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NIMH Lost a lot of capacity how come?

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NIMH Lost a lot of capacity how come?

Old 09-12-2009, 08:26 PM
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klaze
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Default NIMH Lost a lot of capacity how come?

Just curious if I can get the capacity in my NIMH packs back and if not why did they drop so fast?

I have nimh packs for my rc18..

They are 1600 mah.. I charge them, run them, recharge them and wait until I use them again.

My 1600 packs are only charging to about 1000mah..

Does draining the pack too far lower the capacity? I run them until I feel the car slowing down..

Anything I can do?

Old 09-12-2009, 09:55 PM
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Default RE: NIMH Lost a lot of capacity how come?

My guess is that you're only using about 1000 mah's from a full charge..............thats what your putting back in.
Old 09-12-2009, 10:23 PM
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Default RE: NIMH Lost a lot of capacity how come?

They seem to be self discharging in between the recharge and then the charge. If I understand then you recharge at end of the run and then let them set until the next charge. The 1000 mah is the self discharge plus the warm up plus the part that is lost. The important thing is that they are full and warm right before the run.

If the charge shows 1 ah then what does the recharge show after the run?
Old 09-12-2009, 10:37 PM
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klaze
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Default RE: NIMH Lost a lot of capacity how come?

I run them.. Let them cool and recharge them..

They recharge to about 50 - 60% of their capacity. 800 - 1000 mah..

I really doubt they still have another 40 - 50% mah left in them when I put them on the charger because I run them until the car is very slow..

I am using 5mv peak also..
Old 09-12-2009, 10:38 PM
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Default RE: NIMH Lost a lot of capacity how come?

What brand cells are they and how old are they?
Old 09-13-2009, 04:51 PM
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Default RE: NIMH Lost a lot of capacity how come?

I'm guessing that they are not getting full.
Old 09-13-2009, 05:04 PM
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Default RE: NIMH Lost a lot of capacity how come?

Actually, running a pack down to 600mAh from 1600mAh (37% of the batteries capacity) is probably about right. NiMH batteries voltage doesn't stay constant; their voltage drops as the batteries discharge. Your car will stop running when the FETs aren't getting enough juice, not when the battery fully discharges. These two events may not be related. At 600mAh capacity, the cells' voltages may only be .5 volt under a 10A load (5w power) instead of the .8-.9V under a 10A (8-9W) load when the battery is freshly charged. The more efficient the ESC and drivetrain, the lower voltage it can use. Conversely, if you put on larger tires or put on taller gears, this will also effect the power needed by the motor necessary to turn the tires.

you can cycle the NiMH and see if you can get its capacity up but I think it is probably about right.
Old 09-14-2009, 12:55 PM
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Default RE: NIMH Lost a lot of capacity how come?

What batteries and what charger are you using? How long is it between runs? and the time period that the 600mah was lost? very important questions..

losing 600mah over several years is reasonable, but over the course of a month or two is really poor.
Old 09-14-2009, 01:09 PM
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Default RE: NIMH Lost a lot of capacity how come?


ORIGINAL: rebuilder

What brand cells are they and how old are they?
Klaze?
Old 09-14-2009, 01:12 PM
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TIGER76
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Default RE: NIMH Lost a lot of capacity how come?

Does draining the pack too far lower the capacity? I run them until I feel the car slowing down..
Shouldnt do m8 i run mine like yours til the car creeps but i discharge them after before recharging them.
Like dale said there start to lose power as soon as there off the charger my 5000mah left for a day or too drops to about 3800-4000mah but as long you cycle your nimhs and look after them they should be fine but the discharge rate is rubbish unto lipo batterys

My 1600 packs are only charging to about 1000mah
That doesnt sound right its usually over the mah like my 4600s on a multimeter read over 4900mah after a charge so i would try cycle the pack and see if that helps out
Old 09-14-2009, 02:01 PM
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Default RE: NIMH Lost a lot of capacity how come?

Age, use and how they have been treated are the primary factors. Until we hear more about that, then everything is simply speculation.
Old 09-14-2009, 02:44 PM
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john01374
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Default RE: NIMH Lost a lot of capacity how come?

It's not unusual to have 600 to 800 mah left in a pack after running. I use to run my old Nimh batteries until the car wouldn't move. Even on good packs I was only putting 3000 to 3200 back in them (they where 3800mah packs). If your packs have been sitting for a while just cycle them a few times and see if they improve but I wouldn't expect much from a 1600mah pack. Maybe it's time for some new packs. If you're just bashing then pick up some Tenergy packs or make the jump to Lipo. If you can afford a new charger and balancer then Zippy Lipo's are a much better option.

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