Caps on your ESC leads help with battery wire induced inductance spikes… they will help with smoothing out spikes, you going WOT, your motors drawing peak and it taking time for the current to hit your motors from your batteries and you adjusting…
As I understand it
SAG on the other hand comes from the “c” rating of you batteries not being able to provide the amps your motors want.
Agree with @Cobber. The smoothing ability of caps is not going to help with voltage sag.
You will see sag if your setup current capacity (delivery of amps) in C is insufficient.
I guess theoretically you could do a huge cap bank, but not very feasible or practical. Caps are good at delivery power in milliseconds - not seconds long delivery under heavy load… As I recall with my limited understanding (not an EE).
I would instead work on a better battery solution - add more in parallel to reduce sag.
The 25R is a great cell for mid-large, high discharge packs. ITs basically perfect for a 4P at 20amps continuous and 100amp pulse. I went with 30Qs on my 5P because more cells means each one can do less for longer and the range dramatically increases because of it.
Technically you could use a super capacitor between the battery and the ESC that has the ability to expel a much higher current than your batteries, in much the same way as the lipo/li-ion based spot welder does.
The super cap will need time (not that much) to reach full capacity, then when you need a burst of power it can supply it, all while getting topped back up by the slower, less current providing cells. This could even out the voltage/current supply from your battery and ultimately stop voltage sag. But it could only be sustained for short bursts.
that is correct. We need one in the form factor of either an 18650, a 26650, a prismatic, or one of those new 207xx cells and i don’t think materials science is quite there yet, and if it is, the demand hasn’t been recognized. I have about 4-6 cubic inches of space for it, so they need to get on it.