48v Li-ion charger reading 55.12v on multimeter
- Thread starter Klauts
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What is the series count of cells for the battery?
55.12f would be insufficient for a 14s pack, but high for a 13s.
Has the charger gotten wet like the battery did? (may cause corrosion, etc).
What voltage is your multimeter battery? (a low battery causes a high reading on most)
55.12f would be insufficient for a 14s pack, but high for a 13s.
Has the charger gotten wet like the battery did? (may cause corrosion, etc).
What voltage is your multimeter battery? (a low battery causes a high reading on most)
it's a 13s pack and the charger hasn't gotten wet no, a low voltage on the multimeter could definitely be the culprit Its been months since the batteries were changed. the chargers been subjected to some vibration riding in my backpack but that's the worst stress.
the battery that got wet is working perfectly and not displaying any abnormalities thank goodness!
the battery that got wet is working perfectly and not displaying any abnormalities thank goodness!
As long as the BMS is correctly operating and well-designed, and always shuts charge off when any cell hits it's HVC (and that HVC is below the max spec limit for that cell model), then there's no damage happening.
If the BMS for any reason does not shut charge off when any cell hits it's HVC, then there is the potential to overcharge the first cell to reach full (the worst cell, which would have teh lowest capacity, highest Ri, and fill up first).
In a worst-case but unlikely scenario, it could overcharge it by the *entire* extra voltage if the HVC doesn't work and all the other cells *are* equal to each other and fill up later. Meaning, if all 12 other cells happen to be the same and fill up to 4.2v, then 12x4.2=50.4, which leaves about 4.7v across the other cell that already filled up, which is probably quite an overcharge for it.
If the cells are 4.1v cells instead, then it's even more of an overcharge potential.
I wouldn't generally recommend relying on the typical cheap BMS to prevent this situation. ****
****(I don't actually use a BMS,as I don't trust the ones I can afford, but that's because I'm using large-format automotive-EV cells that are even now, well-used and a decade-and-a-half after manufacture, still well-matched to each other and stay balanced on their own without intervention or electronics to do this. )
If the BMS for any reason does not shut charge off when any cell hits it's HVC, then there is the potential to overcharge the first cell to reach full (the worst cell, which would have teh lowest capacity, highest Ri, and fill up first).
In a worst-case but unlikely scenario, it could overcharge it by the *entire* extra voltage if the HVC doesn't work and all the other cells *are* equal to each other and fill up later. Meaning, if all 12 other cells happen to be the same and fill up to 4.2v, then 12x4.2=50.4, which leaves about 4.7v across the other cell that already filled up, which is probably quite an overcharge for it.
If the cells are 4.1v cells instead, then it's even more of an overcharge potential.
I wouldn't generally recommend relying on the typical cheap BMS to prevent this situation. ****
****(I don't actually use a BMS,as I don't trust the ones I can afford, but that's because I'm using large-format automotive-EV cells that are even now, well-used and a decade-and-a-half after manufacture, still well-matched to each other and stay balanced on their own without intervention or electronics to do this. )
docw009
10 MW
If the BMS overvoltage protection circuits is a good design, there's no problems.. Requires the design spec to handle some overvoltage. I believe the UN3480 specification requires a battery over 18V must pass 20% overvoltage for 24 hours.
Back in 2015, a US vendor shipped me a 14S battery and a 58.6V charger when I ordered a 13S. I never thought to verify the voltage or look at the labels. I used it with my other 48V battery, mixing the chargers thru chance for a year. No problems occurred til I knowingly bought a 14S battery and needed to read the charger labels. Panic! But I quickly calmed down and realized the BMS did its job, Of course, maybe it could have failed over time.
Back in 2015, a US vendor shipped me a 14S battery and a 58.6V charger when I ordered a 13S. I never thought to verify the voltage or look at the labels. I used it with my other 48V battery, mixing the chargers thru chance for a year. No problems occurred til I knowingly bought a 14S battery and needed to read the charger labels. Panic! But I quickly calmed down and realized the BMS did its job, Of course, maybe it could have failed over time.
sounds good to me! I setup an Arduino to monitor the battery voltage while charging and trigger an alarm at 53V so I've got another lay of failsafes before the BMS.
I'm going to attempt to open the charger up later and see if there is an adjustable potentiometer inside in hopes it was the vibrations of my bike that caused the voltage to drift too high.
it's also a 3 year old charger, so possibly just at end of life. I've got another brand new charger too that's outputting the correct voltage so will only use the faults one in an emergency anyways
I'm going to attempt to open the charger up later and see if there is an adjustable potentiometer inside in hopes it was the vibrations of my bike that caused the voltage to drift too high.
it's also a 3 year old charger, so possibly just at end of life. I've got another brand new charger too that's outputting the correct voltage so will only use the faults one in an emergency anyways
Just curious: what are you using to buffer / step down / etc the voltage to the Arduino's input?
If you're opening it up anyway, check all the capacitors. They are rarely glued down very securely, so vibration can break legs, and then they're not filtering what they should, and damage can occur to other parts because of that.
Failed caps (leaking, swollen, exploded, or otherwise just no longer enough capacitance) can do the same thing.
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