Solar Calc.

[Kelvin12]

Bruce,

48v to the regulator. Approx. 5.2m from the switch to the regulator then 3.8m or thereabouts to the batteries. From the switch 9m in total plus the 3m from the panels to the switch. In total 12m run from the panels to the batteries.

Hope this is making sense.

Dirk

[T1 Terry]

Is it correct that it'll be 48V all the way to the regulator & then a short run to the batteries?
My first impression is that you might need heavier wire for the 24V section.
Some sparky will no doubt confirm or suggest something.

Other way around Bruce, the higher the voltage the lower the amps for the same number of watts. The size of the cable directly relates to the amps that will pass through it, 6 B&S cable should be fine if those length include the return path.

[Kelvin12]

Terry,

Nope that's one way, well as I am understating you. The total length is 9m one wire only, no return. So I will need to buy 18m in total of wire to run 2 - 9m lengths, pos. and neg.

Is this making sense.

Dirk

[T1 Terry]

Here ya go, http://www.kilowatts.com.au/calculator-voltage-drop.php 2% voltage drop, return run length 18mtrs, amps 15, voltage 65v (Vmp for each 24v panel roughly 32v x 2 in series x 2 in parallel) Comes out to around 10mmsq, so look that up in this table http://www.engineeringtoolbox.com/awg-w ... d_731.html and it says 6 B&S (same as AWG) is 13.3mmsq, so one length of 6 B&S dual core from the switch to the controller. Then 6mtrs return from the regulator, so in the first one, 2(% voltage drop), next 6 (mtrs) next 30 (amps) next 24 (volts at the battery) calculates to 25mmsq, so 2 lengths of 6 B&S twin core required.

[oldtrack123]

Is it correct that it'll be 48V all the way to the regulator & then a short run to the batteries?
My first impression is that you might need heavier wire for the 24V section.
Some sparky will no doubt confirm or suggest something.

HI Bruce

You do have it right , perhaps Terry misread your post

Hi Dirk
6mm2 [9B&S] Will give you a loss of around 1.5V for a pos & a neg [EACH 9M long] at max panel current.
Since that is before the regulator it will not be a problem , just loose you a few Watts [around 30W]
But more important what is the distance from reg to batteries
A Pos & Neg each 1M long will loose around 0.2V per metre at max panel output
That is the total Max,you should think of loosing even with LA batteries

High voltage drop in that distance gives error in SOC sensing for the reg, unless you have a seperate voltage sensor cable on the reg


PeterQ

[Kelvin12]

Thanks Terry, Sort of had this in my mind but wanted to make sure. I use that Tool Box regularly, great help. Now for a question that seems to have lost its value in modern times. What if, like we did in the "old days", use the chassis as a return rather than an return earth. Seems to me we are missing a better return earth path. Then again maybe I have lost touch with "new" thinking. The only return earth I remember was on the pommy engineering stuff, god help us, some nightmares there.

Dirk

[oldtrack123]

Thanks Terry, Sort of had this in my mind but wanted to make sure. I use that Tool Box regularly, great help. Now for a question that seems to have lost its value in modern times. What if, like we did in the "old days", use the chassis as a return rather than an return earth. Seems to me we are missing a better return earth path. Then again maybe I have lost touch with "new" thinking. The only return earth I remember was on the pommy engineering stuff, god help us, some nightmares there.

Dirk

HI
A quick sensible answer
The chassis is an unrealiable circuit path , unless you are sure of continious metal from end to end' [ NO JOINTS]

PeterQ

[T1 Terry]

Yeah Peter, must have read that bit back to front, I'll go and stand in the corner for a while, but my other set of calculations was about right wasn't it?

Don't do an earth return with solar, you will have as many problems as the pommie vehicle electrics with Lucas electrics, then add body corrosion due the voltage differences between panels

[Kelvin12]

G'Day Peter,

Bit slow at getting back to this question, getting rid of the grandkids....peace at last.... Haven't seen you pop up for ages now, hope all is well with you.

Reg. to batteries 4.200 or so, one wire. So a total with 2 wires of 8.400. If things get to far away I can relocate the reg to the interior of the bus from the bins, that way it would be 3.500, total 7.000. I would prefer it down in the bins along with the inverter but if its to far away then happy enough to relocate to the interior cupboards.

Hell this stuff gets confusing.

Dirk

[Kelvin12]

Terry,

How was the pos. earth days and generators. Almost made me give up my apprenticeship. We had a pom tech teacher that thought the Brits. made the most perfect vehicle ever to grace the roads..... the stuff of nightmares.

Dirk