Lithium batteries

[tommie]

For what it`s worth, i have a 20" folding ebike that i rarely use now, the battery a chinese 48v 11aH item last saw a charger roughly May-june 2017, it lay at the back of the shed unused.
I took it out again a couple of weeks ago expecting the worst, however checking the battery, it had dropped only one led, powered it up, jumped on and off we went, hasn`t had any negative effect whatsoever.

 

[KEN OPENSHAW]

For what it`s worth, i have a 20" folding ebike that i rarely use now, the battery a chinese 48v 11aH item last saw a charger roughly May-june 2017, it lay at the back of the shed unused.
I took it out again a couple of weeks ago expecting the worst, however checking the battery, it had dropped only one led, powered it up, jumped on and off we went, hasn`t had any negative effect whatsoever.

Thanks Tommie ....it’s only just over 12months and it was fully charged when you put it away..but it goes to show not all Chinese stuff is crap !

 

[KEN OPENSHAW]

Hi Ken, if the battery is a 575Wh it is likely that the battery is in hibernation mode. If the battery was fully charged when stored the battery is probably OK. If you take the battery to a decent ebike shop preferably a Wisper dealer. They will fully charge the battery and test the Voltage. If the Voltage is above 41V you are probably OK. You should expect to be charged for the battery test though.

All the best, David

Thank you David...I doubt the battery was fully charged 50% at best.. in the light of your comments and the rest of this thread I assume that if the voltage is below 41 volts after numerous charges and rest periods then the battery needs replacement ?

 

[flecc]

I assume that if the voltage is below 41 volts after numerous charges and rest periods then the battery needs replacement ?

Although likely, not necessarily if it's not far below Ken, its always worth checking by going for a ride to see if there's useful range left.

Even if not enough for your needs it could be a second battery for use while charging or as a range extender.

You also asked if an out of balance battery can always be recovered. The answer is not always, since a cell can have reached the end of its useful life or even failed prematurely.

There's always an element of gamble with second hand batteries, but the few batteries that have a hibernation mode reduce that and are more likely to be servicable after a year of standing idle.
.

 

[Nealh]

Thank Nealh.....so are you saying that lithium batteries can ALWAYS be recovered by this method of balancing ?
In reply to your latest post ....I informed the seller of my concerns re the battery and made him an offer on the basis of myself replacing the battery....he hasn’t replied !

No not necessarily sometimes they can be manually recovered to the level of the others but require the battery to be opened, then the battery when charged needs to be left to sit for 24/48hrs and then rechecked. A poor failing cell string might see voltage bleed off to a lower level or when in use the battery overall voltage might collapse causing power cut off esp when a heavier amp load is asked of it.

It isn't unreasonable to ask the seller to fully charge the battery, then for you to test ride the bike. Best to test ride up a hill on full power /top assist level and to check the battery charge voltage before the ride for a reading of 41.5v . If the bike power doesn't cut out then you could consider the battery to be in fair to reasonable condition.

 

[Nealh]

If the battery is balanced and reads 41v or less then the cells will have lost capacity and be past it's sell by date.
Though as flecc has mentioned it will still have use as a spare range extender/get me home type of battery, though it will most likely not take to much of a load for the voltage to crash. If this was the case it's residual value will be < £30, the case will be of value as will the internal bms.