11LikesSMC LIPO BATTERY THREAD
... have a feeling that it will do down a bit more too 
12-27-2015 | 11:25 PM
#3934
how many amps are you charging at? note the temp of the pack at the bottom at almost 106 degrees. charged at 20amps (and probably discharged at 20-30a prior to charging). if you are getting your 2.5 reading with a room temperature pack, then you're comparing apples/oranges.
12-27-2015 | 11:30 PM
#3935
how many amps are you charging at? note the temp of the pack at the bottom at almost 106 degrees. charged at 20amps (and probably discharged at 20-30a prior to charging). if you are getting your 2.5 reading with a room temperature pack, then you're comparing apples/oranges.
12-29-2015 | 04:40 PM
#3941
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Worth noting: mah and "c" ratings are arbitrary figures based on how much power (voltage) a battery will provide at load, across a measured amount of time (expressed as mah). I believe these numbers are also theoretical. Is it possible for a battery to push 400amps continuously? Can that be tested without melting connections & wires? If a battery were loaded with 400amps, would it provide 4000mah above threshold voltage?
I'm thinking the 4000/100c is more energy dense, therefore heavier. I would not be surprised if it could easily be rated at a higher mah and lower c (assuming it is fairly rated now).
I'm thinking the 4000/100c is more energy dense, therefore heavier. I would not be surprised if it could easily be rated at a higher mah and lower c (assuming it is fairly rated now).
The C rating is the highly variable, often manipulated characteristic of a pack. I believe Danny has a good write up explaining this on his site and probably on this thread as well. Part of the C rating has to do with the actual cell chemistry, but part of it is assuming an acceptable internal resistive drop.
I would speculate the 100 C pack to be heavier due to cell geometry and/or increased internal conductor thickness (which lowers IR and allows a higher current). But you won't get any more energy out of a 100C pack than you can out of a 1C pack, given the same cell count and charge capacity. Of course you can go really while fast discharging a pack at 100C into your motor, but only for 36 seconds. On the other hand, your motor can pull at 1C and go much slower, but you'd last a whole hour.
...all that to explain that the 100C pack is no more energy dense than the other. And to your point of the practicality of discharging at 400 A continuously, I really wouldn't recommend that. Given that it would only last 36 seconds, maybe doing it and allowing ample time to completely cool back down is feasible, though I would suspect long-term damage from doing this repeatedly. I'd never design a 400 A conductor with 12 AWG wire in a satellite; then again, we can't easily go up and fix it when it fails. In the world of RC, however, these limits are pushed because it's not a catastrophic event in the grand scheme of things if your battery overheats or wire melts during a race. A DNF really isn't that bad in comparison. It's also normal for a racer to replace packs every year, if not more frequently.
I'm sure that's way more than anyone wanted to know, but just trying to give a perspective on ratings. Some ratings (such as the C rating) depend on the intended use and acceptable failure rate, which can be wildly different going from military to consumer to hobbyist.
12-29-2015 | 08:03 PM
#3942
Yeah Rick, that's the idea behind discharging and charging at high rates. You heat up the battery's internal temp which lowers IR. The trade off is potentially safety and battery life. Which is not to mention that it's against ROAR rules but tracks don't care soooo....
12-29-2015 | 08:52 PM
#3943
Joined: Jun 2008
Posts: 5,071
Yeah Rick, that's the idea behind discharging and charging at high rates. You heat up the battery's internal temp which lowers IR. The trade off is potentially safety and battery life. Which is not to mention that it's against ROAR rules but tracks don't care soooo....
