Dead light batteries (not holding charge)

[MTBc]

I've had a 1200 lumen 10w light that came with a battery pack (8.4V / 4400mAh), but damaged the light (battery was fine) - i bought it about 18 months ago.

 

A mate of mine organized another light + battery, but it took a few months before I got it - during this time, the light+battery was left in his car boot. When I got the light, after charging the battery fully, it fails to hold charge - I get light for maybe 10 minutes max before the battery dies. The last time my mate used the light+battery, he got full charge out of it (a couple of hours). So I ended up using my old battery pack with the new light. I used it in December at the VG 24 hour and got normal life out of the battery. Last night, on my ride home, the battery died after about 40 minutes on the 2nd brightest setting (usually get 2 hours). I didn't use my regular charger on my old battery pack yesterday.

1. What could the cause of the dying batteries be? The first one I thought might be damaged due to excessive heat exposure in the boot - would this kill a battery?
   
2. Has anyone else found a sudden drop in battery life after a number of months? Or could it be the voltage / amperage output of the charger that just didn't charge the light yesterday? What should I look out for?
   
3. Lastly, is there anything I can do to make the batteries last long enough for a decent night ride without failing? I used to get laptop batteries repacked years ago, but not sure if they can do the same with these packs, and don't know any contacts offhand (recommendations welcome)
   

[fanievb]

www.extremelights.co.za

[MTBc]

www.extremelights.co.za

 

Yup. Thats where I bought my 1st one from. Does hannes repair batteries too?

[fanievb]

I bought a light from him and six months later the battery packed up, mailed him explaining the problem and he sent me a new battery pack

[scuzzy]

Don't think it can be repaired. The answer will be that the battery looses charge over time and you have to keep it charged. As far as I know there's not much you can do about it

[MTBc]

I bought a light from him and six months later the battery packed up, mailed him explaining the problem and he sent me a new battery pack

 

1 year warranty and 18 month old battery. :-/

[droo]

Li-Ion batteries have a limited life, which can be shortened in a number of ways.

 

If you're interested, http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries will give you all the details.