Rechargable batteries in lights

[WhiteSands]

I tried out my newly bought Eneloop AA rechargeable batteries in my DRIS 1k shorty lights yesterday.

I was quite surprised to find that the brightness of the lights were much reduced when compared to a similar torch using normal alkaline batteries.

One of the torches my buddy was using also flickered and went dead in the middle of the second dive.

Dives were about 50 mins, so they only lasted approx 80 mins.

My gut feel is that conventional batteries lasted much longer, I think I've used my torch with the same batteries for 4 night dives.

The Eneloop batteries are rated 2000mAh, 1.2V.

I'm not electrically saavy, so in layman terms, can someone explain how are these batteries expected to compare to conventional ones?

Thank you!

 

[buddhasummer]

Assuming my understanding is correct. The mAh affects run time, the higher the mAh the longer the run time. Normal Alkaline AA are 1.5v, being higher voltage than your rechargeables I'd expect them have a brighter output.

 

[Tigerman]

For a start you have atleast 3 different rechargeable AA batteries commonly used, namely NiCd, NiMh and alkaline - they all have a nominal cell charge of 1,2v but fully charged theire at ~1.4v and normally rechargeable AAs are available with higher mAh than non-rechargeable.
Theres also a huge difference in quality when it comes to batteries and whats best for one use is not neccesarilly best for a different use..

 

[Doppler]

HI:

One-use AA batteries are rated at 1.5v and many deliver that voltage when new. Most rechargeable AA are 1.2v fully charged. Of more significance, certainly where backup lights are concerned, is the difference in the length of time that rated "strength" is valid. A one-use battery is capable of sitting inactive for years and still being of use... hence the recommendation that this is what's used in backups. A rechargeable will drop voltage in days.

Different brands have different characteristics. To find out whether yours are nice guys or useless bastards, a cheap voltmeter and a few minutes reading the instructions will help out. Fully charge your batteries and test the output every day for a week...

 

[WhiteSands]

Thanks everyone. So the voltage determines the brightness, and the mAh determines run time, got it.

Steve, I'll do the test as you suggested, great idea. But I think the Sanyo Eneloops are well known for very low discharge, retaining 70% of full capacity even after 3 years.

I'll do a test of the battery voltages though. Would be an interesting experiment.

 

[gcarter]

I have tried 3000 mah batteries in my DRIS lights and not been happy at all - brightness or run time. I have gone back to regular batteries.