Lithium Battery - How to tell when bad?

[kyrral]

My lithium ran out of juice for unknown reasons. I jump started off another bike and ran for awhile and put some juice back in the battery.Now I'm nervous not knowing how much juice is in the battery. I have been told you can't load test them. How can I tell how much life is left in the battery. Also can I swap out a 14amp battery for my 7amp?

[07KTM250]

My lithium ran out of juice for unknown reasons. I jump started off another bike and ran for awhile and put some juice back in the battery.Now I'm nervous not knowing how much juice is in the battery. I have been told you can't load test them. How can I tell how much life is left in the battery. Also can I swap out a 14amp battery for my 7amp?

load test the battery to find life.. no issue using 14amp, should last longer than 7amp.

[William1]

If the battery takes a charge, it is good. If not, it is bad, a real Go/No Go with LiFe batteries.

[kyrral]

Hell, I knew that ?

[SnowMule]

They age by holding less capacity.

 

The cells are rated in amp-hours (usually milliamp-hours for phone-style single- or double-style packs, watt-hours for larger packs), which is a measure of charge capacity.

 

Load-testing them like a car battery would (should) trip the internal cell protection circuit, which is why that doesn't work like with a Pb-acid battery.

 

Unless the cell is really bad (outside of acceptable parameters), it'll take a charge even if the capacity is greatly reduced.  It'll finish its charge cycle unusually fast though, because there's not much capacity to charge.

 

The "right" way to test them is to load them at some factor of C (C being the capacity specified by the manufacturer) and measure voltage/current over time to a certain voltage and integrate the area under that curve to give you the cell's capacity. 

 

An easier way is to replace it when it stops holding a good charge.

Ever notice how with your phone, when it's new you'll get 2-3 days out of one charge, as you use it daily for a year or three you only manage to get one day out of it?  That's the cell aging.  Typical prismatic cells are good for about 1k charge cycles.

 

Yes, swapping a 14A battery in place of the 7A in there now is fine.  Gives you more capacity.  You could put a car battery in there if you wanted.

 

Batteries are kind of a thing I get to deal with at work...