48v abused battery severely reduced range.

[Rokokong]

Hello!

Im new here but not new to ebikes, would love some insight.

I have 48v 10ah Hailong battery pack Ive used for about 2-3 years. Ive abused this battery, standing long days in direct sunlight, in rain, temp fluctuations you name it. It first was used on a 500w Bafang hub motor and then a 1000w BBSHD.

The range is about 1/10th of what it used to be, understandably.
But when I measure the voltage of it at full charge it still shows expected voltage. Im a noob when it comes to batteries and electronics and thought that the misuse of this battery would degrade cells and it wont be able to hold proper voltages. What is causing the severe drop in range?

 

[goatman]

probably way out of balance

you really should open it up and check the voltage of each p-group

 

[john61ct]

Voltage says literally nothing about State of Health.

Capacity testing is canonical

but climbing internal resistance can render a worn batt unfit for a given use case too.

Generally, if a battery tests at 50Ah when new, it should be retired / repurposed when that capacity declines below 40Ah, and certainly well before it hits 30Ah.

Depending on how it is cared for, for li-ion chemistries, that might be only 30-50 cycles

or it could be 500 cycles, but that is very hard to achieve in this use case.

 

[Rokokong]

probably way out of balance

you really should open it up and check the voltage of each p-group

Ok good to know! I did open it up to visually inspect it, though it was gonna look like hell in there as it did with the old hub motor I used with it. How do I measure the voltage of each p-group?

 

[markz]

With a multi-meter you can buy from Harbor King ins the USA for $10.
Figure out which is positive, which is negative for the entire battery, work your way from one end.
Its obvious

Snap some pictures

How do I measure the voltage of each p-group?

 

[Rokokong]

I have a multimeter. Today I opened the battery up again and checked voltages of all paralell groups and they all measure more or less 4,150v. Theres 13 rows of these. What am I looking for here to learn and know why the battery range is so bad?

 

[john61ct]

So that is fully charged, and not out of balance.

Put a load on it, draw down say 10% of the energy it is supposed to hold, at whatever current rate you like.

Then do the same voltage measurement again.

 

[justlooking808]

So that is fully charged, and not out of balance.

Put a load on it, draw down say 10% of the energy it is supposed to hold, at whatever current rate you like.

Then do the same voltage measurement again.

x2 - but i would do this at 10% intervals until it reaches 50% capacity and each time check each group. just to make sure the cells are keeping up with each other/draining kind of close to each other. doesn't have to be exact, just so you get a general idea of how your batter group cells are doing.

 

[john61ct]

My point is, as the roughest possible load test

this will just demonstrate the cells are shot and need replacing

nothing to do with balancing.

 

[Rokokong]

Ok will do, appreciate all the help so far!