How to gauge a used batts likely remaining life?

[alban]

Hi
Thinking of purchasing a bike with a 'slightly used' Li-ion (not LiFePO4) batt. I understand that these batts degrade from the first use and lose capacity over time, as well as with usage, usually lasting 2-3 years. Is that right?
Is there any way of telling, such as voltage when fully charged or general oomph up a hill, that the batt has a decent amount of life in it? The cost of a new batt within a few months would make the purchase much less desirable! - but it's a bit of an unknown relying on people's testimony - plus there's no warranty.
Thanks

 

[banbury frank]

Hi To Be on the safe side work on that you need a new battery

Then all the use you get out off the old battery is a bonus




Frank

 

[flecc]

"Slightly used" has little meaning with Li-ion batteries, they die with time regardless. In general that's about a two year life.

Much depends on the make, since the life varies with quality and the life limit is often set by low voltage safety cutoff, that in turn depending on the bike's power relative to it's battery capacity.

 

[Scottyf]

The only way I can think of testing this is to do various cycles to determine capacity of said cells.

Ie.
10ah battery. Fully charge to 4.2v per cell
Discharge at a 1C rating untill 3.6v (10amp draw) (calculate how many mah you have discharged to that point)
charge and record how much capacity is put pack into the cells (accounting for losses in the system)

Do the same as above but at a 2c draw to determine how much voltage sag this induces. Or even how much internal resistance there is.


So in essence its a bit of a gamble. However I've paid for used lipo that was lightly used for 10cycles apparently and it appears to be true. they hold full capacity and balance well.


However untill you get the batteries there's no sure fire way.

 

[alban]

Thanks for the responses guys. Maybe too much of an unknown to risk it then.

 

[johnc461165]

How much fun can you get anywhere else for a couple of pounds a month. E-biking is Orgasmic. ( I have led a sheltered life though)

 

[alban]

Er... what kind of saddle are you using John?!

 

[johnc461165]

Sorry alban I am unable to answer that in case you want to join in.