Lipo Charging

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12-08-2009, 03:48 PM

#31

Dave H

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Quote:

Originally Posted by stu22

I find it curious that you're seeing that much variance in the constant voltage part of the charge. It should be the battery that determines this time. The equation is V=IR, where "V" will be 8.4volts for a 2S, the "R" is the resistance of the battery which increases as you charge it, and "I" being the current that the charger is ramping down to hold "V" constant as "R" increases. I would have thought that it would be the same for all the chargers for a given battery. Kind of makes me want to actually pay attention to my chargers next time to see which ones do what (although I can say from charging the 2 2S packs I use in my RC8e, the ICE and CheckPoint chargers are almost identical.).

One factor that everyone seems to be missing is if you charge at 2C you will have to ramp down from 2C. Instead of going from 5.2 to 0.1 amps you will be starting at 10.4 and going to 0.1. That alone will offset some of the time savings that you get on the constant current portion of the charge cycle.

Some non balancing chargers, an ICE for example, monitors voltage through the main leads. Which are carrying a large current, thus relatively large voltage drops. So more voltage error, the battery voltage isn’t quite as high as it appears. Thus longer charge time to get that last bit in, as it’s done on the slowpoke CV portion. These chargers are also very sensitive to lead size & length. I saved a bunch of time by dramatically shortening the leads, with larger gauge wire.

A balancing charger apparently monitors voltage through the balance wires. Although small, they don’t carry much current, so little voltage drop & error.

So far I’ve tried Hyperion and Orion Clubman Lipo balance chargers. The more expensive Hyperion is more aggressive on cell voltage through the early part of the CV portion, up around 4.21~4.22. Still finishes at 4.2. This requires more exact voltage detection. But allows the Hyp to be a touch quicker than the Orion.

From what I’ve seen, higher charge rates hit the slow CV portion quicker (relative to charge level), negating a lot of the apparent charge time improvement. At this point it doesn’t seem worth it to me, your mileage may vary.

Last edited by Dave H; 12-08-2009 at 04:31 PM.