Adding a large cap parallel with battery's?

[Okta]

I have been mulling over an idea and would like to hear from you guys who have more knowledge on the subject.
For example, my maxx with 9l and 9920 esc and 12 cells. I have some 4200wc ib packs for this but i also have some yum char 3500 nimh's (and some venom 3000) that im guessing can only do 30amps output as opposed to 35amp of good quality cells.

Obviously with the cheaper cells the car has no where near the same punch as the ib's so (aside form only using good cells) i had the idea of running a decent size cap (up to 25000uf 30v) in parallel with the cheaper battery's to act as an energy bank so that under heavy acceleration (for a few seconds) there would be more overall current available between the cap and the batts and prevent voltage drop. Then after i back off to corner the cap would have time to charge again for the next burst. So in theory the esc would be drawing from the cap and the batts at the same time for more amps. The voltage should be same because the cap will only charge up to the maximum voltage produced by the batts.

Q1. Is that what the caps on any esc do in the first place?

Q2. Would this actually help or blow things up? I will have time to test next week on my cheap brushed truck so any advice will help.

Just a idea to get some use out of my cheaper cells for my other trucks.
Cheers.

[zeropointbug]

Go read my thread titled 'Quark fried, blown capacitor'

The only way to get decent energy storage from a cap, is to use ultra-caps, again go check out the thread.

25,000uF will do nothing for energy storage, you need 10,000,000+ uF

[bdebde]

For audio stiffening caps they recommend 1 farad per 1,000 watts

[GriffinRU]

It is not the capacity which counts when you have battery, but ESR, the rest is pure math.

[zeropointbug]

Yes, but he is not talking about powr conditioning, he is talking about energy storage for bursts. You need at LEAST 10F for that, I will be using 15F with mine, and extremely low ESR as well.

[GriffinRU]

Originally Posted by zeropointbug

Yes, but he is not talking about powr conditioning, he is talking about energy storage for bursts. You need at LEAST 10F for that, I will be using 15F with mine, and extremely low ESR as well.

When you put caps in series then you lossing their ESR...

[zeropointbug]

How? I thought it doesn't change at all?

[GriffinRU]

Originally Posted by zeropointbug

How? I thought it doesn't change at all?

That would be nice but you should check what happens with C, R and L when you connect them in series and then apply that to just Cap but treat it as an electrical model.

[BrianG]

Ugg, vector math (I assume you mean AC), not to mention resonances, etc...

[zeropointbug]

ESR, then how does it increase with series connection? Is it multiply by n number of caps in series?

[BrianG]

As far as ESR is concerned, treat the ESR in each cap as a small resistor. In series, they add. Capacitance value adds in parallel though...

[zeropointbug]

whow.... all this time. I thought it had no effect. :036: