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Old Mar 08, 2010, 01:05 PM
grfcon is offline
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Question

nimh charging/discharging quesing Battman B6 (accucel 6 clone)


Sorry to hassle everyone for questions.

this charger didnt come with a temp probe.. I plan to purchase one for it.
I picked up some ultralast green batts from walmart... 2100 mah capacity
http://www.ultralastgreen.com/

I tried to slow charge (.1 amps these but didn't know the timer was on)

will this hurt the break in at all.?

I know heat is the enemy... will overcharging at this slowest rate hurt these if left on too long?

Setting Recommendations/ Questions help please

I got the timer off...what and how do I set the peak detection for NIMH to?
is it by volts? mah? what does the millivolt setting do? Sorry I am just kinda lost on this..and don't want to screw up these new batteries...I am 45 pages into the turnigy accucel 6 thread but still can't quite figure it out ..sorry

thanks
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Old Mar 08, 2010, 02:16 PM
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On that and similar chargers charging NIMH batteries is controlled by current, not voltage.

If you have the current set to < C/.3 (or .7 Amps (700 mAh) on the 2100 mAh battery) the peak detection probably won't work and you'll need to set the timer for about 14 hours. Also, the current is so low it probably won't heat the batteries at all.

Above C/.3 peak detection will come into play and you'll also need to watch the temperature.

For setting the peak detection for NIMH, just use the DEFAULT setting.
If I understand your question about the millivolt setting, that's the amount of voltage drop during charge that will cause the peak detection to cut off charging. The DEFAULT setting for NIMH batteries is 7 millivolts. You can set it lower (might cut off the charger too soon due to false readings), or higher (might allow the charger to overcharge the battery by not sensing the voltage drop at all), so be careful when changing this setting.

Bill
Last edited by Sir Raleigh; Mar 08, 2010 at 03:58 PM. Reason: Corrected NiMH peak detection Default from 0.7 millivolts to 7 millivolts.
Old Mar 08, 2010, 03:11 PM
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Originally Posted by Sir Raleigh View Post
On that and similar chargers charging NIMH batteries is controlled by current, not voltage.

If you have the current set to < C/.3 (or .7 Amps (700 mAh) on the 2100 mAh battery) the peak detection probably won't work and you'll need to set the timer for about 14 hours. Also, the current is so low it probably won't heat the batteries at all.

Above C/.3 peak detection will come into play and you'll also need to watch the temperature.

For setting the peak detection for NIMH, just use the DEFAULT setting.
If I understand your question about the millivolt setting, that's the amount of voltage drop during charge that will cause the peak detection to cut off charging. The DEFAULT setting for NIMH batteries is 0.7 millivolts. You can set it lower (might cut off the charger too soon due to false readings), or higher (might allow the charger to overcharge the battery by not sensing the voltage drop at all), so be careful when changing this setting.

Bill

thanks Bill

I had heard charging at .1 amps was good for fomation charging to balance out a nimh pack as at this rate it won't hurt a stronger cell much if the pack is out of balance....
how does this millivolt function work?... does it measure a bad cell? what causes the voltage drop during charging? or is this a function of the software as one gets close to peak voltage? what is the Default voltage setting 1.2/cell? I had heard this can be reset to as high at 1.45/cell

have you used this charger for cycling? would you set cutoff voltage at 8.0volts or 7.2? assume .3 amp discharge? and do you recommend any particular wait time btwn cycles to dissipate heat buildup?

thanks
Old Mar 08, 2010, 03:57 PM
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Quote:
Originally Posted by grfcon View Post
thanks Bill

I had heard charging at .1 amps was good for fomation charging to balance out a nimh pack as at this rate it won't hurt a stronger cell much if the pack is out of balance....
This is correct. Actually charging at or below C/.3 is okay for a forming/balancing charge.

Quote:
Originally Posted by grfcon View Post
how does this millivolt function work?...
As the battery reaches full charge the battery will begin to heat up and the voltage will begin to drop off a slight amount. This voltage drop is sensed by the peak detection circuit and when it drops off by the amount of the peak detection setting (7 millivolts DEFAULT) the charger is turned off. This is assuming a charge rate at or greater than C/.5, or half the battery's capacity.

Quote:
Originally Posted by grfcon View Post
does it measure a bad cell?
No, there's no way to detect a bad cell in Nixx chemistry. You'll have to check each cell individually with a voltmeter.

Quote:
Originally Posted by grfcon View Post
what causes the voltage drop during charging? or is this a function of the software as one gets close to peak voltage?
The voltage drop is caused by the battery chemistry. The software only detects the voltage drop and acts upon it.

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Originally Posted by grfcon View Post
what is the Default voltage setting 1.2/cell? I had heard this can be reset to as high at 1.45/cell
On my charger, which is similar to yours, but not the same brand, has a range of from 5 to 20 millivolts per cell. The default for NiMH is 7 millivolts and the default for NiCd is 12 millivolts.

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Originally Posted by grfcon View Post
have you used this charger for cycling?
Once or twice.

Quote:
Originally Posted by grfcon View Post
would you set cutoff voltage at 8.0volts or 7.2? assume .3 amp discharge?
I would set cutoff voltage to 0.9 volts/cell.

Quote:
Originally Posted by grfcon View Post
and do you recommend any particular wait time btwn cycles to dissipate heat buildup?
My charger will discharge at .5 Amps max, so I've not had any heat problems. However I might give a 3 - 5 minute wait between cycles just to give the voltage of each cell a chance to settle down.

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thanks
You bet...

Bill
Old Mar 08, 2010, 04:00 PM
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awesome Bill

thanks a Ton!!]

Gary
Old Mar 08, 2010, 04:10 PM
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Any time.

Happy flying

Bill
Old Mar 08, 2010, 04:16 PM
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last question I hope


[QUOTE=Sir Raleigh;14541316]This is correct. Actually charging at or below C/.3 is okay for a forming/balancing charge.

As the battery reaches full charge the battery will begin to heat up and the voltage will begin to drop off a slight amount. This voltage drop is sensed by the peak detection circuit and when it drops off by the amount of the peak detection setting (7 millivolts DEFAULT) the charger is turned off. This is assuming a charge rate at or greater than C/.5, or half the battery's capacity.

If I formation charge at 1/10th C say .2 amps in my case for a 2100 mah nimh.... will the the 7 mv default peak detection work or should I slightly adjust it? and where to...thanks
Old Mar 08, 2010, 04:28 PM
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The dependability of the peak detection is very iffy when charging at or below C/.3 and I wouldn't depend on it no matter where the detection voltage is set because the battery is being charged so slowly the battery chemistry doesn't react quick enough for the voltage to drop fast enough for the charger to detect it. In this case I would set the timer for 14 - 16 hours.

Bill


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