Thread: Solar Controller Location

Originally Posted by trout1105

Besides the water issues having the controller in the cab will allow you to monitor it easier

True, but it is Bluetooth so u don’t actually need to see it unless it stops talking to the app

Originally Posted by JimDAUS

the "voltage" drop from front to back of the vehicle will be negligible with the right sized cable, because it is actually "current loss".

The current at either end of the cable is exactly the same. Current is a measure of the number of electrons. You get the same amount out at that end as what you put in this end, much the same as litres of water flowing through a pipe.
Voltage decreases along a wire as a function of current flow and resistance (with resistance being a function of metal type and cross sectional area). Voltage is a measure of the amount of energy each electron has, much the same as the pressure of water flowing in a pipe.
My personal solar setup has the wire coming in through the back door to the regulator in the rear cargo area. There is then a distribution box servicing the fridge and inverter, with an 8mm^2 cable going firwards to the batteries under the bonnet. 8B&S is 7.71mm^2. 8B&S is rated at around 74 amps. My system charges at around 12 amps so I would get minimal voltage drop on 8mm^2 cable. The idea about having the regulator as close to the battery is very valid when you are using thinner cable. Common 4mm automotive wire is 1.84mm^2, while the common 6mm red and black pair in a black sheath is 4.59mm^2 (each wire).

Aaron

Originally Posted by John_D2

That’s kinda what I was thinking too. I’m wondering if I run 8b&s to the battery and mount the controller either under the passenger seat or behind the glovebox. I guess we’re only talking about 6 or 7 amps (110w xtm panel was on sale from BCF) to charge the 60ah dry cell battery not trying to deliver 100amps to my winch!

Just use an online voltage drop calculator.

eg. lets assume you do a 6m cable run:
Using:
8B&S = 8mm²(7.7mm² actually) so the voltage drop on 13.8v would be 0.21v .. so down to 13.6v

6B&S = 13.3mm² so the voltage drop will be 0.12v instead.
Is that 0.09v difference important to you?

Like the guys have already said, you woudln't need 6m, if you placed the controller (say) inside the fuse panel hatch. 2 or so meters would be fine to the battery.
Do you have the rubber grommets on the roof for the original roof bars?(I see some do, some don't). My spare D2 doesn't, but my D2 and brothers D2 has them .. so it's a hit and miss situation.

If so, you could run 2x 8B&S cables from the under dash location, up to the inside of the driver pillar(tweeter panel), up and under the roof lining to the grommet area and out onto the roof, for your solar panels(assuming that you have roof mounted panels).

Excellent explanations.
As a non-tech person, one way I think of this in simple terms is that at times the solar panel will make more than the regulator will allow to go to the battery. For example, the regulator might limit it to say 10 amps, but at times the panel might be putting out 12 or 14 amps. If the regulator were at the panel on the roof then it would knock it down to say 10 amps and then it has to travel down the wiring to the battery, so a bit more might be lost during that journey, so the battery might only receive say 9 amps. But if the regulator is close to the battery then that 12 or 14 amps will travel down the wire and, allowing for a bit of drop, might still be say 11 amps when it hits the regulator, be knocked down to 10 and that 10 will then go the short distance to the battery, with little loss. So that's the difference between the battery receiving say 9 amps or 10 amps, in this very loose, and probably technically incorrect, description.
My panel is on the front of the roof rack and the wires run down the snorkel, across the engine bay, underneath and come up in the battery box under the front seat, where the regulator is next to the battery.

The current, measured in amperes, does NOT drop along the length of a cable. The amps value at one end is exactly the same as at the other end.

Aaron

Originally Posted by AK83

Just use an online voltage drop calculator.

eg. lets assume you do a 6m cable run:
Using:
8B&S = 8mm²(7.7mm² actually) so the voltage drop on 13.8v would be 0.21v .. so down to 13.6v

6B&S = 13.3mm² so the voltage drop will be 0.12v instead.
Is that 0.09v difference important to you?

What current did you base these calculations on?

Aaron

Originally Posted by Aaron IIA

What current did you base these calculations on?

Aaron

Ah! sorry forgot to add that.
I think I used about 8 amps in the calculator .... based on the 6-7 that John quoted, going by the 110w solar panel he mentioned he has.

So yeah, maybe 8 amp max along those lines.. assuming 13.8v out from the controller, then 110(watts)/13.8 = 8(ish) amps.

Again, assuming John wanted to place the panel on the roof(near front) and assuming he would use the shortest possible cables, either inside or outside along pillar, I can't see more than 2m, maybe 3m, max of cabling.
So those figures I noted are going to be worse than what John would end up with in reality.

Note those numbers I noted down are from the first online voltage drop calculator I found too. >HERE<

pop in your physical numbers and calculate to your hearts content!
Also, note that actual real figures will vary in real world too, those calculators are theoretical for use ideal conditions.

I've had this happen to me with other electrical stuff, primarily trying to hook up a radio in my dads chook shed ... many many moons ago.
He got a roll of some cable from a flea market. I remember it being purple and old(ish) looking, snipped the ends as the copper ends were green with oxidation. But after a small snip showed good copper.
No idea what this cable was supposed to be from, but that's what he got.
Chook house was about 20-25m from house(where power was) and running a battery charger to power the radio at the house, ran the useless purple cable the 20 meters for both power and earth, but voltage drop was down to less than 6 volts.
I told him many times over that the cable he got was garbage, he wouldn't have it .. something wrong with the radio or the power supply. Cable looked capable had about a 6 or 7mm outer diameter, maybe 2.5 to 3mm copper core diameter.
Big roll maybe 100m or so(maybe 50, but heaps anyhow .. to have plenty left over after the two 20m cuts.
Anyhow, showed the 'ol man, that two shorter 1m lengths of cable and the radio worked ... but just wouldn't power the radio being so far away.
(ps. didn't do a resistance test, just a continuity test on the cables)
I never chased it up, but I assume one of the cable runs had a slight break in the core or something.
The main point being at 1 amps max(I think 10w radio), over 40 meters there shouldn't have been hardly any volt drop, but the reality using a dubious cable was far from what would a calculator would show nowadays.(back then the internet was only someones wildest imaginings). Radio never ended up getting connected either.