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Walt
9th April 2012, 11:34 AM
Has anyone installed a solar panel using the panel regulator to charge a lead acid battery that is also charged from the vehicle alternator?
If so, are there any issues with both charging sources charging the battery at the same time - ie can the alternator charge damage the solar components and visa-versa?

I have searched the internet for a circuit to do this but I cannot find one also I have asked three on-line suppliers of solar panels who request questions from buyers but none have responded.
I would be most greatfull for any assistance or pointers to sources of information that will help.

Bigrig
9th April 2012, 11:46 AM
Hey mate

No doubt someone will be able to assist, but in the meantime how about slipping over to the introductions section and posting up some info about yourself and the rig ... no harm done mate, but something we ask for from all new members - just lets people know who they're yakking with etc.

That said, welcome aboard mate, hope you hang around and enjoy the place!!

the evil twin
9th April 2012, 12:15 PM
Are you chasing higher charging current? If so I would get a bigger solar array or are you talking about a panel on the roof of the vehicle or whatever to supplement the Alternator as you drive?

You would not connect the Alternator output to the Solar Regulator input if that is what you mean as solar panels may put out up to around 20 Volts depending on SOC of the battery and the regulator and you don't want that feeding into the Alternator circuit.

There is no reason why you cannot connect the Regulator output and Alternator output to, say, an Aux battery but they will essentially load share across the full load not just the chosen battery so the battery may end up with an effectively lower charging current.

Almost all Panels have blocking diodes in them so the Alternator won't hurt the Panel and as long as you stay on the regulated side the Solar won't hurt the Alternator.

What exactly are you trying to do?

Walt
9th April 2012, 01:34 PM
Thanks evil. You summed it up quite well in your reply. Really all I want to do is have a 120w solar panel on the roof of my Patrol feeding via its solar controller a second lead acid battery (the "house" battery) in the vehicle that is also connected to the vehicle battery (and therefore the alternator) via a manual dashboard mounted toggle switch.

When the vehicle is moving both the vehicle battery and the second battery will be charged from the alternator AND the solar panel. When camped up the dashboard switch will disconnect the main battery from the "house" load (a fridge etc) and the second ("house") battery will be charged via the panel until the next time the engine is started. Of course if the switch is left on both batteries will charge from the solar unit as well as supply the house load.

My concern was the two charging systems interfering with each other when the vehicle is moving and from your reply (if I read it correctly) it appears that this should not be a problem.

the evil twin
9th April 2012, 01:53 PM
Cool.

One issue tho if you want "...Alternator AND Solar Panel...".
You will need a Solar controller that has an adjustable cut out. Most fixed Solar Regulators will cut out at 13.5 to 13.7 Volts. This is below the Alternator which is 13.8 or more (usually 14.0 or higher). This means when the engine starts and after a short period the Solar Regulator will "see" more than 13.7 Volts, think the battery is charged and float.
Ergo if you are driving then the Panel will not be contributing to the charging load.

Run your interconnect thru a decent relay controlled by the dash toggle switch as you can get quite high current flow in that circuit (if the switch is on and linking the batteries and you start the vehicle for example or if the house battery is low and you throw the switch) and all should be good.

As you mention be aware that you will also discharge the batteries equally if they are linked and you are camped up so keep an eye out that you don't inadvertently flatten the cranker.

Walt
9th April 2012, 04:52 PM
Thanks for that.

Walt

PS - just typed a longer reply using "reply to post" and lost the lot when I clicked "Reply to thread" thinking that would post the comment.

mudski
26th June 2012, 04:02 PM
On topic. I fail to see the advantage of having both charging at the same time. The alternator will charge faster than a 120w panel. I have 180w panels and the alternator can charge faster. I just us my panels when the car is parked...

megatexture
26th June 2012, 06:31 PM
Just buy a dc-dc charger that has a in built solar regulator they won't charge from both at once they select the one of the two with the best output redarc and ctek have them and are well known. On another note I have a 20watt panel connected to my camper when its not in use to maintain charge and it had a warning on it not to have the pannel connected when starting a car it didn't say why but there must be a reason

Cuppa
19th March 2013, 03:39 PM
Just seen this thread.
I have a bit each way.
On our bus I have solar & alternator charging together as described in the OP without problem. Has been in operation like this for a number of years.
On the Patrol I have a Redarc BCDC1240 combined DC to DC charger & solar regulator. This charges from one or the other (priority to alternator) but not both together. This also works well.

Cuppa