your battery, and charger, or your measurements.

Battery should be 50.4 fully charged, possibly 54.6, or 58.6. Charger should match one of those. Unless you are not a standard Li-ion chemistry and forget to mention it.

EDIT 4/19/22 - Typo on the last voltage number, that should be 58.8
 

alistair1537

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Yeah, I may fudging the numbers, the bike is down in the city workshop, I'm at home replying - I know it was around 48.? V when I figured out the "on" switch, but that was before any charge - from Sept. til now - So I'd expect that to be low. I'll get a more accurate figure after a few charges I'm sure. I'm not used to this 48V regime - My bike is a 52V setup so I'm more familiar with that. To confuse matters even more, I run a 24V LiPO4 system on my barge, as well as a 12V LA starter system, then there's all the other boaters that call on me to sort their 12V LiPO4 systems too. I'm 62 this year, it's getting harder and harder to keep track of all the numbers...
 
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