Battery starting to fail?

[Deacon Blues]

I have two 48 volt batteries for my UC Pro and charged both of them yesterday. One battery charged to 71% even though I set it for max % for a long ride. The other battery only charged to 64%.
Voltage reading on the 71% battery was 53.9.
If 100% is 54.6v shouldn't 53.9v be somewhere around 92 to 95%?
I know that % reading can be inaccurate compared to voltage, but this seem really off.

 

[il Munduato]

Check the voltage output of the charger and /or try another charger.
Output should be 54.6v
I calculate 53.9v to be 97.4% of actual battery capacity, not the usable capacity that most tables illustrate.
But yes it can mean that the capacity is starting to decline. As the internal resistance of the cell starts to increase on older batteries the the low current put out by the charger at the end of the charge cycle isn't sufficient any longer.

 

[Deacon Blues]

Thanks for the response, il Munduato.
I used two chargers, just to make sure that the charger I usually used was producing the correct voltage output.

 

[scrambler]

Do you know the model of the cells by any chance?

With the exact cell model, we can look for the cell discharge curves at various amp draw, and create the appropriate table to match voltage and capacity.

As an example, here is a table I made for my 12S 12P pack of Sanyo NCR 18650GA

 

[il Munduato]

Thanks for the response, il Munduato.
I used two chargers, just to make sure that the charger I usually used was producing the correct voltage output.

Ok... Do you remember if these chargers were able to finish off the batteries at the proper 54.6v? Sometimes if not properly matched they can be too aggressive at the end of charge and though they will bring it to 54.6v, an hour later the battery will have settled a little lower. In most cases still above 54.0v only dropping a few tenths V.
How many amps is the charger and how many ah is the battery?

Do you know the model of the cells by any chance?

With the exact cell model, we can look for the cell discharge curves at various amp draw, and create the appropriate table to match voltage and capacity.

As an example, here is a table I made for my 12S 12P pack of Sanyo NCR 18650GA

View attachment 177552

12P... Now that's my kind of battery!

 

[TDA78]

You would see these percentages for a fully charged 48V battery if your display was set to 52V

 

[Deacon Blues]

You would see these percentages for a fully charged 48V battery if your display was set to 52V

The display is set to 48V.
What I can't understand is why the display shows 71% but reads 53.6 volts (the other battery) and the little battery icon also shows about 3/4 battery remaining.
The battery capacity is 52V 17Ah. Both batteries came with my UC Pro, from Watt Wagons.

 

[il Munduato]

The display is set to 48V.
What I can't understand is why the display shows 71% but reads 53.6 volts (the other battery) and the little battery icon also shows about 3/4 battery remaining.
The battery capacity is 52V 17Ah. Both batteries came with my UC Pro, from Watt Wagons.

You shouldn't need advanced communication such as CANbus to calibrate the battery % shown on the display properly.. but bikes without are often way off.
What may be a reason for some concern is if there is some change from prior charges and/or display readings.

 

[vincent]

How old are these batteries? Did you figure this out

 

[Deacon Blues]

I received the bike in Oct 2021, so, if the batteries were new when they were shipped to me, around 2.5 years. I probably only have around 3000 miles on the bike. Probably less.

 

[vincent]

Hopefully it's just the display is reading weird and not the batteries are losing charge already

 

[ak907]

The percentages for my 52v UC Pro have never been accurate, I was advised to have it display voltage. The battery fullness image has also always been wildly inaccurate, generally displaying 1/2 to 3/4 full until diving to empty suddenly at the last 2 volts of charge left on the battery. Frustrating to be sure.

 

[greeno]

Having the % scale selected on your display instead of the actual voltage is always suspect as far as knowing battery capacity status.
Swap out a different display and see if there’s any difference in the readings.
See if the problem follows the bike or the battery.
Verify Your output voltage on your charger.
Make sure it’s set to 100%.
I have had friends charge there 52v battery’s with 48v and 60v chargers and they then complained on the actual battery charge.
I 100% realize you are using the correct voltage chargers just wanted to show some knucklehead examples of incorrect battery charger usage.

To help t-shoot battery issue just check the voltage at the charge port and then at the main motor connection terminals they should be the same.
If there different then it’s a BMS issue and it’s restricting the charge profile for whatever reason, bad cell, unbalance etc.

For a comparison I regularly use my bigger 52v battery at least once a week and I think it’s almost 4 years old.
It still charges up to 58.8v.
I always charge to 100% to.
I have my charger voltage set to 59.1v because the charger is probably 6 or more years old and it’s capacity has degraded a bit.

71% charge for a 48v battery is about 50.0v.
71% charge for a 52v battery is about 54.1v.
Double check your voltage selected is correct on your display.

 

[Deacon Blues]

Voltage selection on the display is 48v-same as the battery.
I hadn't ridden this bike for a couple of weeks, but up until the recent percent/voltage discrepancy the displace has always read in the 91% to 92% when I set the charger to 100%.

 

[vincent]

That is weird, hope it is just a glitch

 

[Deacon Blues]

I took my UC Pro on a group ride today. Usually, I ride my regular road bike, or my e-gravel bike, but I decided to take my UC Pro to see how it would do on a 50+ km ride.
About half way through the 77km ride my display icon turned red, informing me the battery had nothing left in the electronic tank, but the voltage showed around 50% battery left. Power did not seem to be affected.
2 km from home, at the 75km mark, the battery went into limp mode, with the voltage showing 42.4 volts. Power output maxed 42W in any level.

 

[vincent]

Is that good or bad wh per mile for you?

 

[Deacon Blues]

A year ago I did a 72km ride and ended up with around 29% battery remaining. That was with an old display that was relatively actuate.
Ballpark, I'd say the battery has deteriorated approximately 25-30%.

 

[vincent]

 

[il Munduato]

A year ago I did a 72km ride and ended up with around 29% battery remaining. That was with an old display that was relatively actuate.
Ballpark, I'd say the battery has deteriorated approximately 25-30%.

That sucks.
Are you sure you are comparing apples to apples?
I know my wh/mi can vary a bit taking into account terrain, weather and then add in my aches and pains of the day.
Today was sunny pushing 90°f with a dew point of 70° and I let the battery help with much of my needed wind chill.