Results 1 to 6 of 6
  1. #1
    RC Racer
    Join Date
    Oct 2008
    Posts
    115

    How do I test NIMH battery packs

    What ways can I test a NIMH battery pack? Only thing I know to do is check the voltage with my multimeter. Is there any more sophisticated testing I can do? Is there a way to test the Mah of a pack to see how close to its rating (4200mah) it is performing? What do you all do?

  2. #2
    RC Qualifier
    Join Date
    Sep 2008
    Posts
    606
    You cant test the mah capacity directly, you can only estimate it based on current used during a run and the amount put back in during charging- you need an Eagletree data logger for that. Actually, you need an Eagletree to do any kind of testing really, such as performance under load- testing the voltage droop with increasing current draw.

    There isnt really much to test on them to be entirely honest, so long as they are built well and dont go pop after 5 minutes, thats all that matters- runtime will be pretty much the same with any ~4000mah nimhs; 15-20 minutes at best I reckons.
    Dont consult me, just read the FAQ.

  3. #3
    RC Racer
    Join Date
    Oct 2008
    Posts
    115
    Thanks Oracle. I just recieved a new set of 7 cell stick packs that came with another truck I bought. They were advertised as "brand new never charged". One shows 8.18 volts, and the other shows 6.82 volts on my multi-meter. Before I peak them for the first time I just wanted to make sure there wasn't something strange going on like a dead cell or something.

  4. #4
    RC Qualifier
    Join Date
    Jun 2008
    Location
    UK
    Posts
    254
    'Brand new never charged' is never technically accurate as they will always be charged at the factory. Could be they were charged different ammounts or oner has been sitting on the shelf longer than the other.

    The only way to test them is to use them and then watch very carefully for temperature differences between cells after charge and discharge. Just make sure you balance them by cycling at least once before use. If there is a fault it will usually take a few cycles to materialise. Temperature differences between cells is the key.

  5. #5
    RC Racer
    Join Date
    Oct 2008
    Posts
    115
    Quote Originally Posted by jtek
    Just make sure you balance them by cycling at least once before use. If there is a fault it will usually take a few cycles to materialise. Temperature differences between cells is the key.
    Could you explain how to cycle them before I use them?

  6. #6
    RC Qualifier
    Join Date
    Jun 2008
    Location
    UK
    Posts
    254
    By cycle i mean charge then discharge then charge again. Some chargers support it, some it's manual. If it doesn't have discharge you'll have to just run the packs and undergear or put it in training mode so you avoid fast discharging and cooking an out of balance or faulty cell.

    The difference between discharging in your truck and discharging with a charger is the speed at which you do it. If there is a problem, slow discharging reveals it by creating a temperature difference between cells. Charging can do the same. Fast discharging in the truck on the other hand, particularly this one which has a reputation for destroying NiMH packs, will show a faulty cell by blowing it to bits. I had two packs go that way, the heat killed them but in each case only a slightly out of balance cell blew, because by being out of balance it took the extra strain.
    Last edited by jtek; 11-19-2008 at 07:54 PM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •