Rc amp ratings for esc and battery c rating.

[Nsanti]

Amp ratings are very weird to me in the rc hobby and I was hoping someone could explain. I question some things like how you can have a 60 amp esc when 10 gauge wire is only rated to 30 amps. Also how can a 4s 5500 mah battery at 60c be rated for around 300 amps discharge when it only uses the same 10 gauge wire.

 

[WVNed]

I suppose the simplest answer is that the rating for safe continuous use with a certain temperature rise for 15 feet of wire has nothing to do with how we use the wire in a hobby.

Or how do you explain why cars do not simply catch fire and explode when we go full throttle?

 

[Greywolf74]

Amp ratings are very weird to me in the rc hobby and I was hoping someone could explain. I question some things like how you can have a 60 amp esc when 10 gauge wire is only rated to 30 amps. Also how can a 4s 5500 mah battery at 60c be rated for around 300 amps discharge when it only uses the same 10 gauge wire.

The 30 Amp rating you see online comes from the National Electricians Code. This code is generally referring to single strand copper wire that you would find in your house. The rating is also determined for a certain length of wire too. I forget what that length is but I'm pretty sure its a lot longer than what we use in the hobby. We also dont use single strand wire either. Other things also affect the rating like the type of insulation the wire has. The ampacity of a wire with insulation that has a max temp of 90C will be much lower than the ampacity of a wire with insulation that has a max temp of 200C. A lot of other facotrs play a part too like temperature and length of the wire. a 6 inch piece of wire will have a much higher ampacity than 10 ft of the same wire. Another factor is the amount of time that wire will be transferring that amp load.

As for LiPos the C ratings on them are grossly over rated. The True C rating of a LiPo tops out at about 45C for the best quality batteries on the planet. I think the highest true C rating I've ever personally seen on a typical RC hobby grade LiPo is 35.6C and that was on a $150 No Prep Max Amps pack. And even though that means that No Prep pack can deliver 178A its never going to do that continuously. Even in a big 1/8 scale monster truck your typical amp load is probably fluctuating around maybe 40-70A and may have momentary spikes of 100+A.

Hope that sheds some light on it for you.

 

[Nsanti]

The 30 Amp rating you see online comes from the National Electricians Code. This code is generally referring to single strand copper wire that you would find in your house. The rating is also determined for a certain length of wire too. I forget what that length is but I'm pretty sure its a lot longer than what we use in the hobby. We also dont use single strand wire either. Other things also affect the rating like the type of insulation the wire has. The ampacity of a wire with insulation that has a max temp of 90C will be much lower than the ampacity of a wire with insulation that has a max temp of 200C. A lot of other facotrs play a part too like temperature and length of the wire. a 6 inch piece of wire will have a much high ampacity than 10 ft of the same wire. Another factor is the amount of time that wire will be transferring that amp load.

As for LiPos the C ratings on them are grossly over rated. The True C rating of a LiPo tops out at about 45C for the best quality batteries on the planet. I think the highest true C rating I've ever personally seen on a typical RC hobby grade LiPo is 35.6C and that was on a $150 No Prep Max Amps pack. And even though that means that No Prep pack can deliver 178A its never going to do that continuously. Even in a big 1/8 scale monster truck your typical amp load is probably fluctuating around maybe 40-70A and may have momentary spikes of 100+A.

Hope that sheds some light on it for you.

This helps a lot, thank you so much. I recently got a used xmaxx and needed new batteries and I also wondered what the amp draw was and if 60c was enough. If the amp draw is only 70-100 amps the batteries I bought should be way overkill which is awesome. Thanks again.

 

[Greywolf74]

This helps a lot, thank you so much. I recently got a used xmaxx and needed new batteries and I also wondered what the amp draw was and if 60c was enough. If the amp draw is only 70-100 amps the batteries I bought should be way overkill which is awesome. Thanks again.

The Xmaxx is a 1/5 scale monster truck so its going to potentially pull more amps than a 1/8 Scale will and depending on what lipo you bought the True C rating is probably somewhere between 18C and 30C. If you tell me what lipo you bought I can probably give you what the true C rating is if its one I've tested before.