How do you form (slow charge) a 9-cell pack - RC Groups
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Jan 08, 2003, 09:52 PM
Registered User

How do you form (slow charge) a 9-cell pack

I always use my tranmitter charger to slow charge my 8-cell packs when they need to be equilized. Lately I've built two 9-cell packs which is more voltage than my 8-cell charger puts out.

I like to slow charge the pack the first time and the only other charger I have is an Astroflight 110D. I can charge with this at .1 amp but it will peak in less than 10 hours if the battery pack is less than a 1000 mAH. If I start it again it justs peaks again. I don't think I'm adequately forming the battery.

I can't disable the peak circuit on the astroflight so how do you slow charge a 9-cell or higher battery pack.

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Jan 09, 2003, 09:06 AM
Registered User

If you disabled the peak detection circuit, you'd roast the pack... Not a good idea.

Just do the best with what you have. A slow charge of several hours at .1A is fine. C/10 is not written in stone, it's just a convenient number. You could charge at C/15 or C/5, and the difference would be negligible, IMHO.

All I can tell you is what works for me. I don't like using chargers that don't peak-detect, because I'd be likely to forget the charger and ruin the battery (ask my Craftsman 14.4V cordless saw; left a battery on the 3-hour charger for two days). All my NiMH packs are "form charged" on my SuperNova at .1A, and they've been performing just fine, thank you very much
Jan 09, 2003, 09:21 AM
Registered User
pda4you's Avatar

Radio Shack

You could go to radio Shack and see if they have a cheap wall charger you can use. I know they have a pretty good selection. Something around 13vots DC and 50 or so MA would work fine.

Jan 09, 2003, 10:16 AM
Registered User
LarryFlew's Avatar

Re: How do you form (slow charge) a 9-cell pack

Originally posted by Parkflyer
I can't disable the peak circuit on the astroflight so how do you slow charge a 9-cell or higher battery pack.

Does the 110 go into peak by itself? On most chargers, if you do not start the peak detector portion it is already on trickle where it also ends up after peaking. IE with my Tekins, when you attach a battery it is in trickle until you hit the peak button at which time it goes into peak mode and after the pack is peaked it goes back into trickle mode. In that case, to trickle you just need to hook your battery to the charger.

Jan 09, 2003, 12:18 PM
Space Coast USA
hoppy's Avatar
1. Your Astro 110D reading of 0.1A is probably wrong. Low, <1A, readings on the digital display may be substantially lower than what actually is going into your battery. The Astro 110D will easily deliver .01A but you need an ampmeter in line with your battery to accurately measure currents under 1A.

2. The timer, and all other functions like peak detection can be disabled by holding the start button in while powering up the charger. Just turn the dial to get the current you desire and it will provide it forever.

3. Instead of #2, I just put a microwhattmeter in line with my battery, set it for 0.1C, and let it charge for 6 or more hours. After this, I restart it and let it charge for another 10 or so hours.

4. 0.1C is more than a convienent number as stated above. It is a charge value at which you can moderately overcharge your cells without damaging them. Overcharging at 0.5C will probably damage your cells and values much below 0.1C probably won't provide sufficent energy to charge the battery. I'd stick with 0.1C.

Jan 09, 2003, 04:58 PM
Registered User
I wasn't aware you could disable the peak detect on the Astroflight. I have read the posts about the Astroflight being wrong on the low end but I have a DC clamp on amp meter that reads to .01 amp resolution. In my case the Astroflight reads correctly. Since the Astroflight only reads to the nearest .1 amp I always use the clamp on to set low charge rates since the Astroflight could be inputting .15 amp but read .1 amp.


If you don't disable the Astroflight peak detect how do you keep it from peaking before 16 hours like you stated in #2?

In my opinion nothing beats a good slow charge to equalize the cells.

Jan 09, 2003, 05:06 PM
Space Coast USA
hoppy's Avatar
I have never had a slow charge (0.1C) peak detect shut off. The input is too low to give a peak. Are you getting "time outs" or "peaked" readings?

Jan 09, 2003, 06:42 PM
Registered User
Oh, I see what you mean. Sometimes when I set it for .1 amp, when I come back several hours later the display is reading .0 amp so it times out after 10 hours. Even though it is still putting in a small charge, when the display reads 0 amp it doesn't add that charge to the totalized value. So it may show only 400 mAh went into a 1000 mAh battery. Whatever I set the charge rate to, several hours later it usually drops .1 amp.

I'm going to try your idea.