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Old 09-27-2006, 12:49 PM   #1
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Default Are my Batteries Shot?

I have a few questions about charging and discharging capacities. I have 3 used 3300 mah (4 Cell) matched packs that I got with the 1/12th car I recently purchased (also used). I just got a duratrax Ice charger and now finally have some feedback on what the batts are doing during their cycles.

The Three packs on average over 3 charge/discharge cycles are only discharging about 2000-2200 mah (down to 0.9v) and are only taking 2300-2500 on charges. The Average resistance for the packs on discharge has been about 34 mohms. These numbers are average of the 3 packs and do vary a bit from pack to pack. I have a spreadsheet with precise data if that helps at all.

I am new to racing and dont need top of the line stuff since I cant drive worth a darn anyway, but I do want to make sure that these things are at least halfway decent and also be able to pick the strongest/healthiest pack to use in the main.

The charger settings are all correct. I just have no idea what this data SHOULD be for comparative purposes to judge the condition of these packs.


4 Questions -

1) Is it normal for batts to only discharge and charge at a small portion of their rated mah capacity or should these number be closer to 3300?

2) Is it normal for them to take more mah on charge than they give off on discharge? I would think these two should be darn close to being the same.

3) What should the internal resistance of the packs be if they are in good shape?

4) Are my packs just spent and need to be replaced badly or are they good to go for a while?

Thanks for the help.

-Hank
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Old 09-27-2006, 04:01 PM   #2
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I would especially appreciate the input from someone who uses the ICE charger, but I imagine the numbers will be similar regardless of charger. Any thoughts?
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Old 09-27-2006, 06:52 PM   #3
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Batteries if not cared for properly do lose capacity over time.

I have 8 packs of 3300 practice packs that are only taking 2800-3000 miliams on charge, they will last 5 mins in stock but only just.

As for the discharge about 100-200 mah will be lost to internal resistance etc.
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Old 09-27-2006, 07:01 PM   #4
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Thanks for the reply. So does that mean these are pretty much toast? They should be taking a full 3300 on a charge?
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Old 09-27-2006, 09:49 PM   #5
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Quote:
Originally Posted by hanknmorgan
Thanks for the reply. So does that mean these are pretty much toast? They should be taking a full 3300 on a charge?

You can try to increase the threshold voltage or the delta peak . It should pump in more charge before it peaks.

3300 are one of those cells that can take some abuse.
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Old 09-27-2006, 10:15 PM   #6
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You can try to cycle them back to life, if you have extra funds you can get a Spintec Battery manager type disharger, this device can help lower the IR and breathe some life back into your used packs, but most likely you have some practice quality packs left. You will probably want to invest in some new packs for racing purposes. Good Luck.
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Old 09-27-2006, 10:48 PM   #7
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On the charger, set the mah to the same as the battery. Then scroll sown toward the bottom of the screen. There should be something like "Maximum Charge Capacity". Set this to 150%. Watch your pack while it is cycleing. When it gets done with the charge part, the pack should be about 120-130 deg.
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Old 09-27-2006, 11:11 PM   #8
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Just to make sure that I am 100% here. A new, good condition, 3300 pack when discharged to .9v/cell should accept a full 3300mah or more when being recharged on the ICE charger.

I do have the max charge setup to 150% already. I dont have a temp probe hooked up, but the packs are definately pretty warm when they are done at 5 amps. I guess they are just toast. I have no idea how old they are or what they have been through.

I cant afford a battery equalizer or anything, but I have cycled them 4 times with the ice and they did get a little better. But they are still low in the mah department.

I guess I'll just have to spring for a new pack or two down the road sometime. I have to use what I've got for a while though. I'll keep playing around with them and see if I can get any better results. Mainly, I wanted to make sure that it wasnt normal for them to not charge and discharge their full rated capacity.
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Old 09-27-2006, 11:16 PM   #9
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Actually, a pack will take more than the mah the cells are rated for. Some of the energy is wasted due to internal resistance through heat.

It does sound like those packs are toast. They were probably stored too long with no charge or deadshorted, or theyre just beat.
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Old 09-28-2006, 12:10 AM   #10
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Cool deal. Thanks for help guys. I just wanted to be sure that it's the packs that are the problem, not me or the charger. Take it easy.

-Hank
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Old 10-07-2006, 08:53 PM   #11
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we run about thirty different packs and have used about 20 of them for almost two years. We're club racers. I picked up a Tekin Battery Doctor. I cahrge the cells normally then use a set of bulbs 20 amp total with a cut-off switch. Then I put the packs on the Battery Doctor.

The first time I did this I couldn't believe what a difference it made. It essentially brought old packs back to life.

We're in the same boat in that our batteries aren't what is keeping us from winning races....
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Old 10-07-2006, 10:33 PM   #12
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If you can .. have a friend with an Equalizing tray ,equalize them for you . this will make a noticable diffrence and wake up your paks .... Ive done it and can still practice and race with some of my 1 year old paks ... But its still better to have some fresh new Batteries for racing ...
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Old 10-08-2006, 01:02 PM   #13
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If the original poster is still hitting the walls and being marshalled a few times during a race I take the money he'd spend on new batteries and spend it on practice time at the track and entry fees to as many races he can attend. Once he's getting around well and beating people regularly then I'd spend more cash on batts.

Great thing for us is that the A-Main guys buy new batteries so often that we can buy their "old" packs for a great price and don't notice the difference between those packs and any I have purchased new.
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