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Old 01-03-2006, 10:48 PM   #1066
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Quote:
Originally Posted by asw7576
How about discharging at 25A ? or 35A ? Currently I'm discharging / cycling @ 25A because (1) the air temperature here is 33C (2) many said GFX get damage when discharging / cycling @ 35A.



What is safe number considering the air temp here is 33C.
asw7576,

Considering that 33C is HOT (91.4F) you should discharge at no more than 20A and with a fan on your pack. Do not use a fan while charging.

There is NOTHING WRONG with discharging at lower rates. We have found no differences in performance and the batteries will last longer when charged at lower rates.

I recommend to discharge at rates at or below 20A (see note). That is a safe range.
The issue is that the heat build up and because of thermodynamic issues, you run a very high probability of damaging the cells in the middle of the pack. If you ever measure the temperatures you will notice the difference.

NOTE:
BTW, 30 Amps is ok if the battery pack has been run and you only have <30% of the charge left. This will not affect the battery. The issue is when people cycle fully charged batteries at 30, 35A...then the heat factor becomes an important issue.

Being that it is hot where you are, you should consider charging UNDER THE SHADE... or with some loose cover to protect the batteries from direct sun light (heat). That will affect the charge too.

I hope this helps.

Isaac
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Old 01-03-2006, 11:05 PM   #1067
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Wow thanks man !!

One more question, my buddy said discharging at 20A makes your battery dumb. Current motors like 7x1, 8x1 pull high amperage like 25A range during 5 minutes racing. What is your comment?

I understand your reason for battery lifetime vs discharge rate. However, is it possible the battery become dumb if you often discharge at lower rates, eg. 20A ?
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Old 01-03-2006, 11:20 PM   #1068
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Default What about pulse dischargers?

Don't they keep the heat down and it lowers the IR of a cell? Or has there not been enough long term use with these pulse dischargers to tell how they are afftecting cells?
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Old 01-03-2006, 11:22 PM   #1069
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Quote:
Originally Posted by BATT_MAN
asw7576,

Considering that 33C is HOT (91.4F) you should discharge at no more than 20A and with a fan on your pack. Do not use a fan while charging.

There is NOTHING WRONG with discharging at lower rates. We have found no differences in performance and the batteries will last longer when charged at lower rates.

I recommend to discharge at rates at or below 20A (see note). That is a safe range.
The issue is that the heat build up and because of thermodynamic issues, you run a very high probability of damaging the cells in the middle of the pack. If you ever measure the temperatures you will notice the difference.

NOTE:
BTW, 30 Amps is ok if the battery pack has been run and you only have <30% of the charge left. This will not affect the battery. The issue is when people cycle fully charged batteries at 30, 35A...then the heat factor becomes an important issue.

Being that it is hot where you are, you should consider charging UNDER THE SHADE... or with some loose cover to protect the batteries from direct sun light (heat). That will affect the charge too.

I hope this helps.

Isaac
Maybe this is why LRP limit their charger to 10 Amp as their maximum discharge rate...ehehehe
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Old 01-03-2006, 11:27 PM   #1070
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Is it typically normal for a charger to be excessively hot during/after discharge? No matter what, but I cannot discharge a pack @ 3amps in 92F outside temperatures. I even tried a fan with no sucess.
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Old 01-03-2006, 11:32 PM   #1071
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Quote:
Originally Posted by Team Duratrax
Is it typically normal for a charger to be excessively hot during/after discharge? No matter what, but I cannot discharge a pack @ 3amps in 92F outside temperatures. I even tried a fan with no sucess.
Excessive hot is not good.... what charger do you use ? discharging at 3A ?
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Old 01-03-2006, 11:33 PM   #1072
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Quote:
Originally Posted by Team Duratrax
Is it typically normal for a charger to be excessively hot during/after discharge? No matter what, but I cannot discharge a pack @ 3amps in 92F outside temperatures. I even tried a fan with no sucess.
3 amps ?........ I cycled my new IB's out at 30 amps without any problems.......that was in 30 degree heat (Celsius)..... Its not the packs....
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Old 01-03-2006, 11:36 PM   #1073
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Quote:
Originally Posted by asw7576
what charger do you use ? discharging at 3A ?
Originally, it was designed for airplane batteries, hence the 1 to 25 cells limit.

http://www.rcbatteryclinic.com/nova.htm
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Old 01-03-2006, 11:43 PM   #1074
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I think you bought a wrong charger for RC application.

Don't cry.... I think you should buy MuchMore CTX-D when it release in Febuary 2006 ( automatic discharger up to 30A ) so you can keep the charger.
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Old 01-04-2006, 12:26 AM   #1075
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Quote:
Originally Posted by asw7576
I think you bought a wrong charger for RC application.

Don't cry.... I think you should buy MuchMore CTX-D when it release in Febuary 2006 ( automatic discharger up to 30A ) so you can keep the charger.
I won't cry. Many other people (mostly Aussies) use this charger without any problems, but I really do need a new charger, soon.
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Old 01-04-2006, 12:36 AM   #1076
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Yup, the charger looks good. It can charge 5A.
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Old 01-04-2006, 01:18 AM   #1077
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Quote:
Originally Posted by asw7576
Wow thanks man !!

One more question, my buddy said discharging at 20A makes your battery dumb. Current motors like 7x1, 8x1 pull high amperage like 25A range during 5 minutes racing. What is your comment?

I understand your reason for battery lifetime vs discharge rate. However, is it possible the battery become dumb if you often discharge at lower rates, eg. 20A ?
asw7576;

Does a battery have a BRAIN?
There is NO SUCH thing as a battery becoming dumb or having memory

These are GRANDMA STORIES.

As long as you upkeep your batteries by cycling them and not allowing them to stay for weeks w/o being used then you will be OK.
The battery does not care at what rate you discharge.
When a battery starts to loose its power and charge we cycle them at LOW CURRENT to bring them back to life...I guess that would make the battery smarter... Again...

The memory issue, which is not a memory at all, had to do with crystaline structures that would build inside a NiCd would limit the capabilities of the cell, thus some people called it MEMORY. That could happen in MiMh batteries, but as long as you cycle them and keep them with a charge while stored you will do OK.

Heat build up will make your battery dumber than dumb...

Batteries can not be trained. THAT IS A STOTY...and a GOOD ONE!!!

Don't worry, your battery will continue to be just as SMART if you dischrge at lower rates.

Isaac
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Old 01-04-2006, 01:30 AM   #1078
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i usually discharge mine down on the new 030 untill the lights go out. the last time i did this i didnt put any power back in and didnt use them for a few weeks. this isent hurting the cells is it?
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Old 01-04-2006, 01:34 AM   #1079
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If my battery doesn't care what rate it is discharged at, then what are we doing wasting all this time with 30amp dischargers.

Why not just throw on like a 100 amp load and make it dead in like 1 minute?

In all seriousness though, I am curious to know if you charge at say 10 amps, but don't let the pack peak at that amperage (like you take it off the charge early, or reduce the amp rate near peak mAh) then will that cause any deterioration to the cells. THis is considering they are NOT overheated during the charge.
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Old 01-04-2006, 01:35 AM   #1080
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fjm9898,

If you do not use your batteries for a while, it is a good practice to put a full charge on them. For short periods you can get by with just 1300mah.

NiMh batteries tend to discharge themselves as time goes by, so it is good to have them charged. This will avoid cell reversal and electrode decomposition.

Once you want to race again, I would discharge them on your 030 untill the lights go out (0.40volts), let them cool down and then charge as usual.

Isaac
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