Loading Nimh batteries for the first time?

[Jorgen 56]

Hi all,

I have just bought my first Nimh batteries (4000 mah) and a SkyRc e450 charger.

The thing is that it has different lamps for how much the batteries are charged. After 12 hours of charging its still at the first stage (blinking red/green) In the manual it says that it means "ready for charging)

Im sure that I selected the option -Nimh and 4 A on the charger.

 

Is this normal because its brand new and never been charged or should I send it back?

Any help appreciated

/Jorgen

[LeftyAl 164]

Hey Jorgen,

In step 6 it says to press the button for 2 Secs. Did you do this?

[Jorgen 56]

Thanks a lot LeftyAl, didnt know that 

[Jorgen 56]

It worked like a charm

But it indicated that it was fully charged after about 90 minutes. I was expecting it would take all night?

Could it be that this is a fastcharger? 

There is a option of choosing 1A-4A.  Is 4A the best option or could it wear out the batteries faster?

 

 

[simalarion 2196]

Hmmm it was just when i was a kid it took so long to chsrge batteries.

If you are charging 4A for 90 min on 4000mah battery that is probably min - max charge. I think that was a litle long time, watch out so the battery do not get hotter than 55c, they dont like that.

Edit: most new charger stop after 120min charging. You can change that time or turn this feature off.

[LeftyAl 164]

@Jorgenglad to hear you got it sorted. If the charger is set at 4A then it should normally take about an hr to charge a 4000mAh battery. If you charge the same battery at 2A it should take about 2 hrs to charge and at 1A it would take 4 hrs.

 

"normally" depends on a few things, battery age, existing capacity and the charger. Use the car a few times and keep an eye on how long it takes to charge.

simalarion is right about heat, doesn't help with battery health.

[Jorgen 56]

Thanks a lot. Im completly new to this. 

Is it better for the batteries lifespan to charge at a lower A and longer chargetime?

[LeftyAl 164]

Not sure mate, it has been a long time since I used nimh.

Maybe someone with a bit more experience will be able to chime in.

[simalarion 2196]

As with other Charge batteries the quality is diffrent depending on the quality you bought,  cheap 5000 mah nimh batteries on Ebay can turn out to not be 5000 mah at all but 3000 mah to take 1 example, so if it is a 3000 mah battery then it is not good for the battery to charge 5 A, it will get hot (as mentioned they do not like over 55 c). You can start charging your battery at 3A if it does not get hot at all go up to given capacity 4A.

But again 90 min on 4A was a long time, i think you probably had a lower A.

If given info is correct on your 7.2volt 4000 mah the charge setting is:

Nimh Charge: 4.0A 7.2v (6S)

 

[SupraChrgd82 1425]

The general rule for charging NiMH is 1 amp per 1000 mAH.  The battery will be warm to the touch when peak charged, but not hot.

NiMH will endure a lot of charge/discharge abuse, much more than LiPo. 90 min seems a little long, but give it a few cycles to see if it is a pattern of long charge time.

You’re charging at a reasonable rate with a battery type that is very safe.  If you have any worries, place it on a surface such as a tile floor when charging. I don’t see any cause for concern.

[Jorgen 56]

Thanks a lot. Seems like everything is ok then. It got warm but not overly hot so I guess thats just normal. Now if only it could get a little warmer outside I could test it. 12 degrees below zero here today

[Jorgen 56]

I was really surprised how long the batteries lasted. (4000 mah)

Had a run of approx 1 hour och a gravelfield with my Grasshopper and stock 380. Full gas 90% of the running time.

[Tamiya Fan 1 114]

A 4000 MAH is a bigger battery pack then from back in the day when 1800 MAH was big (1990's). Your charge rate should be 4-5 amps for that battery, so you are doing it right. I charge my 3800 MAH batteries at 5 AMPS and it takes about 45 mins. Yes they will get hot at the end of charge. that is normal. On fire hot no good but will feel hot to the touch, and you could hold on to it if wanted to. (a good hand warmer) The lower the Amps the longer it will take to charge and may not charge completely. So you should charge at higher rate unless trickle charging  (lower Amps.) which helps balance the cells and takes over night.

Hope that helps

[Nikko85 3454]

On 5/26/2021 at 7:39 AM, Jorgen said:

I was really surprised how long the batteries lasted. (4000 mah)

Had a run of approx 1 hour och a gravelfield with my Grasshopper and stock 380. Full gas 90% of the running time.

Nice one

Yes, batteries have moved on a lot since I was a kid, when you'd get 10 mins run time at best. The 380 motor and a large capacity NiMH is going to give a really nice run time. A small brushless might give even more, as they are more efficient.

I also only use NiMH, I tend to charge overnight with an auto cut off - charging at just 1 amp regardless of capacity.

[mike in pa 64]

Should NiMh packs be fully discharged before charging?  Lets say after running and some charge is still left. Keep in mind that I'm from back in the day when we were using 1200 ma NiCD hump packs. LOL  Those needed to be fully dead for a compete charge.

[Nikko85 3454]

I think that NiMH doesn't really care. It doesn't have much memory effect, so you can top up, or let almost go.

I have found that some NiMH won't take a charge when completely depleted, but you can shock them back to life.

 

[alvinlwh 5895]

4 hours ago, mike in pa said:

Should NiMh packs be fully discharged before charging?  Lets say after running and some charge is still left. Keep in mind that I'm from back in the day when we were using 1200 ma NiCD hump packs. LOL  Those needed to be fully dead for a compete charge.

NiMHs do have a memory effect of sorts, just not as bad as the old NiCads. I heard that in the old days, racers will take apart and discharge and charge each of the cells individually. 

[Willy iine 18806]

5 hours ago, mike in pa said:

Should NiMh packs be fully discharged before charging?  Lets say after running and some charge is still left. Keep in mind that I'm from back in the day when we were using 1200 ma NiCD hump packs. LOL  Those needed to be fully dead for a compete charge.

Contrary to NiCd, you will want to leave ample amount of charge in the NiMH cells after you're done driving.  In my case I usually stop driving my car around 800-1000mAh remaining in the battery so that I know for certain the weakest cell in the sport pack is not depleted (which prematurely kills the pack).

 

This is my simple reference running GF01 or WR02 with silver/black can 540 motor, but probably pretty consistent on other factory geared cars.

3600mAh NiMH:   12min drives x 3 cycles (10-15min breaks after each drive).  

2000mAh NiMH:   12min drive x one cycle

 

Then let the battery rest for 12hours+ and then recharge.   Some of you might think I still run 2000mAh??!   Yes, I've had these packs for over 10 years now, no issue with charging.   I take care of my batteries. 

 

 

 

@Jorgen You can charge your 4000mAh at 4A rate safely.  It's really the depleting the NiMH battery pack too far and charging immediately after use that causes batteries to weaken prematurely.  I suggest you get a couple of those battery packs of your choice and only run them no more than once per day.  Give them time to rest before recharge.