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Old Jan 16, 2007, 11:13 PM
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Min safe voltage for 7.4V lipos?

Whats the minimum safe voltage you can drop a 7.4V lipo down to? Specifically I'm looking at the Stormlauncher and XPV lipos. Will they handle 5V and charge again with no issues? Thanks for the info.
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Old Jan 17, 2007, 06:47 AM
Southern Pride
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Haralson County GA. USA
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You can run them down to 2.7V per cell (5.4V for a two cell) but you really should not. The deeper(lower) you discharge them then few number of cycles they will last.

If you use this link and take a few minutes to study post you should develop a better understanding.

http://www.rcgroups.com/forums/showp...68&postcount=1
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Old Jan 17, 2007, 12:59 PM
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and also longer time to restore the low Z ( impedance) if discharged too low
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Old Jan 17, 2007, 11:15 PM
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Thanks for the info. Looks like 6V would be a safe cutoff for a 7.4 and still be above the 80% mark(although barely).
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Old Jan 18, 2007, 07:14 AM
Southern Pride
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Quote:
Originally Posted by Bugman Jeff
Thanks for the info. Looks like 6V would be a safe cutoff for a 7.4 and still be above the 80% mark(although barely).
If you came to that conclusion after using the link and studing the graph then you are mis reading the data.

At 3.2V V per celll under load the cell is approx. 95% depleted.. 1300*80%= appro. 1000 mAh and that amount apacity had been used when the test packs were at 10.5V (3.5V per celll under load).

In fact if you look at the Graph closely at 10.5V (3S pack) 1100 mAh had been discharged so in fact the pack was 84% discharged at this stage.

With 12C cont. and greater LiPolys any cut off below 3.2V per cell is really very risky.

How to read a CBA Graph

http://www.rcgroups.com/forums/showp...89&postcount=2

Charles
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Old Jan 18, 2007, 11:50 AM
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I too have a hard time understanding what hal woo is talking about. I may be putting words in his mouth (if so I hope he corrects me) but I think what he means by voltage clamp is a charging circuit that has a fixed voltage but a current limiting circuit to prevent over current when charging a fully discharge battery. If so this is usually know as a "Limited Current/ Constant Voltage" device.
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