Results 1 to 19 of 19
  1. #1
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47

    Discharnging NIMH

    Just wonder what rates to set the discharge current at on NIMH batteries

    battery Im using is 7cell 8.4v 3000mah traxxas battery.

    Had a few funny experiences with it. Charged it from brand new from recieving it with charger that came in with the car. after 3 hours it was still just showing a red led.

    I also bought a smart charger, 6amp 80watt.

    I charged it at 3 amps and it took a futher 15 mins. When we used it , it lasted about 10 mins when it slowed down. so used the lipo and it cranked heaps better and lasted 40 mins 2s 5000mah.

    So I charged the nimh again and it took 40 mins, and seemed to last along time, a good 40 mins and my son stopped using it. Got up this morning and thought i would top up the nimh as it must be close to empty and it charged very quickly. When we used it it only lasted 5 min maybe?? Put it on charge and it charged in 3 min?? So fig must have memory so was going to run a disharge recharge cylce but dont know what current to set the amps's discharge at?? 0.1 to 2.0 amps are my choices??

    The instructions to set discharge voltage to 1 volt per cell so figure thats 7.0Volts for a 7 cell?
    Last edited by mattryan; 12-25-2015 at 10:46 PM.

  2. #2
    RC Qualifier Whitecobra's Avatar
    Join Date
    May 2013
    Location
    Lincolnton, NC
    Posts
    291
    Quote Originally Posted by mattryan View Post
    Just wonder what rates to set the discharge current at on NIMH batteries

    battery Im using is 7cell 8.4v 3000mah traxxas battery.

    Had a few funny experiences with it. Charged it from brand new from recieving it with charger that came in with the car. after 3 hours it was still just showing a red led.
    I also bought a smart charger, 6amp 80watt.

    I charged it at 3 amps and it took a futher 15 mins. When we used it , it lasted about 10 mins when it slowed down. so used the lipo and it cranked heaps better and lasted 40 mins 2s 5000mah.

    So I charged the nimh again and it took 40 mins, and seemed to last along time, a good 40 mins and my son stopped using it. Got up this morning and thought i would top up the nimh as it must be close to empty and it charged very quickly. When we used it it only lasted 5 min maybe?? Put it on charge and it charged in 3 min?? So fig must have memory so was going to run a disharge recharge cylce but dont know what current to set the amps's discharge at?? 0.1 to 2.0 amps are my choices??
    1 amp is what I would use.
    1997 White Mustang Cobra its not a RC!

  3. #3
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    Ok for info I found to discharge at 1c that I believe to be 3amps for a 3000mah battery correct?

    My charger only goes to 2.0amps so I set it at that and it appears to be discharging at 1.0amps and the charger wont take it higher??

    Is this all ok?

  4. #4
    RC Qualifier Whitecobra's Avatar
    Join Date
    May 2013
    Location
    Lincolnton, NC
    Posts
    291
    Quote Originally Posted by mattryan View Post
    Ok for info I found to discharge at 1c that I believe to be 3amps for a 3000mah battery correct?

    My charger only goes to 2.0amps so I set it at that and it appears to be discharging at 1.0amps and the charger wont take it higher??

    Is this all ok?
    yes, you can charge and discharger at higher amps but it builds heat in the battery and is best avoided.
    1997 White Mustang Cobra its not a RC!

  5. #5
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    I ran the above program and it discharged 104mah and charged 129 mah??
    For a 3000mah battery is this stuffed? Did i bugger it??

  6. #6
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    Battery never got remotely warm??

    Also it appears I can run this for up to 5 cycles?? Good or bad idea??

  7. #7
    RC Qualifier Whitecobra's Avatar
    Join Date
    May 2013
    Location
    Lincolnton, NC
    Posts
    291
    Repeat cycles a few times.
    1997 White Mustang Cobra its not a RC!

  8. #8
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    Cheers white cobra, should I be expecting it to discharge and charge approx 3000 mah when its working properly??

