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Old Nov 27, 2006, 4:00 AM   #1
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Hello every... First post here!

Using the advice found here and on CandlePower forums, I decided to purchase a BC-900 charger. I have been using 20 Energizer 2500 mah batteries with the Energizer brand travel charger for almost a year now.

Along with my new charger I got 20 Sanyo Eneloop AA and 8 Eneloop AAA batteries... Not to mention the four of each that came with the new charger.

I have spent an hour searching the forum for advice on what charge rate is the best to use for optimal battery life, but I can't find anything here.

So, in your opinions, which charge rate should I use? I will occasionally use the fast charge for the Energizers if I need them in a hurry, but typically I will not need to fast charge any batteries. The eneloops will be used for most household applications and the Energizers in some high drain applications like bicycle LEDS, kids electronics, frequently used motorized toys, etc. Also I plan to use some Energizers in D and C cell adaptors for baby toys / vibrating chairs, etc... (Yes, I know they only offer a fraction of the D and C cell capacity... But the money savings could be significant if they are acceptable.)

Thanks for the info folks... And BTW my camera is a Canon Powershot G6, so I can't use my rechargeables in it
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Old Nov 27, 2006, 9:47 AM   #2
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Hello RobSpook,

Battery manufacturers recommend charging on a smart charger at a rate equal to 0.5 C - 1.0 C, where C is the mAh capacity of the cell.

If you are charging a 2000 mAh cell, the recommended charging current would be in the 1000 mA (or 1 amp) to 2000 mA (or 2 amp) range.

The reason for this is that smart chargers rely on an end of charge signal to terminate the charge. If it doesn't detect the end of charge signal, it continues to charge, which can result in damaged cells. The battery manufacturers have suggested this charge rate because it gives a strong end of charge signal.

You can charge at lower currents, but you need to monitor the charge closely and manually terminate it if the cells get hot. Cells will warm up at the end of the charge, but they should not get hot. Hot is around the temperature of a baked potato right out of the oven. You can toss it from hand to hand, but can not hold it in your hand.

You may find that the charger is able to detect the end of charge signal at lower rates, but it is always recommended that you set a timer to remind you to check on things just in case it doesn't detect it. Keep in mind that new cells can be very difficult to charge until they have a few discharge/charge cycles on them.

I always recommend taking some precautions when setting up your charging station. Your charger should sit on a non combustible surface and out of the reach of children. I have already mentioned that a timer is very useful.A smoke alarm and a fire extinguisher may bring you "peace of mind" against any problems that you may encounter. Keep in mind that stored energy can be dangerous, and when you are charging batteries, you are storing energy.

Tom
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Old Nov 27, 2006, 2:24 PM   #3
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All written by Tom is 100% correct. However, when it comes to the BC-900 I prefer to use a bit lower charging rate. After using this charger for a year I settled for a charging rate of 700 mA. I found that, at 1000 mA the cells are heated too much, which causes the thermal protection to be activated, especially if the ambient temperature is above 20 degrees C. 700 mA still gives me strong enough signal to terminate the charge safely, without generating too much heat.
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Old Nov 27, 2006, 8:43 PM   #4
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I charge my 2500 mAh cells @ 500 mAh with the BC-900. I haven't had any charge termination issues, although I did with the 200 mAh setting.
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Old Nov 28, 2006, 5:48 AM   #5
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Thanks for the replies fellows. Very informative indeed! Becuase I live in Germany currently, most charging will be done on tile floors, and fire hazards are not too big an issue because the walls/floors/ceilings are all cement and tile. I have experience in rechargable batteries from my R/C Airplane hobby and am familiar with charging packs. Charging individual cells is new however.

From the advice here, I guess I will use a 700mah setting for charging since our house thermostat is set to 20.5 degress celcius.

Too add to the original question, I have some 600mah Ni-cads that I might continue to use. Does the charge termination issue at 200mah also apply to Ni-cads? I guess using Silver's formula .5-1c I can safely use the 500mah setting, but it seems like it would charge these older cells to quickly.

I found this site: http://shdesigns.org/batts/battcyc.html comparing the discharge curves of Ni-cd and Ni-MH batteries, but was wondering how Ni-cd compare to Ni-MH for shelf life after charging?
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Old Nov 28, 2006, 6:12 AM   #6
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RobSpook wrote:
Quote:
I found this site: http://shdesigns.org/batts/battcyc.html comparing the discharge curves of Ni-cd and Ni-MH batteries, but was wondering how Ni-cd compare to Ni-MH for shelf life after charging?
NiCd self discharge a bit slower than NiMH, usually their self-discharge does not exceed 1% per day, and often is even lower.
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