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Full charge only 97%

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SuperCux
Posts: 17
Topic starter
(@supercux)
Active Member
Joined: 3 years ago

Hello friends,

After 3 months of happy biking on my CUx I've come across my first problem.  The battery no longer charges to 100%, it now only reaches 97%.

It's a relatively minor issue but I'd like to prevent it getting any worse because as we all know the battery charge affects the max speed of the bike.  I'd also expect the battery to stay 100% healthy for a lot longer than 3 months.

So I'm wondering is there any solution to this?  Maybe some sort of trick to reset or re-calibrate the battery?  Also I'm wondering is there maybe something I am doing wring to cause this?  I charge it 100% before every journey and after each day it depletes to 80% if I charge in work and 60% if I skip charging in work.

All safe and healthy according to the manual but this apparently is not good as I'm now losing full charge!

 

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mike4207
Posts: 1
(@mike4207)
New Member
Joined: 3 years ago

Not sure if this is the best solution if its still under warranty, but because I purchased my super soco second hand, when i realized i had problems with one of the batteries, I googled how to fix it and one of the solutions was to reset the BMS (battery management system). 

This also seemed to re calibrate the battery charge percentage that was displayed, if say i charged the battery to full and it would only show up as 87 percent say. I would open the battery, reset the BMS, and it would go back to 100 percent. 

This also fixed the problem when I would try to charge the battery after use, and it would not start charging, as well as connecting the battery to the bike after charging and it would not start up. 

Each of those times resetting the BMS seemed to work. Now i have a problem of my own. After depleting the battery to 25 percent, the bike just shut off on me, (i should note that i had been charing the battery with a 72 volt lithium charger, while i was waiting for my 60 volt lithium charger to be replaced). The battery guage would read incorrect by 20 percent or so, but i thought maybe i could still get the bike to turn on and ride it home the few kms i had left, instead of switching to my other fully charger battery (smh, im an idiot).... anyway the bike would turn on, but then immediately shut off again at 25 percent charge displayed, probably cause i had been charging with the 72 volt charger, the guage was reading incorrectly. 

So i finally switched to my other battery and rode home, but when I tried to charge the dead battery, it would not charge. I tried the BMS reset, and still nothing. AFter checking the battery with a multimeter, i realized it is showing only 25 volts instead of the usual 60 to 70 volts... 

if anyone has any idea as to why the battery would be showing only 25 volts that would be a huge help. I dont think the battery would have discharged that low as i thouhgt 60 volts is usually a dead battery. I dont know that much about electronics so any info would help a lot! thank you all for reading,

-Mike  🙂

 

 

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2 Replies
wagner
(@wagner)
Joined: 3 years ago

Trusted Member
Posts: 51

@mike4207 congrats, you probably killed your battery 😀
But Iam not 100% sure because the BMS normally has a cut off voltage in order to prevent too high charging/regeneration voltages.
But basically your 60V charges goes up until ~71V -> max volts yout 17S battery can handle (4,2V cutoff * 17S= 71,4V) meanwhile your 72V is for 20S batteries so it goes up to 20S * 4,2V = 84V.
Like I said, you BMS should normally shut of in order to protect you and the battery but the 25V seems like some serial connections in the battery itself gone bad.
You could open the pack and measure the voltages of the serial connection on the balancing wires. Values should be between 3,2V and 4,2V.

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Edgardo RS
(@edgardo-rs)
Joined: 7 days ago

Active Member
Posts: 5

@mike4207 , can you explain how to reset the BMS please?

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SuperCux
Posts: 17
Topic starter
(@supercux)
Active Member
Joined: 3 years ago

Sorry that's all a bit over my head Mike!  

My bike is new and has a 3 year warranty on the battery, if its max charge drops below 80% in those 3 years then I'm due a new battery.

Good news is it seems to have sorted itself out.  I was trying to find some info and noticed on a Tesla forum similar sort of issues and the official response from Tesla is that there is no such thing as resetting batteries and that fully discharging the battery and then fully charging is nonsense and does not reset the battery.  They say leave it and just let the software figure it out.

Now I know I'm not riding a Tesla but it's gotta be similar software.  So I just left it and after about 5 days its now charging to 100% again.

Happy biking 😀 

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alexaraducristian
Posts: 97
(@alexaraducristian)
Trusted Member
Joined: 3 years ago

I had similar problem, 1 week ago my battery charged to 96% then charger led light switched to "green" (fully charged).

After reading on this forum, understood it's normal and it will be back to normal without doing anything.

Yesterday I just confirmed this, I charged it to full and the battery reached 100%. Problem solved.

 

May be the fact that I rarely charge to 100%. Most of the times I charge to 80% only and probable the cells become unbalanced. Once every 2 month I charge to 100% only for balancing reasons.

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