capacitors for rc car question.

Jstagzsr · February 8, 2020

On 1/29/2020 at 5:34 PM, meenmeen1103 said:

I've built several impractical speed run cars. Things like 1/10 touring and 1/16 micro on 4s lipo, and a slash 4x4 on 6s.

First I'll agree that the theory of cap packs has been explained in the thread already: stores excess power when system is not under load, and can more quickly release stored power than the batteries in said system.

However, the scope to which this is actually helpful hasn't been explained or argued much. The battery temps increase when under load specifically because of their internal resistance, which IS used to determine C rating but: C ratings are about as accurate as CPU TDP ratings when you consider them as a whole in the industry (not taking shots at specific brands) . They shouldn't be used as an exact basis.

Now, practicality: they don't store anywhere near enough power for long term. A capacitance of 1 Farad (1 million uF's) can hold 1 amp for 1 second. In systems rated over 100 amps, cap packs, which are definitely not anywhere near 1 Farad, can only ever help on startup power i.e. take-off burst power, 'burst' meaning microseconds.

The reason cap packs from known brands even exist is because they are cheap af to manufacture, and marked up substantially to a market that looks for any and every possible advantage for their setups, this also ignores the marketing behind them. Oh, and laziness. I would say some people just can't solder for various reasons and these products being pre-built helps but soldering caps of this size to a board is no more difficult than soldering the leads, which you will definitely have to do anyway.

This is absolutely no solution to helping batteries run cooler, but it's a passion driven hobby so if you want to give them a try, just pick low ESR (again, internal resistance is the biggest factor) and try to ignore any placebo for a validated answer yourself!

much appreciated man. ty

MadAnt250 · February 14, 2020

On 1/23/2020 at 1:09 PM, Jstagzsr said:

i am using two 3S 5200mah 60C lipos. it is very snowy here in NY so ive only got a chance to run the car once for about 5 minutes. when i got inside i noticed that my batteries were warm.

Batteries getting a little warm is normal and it takes more effort to move through snow therefore the motor will draw more amperage because it need to do more work. As an RC hobbyist and mechanic I know that one way to reduce the battery temp is to reduce the amp draw by going to a lower gearing, the lower the gearing the easier the motor has to work and the less stress there is on all the electronic components. So, more stress = higher amp load which = more heat, less stress = lower amp load which = lower heat. Also, lower gearing will also help with the run time but it will lower the cars speed.

Also, the capacitor thing you want to do is usually for helping with power dips, kinda like an anti lag system and I believe your esc already has capacitors on it to help with that, but if you want try experiment then I suggest buying a capacitor pack.