Opinion on Battery Condition - RCCanada - Canada Radio Controlled Hobby Forum
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Old 03-08-2005, 08:59 PM   #1
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Opinion on Battery Condition

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I fully charged my T(x) and R(x). Then, I let them just sit for 6 hours (until I got home from work).

The T(x) is a 8 cell, 600ma, 9.6 volt pack.
The R(x) is a 4 cell, 600ma, 4.8 volt pack.

This is on a Futaba 6YG radio (new last year).

I then discharged the R(x) pack at a rate of 1A (per the Futaba BR2000 battery checker/discharger). After 23 minutes, the pack was at 4.5 volts, and after 30 minutes, the pack reached 3.6 volts and the unit shut off.

For the T(x) pack, I simply left the T(x) on. According to the guage on the T(x), the pack reached 90% after 2.5 hours, and was at zero after 3 hours, 20 minutes.

So are these packs in good condition? I'm fairly confident in the T(x), but not so sure about the R(x).

Colin Jensen
Regina Windy Flyers
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Old 03-08-2005, 09:52 PM   #2
Gary Maker
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Although you can discharge ni-cads lower, it is not recommended to discharge them below 1.1 to 1.0 Volts pr cell or for a 4 cell pack down to 4.4 to 4.0 Volts and an 8 Cell pack down to 8.8 to 8.0 Volts. When discharging below the recommended cutoff voltage, you risk having one or more of the cells in the pack to go down so far that it causes a condition known as "cell voltage reversal". That is, the poles of the cell will actually reverse with the + becoming - and the - becoming +. When trying to charge the pack again the cell could short out and vent, ruining the cell or the entire pack!

You have probably not damaged the pack but you should be carefull when discharging your pack to prevent this known condition and destroying it! It is best to use a charger/cycler that has an automatic voltage cutoff to prevent the cell from going lower than the recommended cutoff voltage!

Use your charger/cycler and cycle the pack a couple of times to get a good reading on the pack. If you get a capacity reading that drops below 85% of the packs rated capacity, then yes, your pack is no good and should be replaced. Anything above this is considered to be ok but even then, you should regularily, while flying ,after each flight, check your packs with an ESV to assure they do not drop too quickly below the safe flying voltage! As long as the ESV gives you a reading in the "Green" its ok to fly another flight!
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Old 03-08-2005, 09:56 PM   #3
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I have read that on this site before - the fact that you should not discharge beyond 1.1 or 1.0 volts per cell. The BR-2000 discharger goes to .9 volts per cell. I presume since Futaba made it, they either know what they are doing, or want to cell more batteries!
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Old 03-09-2005, 07:38 AM   #4
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I don't know that charger but, I assume the cutoff voltage is adjustable?

As I understand it, cells use to power an electric motor should be treated differently than cells used to power a radio, the reason is long and involved but, with every charger manual I've read, lower cutoff voltages are recommended for cycling cells used to power motors....

Great site for a more in depth discussion...


Also, your 1A discharge rate seems a bit aggressive for a 600mah pack. As a rule of thumb (and to prolong the life of my packs), I generally aim for a 1C discharge rate (which would be .6A in this case). No worries, just a comment, Nicads can certainly handle your 1.7C load. Don't forget to allow for a cooling period before recharging (if your charger doesn't already handle this).
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