What kind of terminals?

For whatever it is worth anytime I work with battery cable connections I use 4AWG cable where I can in my battery setup. I use BLUE SEA TERMINAL BLOCKS, FUSE BLOCKs, and SWITCHES so that every thing is designed to terminate into a RING TERMINAL LUG.

I only have one spot where the 4AWG cable slips into a ALLEN WRENCH lug which is at the PD9260C.

I use ANCOR Marine quality 4AW cabling and use the same company provided ring terminals which are hand crimped on the bulk 25-foot roll of 4AWG cable using a 8-ton Hand Crimper.

Having a cable marker kit from my working days I can add a nice heat shrink label to pretty things up with.

Any ring terminal I install also gets a good quality weather tight adhesive heat shrink sleeve.











Roy Ken

Solar mfg don't consider the voltage drop factor
#10 is rated for 30 amps at higher voltages ( 120~600 vac)
But 30 amps at solar voltages creates too much drop ( more drop than we RV`R want to see)
So we use bigger wire to compensate and limit voltage drop
That means we have to trim the wire end or splice to a smaller wire for the controller connection

MotorPro wrote:
Why do you want the bigger wire? If you are putting the big wire so later you can upgrade to a larger capacity controller later then do as described and step down in wire size for now. If you are going to keep that size controller then you are just wasting your money on the large wire. No matter what size wire you run it can only flow the amount the controller is capable of and 10 gage will handle the amps that controller can.

I do plan on upgrading in future. But regardless is't it true that to get the most available current to the battery bank, that the larger the wire the less the resistance, thus less loss from controller. Say I'm getting 20volts at 4 amps (just arbitrary numbers) out of controller. Won't #4 wire deliver more "power" to the battery than #10?

Why do you want the bigger wire? If you are putting the big wire so later you can upgrade to a larger capacity controller later then do as described and step down in wire size for now. If you are going to keep that size controller then you are just wasting your money on the large wire. No matter what size wire you run it can only flow the amount the controller is capable of and 10 gage will handle the amps that controller can.

2oldman: many controllers, especially those cheaper ones, have undersized terminals. I guess they in China don't want to use more metal since they have to import it, and they usually don't give a darn about codes and rules of "our" world.

The ampacity of #10 wire is 30A at 60C (150F). So if OP has solar array 350W or more, he needs a better wire than #10 solely to prevent it from melting.

And then there is a voltage drop. So the cable to battery (and for parallel panels - from panels to controller too), needs to be thick enough. You can connect a short piece of #10 to controller, and use Splicer-reducer to connect it to #4 or whatever you want. Wrap it into insulation tape. Both holes are same size and can accept wire from #14 to #2 max. $5 in Home Depot

PS: I'm getting slow. Westend has already posted a link to slicer-reducer.

westend wrote:
Lug splicer would be my choice if the controller terminal is a set screw .
Lugs direct

For the same purpose but a terminal strip attachment, I used a crimp connector with smaller spade size. The auto parts guys sell gold plated connectors like these for cheap.

That's what I used. Lowes and Home Dept sell a brass terminal lug with a hole in it that you can use to attach the lug to the battery and then there is a set screw at the top. Don't know the proper name but they come in different sizes for different gauges of wire. Simple and clean.

Lug splicer would be my choice if the controller terminal is a set screw .
Lugs direct

For the same purpose but a terminal strip attachment, I used a crimp connector with smaller spade size. The auto parts guys sell gold plated connectors like these for cheap.

jmccen58 wrote:
Yes it is, but all I've heard is that #10 is too small to get maximum amperage and voltage to the battery...???

The wire size will need to be suitable for the maximum amperage of the controller.

What is that number?

I have (rarely) clipped a few strands from a larger gauge wire to allow it to fit a smaller terminal. Works in a pinch, and better, easier (in my opinion) than splicing in a pigtail of smaller gauge wire.

If you are really concerned about voltage drop, you can run heavier wire to within a foot or so and then reduce wire to the #10 to fit the terminals.