Want better runtime from NiMH batteries?

[StorminMatt]

Maybe it's NOT all about the batteries. Maybe one place you should be looking is actually the charger. For months and months, I noticed that the runtime I was getting from my NiMH batteries was dropping. This seemed kind of odd, as it didn't seem to be restricted to any particular battery or type of battery. Everything from Duraloops to Harbor Freight Thundebolt Magnum to Tenergy Premium batteries was just not performing like they were before. Lights that draw 2A were dead after little over an hour on 5000mAH batteries. But testing the voltage of the batteries revealed something interesting. Usually, some batteries would be at 1.2-1.3V (plenty of juice). But one or more would be at 1.0V (basically dead). This seemed odd until I noticed one day that a fully discharged C cell (4000mAH) appeared to be fully charged after an hour (impossible!). Apparently, the charger was terminating early, leaving me with batteries of mixed state of charge in my lights. This not only results in reduced runtime, but can damage batteries. So it was out with the TN190 and in with the MH-C808m. Not only can I now charge more batteries at a time. But they charge both more fully and equally. I'm getting MUCH longer runtime. And all batteries both start and finish with VERY close to the same voltage. So if the numbers just don't add up (or, should I say, divide out) between runtime, tailcap current, and battery capacity, it just may be your charger that is to blame.

 

[lwknight]

My experience has been the same. I had a Md3000 that was goofy.
Like you , the C808M solved the problem.

 

[jhn.holgate]

Ditto here. I have a **** Smith (Aus brand) 'intelligent' charger that would often tell me my batteries were charged well before they should have been with resulting rubbish run times. Lots of reading here and I bought the MH-C9000. Now I can easily sort the good from the bad and revive some of the rubbish cells. A decent charger is at least as important as decent batteries....if not more so.

 

[Cereal_Killer]

A decent charger is at least as important as decent batteries....if not more so.

this is so true! Even using the best cells you can't expect to get good performance out of them if your treating them like poop, as long as your using a good charger even crappy cells will be able to perform to the best of their ability. Today's worst performing AA NiMH's can manage 1000mAh or more and discharge at 2A, most of our AA lights arnt pulling over that, if you've got a bad charger you might not be getting half that in there if it terminates early.

 

[SilverFox]

Hello StorminMatt,

I love stories like this. You are now taking charging to a new level.

One think you may want to consider adding to your charging station is a simple countdown timer. The 808 is a great charger but all chargers miss a termination from time to time. Using a timer you can often find this before you go to use your batteries.

When I charge I expect the charge to be completed in around 2 hours and the cells should be warm. If the charger terminates early you will find that the cell is cold. If the termination signal is missed you will see other cells finish and end up with a cell or two that just keeps charging. I check progress in 2 hours and if some cells are still charging I reset the timer for another 30 minutes. That allows for any mismatch and if the cell is still charging I manually terminate it.

At this point I mark the cell and if it happens again I move to a full analysis on my CBA to see what is going on. I will also change chargers to see what happens. I also take this time to clean contacts on the charger(s) and cells.

While some of this may seem a little extreme I justify it by enjoying wonderful run time on my various devices.

Tom

 

[lwknight]

Silverfox , I like how you think.
Any recommendations on a timer?

 

[SilverFox]

Hello Lwknight,

My favorite is the Talking Timer by Voice Zone. Other than that any kitchen timer will work fine.

If you move around a lot you can set an alarm on your phone and just drop it into your pocket.

Tom