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Old 02-03-2003, 11:52 AM   #1
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Default Battery Maintenace for GP/Nimh Batteries

Hi,

I've just ordered some new GP3300 NIMH batteries and wanted some advice on how to care for these batteries.

RacerHobbies.com recommended with this:

These cells should be charged at 5-6 amps with a re-peak of 5-6 amps just before you race. When finished racing, discharge pack to .90 volt per cell in the pack. The next time you plan to use these cells, discharge them at 1-4 amps down to .2V/cell before you charge them.

Promatch Racing wrote this on their web site:

The following information is for Panasonic 3000 UMH, GP3300, Sanyo 3000HV, and Sanyo 3300 cells.
Excellent results can be obtained by following these guidelines. After using the packs you need to determine if they are completely discharged or not. If you are not going to race the packs again for more than a week you should put at least 10 minutes of charge (at 4 amps) back into them. See footnote below** Leave the packs alone until the day before you are going to use them again. The day before you use them discharge them down to .9 volts per cell (5.4 volts for 6 cells and 3.6 volts for 4 cells) and let them sit overnight.
**Footnote: The longer you plan to not use the packs the more charge you should leave in them. For long term storage (more than 30 days), I would completely charge the packs before storing them. Also expect some false peaking problems of these cells after a long period of inactivity. This problem should correct itself after one or two uses.

For Panasonic 3000 UMH and GP 3300 cells. Right before you plan on charging your packs place them into the Smart Tray II to equalize the cells. After the last led on the tray goes out or 20 minutes on the tray (whichever occurs first) immediately put the pack on your charger and begin charging them. DO NOT DEAD SHORT NIMH CELLS! This will adversely affect them in the long term.


Question: What discharging device would you recommend that will discharge to .9volt per cell, and also can drop it down to .2 volt per cell. What's your opinion on this discharging method? They also mentioned that I need to avoid dead short. Can you tell me what dead short means?

One company recommends equalizing tray, and the other doesn't say anything about it. The one comment might be only to push their products. Any opinions on this would be appreciated.


If you guys do recommend a equalizing tray, any opinions on the Integy discharging trays?

Also based on what I'm reading, it doesn't appear to be harmful to NIMH to leave a charge on it. I'm gonna assume that based on what I've read, I need to ONLY discharge the night before I need to use them again.

I guess what I need is how you handle your new GPs, from charging to storing. Thanks a lot.

SpeedChair






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Old 02-03-2003, 12:08 PM   #2
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i have only had mine for about 4 weeks and i charge at 6 amps w/ .03 and repeak 6 amps w/ .02. discharge 25 amps to 5.4 and tray. i am using these about once a week and the punch has come up in them and seems to be leveling of now. i am happy with them.
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Old 02-03-2003, 12:13 PM   #3
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I'm sure you're going to get various replies but....I run nothing but Pro Match. Follow Jeff's suggestions. Buy a temp guage from them also. It works and my Turbo 35 confirms that every time I charge them.
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Old 02-03-2003, 03:04 PM   #4
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Do the cells get really hot because of the high current? I have been charging mine a 3.5 amps.
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Old 02-03-2003, 03:13 PM   #5
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3.5 amps is way too low and you will have a lack of punch and top speed. If you want to be conservative, charge at 5 amps with a .03 cutoff and repeak at that as well right before your run. For discharging, discharge at 20 amps to .90 v per cell or 5.40 v for the whole pack. I have heard traying the GP's hurts their performance so I have not done that to mine.
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Old 02-03-2003, 03:44 PM   #6
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Axiom --

What do you mean when you say you don't tray them? I wasn't sure if you meant overnight or the deep cycle discharge. I'm thinking about getting an Integy or Trinity discharge tray, that discharges each individual cell down to .9 volt per cell.

Thanks ahead for the clarification.

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Old 02-03-2003, 03:48 PM   #7
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Exactly what i said...don't tray them...don't put them on a discharge tray as I have heard from Danny of SMC that this hurts their performance.
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Old 02-03-2003, 03:51 PM   #8
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Axiom --

If I don't use a tray, can you suggest how I should discharge them down to .9 per cell. What discharge method do you use.

Thanks.
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Old 02-03-2003, 03:55 PM   #9
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Well what charger to do own?
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Old 02-03-2003, 03:59 PM   #10
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I own a Novak Mill Pro, and I currently use a Deans lightbulb discharger with a MP Product auto cut-off. I'm not sure what the cutoff value on this MP Product is?

BTW - we are talking about GP3300, right? It appears GP3300 and Sanyo 3300 should be maintained a little different because of their differences. What's SMC website address?
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Old 02-03-2003, 04:28 PM   #11
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I have been using the Turbo 35s to drop my GPs down to .9 per cell, but this is not the most accurate method. You are still looking at a 5.4V cutoff for the entire pack, not really at individual cells.

What you want is a tray that has a per-cell cut off, NOT a tray that takes them down to zero. Make sure you understand what kind of tray you have before you put the GPs on it.

Once the cutoff has been reached, take the pack off the tray and store it for the next use.

If you are planning on not using them for awhile, go ahead and put some charge back in, if you like that method. As a matter of personal preference, I drop mine to .9V per cell and leave them until next use. If I am not going to be racing for more than a week, I try and cycle them in between races.

For GPs:

Charge at 6A with a .05 threshold
Re-peak at 6A with a .01 or .02 threshold

I have had excellent success with mine so far.
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Old 02-03-2003, 04:30 PM   #12
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Quote:
Originally posted by Axiom5B
Exactly what i said...don't tray them...don't put them on a discharge tray as I have heard from Danny of SMC that this hurts their performance.
There is a difference betweening traying a pack for discharge purposes and leaving it on a tray for a longer period of time. A good tray that has a .9V cutoff is still the best way to drop your batteries down. Dump them on a charger to 5.4V and then tray it for the rest.

And, as I said, make sure you are using a tray that does not take the battery down to dead-short levels (like the ones we used to use with our Nicads).
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Old 02-03-2003, 09:06 PM   #13
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I've been charging at 5amp .02 cutoff (repeak with same charge 3-5 minutes before race). Discharge on Turbo35 at 30amp to 5.4. Then put on a Trinity tray until the bulbs are almost out. The longest my packs have ever gone without use is 4 days, so I don't know about long term storage.
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Old 02-03-2003, 09:28 PM   #14
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I appreciate all the information that you guys have provided. I guess there's more than one way of doing things, and maybe they all achieve the same result. Thanks again for the comments.

I won't comment on the cost issue of batteries for this hobby, that's been discussed enough and I've already shilled out my money for the GPs......

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Old 02-04-2003, 03:59 PM   #15
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Cany anyone recommend a discharge tray that has a cutoff of .9 volts per cell. I checked with Integy and all of their trays cutoff at zero.

Thanks.
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