Placement of solar panels!?

Jeremyc · 02-22-2018, 05:19 PM

Hi all,

Trying to decide on the placement of my solar panels. My batteries will be located on the front right side in an outside compartment underneath the bus, and beneath the passenger seat.

I understand that you really want the shortest distance possible between the panels, charge controller and batteries to minimise resistance.

As such, should i put my panels on the front of my bus so they're closer to the batteries?

We'd rather but our roof fan at the front, but I am worried that the extra feet of wire required if we were to put the panels at the back would allow more resistance than we prefer...

Would it make much difference?

Thanks in advance - this forum has been an amazing community to learn from

Jdawgsfanasty · 02-22-2018, 05:39 PM

Quote:

Originally Posted by Jeremyc

Hi all,

Trying to decide on the placement of my solar panels. My batteries will be located on the front right side in an outside compartment underneath the bus, and beneath the passenger seat.

I understand that you really want the shortest distance possible between the panels, charge controller and batteries to minimise resistance.

As such, should i put my panels on the front of my bus so they're closer to the batteries?

We'd rather but our roof fan at the front, but I am worried that the extra feet of wire required if we were to put the panels at the back would allow more resistance than we prefer...

Would it make much difference?

Thanks in advance - this forum has been an amazing community to learn from

How about fan b/t the panels and the main drop close to the controller?

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bus-bro · 02-22-2018, 06:08 PM

It all depends on what the output voltage is of the panel you use.
The panel voltage is dependent on the number of solar cells on the panel.

To make an electrical cable electrically shorter you use thicker wire.

Jeremyc · 02-22-2018, 06:57 PM

The fan in-between the panels might be a solution... We will be stealth moding a bit so i wonder if that might give us away?

We will be using 12v power from the panels. What size wires should I use to the controllern toi minimise resistance?

Jeremyc · 02-22-2018, 07:32 PM

I just measured the size of the panels and I can fit with 3 side-by-side on the roof with the 4th going horizontal across the bottom.

Alternatively I could do them horizontally on the roof and just do all 4 next to each other.

So i think i will position them at the front and that will give me the shortest cable distance.

Then the question is... Do you think it matters if the panels are close to the edges of the roof.... Do you think this is `too close`as they will be 153 total width and the roof is 170 total width

will it give away out stealth mode or will they be visible anyway haha

Jdawgsfanasty · 02-22-2018, 07:40 PM

Quote:

Originally Posted by Jeremyc

The fan in-between the panels might be a solution... We will be stealth moding a bit so i wonder if that might give us away?

We will be using 12v power from the panels. What size wires should I use to the controllern toi minimise resistance?

It's about amperage...which is wattage divided by voltage...try your app store for "wire sizing calculator" or "wire gauge calculator"...that should help...I tend to do badly trying to write stuff...hopefully you can find a good calculator

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Johnny Mullet · 02-22-2018, 07:40 PM

I mounted mine on the right (passenger) side of the bus. My thought is that before parking/camping, I would face the front of the bus East. This would get the panels at a pretty ideal location to get the most sun and also allows morning sunrise to start warming up the bus through the large windshield.

Jdawgsfanasty · 02-22-2018, 08:04 PM

Quote:

Originally Posted by Johnny Mullet

I mounted mine on the right (passenger) side of the bus. My thought is that before parking/camping, I would face the front of the bus East. This would get the panels at a pretty ideal location to get the most sun and also allows morning sunrise to start warming up the bus through the large windshield.

That's rather clever in regards to the windshield

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bubb, the real one · 02-23-2018, 08:34 AM

Distance between panels, controller and batteries does matter, it matters most if your entire system is 12v, if you can get 24 or 48v panels the distance matters less especially since we are only talking about an extra 10 to 15ft of wire length. If you already have 12v panels then you can hook them up in pairs so it is a 24v system,
What is the number and type of panels that you have, what controller do you have?

Jeremyc · 02-23-2018, 01:13 PM

Quote:

Originally Posted by bubb, the real one

Distance between panels, controller and batteries does matter, it matters most if your entire system is 12v, if you can get 24 or 48v panels the distance matters less especially since we are only talking about an extra 10 to 15ft of wire length. If you already have 12v panels then you can hook them up in pairs so it is a 24v system,
What is the number and type of panels that you have, what controller do you have?

