[NSRCA-discussion] NiMH Question

[vicenterc at comcast.net]

If I were you I would keep the C/10 rates to charge and discharge.  I always noticed that the life of the batteries goes down when we go over C/10 rates.  In any event, the actual discharge rate when you use the batteries is never that high.  I strongly recommend that you replace those batteries.  Your plane is a lot more expensive.  When you get the new ones, keep C/10 rates for everything you do.  That is my personal advise.

Vicente Bortone

-------------- Original message -------------- 
From: "Michael Cohen" <precisionaero at comcast.net> 

I have 4 cells on each pack.  I am using the Hobbico Accu-Cycle Elite charger.  I know when I got the packs at first, I did a 0.1C charge/discharge cycle several times to get the packs up to their full potential.  I forgot who recommended that, but it seemed to work great.  After that, I never did cycle them again until this season.   As far as the other data, after this next round of cycling, I'll let you know.



----- Original Message ----- 1
From: Grow Pattern 
To: NSRCA Mailing List 
Sent: Thursday, February 23, 2006 8:58 PM
Subject: Re: [NSRCA-discussion] NiMH Question


I don't think that there is any value or advantage in cycling down an NiMH pack because they do not display any memory behavior. (Like a Nicad)

On the other hand I guess you/we will always need to know how much a battery has left in it.

I was told that you should not take an NiMH battery down too low. I have killed a few of them by leaving them on too long and once flew too many times and was lucky to get the plane down with one servo action at a time. The pack would not charge back up!

I am curious as to what charger/cycler you are using. How many cells and what voltage you show after charging and then with a 500 ma load?

Regards,

Eric.


----- Original Message ----- 
From: Michael Cohen 
To: NSRCA Mailing List 
Sent: Thursday, February 23, 2006 9:48 PM
Subject: [NSRCA-discussion] NiMH Question


I am cycling my batteries and getting ready for the flying season.  On my initial 5 cycle run at my NiMH batteries, both my 1650 mAh packs cycled very low.  One pack that I have not used since end of November only cycled up to 850 mAh and the other pack I have not used since end of September only cycled up to 1000 mAh.  My charger is set to 5 cycles, charge and discharge are set to .65 amps with a cutoff voltage at 1.1 Volts per cell.  I am now trying 1.00 amp charge/discharge with a 1.0 volt per cell cutoff and it is looking better, but I have some questions:

1)  Did I damage the batteries by letting them self-discharge too low?  I know NiMH batteries have a higher self discharge rate than NiCD batteries, but I am not aware letting the NiMH batteries run down could cause damage.

2)  Is this a normal behavior?  Maybe NiMH just need a little more juice at the beginning of the season.

3)  Is the cold garage a factor?

Thoughts?

Mike Cohen



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