Solar panel question

I have a 2nd battery in the car operated through a Redarc system. I have today mounted a panel on the vehicle and intend to use it to charge the battery to save starting the car. This is regulated via good quality reg not a plastronic but still a good one.

My question is can I leave both systems connected when Iam driving and let the regs to do the switching. Given that the solar reg has the anti backflow diode thingy.

Appreciate your time and thoughts,
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Reply By: Member - John and Val - Sunday, Jan 02, 2011 at 07:39

Sunday, Jan 02, 2011 at 07:39

Should be no problem having both running at the same time. An advantage is that the solar setup can provide a slightly higher voltage to push the battery up further than the alternator will. For solar to make a significant difference though you will need enough solar capacity to meet your electrical demands - suggest check out our blog Electricity for Camping where supply/demand is discussed in some detail.


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AnswerID: 440417

Reply By: Member - Robert R1 (SA) - Sunday, Jan 02, 2011 at 11:27

Sunday, Jan 02, 2011 at 11:27

I had a Redarc and panels charging my batteries at the same time in my old Hilux and it worked okay. I used a Plasmatronics regulator and the charging and load current went through a shunt and I certainly got more charging current when I started the engine compared to with the engine stopped so I figured it worked. Check it with an ampmeter and you will soon know.

AnswerID: 440437

Reply By: Mandrake's Solar Power- Sunday, Jan 02, 2011 at 13:22

Sunday, Jan 02, 2011 at 13:22
This is the best of both worlds as long as the current from the alternator does not go into the Solar Reg Input - Had one customer do this and asked why his nice new Solar Reg melted !! 110 Amps off alternator going into a 12 Amp reg --- BAD very very BAD...

2 seperate circuits and no problems at all ..


AnswerID: 440455

Follow Up By: sandk33 - Sunday, Jan 02, 2011 at 14:38

Sunday, Jan 02, 2011 at 14:38
I thank you everyone for their input but if I can just clarify one thing Mandrake.

You speak of 2 separate circuits...I will have a feed coming from my 20amp solar reg to the terminals on battery...and also have a feed coming from alt via redarc to battery terminals. Does this fit the two separate circuits or do I need an isolator in say the solar feed to block the alt feed getting to the solar reg. It does have electronic blocking and fuse control.
PV Charge Controller SBC7120

FollowupID: 712351

Follow Up By: Mandrake's Solar Power- Sunday, Jan 02, 2011 at 16:20

Sunday, Jan 02, 2011 at 16:20
Kevin ,

Yes what you are doing is fine ...

As I said some people have been known to assume the Solar Regulator will handle what comes out of their alternator and will common wire it with their Solar Panels .. ..

Circuit one - Alternator to Battery
Circuit two - Solar Panel to Solar Regulator to Battery ..

Cheers and happy camping ..


FollowupID: 712360

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