How to "Solar Charge" your Starter Battery

[chas142]

You could add a voltage booster on the output? Set it at ~27.6V to give a constant maintenance charge when solar active and would match what the alternator would output.
Something like this for example - https://www.amazon.co.uk/Boost-Converter-Yeeco-Voltage-Regulator/dp/B014IVDIXM/ref=sr_1_14?
I use a similar unit to make sure the voltage to the diesel heater doesn't drop below ~12.5V under load (saves having to start the engine to boost the voltage when starting it sometimes)

If you used this type of booster I think you would need to fit some sort of cut out system, if directly wired in it would try to increase the voltage when a vehicle load or the ignition is turned on, or whilst cranking. A change over relay on the ignition, (using it in the reverse, I know what I mean, I think), might solve some of the problem, dependant on ignition switch configuration. Another option might be to fit something like a low amperage bi-metallic circuit breaker, (auto resettable), in the system, or both!! Well that was one of my thoughts.

I came across a similar sort of thing years ago, but the other way round, 12 volt vans running around starting 12 & 24 volt trucks, they used relays solenoids and switches. It sort of worked ok, they always wanted an instant start so never allowed any charge to go into trucks batteries, so kept blowing up the system in the van. Still thinking about if any of that could be of use to you.

 

[chas142]

This is the dual battery solar controller that I use on my system;_ https://www.ebay.co.uk/itm/20A-Dual...=item4b29d2e87f:g:UP0AAOSwt8JZ4G7K:rk:47:pf:0

 

[Freespirit648]

I bought a 10w (yes 10) solar panel years ago so it does not require a regulator.
It has a long wire fitted so cut it and added a plug & socket and an in-line fuse,
The connector sits in the passenger footwell out of the way.
It sits inside the windscreen and still works efficiently through the glass.
I connect it up when it's parked on the storage site and when wilding for an extended time.
I have never had to have a jump start even when in storage for several weeks in the winter.
It lives in the passenger door pocket when not in use, I am no electrician and this was a simple fix for me.
I have a 120w panel for the 2 x 85a leisure batteries.

Freespirit648

 

[chas142]

I bought a 10w (yes 10) solar panel years ago so it does not require a regulator.
It has a long wire fitted so cut it and added a plug & socket and an in-line fuse,
The connector sits in the passenger footwell out of the way.
It sits inside the windscreen and still works efficiently through the glass.
I connect it up when it's parked on the storage site and when wilding for an extended time.
I have never had to have a jump start even when in storage for several weeks in the winter.
It lives in the passenger door pocket when not in use, I am no electrician and this was a simple fix for me.
I have a 120w panel for the 2 x 85a leisure batteries.

Freespirit648

Yes its a small panel but it will hopefully replace the small drain on the battery and the internial drain inside the battery. I have just got a small 20watt that I was going to fit facing south on my top box, not sure what I will do with it at the moment as I'm moving but as I seldom use the car now I may fit it in that like you have done. In the summer I may require a controller on that, but it would probably be ok now. I was an Auto Electrician. Oh just to mention that not all cigarette lighters are connected to a permanent feed, not on my Peugeot, so that will need to be changed or a separate socket wired in as I assume you have fitted.

 

[nabsim]

I bought a 10w (yes 10) solar panel years ago so it does not require a regulator.
It has a long wire fitted so cut it and added a plug & socket and an in-line fuse,
The connector sits in the passenger footwell out of the way.
It sits inside the windscreen and still works efficiently through the glass.
I connect it up when it's parked on the storage site and when wilding for an extended time.
I have never had to have a jump start even when in storage for several weeks in the winter.
It lives in the passenger door pocket when not in use, I am no electrician and this was a simple fix for me.
I have a 120w panel for the 2 x 85a leisure batteries.

Freespirit648

I did exactly the same with an outfit that used to live outside, kept the battery topped up all year round when not being used.

 

[bartman]

Thanks - this is the most straightforward explanation I've seen of what's needed to keep the vehicle battery topped up.
I gave up trying to sort out the best method ages ago and put one of these on my Christmas list!
I just keep an eye on the voltage level, and if I think the vehicle battery is low I run this from one of the sockets in the habitation area to the socket in the cab - both are permanently live.
I suppose I really should make a proper link via a relay, but the van isn't left sitting around for long enough for the vehicle battery to run down too much.

 

[chas142]

Thanks - this is the most straightforward explanation I've seen of what's needed to keep the vehicle battery topped up.
I gave up trying to sort out the best method ages ago and put one of these on my Christmas list!
I just keep an eye on the voltage level, and if I think the vehicle battery is low I run this from one of the sockets in the habitation area to the socket in the cab - both are permanently live.
I suppose I really should make a proper link via a relay, but the van isn't left sitting around for long enough for the vehicle battery to run down too much.

I assume you have solar for your habitation? I have a solar control which charges 2 banks of batteries, when there is enough sun and I haven't got two much on.

I also just order a Draper 12V Vehicle to Vehicle Car Battery Charger/Booster Cable Lead Car to Car, it might come in handy at some point as I think it boost the voltage to speed up charging.

https://www.ebay.co.uk/itm/Draper-1...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

 

[witzend]

This is my set up to get solar to engine battery didn't cost much either just remember to remove fuse before starting engine

 

[chas142]

View attachment 42386

This is my set up to get solar to engine battery didn't cost much either just remember to remove fuse before starting engine

Oh that looks technical,, I'm sure it will work fine!! You could replace the fuse with a trip & resettable circuit breaker, for the people like me who would forget to park the fuse, and make sure there is no chafing points in the cable run if you are running cable a long way, or fit higher rated safety fuse by both batteries.

 

[bartman]

I assume you have solar for your habitation? I have a solar control which charges 2 banks of batteries, when there is enough sun and I haven't got two much on.

I also just order a Draper 12V Vehicle to Vehicle Car Battery Charger/Booster Cable Lead Car to Car, it might come in handy at some point as I think it boost the voltage to speed up charging.

https://www.ebay.co.uk/itm/Draper-12V-Vehicle-to-Vehicle-Car-Battery-Charger-Booster-Cable-Lead-Car-to-Car/183098562857?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Yes, I have a 150w solar panel charging two leisure batteries.
The kit you have ordered looks as though it will do the same job as mine. I've only used it a couple of times, probably didn't need to, but it's handy as backup.

 

[chas142]

Yes, I have a 150w solar panel charging two leisure batteries.
The kit you have ordered looks as though it will do the same job as mine. I've only used it a couple of times, probably didn't need to, but it's handy as backup.

I mainly got mine to go from camper to car, or car to car, or car to camper, lol. I thnk it's just another tool in the tool box really.