I have these panels and bought 2 sets - so 400W total:

https://www.amazon.ca/Renogy-Monocry...2GBN39555GQEC0

I have this controller:

https://www.amazon.ca/Morningstar-TS...pwm+controller

What is the benefit of hooking them up so they are 24v? I actually only have two 235 amp batteries that are 6v and was going to hook them up in series to make 12v so if feel 24v will not be possible

PNW_Steve · 02-23-2018, 01:32 PM

Quote:

Originally Posted by bubb, the real one

Distance between panels, controller and batteries does matter, it matters most if your entire system is 12v, if you can get 24 or 48v panels the distance matters less especially since we are only talking about an extra 10 to 15ft of wire length. If you already have 12v panels then you can hook them up in pairs so it is a 24v system,
What is the number and type of panels that you have, what controller do you have?

It appears to me that the OP already has a PWM controller and a 12volt battery bank (2x6v in Series).

If that is the case high voltage panels would not work for him.

If he switched to an MPPT controller he would be ok with multiple 12v panels in series or higher voltage panels. Up to the limitations of the charge controller.

PNW_Steve · 02-23-2018, 01:36 PM

Quote:

Originally Posted by Jeremyc

The fan in-between the panels might be a solution... We will be stealth moding a bit so i wonder if that might give us away?

We will be using 12v power from the panels. What size wires should I use to the controllern toi minimise resistance?

Renogy has a wire size calculator on their website:

https://www.renogy.com/calculators/#tab_solar-cable

BurlKing · 02-23-2018, 03:30 PM

Optimum Operating Voltage: 18.9V

looked up your panel on renogy.

so IF you ran it in series, youd have a 37.8V, 5.29Amps.a mere 5 amp wire, you dont need to worry about any loss, just get 10gauge wire or so for your whole run and you'd be fine.

even in parallel though you'd be running at 18.9v, and 10.58 amps. your controller probably handles that better. still wouldnt kill you on money for wire

the MPPT charger i have will step down your volts to match your battery bank. not sure about yours.

bubb, the real one · 02-23-2018, 05:04 PM

the controller can take 12/24/48v from your panels and can charge batteries in a 12/24/48v configuration,
Hook your panels up so you have 2 pairs of 24v panels, this means you can run a smaller wire without loosing voltage,
As you said, hook your batteries up as a 12v pair,
Be sure you read the manual several times before you start connecting wires, make sure you hook the batteries to the controller and wait a minute before you hook up the panels to the controller, the controller gets it own power from the batteries, it will turn itself on and sense the battery voltage, then you connect your panels.
Cover your panels with a blanket as you make the connections, it keeps the sparks down,
If you are sure you are never going to enlarge your system in the future connect each panel to a breaker before the controller, for safety and it helps you troubleshoot in the future.
If you will upgrade the system they make some bus bars between the batteries and the controller,
Fuse the positive wire on each battery, unintentional welding is scary.
Put a battery screw-in disconnect between the positive bus bar and the controller if you do a bar, it is so nice to be able to disconnect cables without all those pesky sparks.
It helped me a lot to study a dozen systems before I designed and built my system,

PNW_Steve · 02-23-2018, 05:11 PM

OP: If I understand some of the posts correctly, some are telling you that you can put 37v-48v into your PWM controller and charge a 12 volt battery bank.

That is not correct. If you had an MPPT controller then it would be correct.

Please forgive me if I am misunderstanding. I would hate to see the OP damage his controller and possibly his batteries.

bubb, the real one · 02-23-2018, 11:07 PM

• Do not connect a solar input greater than a nominal 48V array for battery
charging. Never exceed a Voc (open-circuit voltage) of 125V.
• Charge only 12, 24, or 48 volt lead-acid batteries when using the standard
battery charging programs in the TriStar.

I just copied this from the morningstar ts45 manual, If I read it correctly it states the voltage the controller can receive and what voltage of batteries it can charge.

ThunderstruckStudios · 02-23-2018, 11:28 PM

Quote:

Originally Posted by PNW_Steve

OP: If I understand some of the posts correctly, some are telling you that you can put 37v-48v into your PWM controller and charge a 12 volt battery bank.

That is not correct. If you had an MPPT controller then it would be correct.

Please forgive me if I am misunderstanding. I would hate to see the OP damage his controller and possibly his batteries.

I second this. I've always read that with the smaller/cheaper PWM controllers, your solar array voltage has to match your battery voltage.

It's a different story with an MPPT controller - you can put in any voltage up to its maximum and it will boost/buck it to the appropriate battery charging voltage.

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