Fixed and portable solar input into to 1 charging system

Submitted: Saturday, Jan 11, 2020 at 08:56
ThreadID: 139541 Views:2344 Replies:7 FollowUps:8
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I am going to run a fixed solar panel on the roof of my van. I am considering running a portable solar panel so that I can have time in the shade if it’s stinking hot. My question is this achievable by simply plugging in the portable solar panel in correctly via an Anderson plug etc. I am aware that it would require the correct wiring setup. My aim is to keep my batteries charged without buggering them. Thanks
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Reply By: Banjo (WA) - Saturday, Jan 11, 2020 at 09:01

Saturday, Jan 11, 2020 at 09:01
As long as your Solar controller is capable of handling the extra input the answer is yes.
AnswerID: 629477

Reply By: 2517. - Saturday, Jan 11, 2020 at 09:14

Saturday, Jan 11, 2020 at 09:14
Hi if you have two batteries you will need more then 2 panels to charge them ,why not mount 3 or 4 panels on the roof and then you can forget about it. Over the years I have had little or no problems with shade.
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Follow Up By: Peter_n_Margaret - Sunday, Jan 12, 2020 at 13:19

Sunday, Jan 12, 2020 at 13:19
I suggest that the charge capacity required is relative to the power consumed from the batteries rather than the size of the batteries.
Cheers,
Peter
OKA196 motorhome
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Reply By: HKB Electronics - Saturday, Jan 11, 2020 at 09:39

Saturday, Jan 11, 2020 at 09:39
Just make sure solar controller can handle the extra input as pointed out above, and make sure the new panel specs are as close as possible to the present panel, ie open circuit voltage and max power voltage assuming you will be putting the new panel in parallel with the old one.
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Reply By: RMD - Saturday, Jan 11, 2020 at 09:49

Saturday, Jan 11, 2020 at 09:49
Trevor
Does your original panel have a blocking diode on it's output? If not, if it is in shade and another is connected in parallel the higher voltage may try and back feed to the original panel with some loss experienced. The Regulator has to have sufficient capacity to handle both current sources as the panels might both be in full sun sometimes.
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Follow Up By: Dave B18 - Sunday, Jan 12, 2020 at 14:05

Sunday, Jan 12, 2020 at 14:05
You have never been able to buy a retail solar panel without diodes in the panel - NEVER.
Even if there wasn't a diode in the panel, electronic solar regulators have never allowed the batteries to drain back - NEVER
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Follow Up By: Frank P (NSW) - Sunday, Jan 12, 2020 at 21:09

Sunday, Jan 12, 2020 at 21:09
I know he's gone now, but Dave B18 has missed the point.

Panels may be made with bypass diodes but to my knowledge none are made with blocking diodes.

Panels in parallel should each have a blocking diode in the output if it is likely that some will be in shade and some in sun.

It's not about blocking current from the battery to the panels. As Dave B18 suggested, the regulator does that.

It's about blocking current from lit panels in a parallel array backfeeding into shaded panels in that array. This happens within the array, before the regulator comes into play.
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Follow Up By: Peter_n_Margaret - Monday, Jan 13, 2020 at 15:27

Monday, Jan 13, 2020 at 15:27
And the absence of those blocking diodes can cause hot spots in the shaded panel.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: HKB Electronics - Monday, Jan 13, 2020 at 17:49

Monday, Jan 13, 2020 at 17:49
I have tested many panels over the years and found if the panels are of similar specs you only get a few milliamps flowing back into the shaded panel at its max output voltage. In my opinion if the blankets max output voltage is similar to the existing panels fitting blocking diodes would be a waste of time.
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Reply By: CSeaJay - Monday, Jan 13, 2020 at 14:58

Monday, Jan 13, 2020 at 14:58
Not only is the answer a simple "Yes" (as stated if the controller has capacity) but I would add that it is indeed preferable to do it that way as opposed to any other arrangement.
CJ
AnswerID: 629511

Follow Up By: Peter_n_Margaret - Monday, Jan 13, 2020 at 15:31

Monday, Jan 13, 2020 at 15:31
Alternatively, there is no problem using multiple solar regulators into the same battery, if that is a convenient solution or if the original regulator is fully loaded.
The multiple regulator approach also provides for some redundancy.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: Genny - Tuesday, Jan 14, 2020 at 08:27

Tuesday, Jan 14, 2020 at 08:27
I don't believe that is correct, or at least, not always.
At least some regulators will shut down when multiple regulators are in use. Presumably, they sense the higher voltage (from the other regulator), assume the battery is full, and shut down.
Certainly my two portable panels do that.
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Reply By: Member - Rustygq - Saturday, Jan 18, 2020 at 08:34

Saturday, Jan 18, 2020 at 08:34
I do a lot of free camping and use a portable panel as well as the one on the van roof. I plug the portable into the start battery on the truck, which then feeds the aux battery. I then run a lead to the Anderson plug on the van which in turn is connected direct to the van battery. I asked my auto elect before I did it an he said it should work. Ive been doing it for a few years now with no probs. Truck batteries are always charged up as well as the van, even when running the fridge in the truck. I also carry a longer (13 mts) lead that I can use if the van is in shade

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Reply By: Don H7 - Thursday, Feb 13, 2020 at 17:18

Thursday, Feb 13, 2020 at 17:18
As I understand it, the output voltage is too high at around 18VDC for a 12 v lead acid battery to survive for long. It's quite simple to wire in a DC/DC converter and enjoy hassle free charging. I did it to mine ages ago and can't remember the details. I run only the one battery so I set out 2x160 watt panels (overkill) and leave fridge on 24/7. I do, however set the fridge cut off voltage at 12.5 volts as a safety. I have run into grief once but have made the cutoff voltage change and had no issue since.
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Follow Up By: Frank P (NSW) - Thursday, Feb 13, 2020 at 20:40

Thursday, Feb 13, 2020 at 20:40
I don't know about a DC/DC converter doing the job, but a solar controller would certainly be a help.

If your DC/DC converter had a solar input, then yes, but not all do.

Other replies have answered the OP's question, particularly HKB's.
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