Where to get a battery repaired?

[Quahogwi]

My bike has a 1000w rear hub motor. The battery label tells me that it is 48v, 20ah. Both are approx 1 year old.

I don't know what prompted me to dig out my multimeter, but I did. At full charge at the charging port and at the power out port I get a reading of 33.3v instead of 48+v as it used to. Doing the math I come up with a group of 5 batteries that seem to be off line.

I may have the ability to open the battery pack and check connections and the BMS and do a little soldering if need be. But I don't have quite that much faith in my abilities and figure that finding someone to diagnose and fix my battery pack would be a better deal than buying a complete and new battery pack.

What's interesting, though, is that at the lower full charge reading, 33.3v, the bike runs just fine, although a little slow (18mph -20mph on flat smooth road).

Any advice out there for getting the battery pack repaired, or should I just run it as is?

 

[harryS]

Change the battery in your multimeter. That's the one that's likely to be bad. Two reasons....

A 48V battery's internal control circuit will shut it off if it's below 40V. You would read an open ciircuit or zero volts.

A 48V ebike controller won't run the motor when the battery hits its low voltage setting, which will vary by design but is between 40 and 42 volts. You couldn't be running at 33V. If you can see the label on your Voilamart controller, it should say something like "Undervoltage: 40V".

 

[dodahman]

https://netherswholesale.com/ You might look here.

Also, when reading voltage with a volt meter, the internal battery is not used. The battery is for resistance measurement, I think.

 

[harryS]

https://netherswholesale.com/ You might look here.

Also, when reading voltage with a volt meter, the internal battery is not used. The battery is for resistance measurement, I think.

That's for the old analog meter voltmeters. This one uses a 90 volt RCA battery, last made in the 80's?.

 

[dodahman]

That's for the old analog meter voltmeters. This one uses a 90 volt RCA battery, last made in the 80's?.
View attachment 47021

I see you are ready for post EMP war fare...Always good to have one analog device around...

 

[Quahogwi]

The battery in my multimeter is fresh. I have tested other known power sources, both ac and dc, and got correct readings. I will check the controller's label later.

Thanks.

 

[harryS]

Is it a Voilamart kit that is possibly set for 36V? The battery still shouldn't go that low, 33V is like 2.5V per cell, which is right at the point where you kill them.

 

[harryS]

I see you are ready for post EMP war fare...Always good to have one analog device around...

Back in the 80's, our company sold a bundle of mechanical teleprinters to the government. EMP resistant.They ran on an RS232 current loop.

 

[Explorer-1]

What is the open circuit voltage of your charger? Did you measure that?

 

[WinterKill]

Court toured this battery rebuilder.