# Gemini battery replacement?



## Casual Observer (Jan 12, 2004)

Anybody have issues with Gemini light batteries? Have the duo system with the 4-cell battery. Ran it fine all last season. Could get over 3 hours on high on one charge. My first ride this season, it would dim about 10 minutes into the ride, and then go to full power a couple minutes later. 

I'm in AZ, and stored it in my hot garage, so I'm assuming I damaged the battery. I tried to order a replacement, but apparently Gemini stopped shipping just batteries, so I'd need to purchase the entire unit. I have a cheap battery I got from Amazon, but it lasts about an hour on high. Any recommendations for a replacement?


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## tigris99 (Aug 26, 2012)

Action led has a bunch that all gave the same connector just with a different "brand". Or mtbrevolution in Australia


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## indebt (Nov 8, 2009)

If I'm understanding you correctly you turned the light on,(was it on the high setting?) and within ten minutes it dimed,,, and then went back to full power again?? I have the same light with the four cell battery. The one thing I don't like about the Duo is its thermal step down. It is not gradual, but will step down to the low setting until cool enough and then will be able to go back to the highest output until the thermal steps in again. Not a great light to run where the nights are still really hot.

Did it step down at all with that Amazon battery? If not then yes I believe you have found the problem in your original battery which sucks!! If it is the battery for sure, tigris99 has given you good advice. I have yet to fire up my Duo this coming night riding season which will be a while as I just crashed the other day and broke my collar bone, but once healed I'm hoping mine is still ok. Cheers!!


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## Casual Observer (Jan 12, 2004)

indebt said:


> If I'm understanding you correctly you turned the light on,(was it on the high setting?) and within ten minutes it dimed,,, and then went back to full power again?? I have the same light with the four cell battery. The one thing I don't like about the Duo is its thermal step down. It is not gradual, but will step down to the low setting until cool enough and then will be able to go back to the highest output until the thermal steps in again. Not a great light to run where the nights are still really hot.
> 
> Did it step down at all with that Amazon battery? If not then yes I believe you have found the problem in your original battery which sucks!! If it is the battery for sure, tigris99 has given you good advice. I have yet to fire up my Duo this coming night riding season which will be a while as I just crashed the other day and broke my collar bone, but once healed I'm hoping mine is still ok. Cheers!!


Yes, that's correct. It will step down, so quite possibly it's overheating. I ordered a new battery, and I'll see if it makes a difference. I needed a second, 4-cell battery any way for the cooler months, so if it's a weather thing, I might need to look at an alternative warm weather light.


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## indebt (Nov 8, 2009)

Sorry if I'm bringing up something your already aware of, but two things to look for in a warm weather twin emitter lamp head is one with a little larger mass than the Duo say 80/100 grams. This should help handle the heat better and step down less often than the Duo does. The other thing and IMO more important,,, make sure the thermal in that lamp head steps down gradually and only to where it needs to be to keep the internals safe,,(usually below60/80 degrees C.) I know the Gloworm X-2,, Lupine Piko have the better step down thermal protection than the Duo for Ex. There will be many others as well.


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## MRMOLE (May 31, 2011)

Here's a couple of possible solutions to your problem.

A - (Light @ left) = Duo + Vancbiker Finned heat-sink GoPro mount ($18) + Amazon alloy Gopro handlebar mount ($8). Weighs just under 100gm with extra mounts and makes the light act like the ambient air temp. is 10°+ cooler.

B - (Light Kit @ right) = Nitefighter BT21 kit (approx. $60 ($25 light-head only) @ gearbest). Weighs 125gm with extra mounts (recommended for AZ, I've ridden in 105° ambient air temps. with the light on turbo with no thermal step down using this set-up), more measured lux than even the Gloworm, wider beam pattern than the Gloworn/Duo with identical optics, a 5200ma battery (BAK cells) that equals the runtimes of my 4 cell Gemini batteries (when new) and a good quality charger, heavy gauge extension cable, mounts and that nice carrying case. This is the best deal for a great light that I know of.
Mole


Casual Observer said:


> Yes, that's correct. It will step down, so quite possibly it's overheating. I ordered a new battery, and I'll see if it makes a difference. I needed a second, 4-cell battery any way for the cooler months, so if it's a weather thing, I might need to look at an alternative warm weather light.


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