Charging. Am I doing it wrong?

[jo060]

I have 2 brand new 5000mah NIMH batteries, I've used them about 5 times now.
When I charge them (I use an old Prophet and a new Sigma EQ mini charger) I set the Amps to about 4 (prophet) and 4.5 (Sigma). The Sigma has a digital readout and I can't get the charging amps to go above 2.8, sometimes it'll go to 3 when charging. I asked my local hobby shop why this is happening and he said because when the charger is plugged in the wall it doesn't have enough juice to make it past the 2.8 volts but it would work perfectly if I used DC from a battery. I hooked it up to a 12v car battery and it still says the same 2.8 and takes about 1.5 hours to charge. Any ideas?

[fvj]

Ok, first thing to check is what is the max power in your charger. Usually the entry level ones are 50W. Then next question is, how many cells in your NiMH?

The max current (amps) your charger will handle is the Power / Voltage. If your charger is 50W rated, you could reach 4 amps easily in a 7 cell or even a 8 cell NiMH.

With the above said, my next question is: Does it reads 2.8Ah all the time or only when is almost charged? Do you feel the battery is fully charged at 1.5h? If it is only taking 1.5h to charge and if the 2.8 reading is correct, you are only putting 3600mAh on a 5000mAh batt. So or you have a problem in your charger or the batteries are not good.

[trax de max]

check the sigma isn't in auto mode for nimh which sets the charge current at the correct limit to what you set the capacity at.
The prophet is just an old charger and don't know about that one.
But the forum is only for traxxas products only, so can't help any more than that.

[jo060]

Ok, first thing to check is what is the max power in your charger. Usually the entry level ones are 50W. Then next question is, how many cells in your NiMH?

The max current (amps) your charger will handle is the Power / Voltage. If your charger is 50W rated, you could reach 4 amps easily in a 7 cell or even a 8 cell NiMH.

With the above said, my next question is: Does it reads 2.8Ah all the time or only when is almost charged? Do you feel the battery is fully charged at 1.5h? If it is only taking 1.5h to charge and if the 2.8 reading is correct, you are only putting 3600mAh on a 5000mAh batt. So or you have a problem in your charger or the batteries are not good.

The max power in the Sigma is 45w
I'm running two 6 cell packs (Onyx)
It reads 2.8 every time with the exception of once or twice

check the sigma isn't in auto mode for nimh which sets the charge current at the correct limit to what you set the capacity at.
The prophet is just an old charger and don't know about that one.
But the forum is only for traxxas products only, so can't help any more than that.

I don't thin the Sigma has an auto mode, but the instructions are a bit tricky.

[trax de max]

when setting the current to charge press inc and dec at the same time.

[jo060]

when setting the current to charge press inc and dec at the same time.

Pressing both simultaneously didn't change anything, If I did increase/decrease by it would change the amps which I already have set to 4.5.

[trax de max]

hmmm does it not read AUT or MAN

[jo060]

hmmm does it not read AUT or MAN

Nope. I didn't see those 2 options

[trax de max]

i'll have to look at my old charger tomorrow, if i remember on the screen where you can change the charge amps press the inc and dec together and it flips from auto to man. But i'll have to check to make sure.
If you can't get it and you have the battery capacity set, change that setting to 8000 to see if that changes the charging amps, If it does change the amps it is in auto mode. If it stays the same the problem is elsewhere.

[trax de max]

Ok on the screen where you can change the amps, for the nimh charge adjust the amps to the setting you want and while its flashing, then press inc and dec together. I thought it was on that main screen but you need the charge rate flashing to change it.

[jo060]

Ok on the screen where you can change the amps, for the nimh charge adjust the amps to the setting you want and while its flashing, then press inc and dec together. I thought it was on that main screen but you need the charge rate flashing to change it.

When I change the amps it doesn't flash it just scrolls. I tried pressing them together anyway and it still just scrolls through.
:-/

[trax de max]

Try raising the capacity cut off and see if that raises the charging amps.
If you feel unsure about this, half the setting you have now and see if that lowers the charge amps.
If it doesn't change there is something wrong somewhere, if it does change it's on auto and needs changed somehow.

[jo060]

Try raising the capacity cut off and see if that raises the charging amps.
If you feel unsure about this, half the setting you have now and see if that lowers the charge amps.
If it doesn't change there is something wrong somewhere, if it does change it's on auto and needs changed somehow.

I don't think there is a capacity cut off.
The only options I have are the type of battery to charge and how many MAH to amps to charge at.