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HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › NiCad and NiMH question
01-17-2009 07:19 PM  9 years agoPost 1
synodontis

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United Kingdom

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here's the problem:

3 RX packs 2400 mAh NiCad
1 TX pack 2700 mAh NiMH

when I put them on the charger to charge I could only get about 100 - 150 mAh before the charge cuts out saying that the batteries are full. I obviously can't use them like this, so I'm asking, should I get rid of these batteries (they are over 4 years old but not had that much use and I probably stored them at low charge - I know I shouldn't of). I tried using my charger to cycle them, but all that does is reach about 100 - 150 mAh and switches to charge/discharge again, never reaching full capacity for the pack.

The strange thing is that I can put the RX pack on a straight trickle charger that came with my PCM 10X (output 120 mAh) for 20 hours and the RX pack seems fine, just the microchip charger cuts off when the pack reaches a certain voltage.

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01-17-2009 07:41 PM  9 years agoPost 2
tadawson

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Lewisville, TX

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Try cycling them at a pretty low charge/discharge rate, and if they don't come back, they are dead. When cells need to be "reformed", the internal resistance can go up, causing higher charge rates to false peak . . . .

And you say that after 20 hours on trickle, the RX pack seems OK. Have you done a discharge test to verify capacity, or how do you come to this conclusion? 5000 hours on a trickle charger on a bad pack, and it *still* won't be able to deliver much usable power . . .

- Tim

Friends don't let friends become electrotarded . . . .

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01-17-2009 07:56 PM  9 years agoPost 3
synodontis

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United Kingdom

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they cycle at low rates, but they just DON'T reach their full capacity, just 1/20th of it!

20 hours on a trickle charger at 120 mAh gives me 2400 mAh which is the capacity of the RX pack, this is a force charge, the proper charger won't let me do this since it has a cut off voltage. I will do a discharge test now on the packs . . .

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01-17-2009 10:10 PM  9 years agoPost 4
tadawson

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Lewisville, TX

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And you can discharge the 2400 mah from that battery at a normal rate? If that is the case, then you might want to check the connectors and plugs on your "smart" charger - if you have a wire breaking, it can cause a high resistance, and your charger can react in exactly that manner, due to the voltage drop across the flaw. That, or check you charger setup . . . if you can draw power from a battery at a normal rate, there should be nothing stopping you from charging it at that same rate . . .

- Tim

Friends don't let friends become electrotarded . . . .

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01-17-2009 10:59 PM  9 years agoPost 5
synodontis

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United Kingdom

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erm, no.

discharge of RX pack which should have 2400 mAh in it only gave 1000 mAh on discharge. I take it my battery is old, compromised but still usable? Although at less capacity than before?

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01-17-2009 11:10 PM  9 years agoPost 6
tadawson

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Lewisville, TX

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It's what you can draw out of a pack that matters, not what you can put it . . .

Normally, somewhere between 80 and 90 percent of rated capacity is considered the standard for usability. Since you are only getting somewhere around 40 percent, I would not trust it for anything beyond a paperweight . . . . that battery has some serious internal degradation! What happens is that the internals on a battery tend to decay, causing both the current delivery capability and capacity to degrade. In the early stages, some charge/discharge cycles can bring the chemistry back to life, but that far gone, it's likely that mechanical damage is happening as well, which could result in a sudden, catastrophic failure of the pack.

Pitch it . . . .

- Tim

Friends don't let friends become electrotarded . . . .

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01-17-2009 11:28 PM  9 years agoPost 7
synodontis

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United Kingdom

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well, thanks for the advice. I will dispose of them all at a NiCad recycling store and get new packs. That will teach me to store things uncharged and for a very long time...

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01-19-2009 04:58 AM  9 years agoPost 8
tadawson

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Lewisville, TX

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I don't think it's as much the uncharged as the amount of time. NiCd/NiMh will self discharge, so over a couple of years, starting with them full would make no difference in the long run. Myself, I try to cycle things at least once in the middle of the off season (which reminds me, I am due . . . ) and have some 4 year old or so packs that are still at better than 90% capacity.

- Tim

Friends don't let friends become electrotarded . . . .

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01-19-2009 05:03 AM  9 years agoPost 9
oysifly

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Bentonville, AR

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Sounds like you are getting a false peak from the battery...try turning down your MW setting and charge it again.

Quick...here comes my wife....hide that new Heli !!!!

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