Hello!
after watching this video
[using a 4s 18650 Sony VTC6 battery pack for a quadcopter]
I noticed that there is a very high voltage sag, about 3 Volt.
so I thought of asking, Which 18650 battery has the lowest internal resistance ratings?
and what are the ways to reduce this sag?
Thank you
Under high current load it is not unusual for a pack to sag 25%, that’s the price for the blistering current draw.
The cell with the lowest IR is a new one that has never been used; IR is a just a weak concept created by EEs who don’t know anything about chemistry and chemical reactions. Both charging and discharging of a cell are chemical reactions that are highly influenced by temperature.
Thank you for the info Kenny.
I wonder if adding more batteries in parallel+Thicker Gauge wire will decrease this voltage sag?
If you have high voltage sag you probably are asking too much from the batteries. Estimate your current requirements and go to HKJ’s Battery test 18650 comparator to compare the VTC6 3000mAh against other cells. At 3000mAh I think only the VTC6A (not tested there, tested by mooch) would be better if you can find it somewhere. A good candidate is the Samsung 25S at 2500mAh or maybe the Molicel P26A at 2600mAh (or the elusive P28A). Also you may consider using a larger cell like a 21700.
Thank you for the valuable information ggf31416.
apparently 21700 is the way to go for such high draw battery pack. :+1:
Yes either bigger cell with higher capacity, or add cells in parallel, is the only way to reduce the sag effect.
Yeah if you’re looking for a low IR high discharge rated pack you’re probably better off going with a 21700 cell. I plan on building a 3S 21700 pack for a long-range drone build using some Molicel P42A cells as they’re rated at 45A continuous vs the VTC6’s 15A continuous, 30A continuous with an 80C temperature cut-off.
samsung 18650 20S AC 1khz internal resistance is about 8 milliohm
The most powerful power battery found in 18650