Electronics, Lighting, & Gadgets - How to tell when NiMH cells are dead?

How does one tell when a set of NiMH cells are at the end of their useful life? I have a set which appears to charge OK, but then suffers voltage depression after 20 or so min of riding (albeit in freezing temperatures). Having just cycled it once to 1 V per cell and having seen no improvement, are these cells dead for good? The cells have served for around 2 years, FWIW.

If the run time is considerably less than when new then yes, there "dead". Don't just toss them in the trash, take them to a place that has a battery recycle box. Also don't consider them useless for the job they were designed for. I use 4 very old Ni-Cad batteries as voltage and current regulators for a dynamo lighting system. They keep the voltage at 5.2 volts no matter how fast I'm going and excess current not used by my lights get absorbed by the batteries. I also have no worries about overcharging them as there so inefficient they simply get a little warm blowing off the excess current as heat. They even keep my lights on for about 15 minutes at stops.

How many discharge cycles? Do you have a smart charger with a refresh function that will cycle them many times and determine when capacity can no longer be increased? This will tell you each battery's maximum capacity. If you put them on a smart charger, you may find that only 1 battery is weak or that 1 can be refreshed. Runtime is limited to the battery with the lowest capacity.

Most folks just throw them away and get new ones if they do not perform well. They are not that expensive and capacities are much higher for new batteries compared to 2 year old batteries.

+1 for dekindy! Rechargeable batteries need more than the free 1 hour charger that comes with batteries at xmart. I have given up on rechargeables until next year. By then, I will have invested in a Maha charger that can do AA AAA D and C cells in any combination.

One weak rechargeble will make the whole fail. Fast rechargers damage your rechargeable batteries.

I just scored a 48 pack of alkaline AA's at BigLots for 11.00. That should carry through to the resumption of Daylight Savings Time, this year. Next year will be different.

One Answer: Get a LaCrosse BC_900 or a Maha C-9000. These are the best battery rechargbles out there. Do some some searches and teach yourself something.

One Answer: Get a LaCrosse BC_900 or a Maha C-9000. These are the best battery rechargbles out there. Do some some searches and teach yourself something.

If you get the Lacrosse BC-900 make sure you check/ask to confirm that the firmware is v3.3 and /NOT/ v3.2.

Firmware v3.2 had higher thermo cut-off/trigger issues which have had a lot of people report that there cells got so hot they can't hold them to the cells leaking to the cells fusing to the charger because the plastic melted.

To my understanding v3.3 is the newest firmware out right now.

Here is a thread on a digicam website to check up on. http://www.stevesforums.com/forums/view_topic.php?id=79311&forum_id=51&page=2

The camera folks there are pretty critical on thier gear as they want thier stuff to last long and always in good condition as they don't want to miss the shot because of damaged/faulty stuff.

Anyways, I went with a Maha C-9000 because it was the newer charger out. It had a large backlite screen, a company I knew that was a leader in charger technology with a long history, highly regarded by both the camera/flashlight folks and tested by them, and ample modes for the advanced user yet still simple enough for basic users.

If memory is correct the Lacrosse BC-900 is cheaper by a few dollars and comes with a small package. There was a comparison of the BC-900 vs C-9000 on Steves Digicam a while back.

Pro/Cons here. http://www.stevesforums.com/forums/view_topic.php?id=119951&forum_id=51

It seems Lacrosse is on a don't ask don't tell policy which was one strike that turned me away from them. If you had to call the company up and they did that to you I'd be kinda worried about how well the return and warranty policy will hold up. I've heard many a good things from Maha and thier support. The few I've that were bad was partly the user chewing out the company with beyond brutal language but once the user calmed down and called back in a better tone the company worked to solve thier issues and resolved there issues.