Solar to top up starter battery

[glennm]

I've put a 40W panel in the roof tray and connected it (via a PWM charger and a ignition-on relay that disconnects it) to the starter battery. Means my starter gets topped up all the time, so the car can sit idle for a month and it'll crank over without pause.

Tony
I would like to setup solar on the roof of my son's Adventra to keep the starter battery topped up as it really doesn't lend itself to a dual battery setup and he now has a 40l fridge in the back. I note you have setup a small panel (I want to put a 250w up top) to keep your starter topped up. What does the ignition-on relay setup look like wiring wise?
As an aside I just finished setting up a 130w panel on the roof of the Nav to look after one of my auxilliary batteries and so far it works brilliantly. Should have done it ages ago.
Thanks as always.

 

[glennm]

I think i have it? Changeover relay, ignition on source to pin 86, earth to pin 85, pin 30 to battery, solar regulator positive to pin 87a?

Solar regulator negative to battery negative?

And where did you mount the pwm regulator?

 

[bods]

Not sure if anything has changed technology wise since the original thread you are looking at, but, I have a 150w solar panel on my d22 roof rack. This is connected through a pwm solar regulator to the starter battery and then through the dual Battery isolator charges the second battery too.

I don't have a disconnect relay, the solar regulator reduces its output automatically when the alternator starts charging. I don't know how well a relay would work, the regulator I have states to disconnect the panel before disconnecting the battery, so you'd have to take that into account.

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[glennm]

Thanks bods that makes it even simpler and I am all for that.

Anything I need to take into account other than connecting/disconnecting in the right order?

Where did you mount the regulator as mine doesn't mention any water resistance unlike the ctek in mine.

Tony's post was from October 2017 http://www.navara.asia/showthread.php?t=173&page=20&highlight=starter+battery where I recalled he had mentioned hooking up solar to his starter.

Just want to make sure I don't cook anything.

 

[bods]

Not sure on an adventra. I have mine behind the back seat in my D22 as I have wiring to feed back to the battery from there. I guess it depends where you want to run the wiring from the panel inside the vehicle. You're better off having the regulator close to the battery and the panel further away if need be as you will get less voltage drop between the panel and regulator than the regulator and battery.

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[glennm]

Thanks again bods. the distance to the battery was on my mind too. it is a long beast and can't simply run it behind the cab like the d22.

 

[bods]

Yeah I know what you mean. If you run decently sized cable, say 0 gauge amp cable or similar to the boot, you shouldn't have too much trouble with voltage drop from the regulator to the battery. I can't really picture anywhere else to be able to get wiring from a solar panel inside, except going in through the boot.

Hopefully that helps a bit.

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[Old.Tony]

Sorry I'm late to this party!

Bods has it on the money. My PWM controller is actually up against the battery and the cables are about 200mm long, so there's no drop at all.

For the small amount of load a 40L fridge draws (about 4.5A peak, they usually are, since they're usually BD35 Secop/Danfoss) you'll probably find 8Ga cable is enough to keep voltage drop to a minimum. Jaycar sells this in Fig8 (so you have 8Ga positive and 8Ga negative bonded together, easy to do cable runs). You could use 4Ga, but over 6m I found the 8Ga cable lost 0.3V when 7.5A was drawn through it.

Your relay wiring looks spot on. If the relay - edit: I meant solar controller supports additional external chargers like bods' seems to, then by all means ignore the relay. If you use the relay in the way you've described, the PWM regulator is not exposed at all to the alternator while the ignition is on so it can't be damaged by the alternator. Also, do NOT use the regulator's load function, just its charging function.

Disconnecting most regulator/battery setups works as bods described - unplug the panel first, then the battery, so doing it the way you've described (which is how I do it) does carry the risk of the regulator getting all screw-balled because the battery has gone missing. You could interrupt the solar line instead which effectively stops the charger from doing anything to the battery but does leave it exposed to the wonders of automotive alternator surges on the battery side. Personally, I chose to risk a little screwball now and then over total failure of my massively expensive $11 PWM controller.

Yeah, I carry a spare.

 

[glennm]

Thanks bods and tony all sounds good. now looking forward to getting it all setup.

 

[bods]

No worries. I guess disconnecting the battery side of a 40w panel might not be too big a drama. Being that the 150w panel I have puts out almost 10a (I only have a 10a regulator anyway) it could do some damage I'd say. I have had mine set up the way it is for around a year now I'd say and haven't had any dramas. The regulator is only a cheap Supercheap Ridge Ryder one but has low and high voltage cut outs anyway so the alternator charging while it is still connected doesn't affect it.

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[glennm]

Thanks bods that does simplify it. just ordered a 200w panel and 20a regulator. pretty sure it has high/low cutouts but will double check.