This year are team is thinking about switching to 2 AWG battery wires and SB120s but only if the price is reasonable. I was wondering if someone could recommend a low cost supplier for 2 AWG welding cable as well as an affordable but high quality crimper for the SB120s.
The hydraulic crimpers from Harbor Freight/Amazon work really well.
Don’t know about Amazon but we got a hydraulic crimper from Harbor Freight a few years back that self-destructed the first time we used it (literally liquid spewing out of it onto everything)… never again.
Bought one made on a Friday shift huh?
Don’t skimp on the crimper or wire. You can ruin the benefits of converting if you do. Cheap crimpers won’t crimp well and will break. Cheap wire won’t be flexible enough and trust me when dealing with that size of wire in small space on a FIRST robot you need all the flexibility you can get.
The initial investment was pretty rough (crimper, converting chargers and all the batteries) but now that we have paid that life will be much cheaper.
Very happy that we did it.
The thing to keep in mind: an industrial crimper of this size can easily run $1k or more. Affordable is relative.
Just before Christmas break…
Red post, Blue post?
Why make a new post?
We made the switch to 4 AWG and SB120 this year following the linked posts. Costs were
~$10 per connector ~$200
$60 for 25’ ea of cable
We used the Harbor Freight hydraulic crimper. Worked perfectly for us. We also used it to crimp swage sleeves on wire cable for our elevator.
How many teams actually do this? I assume the purpose is to reduce resistance in the wiring and therefore the chance of brownouts?
Also, is the 2AWG used only on the battery terminals (and not the connector to PDB, which is 6AWG)? In this case, no additional measured weight is added to the bot from the thicker wiring.
From there to here, from here to there, funny things are everywhere!
We run 2awg from battery to PDP. The weight is a worthy investment IMO, and further rewards the good practice of minimizing main power wire length.
I never come here to have fun. Robotics is not fun. Duh.
Although this means that you will not be able to borrow or lend batteries in the pits.
Also, I like green eggs and ham.
Out of curiosity, has anyone ever actually measured the real-world effect that a larger battery wire gauge has on FRC robot performance? I’ve been considering doing this sort of thing for a few years, but without any actual performance impact data the cost and time required has been a hard sell.
I get how going to the larger wire gauge reduces resistance, but when I ran the numbers a while back it looked (to me at least) like the impact of going from 6 gauge to 4 or 2 gauge would be relatively insignificant.
There’s some more discussion from teams who have done similar wiring upgrades on this thread.
Measured? Nope, but I’ve done the calculation.
Resistance is typically given in a table of wire gauge per feet at a temperature.
So 6 awg would be 0.3951 ohms per 1000 feet @ 20C, 2 awg would be 0.1563 ohms.
If you assume 4 feet of wire at (peak) 600 amps, that’s a .94824 volt drop for 6 awg versus .37512 volts for 2 awg wire, a difference of 344 watts.
Here’s the kicker. All of that power is going into heat. And when the wire heats up, the resistance increases.
And the other kicker. The larger wire is going to have a bigger thermal mass, so it won’t heat as quickly.
It adds up fast.
At 50C, 6 gauge wire resistance increases to .4416 Ohms per 1000 feet.
2 gauge is .1747, so approximately an 11.8% increase in resistance.