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Old Sep 30, 2008, 08:27 PM
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Colorado
Joined Jul 2007
567 Posts
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CellPro 4S: 1C Fast Charge vs Actual 1C Charging?

Now that some of my batteries are getting high cycle counts on them I'm starting to notice that it takes longer to charge on the 1C Fast Charge setting.
As I watch the charge it seems that it is taking longer for the charger to reach the true 1C charge rate, it doesn't stay at that rate as long and the charger starts to ramp down the charge rate more quickly.

I assume this is happening because the batteries are starting to weaken and the charger is sensing that and adjusting the charge rate accordingly.
Is my assumption correct?

Now, when I manually set the charger to a charge rate that coincides with a true 1C rate (1.75Ah for a 1800mAh lipo) the 4S immediately goes to the set rate, stays there longer and doesn't start reducing the charge rate until the balancing, last 10%, stage.
This results in a much faster charge.

So, is it better for the Lipo to use the 1C, 2C or 3C Fast Charge modes?
Does this allow the charger to determine what is best for the battery?
If my batteries are getting weak is setting the charge rate to a real 1C a bad idea?

I really don't think I fully understand what's going on here.
Thanks for any insight you can give me.
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Old Oct 01, 2008, 03:53 AM
Baptised Heathen
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Bundaberg, Qld, Australia
Joined Jun 2002
1,365 Posts
I am no expert by any means, but I think that as the IR builds up in the pack the charger sensing software takes a bit longer to get to the 1C rate. By setting the charge rate you bypass the sensing software and the charger goes right to the 1C rate resulting in a faster charge. By the way, "seems to take longer" is very subjective and it could be just that you are getting more impatient waiting for the pack to charge. :-) Perhaps some one more knowledgeable than I will chime in here.
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Old Oct 01, 2008, 06:41 PM
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Colorado
Joined Jul 2007
567 Posts
Thanks for the reply, batman.

That makes sense and I guess that means setting the charge rate is not the best option especially for aging batteries. The Fast Charge setting seems to do what's best for the battery.

Sorry for not being more specific but the charge times are without a doubt getting longer.
On the two batteries in question charge times for the 1C Fast Charge setting ranged between 1hr and 1hr10min for about the first 100 cycles. Now charges on that setting are from 1hr20min to 1hr30min.
BTW, if I set the charge rate to an actual 1C it takes about an hour as expected, slightly longer due to the rate reduction during balancing.

Thanks again.
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