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In an effort to better understand the apparent differences in capacity I have observed between similarly rated batteries, I pulled a 1.5-2C discharge on three of them, recording the voltage and current at 30 second intervals, then computed and plotted discharge curves. The result is elucidating:
Under heavier loads of 100-150A that we commonly see in R/C cars, the voltage will drop much more quickly than shown here mainly due to internal resistance of the cells, which in my case typically leads to the ESC's LVC triggering at about the equivalent of 3.6V/cell in the above chart for both my Kraton and Vorteks with stock electronics. The big Zeee and the much derided Spektrum battery have discharge curves similar to what I assume the engineers who programmed the LVC settings were working with, as the behaviour is almost perfectly optimised. It uses up nearly all the energy and then cuts off just before the voltage takes a dive to prevent damage to the cells. Notice however that the small Zeee has only used about half of its rated mAh capacity by the time it reaches the expected cutoff voltage. This explains why the Spektrum close to doubles my run time in the Vorteks!
Also noteworthy is that all batteries in the test were able to supply their rated mAh capacity at a 1.5-2C discharge. I suspected Zeee might be stretching the truth with their rating of the small one, but I was wrong. It will in fact supply 6000mAh, but the shape of the curve is far less than ideal for R/C use, and you can only get a fraction of the energy out safely when accounting for voltage drop through the cells at high current. This also makes me wonder: Is there really an LVC issue with the Vorteks as many have discussed, or is it a case of people trying to use batteries with poor discharge curves? In my case it's the latter; my galaxy brain fell for internet wisdom that compelled me to buy 'just as good' batteries for half the cost, but it turns out they're not just as good and in fact led to frustration and wasted time. Oh well, at least they gave me an excuse to draw charts, my favourite pastime after R/Cing, [redacted], [redacted], and [redacted].
Verdict: Size matters, but only if you can use it, and maybe it's not lied about as much as we think.
Under heavier loads of 100-150A that we commonly see in R/C cars, the voltage will drop much more quickly than shown here mainly due to internal resistance of the cells, which in my case typically leads to the ESC's LVC triggering at about the equivalent of 3.6V/cell in the above chart for both my Kraton and Vorteks with stock electronics. The big Zeee and the much derided Spektrum battery have discharge curves similar to what I assume the engineers who programmed the LVC settings were working with, as the behaviour is almost perfectly optimised. It uses up nearly all the energy and then cuts off just before the voltage takes a dive to prevent damage to the cells. Notice however that the small Zeee has only used about half of its rated mAh capacity by the time it reaches the expected cutoff voltage. This explains why the Spektrum close to doubles my run time in the Vorteks!
Also noteworthy is that all batteries in the test were able to supply their rated mAh capacity at a 1.5-2C discharge. I suspected Zeee might be stretching the truth with their rating of the small one, but I was wrong. It will in fact supply 6000mAh, but the shape of the curve is far less than ideal for R/C use, and you can only get a fraction of the energy out safely when accounting for voltage drop through the cells at high current. This also makes me wonder: Is there really an LVC issue with the Vorteks as many have discussed, or is it a case of people trying to use batteries with poor discharge curves? In my case it's the latter; my galaxy brain fell for internet wisdom that compelled me to buy 'just as good' batteries for half the cost, but it turns out they're not just as good and in fact led to frustration and wasted time. Oh well, at least they gave me an excuse to draw charts, my favourite pastime after R/Cing, [redacted], [redacted], and [redacted].
Verdict: Size matters, but only if you can use it, and maybe it's not lied about as much as we think.
