CygoliteExpilion Series Battery Stick, Black

I've had the Cygo Expilion 850 light for several years and it worked like a charm. Until all of a sudden it didn't. Suddenly wouldn't turn on, wouldn't take a charge. I decided to take a chance on spending $35 to fix a $110 light. I'm so glad I did. I popped the new battery, right out of the box, into my light and it turned right on. Two weeks now and it works GREAT. Even though the New England weather has turned cold, it holds a charge for more than five 1-hour rides with intermittent flash mode. I'll update this review if anything changes over the next year. Right now, it seems like a great deal.

So this "new" battery doesn't seem to last as long as my 6 year old battery does that I replaced. I noticed on longer rides the old battery just wasn't lasting long enough on the flashing mode so I bought a new one. I have to admit, I'm highly disappointed in the new battery. 5 hours into a ride and it's not even really noticeable anymore. I only use the flashing function of the light and I used to get a solid 8 hours on a charge. This new one just isn't as good as the old one is, let alone anywhere near as good as the old one was when it was brand new. So far this has been a waste of money.

Great replacement battery. But have to ding one star because my batter was missing the flat rubber washer that sits under the “head” of the battery and provides some compression and a seal when installing the battery in the light.

This works perfect for my husbands light on his bike!

Very satisfied...

In case anyone is wondering whether these are authentic, the short answer is I don't know, but it looks and performs exactly like the original that came with my light. That's good enough for me. Still insanely expensive for a dressed-up 18650 battery, though. I bought mine from BikeZilla Bike Shop (Roy's Bike Shop), in case that helps.

I have tested this once and so far it works as stated. I got 4 hours of life on the second light setting which is what I need for my long night rides. Changing batteries is easy but I wouldn't try it while riding. Haven't had it in the rain yet.

I've been using cygolite in my bike rides for the past 5 years. It is almost perfect, if not for the cover of usb charging port which detaches easily after some use.

Exact replacement/extra battery for these bike lights. Unfortunately the one shipped to me lacks a thin washer that helps secure the battery inside the light. Consequently the battery fits a bit loose and sometimes the light flickers as a result. I'm not sure if this is isolated to the battery I received, or if this doesn't ship with the washer. Otherwise I'm pleased with the purchase.