Easy Peasy

I thought my Planet Bike Superflash was defective, because it shut off in the cold despite installing a new pair of batteries. I was just about to ship it off for service/replacement, but I checked the charge on the batteries anyway. Much to my surprise one had a full charge and the other was dead. Note: these are supposedly fresh batteries from the same blister pack.

Since replacing the dead battery, it's been working now for several weeks without a hitch, and I've been riding in cold temps. Before you blame the light, check your batteries.

pdlamb

I always assume any rechargable batteries are dead on arrival. Cheap green AAAs are OK for one ride, then get replaced with real ones.

Mondoman

I had the same problem with a pair of Costco house-brand Kirkland AAA alkaline batteries yesterday on my Mars 3.0. The light was nice and bright at first, indicating proper voltage in both batteries, but was very dim by the end of my ride. Voltmeter showed one of the batteries reading only 0.6V. It would be nice to know about short-life defective batteries in advance -- does anyone have suggestions for a load tester or similar that would help sort the wheat from the chaff in a 20-battery bulk package?

alaskanb3arcub

batt tester that simulates load:

https://www.amazon.com/ZTS-Mini-Batte...8&sr=1-1-spell

I have used this before on alkaline batts, as well as rechargables. Cheaper batteries do not withstand refreshing as well as name brands, though.

https://www.amazon.com/gp/product/B00...00_i00_details

Spld cyclist

My gut feeling is that if you checked the voltage of both batteries with a volt meter before using them, the bad one would have been too low to start with. If it started at 1.2 V and the good one was close to 1.5 V, the light would have been pretty bright for a while. I've seen this happen with rechargeables that are starting to go bad.

Mondoman

Thanks for the tester link, abc!