battery not fully charging

[Aviad1p]

I have a 52 volt battery, when I charge the battery fully and check with a multimeter it always shows me 0.2 volts less instead of 58.8 58.6, the same with when I charge to 85 percent instead of 56.6 56.4, I built the battery in 2020, with batteries of production date 2018, the question asked For those who understand batteries, is it normal for a battery at this age, when should I be careful/change the battery? Because the battery is working properly

 

[harrisonpatm]

Because the battery is working properly

That's probably going to be the biggest takeaway, given the limited information you posted. If it's working, it's working. True battery degradation can be most accurately measured by capacity: What was it's real capacity in amp hours when you made it? What is it's real capacity now? Preferably measured via dummy loads and controlled variables, but in an ebike, you can get a good idea of capacity using range. Could you power 30 miles in 2020 when it was new, but only 25 miles now?

State of Charge, SOC, is a weak determination at best of battery capacity, and thus not a great determination of battery aging. Furthermore, you're reporting a 0.2V deviation from expected, and depending on your multimeter, that could be within its margin of error. We also know that batteries, both new and old, experience a bit of self discharge when completely topped off to 100%. Are you measuring your battery's voltage directly after charging it, or waiting a day or hour?

In short, it doesn't sound like your battery is old or failing, especially since you say that it is working properly, but there's plenty of unknown variables.

 

[E-HP]

Is it staying balanced? I wouldn't worry unless it degrades to the point that balancing isn't triggered (if the BMS is the type that only balances at full charge).

 

[docw009]

Your voltage measurement isn't directly across the cells, but also thru the BMS. Maybe you're losing .2V across the BMS.

 

[Piorun]

Voltmeter your cells.
Write down the Voltage on Every cell. Get a small usb charger to charge any low cells and rebalance the pack manually.
Eventually you'll have to rebuild the pack if one cell doesn't hold a charge as long as the others.

At that age, I'm sure it's fine. Untill it starts dying on you earlier in a ride. I wouldn't worry too much just don't discharge it all the way too often and it will last you a long time.

 

[gobi]

I have a 52 volt battery, when I charge the battery fully and check with a multimeter it always shows me 0.2 volts less instead of 58.8 58.6, the same with when I charge to 85 percent instead of 56.6 56.4, I built the battery in 2020, with batteries of production date 2018, the question asked For those who understand batteries, is it normal for a battery at this age, when should I be careful/change the battery? Because the battery is working properly

One of more cells are running away aka less capacity or not balanced, so the voltage of those cells rise faster and then when it reaches the cut off max, the bms disconnects.

You can disconnect the BMS ribbon cable and take the voltage of each cell and figure out what is going on.