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Old 03-16-2008, 02:58 PM   #1
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Default Need charging help please!

Could someone tell me the best charge rate for 7.2v 3600 and 7.2v 4200 mah sport packs. These are used for bupm boxes. I have been charging them at 3 amps but dont know if this correct. Thanks!
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Old 03-16-2008, 03:50 PM   #2
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You might not be get many replies in the nitro forum

3 amps sounds OK to me.

Remember, more amps = more torque, but lower amps = more runtime.
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Old 03-16-2008, 04:31 PM   #3
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You could do them at higher rates too.. it won't hurt them. About 5 amps is pretty common.
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Old 03-16-2008, 05:08 PM   #4
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Yep 5 amps is ok for race packs, charging them quickly allows them to "dump" quicker, but it will shorten their life too.
Remember heat is the enemy, if they get hot charging, or discharging, you are shortening their life.
IMO 1 amp if your not in a hurry, 3 if your a little pressed, and max 5 if your in a hurry.
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Old 03-16-2008, 05:12 PM   #5
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first discharge them as low as you can get them. Bug them even to take them down as deep as possible. Nothing wrong with charging them at 5amps. Discharging like every other recharge will help them not get a memory.
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Old 03-16-2008, 07:09 PM   #6
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If its not listed on the pack the best thing to do is charge it at its pack rating 3200 3.2 amps 4200 4.2 amps etc. You can usually get away with charging them faster though.
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Old 03-16-2008, 07:52 PM   #7
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As mentioned above, charging at 1C (3.6A for 3600mAh, etc.) is generally safe for NiMH packs. However, I disagree with the "discharge as low as you can" statement. Different vendors batteries generally have different likes and dislikes. Most of the new cells will die permaturely if you take them below 0.9v/cell. Since these are "sport packs" and probably are pre-assembled, you can't do what the on-road guys do and discharge each cell individually. Most people only discharge the individual cells down to 0.9 to 1.0V per cell (5.4 to 6V for a 6 cell stick). Since "sport packs" aren't generally comprised of matched cells, discharging them as a pack will result in individual cells being discharged to slightly different voltages.

Thus, even if the pack voltage is 6.0v, all of the cells probably won't be 1.0v each. Some more, some less. Then when you charge them up as a pack, some batteries will "peak" before others, creating the chance of overcharging one of more cells in the pack. Overcharging = heat = bad. I have had a pre-made "sport pack" pop a cell. It ain't pretty. If your charger has a temp sensor, use it.

With good quality matched race cells, most of the on-road guys charge around 6A.
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Old 03-17-2008, 10:32 AM   #8
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6.0 amps if you want a little extra power you could charge at 6.2a
also if you have a charger where you can ajust the peak sensor put it at 4-5 mv if you put it on the higher side the batterys are just going to get hotter.
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Old 03-17-2008, 10:45 AM   #9
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Thanks guys for all the input! I have been using a duratrax intellipeak until now. I felt like I keep getting false peaks with it. I just picked up the orion carbon charger. It says it does Lipo but only 2s? I take this means I could only do reciever packs with it. I would not be able to charge bump box packs. Is this correct? I'm just trying to learn how this stuff works.
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Old 03-18-2008, 06:49 AM   #10
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I have the orion advantage too. I don't know about the lipos yet. I haven't tried them yet.For now I'm sticking with brushless with regular batteries. lipos expensive and I'm worried about them starting on fire.
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Old 03-18-2008, 09:54 AM   #11
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Li-po's are easy most batt that are used in like 1/10 scale that drive the car are 2 cell 7.4 volts, then the traxxas came along with there 60 + brushless stuff and then all these company's said ohh boy to get these speeds we need to make up a 11.1 volt cell with 3 cells and this has now confused everyone mainly caus alot of company's came out with chargers made for the market that only charges 2 cell li-po, there are some guys that are running 11.1 li-po in there cars but u have to have a speed control that will handle it, I have a gtb control and I call novak and asked them if I could run a cell like that and I thought he blew my ear drum out with his nooooooooooooo. It seems a few people are doing this and speed controlers are going poof and then saying why? If u had a charger that chages 3c then a 11.1 volt li-po would be good for that starter box but if your charger doesn't
To this guy that is scared of a li-po pack starting on fire, it was the same thing when we went from ni-cd to ni-mh batt if people charge a batt with the wrong charger things will happen, last summer I was running 1/10 cale electric and 1/8 buggy at a race and I was charging my li-po batt then it was done and I told my wife to hook up my receiver pack (ni-mh) for a quick charge and she left on the li-po setting and after a couple min I smelled smoke and that receiver pack was up in flames, it can happen to any batt if charged wrong. I have been sitting back and listening to everyone about li-po's for awhile and it seems that the hobby stores are the one's really saying bad things about li-po's and brushless, I was in a hobby store (and I wont say which one) in milwaukee, wi and the guy behind the counter was doing this and I pointed out the pro's of li-po and brushless and he said thats right now we don't sell brushes,springs, motor lathes, batt bars,shrink wrap,and wire.
Saying they are more expensive my 2 daughters and my wife all have one batt and one charger, we go to the track they charge up practice, then run a heat or 2 and then recharge and run a main and then go home, batt-$90+charger-$79= $160 With the ni-mh batt each person had 4 batt-$30-$50, charger-$60 and then I would have to sit around and match cells, build packs all week and forgot about the discharger-$25 so total up around $250-300 each
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