RunRyder - Questions about charging NIMH batteries

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e-Electric Batteries & Chargers > Questions about charging NIMH batteries

jjvwg
Senior Heliman
Location: Boulder, CO

I am currently using the stock dx-7 1500mah battery and a hydrimax ultra 2000mah battery for my tx and rx. I plan to replace the tx battery with li-ion as soon as more are in stock from rodney. The rx battery is fairly new but i noticed today that when I charged it I only put back 1349mah of the 2000mah, and I discharged before hand. I have charged this battery less than 10 times.

I am concerned that I am not discharging and charging right and was wondering if you guys could clear some things up for me. My usual routine after a running the batteries down after a day of flying is to recharge the batteries the night before I plan to go flying again. My flying is sporadic as I am a busy college student so I'm wondering if there is any certain way I should store my batteries between flying sessions, should I leave them where they are at after the last session or should I store them fully charged?

I use a triton jr. charger and every time I use the discharge to charge function, discharging at 1A and charging at the appropriate current to do it in an hour according to the batteries capacity. Do I need to discharge all the time, or can I just recharge without discharging? If thats the case than should I be cycling the battery every so often? How often?

If I should be discharging every time before charging, should I use the discharge to charge function, or should that be used for cycling only? Should I just use the discharge function and then switch to the charge function?

Thanks in advance for the help guys, I really want to take good care of my batteries but it doesn't seem to be going to well right now.

Jeff

06-28-2008 10:05 PM

JKos
Elite Veteran
Location: City of California in the state of Maryland

NiCd and NiMh cells are typically capacity spec'd at a discharge rate of 1/5 C (or 400 mA for your 2000 mAh pack) down to 0.9 V. Discharging at a higher rate or higher cutoff voltage will yield a lower capacity reading.

Also not all NiMh cells like being charged at 1 C, especially high capacity AA size cells. Does the pack get overly warm when charging at 2 A?

- John

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06-30-2008 04:29 PM

jjvwg
Senior Heliman
Location: Boulder, CO

when I charge at 2A the battery feels fine, it just gets slightly warm.

So you are saying I shouldn't be discharging at 1A, but instead at 0.4A. I usually use the discharge to charge function and that automatically sets the cutoff voltage, if I use just the discharge option I set my cutoff voltage according to the 1.1*# of cells rule.

Do I even need to discharge every time before I charge my Nimh batteries, or can I just charge them back up to full and cycle them every once in a while to prevent cell memory.

Jeff

06-30-2008 05:26 PM

JKos
Elite Veteran
Location: City of California in the state of Maryland

> So you are saying I shouldn't be discharging at 1A,
> but instead at 0.4A

Basically, if you wish to compare the capacity of the pack to the stated capacity, you have to discharge under the same parameters that the manufacturers do. If you simply want to check the pack periodically, then you can discharge how you have been and just keep track of the results. If you see the capacity dropping off, then that would tell you the pack is degrading.

> Do I even need to discharge every time before I charge
> my Nimh batteries

No, you do not need to do that.

> cycle them every once in a while to prevent cell memory.

NiMh cells do not have memory issues. The only reason to cycle them is to check the capacity.

- John

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06-30-2008 05:58 PM

jjvwg
Senior Heliman
Location: Boulder, CO

Thanks

that helps a lot.

Jeff

06-30-2008 10:37 PM

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e-Electric Batteries & Chargers > Questions about charging NIMH batteries

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