#172044  by sjb
 Sun Apr 11, 2021 9:21 pm
Hi there, first time using this forum and have some Q's about first time solar installation on our caravan that we have just bought. Hopefully they are pretty straightforward and apologies if these have been asked over again. I've noted some photos which might be clearer. I've not bought anything yet, I just want to check I've got my head around this before I commit. Many thanks.

From solar panel to ideal location of controller would be about 1.5m and then 2.5m to battery. Is length to battery too long? To get the controller right near battery, the controller would have to be either surface mounted or in a storage space under seating.

I'm confused by what the shunt is on the wiring diagram in another post. As this has an existing installation, will it already have a shunt?

Can I take just the red/positive cable up to the battery and the negative/black connects to the common at the existing control panel? The single chocolate box connection in photo is on common negative. Or would I take the black/negative from the controller and connect to the existing chocolate box connection near the battery and is this where I would add a shunt?

Assume red/positive from controller connects between the battery and the existing fuse in this photo adding in a fuse for the controller cable?

Presumably the existing battery meter is okay and will still work ignoring that it is quite small scale?
80F1A0BA-9048-41C2-85FB-24D9247888BC.jpeg
7E374DAB-31BE-4E1E-8CB7-0390CC489668.jpeg
6D065478-3EFF-42BA-AF0A-D0B4D749FB9E.jpeg
94A49B42-C0A5-4C12-80D2-E91C59716073.jpeg
 #172058  by Neddy
 Mon Apr 12, 2021 8:55 am
"From solar panel to ideal location of controller would be about 1.5m and then 2.5m to battery. Is length to battery too long?"
No, it's not, but you could do a lot better. The ideal position for a solar controller is as close to the battery as is practicable.

"To get the controller right near battery, the controller would have to be either surface mounted or in a storage space under seating."
Right. I have got my controller in a storage space under seating. Alongside the battery - where most people put them. You could too!

"I'm confused by what the shunt is on the wiring diagram in another post. As this has an existing installation, will it already have a shunt?"
No, it won't. Shunts are usually mounted right on the battery Negative terminal.

"Presumably the existing battery meter is okay and will still work ignoring that it is quite small scale?"
Your existing "battery meter" is just a voltmeter and is not worth retaining if you install a "proper" Battery Monitor - which could go in its place.

Make sure that the panel(s) you buy are 12 volt not 24 volt. If more than one, connect them in Parallel.
Get an MPPT controller with a "remote" monitor. (The space you had earmarked for a controller would be ideal for this).
You really do need a proper "Shunt based" Battery Monitor. Now is the time to fit one. They start at $50 or less.

Here is a wiring diagram that you might find useful.
Solar Wiring Simple.JPG
 #172062  by Paul-Carter
 Mon Apr 12, 2021 9:34 am
As far as cable length goes, you can offset that buy using largest possible cable and any good controller will have adjustment available for the setpoints so you could measure any volt drop in the cables and alter the set points accordingly.
 #172066  by scubadoo
 Mon Apr 12, 2021 10:21 am
All good advice but I disagree with:
Neddy wrote:
Mon Apr 12, 2021 8:55 am
...Make sure that the panel(s) you buy are 12 volt not 24 volt. ..
Opinion only.


Buy 12V or 24V panels according to your preferences re output watts, cable size, placement, roof space, solar controller etc.
Total daily output in any light conditions for similar accurately rated wattage panels will be all but identical regardless.

Check Mr. Google, Mr. Victron, diysolarforum.com (Will Prowse) etc.etc. and etc. :?



PS My Victron MPPT solar controller is mounted at the battery for minimum cable losses and ease of wiring.
Daily data is displayed and stored via Bluetooth to our phones/tablets for future reference.
 #172067  by Neddy
 Mon Apr 12, 2021 12:05 pm
Opinion only? Nah. It is a matter of fact that for 12 volt MPPT systems, 12v solar panels are more efficient than 24v panels.
The higher the panel voltage, the lower the MPPT conversion efficiency.
Here, for example, are efficiency curves for a typical MPPT controller :-
SolarPanel Config.JPG
 #172070  by scubadoo
 Mon Apr 12, 2021 12:50 pm
Neddy you have shown that graph several times in the past. Who says that is "typical" of recent controllers?
It is certainly does not apply to our controller.

Victron even recommend 24V panels for 12V setups in a couple of their YouTube videos.
As posted in another thread here is my "proof" of our 800W worth of 24V panels delivering just 5W into our 50A Victron MPT controller at 97% efficiency into the battery. Nothing like your graph.
12V panels would be no better. Even at 99% efficiency the gain would be 2% of 5W or even 50W for 30 minutes = nothing.
Screenshot_1 (1).jpg
 #172076  by sjb
 Mon Apr 12, 2021 2:33 pm
Thanks - that was the wiring diagram i was referring too.

Ahhh! So the controller can be concealed. I didn't realise. That means I can place right next to battery under seat which is dead space anyway. I'll have about 4m from roof panels to controller and bugger all from controller to battery (just enough cable to make it easy for me to make the connections to battery which will all happen by the battery including adding the shunt). Assume that is optimal? This is making it sound even easier!

The battery monitor would have to be ran back to the existing panel though unless i find somewhere else for it. Is the shunt optional if the controller comes with bluetooth like scubadoo suggests? Without a shunt or bluetooth you wont know what is going on with battery?

When you say shunt based battery monitor - is it something like this: https://www.jaycar.co.nz/100a-6-5-100v- ... -IQAvD_BwE

Any recommendations for where to buy in CHCH?
 #172078  by scubadoo
 Mon Apr 12, 2021 3:25 pm
sjb

It all depends somewhat on your eventual selected solar panel wattage and budget.
My suggestions solely based on my experience over the years.
Others will have their own preferences.

Victron SmartSolar MPPT 75/15 controller good for up to 220W. Size to suit.
Mount beside the battery. Control parameters and display data via your phone/tablet.
e.g. Direct from Victron
There are cheaper less configurable controllers available. Avoid anything under $100.

Add a $50 Juntek battery monitor display at eye level in your RV. The shunt is mounted close to the battery.
e.g. Juntek 1300
The display can be wireless or hard wired to the shunt module.
All credit to Neddy for the original thread:
https://nzmotorhome.co.nz/forum/viewtop ... 55&t=17215
https://nzmotorhome.co.nz/Forum/viewtop ... 55&t=19169
https://nzmotorhome.co.nz/Forum/viewtop ... 0&p=171366
  • 1
  • 2
  • 3
  • 4
  • 5
  • 9
Pay with Paymate Express