Charging 9.6v NIMH Batteries issues - Help Pls

[Andy1966uk]

I have bought a couple 9.6V NIMH batteries and have a NUPROL smart charger. The Battery rating is 9.6V 1600mA.

I set the current charge limit to .05A , however the voltage of the battery goes up to 11.4 V when finished charging, and as a result is causing issues on my Airsoft Rifle, which requires a 9.6V Battery.

I have tried this with two batteries and I get the same issue...

Question : Surely the number of cells for the battery limits the ultimate battery voltage ?

Question: Are both these batteries no good, as I can discharge them on the smart charger, but I do I set a voltage limit

Question: what could I being doing wrong ?

I also have a 7.4V LIPO for another rifle, which I have no charged yet, but am concerned if I use a smart charger (this charger is a NUPROL NP60W Smart and works with LiPo, NiMh and is selectable as to battery type and charge current etc.) that I damage or over charge another battery...

I presume the fact the 9.6V battery has 8 cells, the maximum voltage would be the limit...

Any ideas what could be happening ?

Should I get a charger just for NiMh and another for LiPo ?

Help as I feel I am wasting these batteries......

 

[Druid799]

To be honest bud I’d say ditch the nimh and the Nuprol charger and just use LiPo or LiFe batteries and get a quality smart charger (imax/acucell/etc)  , just so much better than the nimh batts And Nuprol chargers are renowned for killing batteries! ?

plus I’d recommend (and most over experienced players I’d think)changing all your connectors to deans or another more efficient connector . Yes I know it’ll be a fair old outlay to start afresh but so worth it in the long run .?

 

[Samurai]

OK, let's do this.

The charger looks like a B6AC in a different box (WTF? I just saw the price). Anyway, let's do the basics.

9.6V or 1.2V per cell for a NiMh battery is the nominal voltage, meaning it stays at 1.2V for most of the time when being used. However, fully charged is 1.5V per cell, in your case 12V. It is considered to be discharged at 1V/cell (8V for yours). This doesn't cause problems, the gun is designed to take it if it came with that battery.

Other types of batteries have the same, but the voltage values are different.

The smart charger detects a voltage drop when the battery is full, it won't overcharge it. You don't need to worry about the charging voltage.

The charging current of 0.05A looks way way too low. I guess you meant 0.5A or it would take days to charge it. 0.5A is still low, you can do 1-1.5A with that 1600mAh battery.

 

[Andy1966uk]

Thanks, I did mean 0.5amps btw. I’ll use 1.5amp going forward. Appreciate the guidance.

 

[Prisce]

As a beginners guide to batteries we usually say  a 1700Mah battery can be charged at 1.7A, and a 1100Mah battery at 1.1A if that helps.

The whole voltage thing got me begin with. Your 7.4V battery is the voltage uncharged, storage charge is around 7.6V and full charge is 8.4V.

 

[Rogerborg]

Pretty much covered above, just +1'ing.

I agree that looks like a generic B6 in a small case (thus poor heat sinking, do not want).

Still, unless Nuprol have sprinkled their exploding-magic in it, it should work OK for both Nimh and lipo, but they charge in very different ways.

With the lipos, you tell it the number of cells and it will balance-charge them to about 4.2V per cell, i.e. 8.4V for a nominally 7.4V battery.  This is normal and fine.

With nimh, it doesn't know the voltage and as @Samurai said, it has to look for a voltage drop when the battery is full.

But here's the kicker: it needs to be a fairly sudden drop, and it has a harder time spotting it if you're charging at a lower current.

So I'd agree with @Prisce that you'll want to charge at a "1 hour" rate, i.e 1A per 1000mAh capacity.  It seems counter-intuitive, but it makes it easier for the charger to not over charge.

In general, I never leave batteries charging unattended, and with nimhs in particular, I'll stop the charger if they heat up.  There's little benefit to trying to cram every last electron in there if it ends up wrecking the battery.

And aside, I regret ever buying nimhs, and should have gone straight to 7.4V lipos and a SKYRC B6 charger.