Just an interest thing:
So while I’m waiting for my new power switch to arrive, I decided to try your crazy soldering idea :). It took the resistance of the switch down by 1/2, so that’s definitely worth it. It still winds up being ~10W of loss at full throttle, so hopefully the system can dissipate it.
Great your in a position to gather some data on the switch mods.
I noticed a bit of an oxide residue on the bus bar of the switch, which affects conductivity. Arcing and heat increase this oxide layer, further increasing resistance.
I gave my bus-bar a light brushing with a stainless steel bristled brush to remove this layer and restore a bright lustre to the copper without scoring it.
I’d be really interested in some data if you C.B.F doing something similar to your switch.
Yeah, I noticed a similar layer of oxide so I polished it off until it was shiny again. No connectors use bare copper for exactly this reason, they are either tinned or silver or gold plated.
@Lukas where did you get those bus bar terminals from?
Local overpriced electronics store.
Then it met the hacksaw
I’d strongly recommend you do a bunch of static testing on the ground and run through a full battery in a strapdown test. Brass isn’t super conductive, and when 300A is running through, a few mOhm generates a bunch of heat. Even the screw terminals aren’t particularly efficient at conducting - esp if there is any oxidization.
6 AWG is for 250A and up to the max output for the ESCs with short wiring. I’m not sure why people are trying anything smaller just because they can get away with it, it’s very little difference in weight between the 8AWG.
-Electrician
But that is 250A for the total system draw
So say about 65A per ESC/motor , chart indicates 12ga, at least in areas that are getting only 65A.
If your running from a busbar r out to the ESC than 10 should be fine. From the bats to the busbar you will need 6ga by the looks of it…but, is each battery putting out 250A - no. If you have 4 batts then that is again approx 65A per bat and 130A if you have 2 bats, so max 10ga. The bats to the switch/busbar is a bottle neck and will get the most power, if you are doing it that way, so make that robust. IMHO
Sorry, forgot the bats in series to get 48V - thus drawing 130A from just 2 batts
Cheers. Patrick
With the 22x14 props(75kg static thrust), each ESC pulls over 110A at max load
@Codemonkey is that something you measured directly?
Paul did. I calculated that it would need 121A, but Paul insisted it was closer to 110A
Not sure where I said that, but at full throttle with the 22x14 I measured 96A peek.
Ok thanks for the link, I think I was talking about the max the ESC I tested could handle. With the newer motors the number is closer to 96A.
For both the 96A data how did you measure the current draw? If the ESC is rough with the supply (allowing for the DC bus caps in the ESC - although they will likely have an average ESR), then the measured current can be incorrect on the wrong device/if the device is placed too close to other current carrying devices.
It was measured inline with a watt meter like this one Other RC Model Vehicle Parts & Accessories for sale | eBay
I can can get you a prop if you want to measure yourself. More measurements the better.
Hi
So max draw per motor arm is 96A – so 384A total???
Thx
yes it can burst up to that amperage for a half second or so but the continuous amp draw is not that.