Recharge went well: as they were below 3V initially, the charger started by putting just 150mA into each one as it should, and when the 3.00V mark was reached, quickly ramped it up to the full 3.0A per battery, and when they reached 4.20V, tapered all the way down to 70mA, with the last battery (about a minute after the first one) finishing about 1h21m after starting the charge.
Now I’m going outside to test them under the 10A I can safely drawn using my strapped-down drone, and will use the drone’s voltage and current sensors (which I have previously calibrated) to see how much energy they are capable to provide under that kind of load. Should be posting the results here in about an hour.
From left to right: the tablet where I run the VRX software showing (and recording) the image from the drone’s OSD; the RC transmitter I use to start/stop the drone’s motors and control their speed, and also to receive and record flight telemetry (including battery voltage, current, and accumulated mAh) back from the drone; and finally the drone itself, strapped with two separate thick straps to the stack of three concrete bricks shown right below it (otherwise with 10A going through its motors, it would go up and try to climb to the Moon). The data below was compiled from the recorded OSD data, and confirmed with the transmitter’s recorded telemetry.
And here’s my final data:
1st pair of batteries (i+iv): the drone turned itself off (not enough voltage to sustain its electronics) at 2.33V, last recorded measurement showed batteries supplying 7.68A despite motors being at full throttle (this means these batteries were simply not able to supply 10A at the end of their discharge curves), after supplying 2638mAh over the course of 15m52s; These 2638mAh is quite a bit less capacity (~7.1% to be precise) than the 2840mAh that can be interpolated from the graph published in @Mooch’s JP30 test; During recharge, these batteries took 2808+2810/2= 2809 mAh, which represents 2638/2809-1= ~6.1% of discharge/recharge inefficiency.
2nd pair of batteries (ii+iii) fared a bit better, being able to supply 2702mAh over the course of 16m11s before the drone again turned itself off due to low voltage at 2.33V, and at that time they were only able to supply 7.46A at the end of their discharge, despite motors also at full throttle; this would mean 2702/2840-1= ~4.9% less capacity than the ones Mooch tested (URL above); during recharge they took (2832+2823)/2= ~2828mAh between them, meaning 2702/2828-1= ~4.5% discharge/recharge inefficiency.
In conclusion, it looks like the general concern about buying batteries from AE is not unfounded. While not too much worse (only ~4.9-7.1% less capacity) than the ones Mooch measured, they were quite disappointing to me as they perform worse than the Molicel P30Bs I previously purchased also from AE (which lasted less, with the drone going dark at 2.33V after 14m57s and 2596mAh, but being capable of supplying the full 10A until the end – unlike these JP30s, which are supposedly much better at supplying high currents than the JP30).
Given it comes from factory, I believe the manufacturer probably choose one with very low contact resistance – specially since they market it as a “long range” drone, and any resistance would end up eating flight time.
Also, on one of my flights just last week, I’ve personally seen this drone pulling almost 30A from the batteries (when I was ascending a 300m hill almost vertically) – to the point I got a warning message about overheating the motor controller FETs. I think this would only be possible if the overall resistance – including contacts – was very low indeed.
Spot welding is what most battery packs for “normal drones” use; (the ones that come from factory with XT30/60/90 connectors instead of 18650 battery holders). Not the case of the Rekon35.
I managed to buy a couple of similar (which I believe are high-current) 18650 holders, and plan on building a 4x battery pack for my new 4S drone that comes from factory with a XT30 connector. I can then take a total resistance measurement with a dedicated drone battery pack charger and compare to the individual batteries’ resistances as measured by my Gyrfalcon S8000 charger, to figure out exactly how many milliohms the holders themselves (plus the XT30 connector and wires) are adding. If interested, let me know and I will publish the results here.
I was actually planning to order a couple from them (when they were actually in stock in stock a couple of days ago, but I was looking to ad a couple of other batteries to the order and when I was ready to order the next day… The JP30’s were already out of stock again!
Thanks for letting us know, @Wingman – and sorry to hear you didn’t manage to buy them in the end
These batteries seem to be selling really fast, at least as fast as Ampace can make them.
On my end, I’ve put mine through their paces a couple more times and in actual flight conditions, they seem to perform a bit better in my drone than the Molicel P30Bs; unlike in the bench, it’s hard to test them in the field under the exact same conditions as winds change, etc but my subjective feeling is that they seem able to be drawn a little longer and farther (perhaps 5-10% more) than the P30Bs while still providing usable current for the drone electronics and motors.
