Battery issues

ClaytonB

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Aug 15, 2019
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Hi I’m new to Ebikes I purchased one last night that I know nothing about I’m told it has an 84v 18 ah pack the bike came with two identical chargers When I plug the charger into the pack the bikes screen lights up and say 84 v 0 ah and as soon as I unplug from 110v the screen shuts down and nothing functions . The charger lights up green showing the pack is fully charged when I check the pack voltage with my meter it shows 60 volts any suggestions on were to start thank you
 
Try leaving the charger plugged in overnight and check the battery voltage in the morning.

If that doesn't work it may be that the battery pack has been discharged below the point where the Battery management system will allow the pack to be charged. There are ways to charge the battery manually but that would involve taking apart the battery pack which you may not want to do with a new ebike. If the charger won't charge the battery I'd contact the vendor and ask for a new battery pack.

Warren
 
ClaytonB said:
84v 18 ah pack
my meter it shows 60 volts

If the 84v is the average voltage, which is the normal way to list a pack, then it's 22s, but that means it's average voltage is over 3.8v, which is unusual. But, if that is true, then it's full voltage should be 92.4v, so the charger should measure that voltage with your meter. If true, then 60v / 22 is less than 2.8v, which is pretty much completely drained, and probably too low for the BMS to allow a charge. It does this to prevent a fire, and the cells would have to be replaced, if you prefer safety. (it's possible to recharge them anyway, but you risk a fire at any moment from then on, anytime at all in the life of the pack--the risk is higher the closer the cells got to zero volts).


It is more likley that the 84v is the fully charged voltage of the pack, which makes it a 20s (72v) pack. So the cahrger would measure 84v with your meter. If true, then 60v / 22 is only 3v, which is perfectly safe and normal, and the BMS should not shut off the input to prevent charging. So it could be one bank (group) of cells that is too low to allow charge, (or too high, but that would fix itself over time), and that bank would have to be replaced, if you prefer safety, to be able to recharge the pack.



If the charger measures zero volts on it's output, then it's possible it has a broken connection on its output cable. (it might also just turn off the output when no chargeable battery is detected). Two chargers with broken wires on output is unlikely, but not impossible. A blown fuse is also possible, but most of those are on the AC input side, not the DC output side.



60v is *also* just over the full voltage of a 52v (14s) pack, so it is possible it is not the right pack for those chargers, and it's actually already full, so the BMS shut off to prevent overcharge. Can't tell without opening it up to count the skinny wires from the BMS to the cells.


I would check with the seller first before opening anything up, because sometimes taht voids warranties.
 
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