Cables and Connections
Cable size is critical when you’re working with current-hungry electric motors that can suck up 100 amps or more. At issue is voltage drop, power loss in long runs of cable. The smaller the cable, the greater the voltage drop, and a motor can be damaged if it tries to draw more power than a cable can supply. Undersized cables can overheat and possibly burst into flame.
To calculate voltage drop (no more than 10 percent, according to Maxwell) you first must measure the length of the cable run and double it—it is the there-and-back measurement that’s critical. Then find out the current rating of the motor—the RC8/8’s is 83 amps. After that you can use an online calculator that lets you enter all your parameters and then spits out a recommended wire size. Blue Sea Systems has a good one (beta.circuitwizard.bluesea.com).
10. Now I had to insert myself upside down into the anchor locker, lift the 25lb motor and gearbox over my head with one hand, slide it onto the shaft, and tighten up the collar to hold it in place. Amazingly, I managed it all the first time! 11. And we're all done! All that remains is to see if it works...
I cheated and used the cable-sizing table in the Maxwell installation manual, which informed me that for the 46ft round trip from my battery to the windlass motor, 4 AWG cable would be sufficient. When you’re paying several dollars a foot for battery cable, it behooves you to make your measurements carefully. I had a few yards of 2 AWG stashed in the garage, so used that for the longer runs.
Of course, I could have installed a dedicated windlass battery in the bow and thereby gone down a size in cable, but I could not see the point. Either way, I’d have had to snake cables through the boat, and the hassle was the same no matter the size of the wire.
With the new windlass sitting in a box in the garage and the boat still ashore, it was time to act. I ordered the cable and relevant terminals from an online supplier, then purchased a terrifyingly large hole saw to make what I not-so-laughingly called the Cut of No Return.
That aside, it all looked simple enough. Basically, all the installation involved was running cables through the boat, connecting lugs to the cables and cables to the proper terminals, and making sure the windlass wildcat was oriented correctly and was secured with a suitably large backing plate to help distribute the loads. I took my time, double-checked everything before pressing the hole saw into service, and set to.