This year, we decided to make the switch to 2awg wires. we ordered all of our wire and connectors from powerwerx and when we got it all, everything was fine, but the lugs were too wide and dont fit in the socket for the PDB. Could someone recommend lugs the fit the 6mm screw and are narrow enough for the PDB?
FWIW We normally sand our 4 awg lugs slightly on a belt sander to make them fit our batteries and into the PDP.
We trimmed the edge of the lugs on a grinder.
We trim and sand to fit, as well.
Is there truly a benefit from using 2AWG? The CTRE nice battery cables are 6AWG, and I could understand going up to 4AWG, but to me, 2AWG seems excessive. Not to mention, to get a welding-type of wire that’s really flexible would be quite pricey (~$150 for 50ft,) and bending the normal stranded wire would practically take a pipe bender, especially within the confines of a robot…
Our testing showed transient voltage improvements of around 0.7V, enough to keep us out of brown-out territory with an aggressive drivetrain.
We bought 20 or 30ft lengths of finely stranded 2awg wire and have made 4x robots and ~12x battery terminals from that and have plenty left for this year. It’s not a huge investment for some wiggle room in drivetrain performance.
Ironically, the 2awg we bought this year is more flexible than our regular battery cables. We decided to go with 2awg because 1) we have heard of benefits and found that we would get at least 0.2V more overhead on brownouts, and 2) we didn’t crimp batteries before anyway, so we have nothing to lose by going 2awg from the get-go.
Do the robot construction rules address this under “branch circuits”?
“R61. Branch circuits may include intermediate elements such as COTS connectors, splices, COTS flexible/rolling/sliding contacts, and COTS slip rings, as long as the entire electrical pathway is via appropriately gauged/rated elements.”
The “entire electrical pathway” would include the terminal/lug at the PDP.
Thus, a terminal with material removed would likely not be “appropriately rated” by it’s manufacturer after the material is removed.
It’s a common safety requirement for terminals, that they only be used as specified by the manufacturer. The National Electrical Code (The NEC) requires following manufacturer’s instructions when installing equipment (110.3), and this applies to terminal devices. And another safety document, The National Electrical Safety Code (NESC), requires “…connection…shall be made…by methods that provide the required…appropriate mechanical characteristics.”
I suspect there aren’t manufacturers that provide ratings (electrical or mechanical) for their terminals after material is removed.
No; R47 and R50 are the two rules that cover the design & construction of the robot’s main power pathway. “Branch circuits” refers to those connected to the PDP’s branch terminals.
We are talking about a slight material removal from a 2 AWG lug which is substantially larger than the 6 AWG lug required by R47. Even after the material removal, the conductive area is still enormously larger than the requirement. After all, this is why we were attracted to the larger wire size in the first place.