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Old 11-07-2002, 12:40 AM   #1
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Default Help needed!! Please reply fast! Thank you

Hi,

I would like to know why is it that when charging the battery the thrushold voltage between Ni-Cd and NiH battery are so different? Also, why is it that this method is used to detect the full charge of the battery? Why not just use the make the charger recognize the very peak of the pack, instead of having it check for the sudden drop in the pack?

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Old 11-07-2002, 01:55 AM   #2
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because different packs will peak at different voltages?
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Old 11-07-2002, 02:06 AM   #3
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The reason why it senses for a drop in voltage is due to the battery 'not allowing' those volts to be put into the battery. Its like feeding the battery until it starts puking up loads of volts (gross reference huh.) The reason why we can't stop batteries after it starts to drop just a little, the closest to its peak is b/c the pack may be old and have more resistance (I know its something else; help me) and if you were to cut charging as soon as the voltage began to drop, the battery would not be fully peaked.
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Old 11-07-2002, 07:00 AM   #4
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Default Re: Help needed!! Please reply fast! Thank you

Quote:
Originally posted by TRF-Powered
Hi,

I would like to know why is it that when charging the battery the thrushold voltage between Ni-Cd and NiH battery are so different? Also, why is it that this method is used to detect the full charge of the battery? Why not just use the make the charger recognize the very peak of the pack, instead of having it check for the sudden drop in the pack?

thanks for all replied
Thrushold? I've heard of pigeon fancying but that is just ridiculous...

So far as I am aware the voltage actually continues to rise as you charge the pack, so you can't detect the peak itself.
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Old 11-07-2002, 10:37 AM   #5
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Ok it's quite simple, Ni-CD cells aren't as stable while charging as Ni-MH cells. So if you where to watch the battery charge on a digital voltmeter that can read out to .001 volts you would see Ni-CD's go up a little, slightly go down, go up some more.....ect.. where Ni-MH cells you wuld almost need a voltmeter to read .0001 to see as much activity during the charge.

Now some Ni-MH cells rspond tobeig a little more over charged than others... for instance----

Most 3000's like a delta peak between .003-.005 per cell....
Where 3000HV's prefer a delta peak around .007-.009
And most Ni-CD cells like .013........
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Old 11-07-2002, 09:47 PM   #6
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Quote:
Originally posted by Im2lazy
...and if you were to cut charging as soon as the voltage began to drop, the battery would not be fully peaked.
I don't know much about NiMHs but Nicads exhibit a small voltage drop at the start of charging, after which the voltage just starts increasing. Some chargers start charging with 0.1C for a few minutes to work around this voltage drop, then starts hammering the battery with the full charging current.
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Old 11-08-2002, 02:05 PM   #7
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Why even PEAK. I charge my 3000HVs at 7 amps. I watch the mah on my charger, and when it gets to about 2.4 or 2.5 I cut it off manually. (2400-2500 mah) Then right befor the race, I charge again for about a minute, just to warm them up a little. I never let them charge all the way to 3000 mah. They would get too hot. When I have cycled the batteries like this on 20 amp light bulbs, with a volt meter. the voltage is incredible. It will stay above 7 volts till about 4:15. For stock racing that is great. I have found the same thing with my 2400s....cut them off around 2200mah and WATCH OUT!!!!
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