  9. #9
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    So just put it in the car and it lasted 2 mins if that and the car stopped. Is this a warranty case or did i destroy this battery? If so how did I damage it?
    How can I possibly revive it??

  10. #10
    RC Qualifier Whitecobra's Avatar
    Join Date
    May 2013
    Location
    Lincolnton, NC
    Posts
    291
    Quote Originally Posted by mattryan View Post
    So just put it in the car and it lasted 2 mins if that and the car stopped. Is this a warranty case or did i destroy this battery? If so how did I damage it?
    How can I possibly revive it??
    If its new, warranty case.
    1997 White Mustang Cobra its not a RC!

  11. #11
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    Yep car and battery are brand new for xmas.

  12. #12
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    Put it on charge this morning at 2.8 amps, been charging for 76 mins and has taken on 3400 and counting at 10.18v??? Its hot but not so hot you cant hang onto it?? Should I switch it off????

  13. #13
    RC Qualifier Whitecobra's Avatar
    Join Date
    May 2013
    Location
    Lincolnton, NC
    Posts
    291
    yes, let it cool and charge again.
    1997 White Mustang Cobra its not a RC!

  14. #14
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    Cheers Cobra and now the battery just worked great??? Lasted ages?? I dont understand whats going on with it ot what I might be doing wrong???

  15. #15
    RC Qualifier Panamon Creel's Avatar
    Join Date
    Oct 2014
    Location
    Central Mexico
    Posts
    427
    Mattryan, an advise I can give you is to forget about " memory " on modern day NiCd and NiMH batteries. That's something that happened under specific conditions in the early days of these types of rechargeable batteries and modern day manufacturing processes and chemistry of these batteries gotten rid of that issue.
    The one problem that can occur with modern day Ni based rechargeable batteries is that their self discharge rate gets very high if the battery was not in use for extended periods of time but that should not be the case with your batteries.
    Make sure that the connection between your battery and charger is good, otherwise the charger may stop early. Also for some reason or another new batteries sometimes require a few cycles to take on the full capacity.

    Re: charger discharge current, your charger likely only has a 10W max. discharge rating, that's why you won't reach the 2A discharge current since it hits the 10W limit before that.

  16. #16
    RC Enthusiast
    Join Date
    Dec 2015
    Posts
    47
    Cheers Panamon

    The only difference i can see and unfortunately i didnt check voltages on either occasion.

    But provided I run the battery down to where the car is going slower it appears to then recharge and work fine, typical run time to do that is 40 mins, dont drive it flat out everywhere.
    If however I run it for 30 mins or so, a decent run but the car is still running fast, then we finish for the day and I charge it so its good to go the next day, then it charges super fast and discharges in 5 mins as in slows right down 1st run the next day? it appears then i need to run it till it stops the moving the car then charge it and all is good??? It seems it wants to be totally discharged before accepting a full charge again??

  17. #17
    RC Qualifier Matrix243's Avatar
    Join Date
    Apr 2003
    Location
    Calgary, Alberta
    Posts
    728
    I'm experiencing similar problem with the same batts. Back in my old RC days, when the car slows to a crawl and stops, we would flip it over and let it free spin till its completely drained. Is this the same case for the new NIMH's?
    Merv
    ERBE
    T-Maxx Classic 3.3
    Axial Scx10

  18. #18
    Marshal ksb51rl's Avatar
    Join Date
    Nov 2006
    Location
    Northern NJ
    Posts
    20,524
    My advice is to STOP DRIVING as soon as you see/feel the vehicle slowing. Charge as soon as possible and repeak before using. Do not let NiMH cells discharge all the way.
    Alt-248 on the number pad =

  19. #19
    RC Qualifier Matrix243's Avatar
    Join Date
    Apr 2003
    Location
    Calgary, Alberta
    Posts
    728
    I think either my thunder ac6 charger is fried or my batts are defective, with only 2 runs on them. Can only get it to charge for 12 minutes and power loss is almost instant. Thought it needed discharging but apparently isn't the case.
    Merv
    ERBE
    T-Maxx Classic 3.3
    Axial Scx10

Posting Permissions

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