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Jun 23, 2019, 10:00 AM
Youtube channel : solentlifeuk
solentlife's Avatar
Originally Posted by dshriver
The real problem is that advertised C rating is seldom accurate. Sometimes it’s just an outright lie. Other times it is only accurate in highly controlled lab conditions. Then as a pack ages it’s C rating drops. Higher C packs are heavier and more expensive.

For what it’s worth I run 45C Pulse packs. I would like to try Dinogy though.
I used to buy based on C rating ... but now after having various higher C rated packs fail faster than a rabbit gets **** ... I now buy lower rated, use the difference in weight to get more capacity .. which in fact increases the rate I can draw ( C x A/hr) .... and then I see what temp. pack has after flight ... if only just warm to touch ... its near max and Ok ... if warmer - its being pushed too hard and is relegated to lesser role ... if cold - it can be pushed a bit harder.

What is interesting is that temp. does not always agree with labeled C-Rating and is why I came to like Rhino packs that now no longer are available.
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Jun 24, 2019, 10:07 PM
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Fallguy44's Avatar
Thanks for the battery info all.
Jun 25, 2019, 09:58 PM
If it flies, I can crash it.
rocketsled666's Avatar
Originally Posted by JoeDirtRC
Actually higher C rating has nothing to do with voltage. It's a rating on how rapidly the battery can discharge it's current. The only effect on voltage is that a higher C battery will likely drop voltage faster.
No, it has literally everything to do with voltage. "C" rate is inversely proportional to IR. In fact, knowing the IR of a battery allows you to verify the C rate. IR dictates voltage drop under load. So C rate also dictates voltage drop under load.

When you put the battery under load, it supplies current. The voltage output will drop from the no-load voltage an amount equal to the battery's IR multiplied by the current being drawn.

For a made-up example... Pulling 10A from a 20C battery with a 50mOhm IR would result in a 0.5V drop. Pulling 10A from a 100C battery with a 5mOhm IR would result in 1/10th of that drop, 0.05V. Say you make two 4 cell packs from these batteries. The 20C pack has a 2V drop (0.5V * 4) under load. The 100C pack has a 0.2V drop. 13% lower voltage for the 20C pack compared to the 100C.

C rate absolutely governs voltage under load. And that's the only voltage that matters. It's why you can get better performance from a higher C pack, it delivers more Volts for the same load as a lower C pack.

The reason C rate matters for discharge current is because IR also generates heat. Too much heat will damage or even explosively destroy a LiPo. When you pull current from the battery, the battery dissipates heat according to I^2R (where "I" is the current being drawn and "R" is the IR of the battery). The battery is rated for the current you can safely draw without the battery heating destructively due to the IR. So that's what "C" means in terms of maximum discharge current.
Last edited by rocketsled666; Jun 25, 2019 at 10:05 PM.
Jun 25, 2019, 10:34 PM
AMA Another Mans Airplane
cale10's Avatar has a wide range of great batteries. ive had my Glacier 4S 2200 for years now and its still as powerful as day one.

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