MRC Super Brain 960 - my first charge of 6-cell pack  
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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> MRC Charger Product Support (i.e. Super Brain, etc) >> MRC Super Brain 960 - my first charge of 6-cell pack
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MRC Super Brain 960 - my first charge of 6-cell pack - 11/2/2007 4:59:32 PM   
jolynsbass


 

Posts: 6
Joined: 11/2/2007
From: Norman, OK, USA
Status: offline 		Please forgive my ignorance and the inevitable length of this post. I'm a total newbie to the rc hobby scene (just bought a Rustler xl-5, have yet to actually run it!) I just got an MRC Super Brain 960 along with a Tenergy 4500mah 6 cell pack.

Now, everyone seems to say that batt packs comes un-charged, and that you should charge them slowly the first time, and then you're good to charge 'em quick. So, I plug in my 960 to AC power, then plug in the battery. The voltage reads 7.6 V, which I think is a little odd for 7.2V pack, but since I had no experience whatsoever, I figure I'm good to go.

Having read about the "false peak" issue when charging a new battery, I thought that I'd set the mv a bit higher, so it wouldn't stop early. I set it to 50mv, and a charge rate of 0.5 amps. I figured it ought to take about 9 hours to charge up full, since it would be 500ma * 9 hours = 4500 mah, right? Well, over the course of the next hour and a half or so, the voltage keeps climbing slowly, and eventually the battery pack gets quite warm(after about 90 minutes). The voltage is now reading 8.9V, and I get a little worried, so I turn the mv down to 0.3mv (default, yes?), and after about 5 minutes or less, the charger shuts off with the "beep beep, I'm done" business. I feel the batteries and they are actually hot to touch! Not mega-hot, but really toasty. So, I put a fan blowing on them to help them cool off faster(having read that heat is not good for batts), and I notice that the voltage is slowing dropping on the readout, slowly going down to 8.6 or so before I finally unplug it and go to bed. After letting the battery sit overnight, I plugged it back in this morning, and it reads 8.3 V. Isn't that a little high for a 7.2V 6-cell battery?

And what about the time? Did they actually pre-charge these batteries or something? 'cuz they shouldn't get warm unless they are totally charged, right? especially at 0.5 amp charge rate. I expected 9 hours, not 90 minutes

Please help me out here folks! I don't know if I've done something bad to the batteries, or if this is normal... I'm hoping to play with my new rc today, but I don't want to use a dangerous battery or anything...

Thanks in advance!
       Post #: 1

RE: MRC Super Brain 960 - my first charge of 6-cell pack - 11/2/2007 5:23:25 PM   
SS Pede



Posts: 326
Joined: 2/2/2006
From: Reading, MA, USA
Status: offline 		The voltage you saw is normal. If it's not under load, a 6 cell pack will often read 7+ volts even when it is discharged. 8 or 9 volts when it is fully charged is also normal. The voltage dropped after you stopped charging because the charger "sees" a higher voltage when it is pushing energy into the pack. Once the charger stops, the voltage value comes down to a more accurate number. 1.2 volts per cell (7.2 volts for a 6 cell pack) is the nominal voltage. Fully-charged voltage is higher than this (8.3 volts the morning after sounds just right).

90 minutes is indeed a short amount of time to charge a 4500 mAh pack at .5 amps. So the only logical answer here is that the pack was partly charged when you bought it. Batteries get warm when they are fully charged, so that's normal. They can even get "very warm." Now, 50 mV is kind of a high peak threshold, even for a first charge, so your pack maybe got warmer than it normally would. But it is probably still fine. 30 mV is OK for the peak threshold, but don't go any higher. 20 to 25 mV might work fine too as long as you don't get false peaks.

The extra heat wasn't good, but your pack is probably fine. Just go for 30 mV or less next time around, and have fun!

(in reply to jolynsbass)
       Post #: 2

RE: MRC Super Brain 960 - my first charge of 6-cell pack - 11/2/2007 5:31:51 PM   
jolynsbass


 

Posts: 6
Joined: 11/2/2007
From: Norman, OK, USA
Status: offline 		Sweet! Thanks for the quick reply and helpful words! I'll keep the mv threshold lower in the future...

I see now why they say not to leaving batteries charging unattended! It's a good thing I was checking on it regularly...

Now, all I must do is stop by my LHS and grab a Traxxas THCC conversion kit for the battery & charger, and I'm ready for some action!

(in reply to SS Pede)
       Post #: 3

RE: MRC Super Brain 960 - my first charge of 6-cell pack - 11/2/2007 5:35:34 PM   
SS Pede



Posts: 326
Joined: 2/2/2006
From: Reading, MA, USA
Status: offline 		Awesome. Be sure to check out the Stampede forum if you have other questions about your truck.

(in reply to jolynsbass)
       Post #: 4

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