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Old 02-28-2008, 04:00 PM   #1
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Default Discharge Rate Question.

I will be getting a Intellipeak AC/DC charge with the LCD screen that has a discharge rate of 2 and 10 amps.Witch one should I use for 3000 and 4200MAH NiMH,the packs are made up of sub-c cells and will be 7.2 packs.
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Old 02-28-2008, 06:38 PM   #2
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I would go with the 10 amps. These types of batteries are routinely matched at 20 to 35 amps. The typical cut off voltage is 0.9v per cell with these types of rates. Or 5.4v for the pack. If they are side by side it's a good idea to use a voltmeter to check them individually towards the end of the discharge. Stop if one goes much below 0.9v.

If you discharge at the 2 amp rate, you should probably use a higher cutoff voltage. Because the voltage drop due to resistance will be lower, meaning that the weakest cells will end up at a lower voltage. And Ni-Mh generally don't like being discharged to a low voltage.

Good luck.
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Old 02-28-2008, 07:41 PM   #3
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If I do use the 2 AMP discharge rate would it help if I put them back on charge for 5 or 10 mintues.Or would it be best to take the batterys and run them down in the car and leave them until I wasnt to charge them and then discharge them before charging the pack.What I thinking is because the cells won't get a chance to rest so would that make a diference as far as the cell going down to a to low of a voltage and the cell will not have a chance to rest in a low voltage stage and then like a little kid that has had something done to them that they do not like and has time to stew about it and then throw a tantrom,what I mean by my comparing a cell to a little kid is that sometimes when you know something is wrong with a kid and the longer you wait to deal with it the more of a pain in the ass it is to make the kid to come around to your way of thinking.
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Old 02-28-2008, 08:41 PM   #4
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if you try to discharge a fully charged 4200 at 2amps, you are gonna be waiting for quite some time. i recommend fully discharging after a run and then peak the cells. also do not leave nimh stored without any charge in them, it will kill the battery life. try to use a discharger like a trinity DPD which will discharge each cell and stop the cell at .9v so you don't ruin the cell
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Old 02-28-2008, 08:45 PM   #5
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Ni-Mhs do like to be stored with some charge, even need to be charged some once in a while if you don't use them.

But, this does not reverse the damage caused by over discharging them. Especially if they are reversed. This is if stronger cells cause a weaker cell to actually go to negative voltage. Not good.

A slow discharge before charging is good, but only with a battery tray or such that discharges each cell individually.

Doesn't matter if you have a Team Whatever matched pack, because Ni-Mhs are not stable enough to stay matched.
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Old 02-28-2008, 09:19 PM   #6
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Bulldawg I would never try to discharge a fully charged pack was just wondering if I should run them down low in my car then store them with whatever charge is left then discharge them before charging and then charge them and go play.
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Old 02-28-2008, 10:22 PM   #7
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No. Top them off before storing them. Top them off every couple of weeks if you won't be using them.

Here's my cycle of batteries.

The day of a race I will use the Tekin tray that discharges each cell. Then charge the batteries full. Run a race. Top them off again. Then I use that battery for the third qual. or the main. A different battery is used for other qualifiers, but it gets the same treatment. When I get home I top off the batteries again and wait till next weekend. A minimum of two Nimh's is needed for a day of racing for one vehicle. Unfortunately I have two vehicles and I require lots of practice so I have 8 packs that get used during one race day.
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Old 02-29-2008, 04:08 AM   #8
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Wade, we are all saying the same thing. Do not store them discharged.

That was Ni-cads. These are Ni-mh.

And we also agree that you need a battery tray to properly do the discharge thing before charging. If not, you will end up reversing and killing cells. Otherwise you are better of not discharging beyond stopping as soon as the car slows down.
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Old 02-29-2008, 04:37 AM   #9
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Oh, and don't be worried about discharging every time. Many of us, including some nationally competitive racers I know, only occasinally discharge their ni-mhs all the way.

Ni-cads are a different story, those do need to be hammered all the way down every time. And are best stored discharged.

Good luck, bud!
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Old 02-29-2008, 06:32 AM   #10
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Dave I understand about storing the NiMH not discharged but where I'm not sure is do I store them fully charged are put 5 or 10 minutes of juice back in them.I know you said they like to sitting with some charge in them how long and at what charge rate do you put yours on for if you are going to fully charge your packs before storing.thanks for all your help guys.
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Old 02-29-2008, 01:35 PM   #11
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If you plan on racing again within one to two weeks just pull the car off the track and put the batteries away until then. If you don't plan on running for longer than two weeks then it's a good idea to peak the pack before you put it away.
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Old 02-29-2008, 01:44 PM   #12
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dude get lipos, nimh is old news. nimh cells go to shit after like 20 cycles sometimes sooner. I know i am gonna get flamed but he is new to eletric side of the hobby and prolly gonna be using these more then once a day.

go lipo and never go back.
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Old 02-29-2008, 01:55 PM   #13
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RB Five, do you think is it feasible to run one lipo pack the whole race night? As in run one heat, throw it on the charger, and pull it off as soon as the next heat comes, etc...

Would the 3600 Orion pack be up to this kind of task? (The 4800-5000 lipos should handle this no problem, I'm thinking)
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Old 02-29-2008, 01:58 PM   #14
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Quote:
Originally Posted by stitchy View Post
RB Five, do you think is it feasible to run one lipo pack the whole race night? As in run one heat, throw it on the charger, and pull it off as soon as the next heat comes, etc...

Would the 3600 Orion pack be up to this kind of task? (The 4800-5000 lipos should handle this no problem, I'm thinking)
I run one pack per car. My 4800 makes it all three qualifiers and a 6 minute main on one charge. I charge my 3600 between round 2 and 3 and it goes all night. Two is optimal, but one is enough to race a whole night.
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Old 02-29-2008, 02:01 PM   #15
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Quote:
Originally Posted by SQC049 View Post
I run one pack per car. My 4800 makes it all three qualifiers and a 6 minute main on one charge. I charge my 3600 between round 2 and 3 and it goes all night. Two is optimal, but one is enough to race a whole night.
wow that is cool. With the 4800, you don't get nervous about running out of juice during the main? How do you make sure you'll last?
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