Zajebisty

seriously looking at various Used E-bikes. any way to tell battery health when inspecting a used bike? Would biking a short distance and observing battery percentage drop be useful? Or do the batteries discharge in a non-linear fashion?

Hard to really tell if battery still good, other than seller's word that it is holding charge, giving certain range etc..

I don't want to make an expensive mistake... ..and it seems like battery is perhaps most expensive (and guaranteed) to fail item on an ebike

Nelson37

Unless you can ride it for a full discharge cycle, assign a maximum value to the used battery of no more than $50.00.

No, they do not discharge in a linear fashion.

Zajebisty

good advice! it could last 1 week more or 3 years more... hmm

dilkes

Other than riding from full charge to full discharge, the only way I know of doing that is:

1. Get an inexpensive wattmeter
2. Fully charge the battery
3. Find a load that you can hook up to discharge the battery (heater, inverter, whatever)...make sure that it is large enough to draw a reasonable current (10 amps +) representative of actual riding.
4. Fully discharge the battery through the load with the wattmeter inline.
5. The wattmeter readings at the end will tell you how many Ah/Wh are available

I have done this on my own packs, but it's a bit of work and it is unlikely the seller (or you?) will be comfortable doing it.

Otherwise as suggested, assume the worst.

Doc_Wui

You could ask the owner what he gets on range, but he could be like me and not really know. I recharge after a ride so I never take a battery all the way down til the bike stops.

I am aware of today's 20%-90% charge recommendation for longevity, but no one told us that in 2015-2016. I kept my ebike batteries fully charged most of the time until last year when I started leaving my batteries sit at partial charge and only topping them off if I planned a longer ride. Or I would do a full recharge after a ride, and then take the bike around the block (half mile) to run off some of the charge. I have done the diilks test on one battery and it still has the AH capacity that was advertised. That battery is from 2015, so I was surprised. Perhaps not running only half way down is also good for longevity.

In any case, ebikes depreciate fast. Getting back 50% of original price is probably common. If it is a name brand ebike, and not used as a daily commuter, maybe you get lucky with the battery.

SimonRider

Thanks for the advice, just recently got myself an electric bike, now I know how to quickly charge it

MikeyMK

Ideally you'd test each cell accross the BMS board in the battery, but you're not gonna go opening up the battery on the test run..



You can ask that the battery be fully charged for collection, and then test it's output voltage against it's max voltage on the casing/label, as it should meet it. But that only tells you it reaches full capacity.