NiMH Charging Question

[Rinskie]

I am setting up my charger and I have no clue how many amps I should be charging my 4000 NiMh pack. Is 1am too hot? Should I do more or less? 

Thanks! 

[El Gecko]

I've found various recommended charge rates for NiMH over the years, from 0.1C to 1C (C = the capacity of your battery)

I just charge mine at 1A no matter the capacity, with no apparent adverse effects even with 5000mAh batteries (which would be 0.2C at 1A charge rate), it just takes longer to fully charge the higher capacity ones.

You're probably good anywhere from 1A to 4A charging your 4000mAh battery (0.25C-1C), although at 4 it would get quite warm, but it would be done more quickly.

[Jonathon Gillham]

I always charge my batteries at a 1C charge rate, so 4amps for your 4000mah NiMH.  No issues with heat and my batteries tend to last quite a few years.

Many batteries will say what charge rate they can handle, with newer lipos having rates up to 5C.

If you want to charge at a lower rate it will just take longer, but it won't have any benefit for the battery (well, maybe last longer, but if they last years then its hard to say whats wearing them out?)

[Rinskie]

Thanks guys. I am slowly getting all this stuff sorted out. I just finished a M08 and finally got my battery and charger in the mail today so I figured I'd try to program the speed controller before soldering up the charging lead. Well either the battery is below the cut off or the speed controller isn't working right so I figured I'd charge the battery to rule out at least one. The battery is on charge now but it's been a little over an hour and 15 now. It's charging at .2-.5A so I guess it's gonna be a little while longer. I'll bump it up to 4amp next time around. 

[Willy iine]

I would use 4 amps for 4000mhA.  If you use 50% of the charge before recharge you would still charge at 4A.   That will still take ~30min to charge.  Some of the newer chargers have an auto charge mode which will charge at various charge rates for a gentler charge.  I use that mode from time to time.  

I recommend you only use half of the battery capacity and not drive until the car slows down.  You will prematurely wear out the weakest cell of the pack.  GL! 

[skom25]

Is there something wrong with charging 3300 battery with 1AMP?

I read somewhere that Lowers Amps = Longer life

 

[alvinlwh]

.

[Pylon80]

I would stick to the range recommended in your charger's manual (for instance 0.5C to 1.5C), with 1C as a 'can't go wrong' value. The reason for this (i.e. not just my opinion...) is that the charger uses peak detection to decide when the battery is fully charged. The chargers normally have their own delta peak value (the amount of voltage drop required before charging stops) programmed inside and if you use too low a current you might spend a lot of time pumping energy into a fully charged battery until you finally hit the magic delta voltage number. While you do that the extra energy just get lost in the form of heat as the pack becomes very hot for no good reason.

In my case I now have a Hitec charger that has a cool 'Auto' feature for NiMh. It finds the optimum current based on how the voltage ramps up during charging and in doing so it never overstresses the battery while charging it quickly. What kind of charger do you have @Rinskie?

[Rinskie]

Thanks guys. I bought a Protek 610ez. Hope it's decent. I ended up charing the battery at 1amp so if I remember correctly, I am under 1C for a 4000mah pack.