Adding solar

[Adam b]

I currently have a 40watt solar panel on my van, so really need to add a bigger panel.
Can I use the existing panel I know I need a bigger controller as it just has a seargent 20/40watt regulator, & can I use the existing wiring from the controller?

 

[I2C]

Looking at the controller it’s limited to 2.5A (40W solar panel) so yes, you will need a new controller if you’re going for a bigger or more than one panel.

If you’re thinking of one panel now and maybe add another one later get a controller that can manage two (or more) panels would be my advice. We have a controller that can take 240W but we currently only have 160W.

 

[Adam b]

I will be fitting a new controller , could I use the existing wiring from the controller?

 

[I2C]

That’s a difficult question to answer without knowing the sizing of the wiring you have. Wire needs to a certain size (cross section) for the amps it‘s going to have travelling down it and the distance from the solar panels to the controller.

There are plenty of sites out there that can give you the figures, one I’ve used in the past is Blue Sea Systems.

 

[monzer]

I did exactly what you are planning. But...

I decided just to get rid of small existing panel as it might not have worked too well with a different panel with different power rating.

I used new wiring down to controller to. Should be easy enough to run in via your existing cable though. Maybe a bit of sealant to remove then make waterproof again.

Double check position of where you want new panel/s and make sure you've enough length of wiring. May need 2 to 1 connectors if you are using more than 1 panel.

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[I2C]

Controllers are another interesting choice Some will say MPPT, others will champion PWM. There’s also the choice of serial or parallel wiring. Personally I went serial (less wire and no obstructions on the roof), 2 panels and a Votronic MPPT 250 controller that can also trickle charge the vehicle battery without having to buy a battery master.

Good luck with whatever you choose.

 

[Adam b]

I might phone seargent tomorrow as the wires from the regulator go straight to the psu am I better wiring direct to the battery?

 

[Stealaway]

I kept my solar panel's completely separate from the on board regulator.
I used a dual battery's solar regulator and wired it directly to the starter and leisure batteries.
There is no need to involve the Sargent

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[I2C]

I wired mine from the solar panels to the charge controller and then to the leisure battery.

Our seargent would only take 100W I think (been a while) as it’s an older van so went straight to the battery (leisure and trickle feed to vehicle). All it means is I don’t get the information on the control panel of what’s happening with the solar but I can live with that - it does tell me the voltage of the batteries so I know they’re charging/charged.

 

[autorouter]

If you're running a new wire from the roof to the controller, the cost of wire is small compared to the effort of rewiring. It's a good idea to use wire at least one size thicker than necessary, so if you want to add more panels the wiring is still good enough. If you use standard solar panel connectors (MC4) they are weatherproof, and you can get 2-to-1 adapters for future expansion.

There are two issues with wire size, safety and voltage drop. In 12V systems, voltage drop is very important. Any wire that is OK for voltage drop will be more than adequate for safety. The higher the amps, the higher the voltage drop. Voltage drop also depends on two things, length and cross-sectional area (CSA). Wire is usually described by its CSA, for example 2.5mm2 or 4mm2.

There are calculators or charts that will give you the voltage drop given the length and the CSA. Typically you should aim to keep the voltage drop below 3%, the lower the better. Don't forget that voltage drop happens equally along the positive feed and the negative return. Here's a calculator, at the end of a page of explanation:

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[Adam b]

Ok so I am going to get the solar panels & a new charge controller which will go direct to the battery, can I leave the existing 40watt panel with its own controller which goes to the Sargent psu ?

 

[Tombola]

Ok so I am going to get the solar panels & a new charge controller which will go direct to the battery, can I leave the existing 40watt panel with its own controller which goes to the Sargent psu ?

Yes

 

[Jimbohorlicks]

Or you could wire the 40 w solar controller to your starter battery to keep that topped up.