chestnutjazz

iTrader: (6)

So as I'm slowly getting back into racing; I'm ready to upgrade some things like
my esc and batteries. So my question is this:

If an ESC is rated at 120A; how much battery is too much battery?
i.e. my understanding is Amp is calculated by taking the Mah of the batt/1k x the the C rating; thus 5000 mah bat with a 65 C rating would technically give me a 325 amp draw right? Likewise a 45C x 5000mah gives 225 amp i.e both being way over the 120 amp max of my esc. So am i just wasting money?

hotrod87

iTrader: (252)

What you are looking at is how much a battery can out out . What you need to know is how much the motor your running will draw . The battery only puts out what the motor needs .

2canSAM

iTrader: (248)

Is 120A on your ESC constant or burst?

+1 you can never have too much battery. Check the amp draw ( max) for your motor and go a little higher on your batteries. The higher C rating will help keep your battery cooler too. Buy the highest you can afford, but to be honest if I could do 3 40C packs or 2 65C, I would probably go with the 3 40C packs.

chestnutjazz

iTrader: (6)

Those are great points: but that leads right back to my question: so if I'm limited by the draw of my motor, am I wasting money on these 65, 90, and 150 C batts? (don't worry, i'm very aware of the controversial C rating) but for the sake of the discussion. In addition, should I be worried about batt temps on my high speed run cars or drag cars or is that something that I should only be concerned when it comes to my track cars? I'm assuming 120 constant/ like in the MMM ESC and it's sister esc's. The other real question is what leads to the burning up of esc's?

2canSAM

iTrader: (248)

Like I said above I would go with 3 40C packs instead of 2 65C packs. So IMHO you are wasting money on the higher C rating unless you are running stock class where you need everything you can get.

chestnutjazz

iTrader: (6)

So now the follow up question is how much Mah do I really need
a) for high speed runs
b) drag racing
c) for 6 min races?

bigwavedave33

iTrader: (1204)

ESC amperage is typically rated for constant. There is also a peak value most of the times not listed.

Your battery calculations are correct, but what you should be looking at is what the motor can DRAW current wise and how many watts the motor uses.

MAH is basically = to run time
C is basically = to torque
The combination of the 2 will basically give you the overall power.

You are asking some very difficult to answer questions which are all mixed together and are either not related or are interrelated.

a)MAH has little to no affect on speed unless you go with a HUGE heavy pack it will slow you down. voltage(1s, 2s, 3s 4s) because of the number of RPMs the motor turns based on voltage and C rating because of the ability to fight drag due to air, mechanical, and other do
b) see a
c) completely depends on the motor. A 4 pole 540 motor can use 3000+mah in a 6 min heat. a 17.5 less than 1000.

chestnutjazz

iTrader: (6)

That is an interesting take; I knew that Mah didn't factor directly into speed; however, always thought it did indirectly in the case of keeping the amps higher for longer; eventhough all of 1-3 seconds.

Now can someone explain what causes ESC to smoke or burn out?

bigwavedave33

iTrader: (1204)

chestnutjazz

iTrader: (6)

Not that I've done it, but I see it happening all of the time with guys I race/bash with. So I don't know if it's b/c they're using cheap batteries, cheap esc, or what? Unfortunately, I'm arrived to the point where I just assume you get what you pay for, so I've not had any unfortunate incidents, but I still want to know how to avoid them.

Cpt.America

iTrader: (52)

In a race environment, the only time a battery becomes "too much battery" (voltage not included), is when the weight of the pack starts to adversely affect your lap times. Sometimes lighter is better.