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Old 09-27-2021, 11:59 AM   #1
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Trickle charge solar panel

I want to purchase a set up to trickle charge my motor home when it is in storage. I have four 6 volt batteries, in the 12 volt system. What watt solar panel would be good for this application?

Thanks

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Old 09-27-2021, 01:05 PM   #2
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Solar panels are so cheap, I would go with a 100 watt panel and an inexpensive PWM controller. You can buy these two items on Amazon for about $100, a Newpowa solar panel for $80 and a Renogy 10A PWM controller for $20.

If all you want is storage trickle charging then you don't even have to permanently mount them, which adds a lot of labor and some cost to do so. I prop a solar panel up on the south facing back bumper at an angle to get most of the sun's energy but also to shed snow.

I also have a rooftop mounted panel (that gets covered by snow) that is connected to a 10A controller and then to the battery. You can do the same, just don't install the controller permanently. Run the wires from the solar panel outside to the controller set inside the compartment where the batteries are located and then to the batteries. Most MHs will also charge the chassis batteries if the coach batteries are being charged.

But having the solar panel and controller permanently mounted is also useful to keep the batteries topped up after a camping trip. This takes mounting feet, a solar port to run the wires into or run them down the refrigerator vent.

Good luck with your choice.

David
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Old 09-27-2021, 02:15 PM   #3
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Originally Posted by smithgarnat@aol.com View Post
I want to purchase a set up to trickle charge my motor home when it is in storage. I have four 6 volt batteries, in the 12 volt system. What watt solar panel would be good for this application?

Thanks
What DavidEM said.

Not knowing what year your Miramar is and if it is pre-wired for solar...I, too, suggest that you invest in a rooftop solar system.

A Renogy 175 watt Flexible panel is under $280 and can be fastened to the roof with Eternabond tape. A very simple DIY.
If you're not pre-wired, it's just labor fish-lining #10 stranded wire to the solar controller, then on-to the house battery bank.

You'll be glad you made the investment.
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Old 09-27-2021, 03:26 PM   #4
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Thanks everyone for the feedback.

My unit 2017 37.1 Miramar
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Old 09-27-2021, 04:14 PM   #5
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Caution using the flat flexible panels. There is technical data showing early degradation of the solar cells from excessive heat build-up due to not having good air circulation under the panel.

While they are aesthetically pleasing being less conspicuous, and fit well to curved surfaces, that tight fit is a known detriment. As with any electronic component, heat is the enemy. Ideally you want maximum sun energy in the form of photons, but you want to dissipate heat energy.
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Old 09-27-2021, 04:23 PM   #6
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Caution using the flat flexible panels. There is technical data showing early degradation of the solar cells from excessive heat build-up due to not having good air circulation under the panel.

While they are aesthetically pleasing being less conspicuous, and fit well to curved surfaces, that tight fit is a known detriment. As with any electronic component, heat is the enemy. Ideally you want maximum sun energy in the form of photons, but you want to dissipate heat energy.
I agree with you. I have solid flat panels on my roof (as I believe you are aware)

That said…many RV owners look at the cost-benefit analysis and decide that a 5-8yr flex solar panel life expectancy that they can easily DIY immediately is worth it.
That in 5-8yrs they may not even own their current RV.
Or, if they still have the RV they can update with newer technology.

So I understand both sides of the flex vs solid panel argument.
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Old 09-27-2021, 04:35 PM   #7
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Solar and battery connections

I am purchasing Whatís required to trickle charge my 2017 Miramar 37.1 while in storage. I just have one question. Based on the picture which negative and positive termination should I use. This is an old picture. I have since replaced the batteries. But the layout is the same.

Thanks
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Old 09-27-2021, 05:10 PM   #8
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Originally Posted by smithgarnat@aol.com View Post
I am purchasing Whatís required to trickle charge my 2017 Miramar 37.1 while in storage. I just have one question. Based on the picture which negative and positive termination should I use. This is an old picture. I have since replaced the batteries. But the layout is the same.

Thanks
No picture here.
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Old 09-28-2021, 12:50 AM   #9
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Attaching solar panel wires

Hi. I have a 2017 Miramar 37.1.the attached is my battery box. I have since replaced the batteries. What terminals would I use for the positive and negative cables?

Thank you
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Old 09-28-2021, 01:26 AM   #10
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Hi. I have a 2017 Miramar 37.1.the attached is my battery box. I have since replaced the batteries. What terminals would I use for the positive and negative cables?

Thank you
Positive to where the white arrow is pointing.
Negative to any metal ground.

And you don't need to start a new thread for each post on your solar project - just add to this thread.
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Old 09-28-2021, 01:54 AM   #11
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Sorry. I donít see the white arrow.
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Old 09-28-2021, 04:40 PM   #12
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Can someone tell me where to put the positive connection for my solar controller, the negative will go to ground to body of motor home.

Thank yoy
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Old 09-28-2021, 04:51 PM   #13
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Solar controller has a Pos & Neg coming in from the roof
And
A Pos & Neg going directly to the posts on the batteries.

Iíll find you a good photo and post it for you in a minute.

Hereís both Series & Parallel wiring set-upsÖ
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Old 09-28-2021, 06:13 PM   #14
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When you are in parallel, all the feed wires come to the controller as separate feeds... you probably should use a bus where you connect all the feeds - THEN a single wire feeds those to the controller. Refer to the (nicely detailed, by the way) diagram posted by taylorbob1.

Notice also in the diagram that the battery negative post is grounded to the chassis. Therefore, you DO NOT ground the negative panel terminals to chassis. The charge controller is merely an intermediate component in a larger DC circuit... in which the battery is the termination point. Current generated by the panels FLOWS THROUGH the charge controller, is regulated, then flows into the storage batteries.
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Old 09-28-2021, 06:44 PM   #15
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Can someone tell me where to put the positive connection for my solar controller, the negative will go to ground to body of motor home.

Thank yoy
Well, wasn't that stupid of me to not post the picture. Here you go:

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Old 09-28-2021, 07:31 PM   #16
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Thanks. Here are the clamps. I plan to use for my one panel and controller to trickle charge the batteries while my motor home is in storage . I add distilled water to my batteries. Are these batteries Flooded, type batteries or acid?

Thanks
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Old 09-28-2021, 07:42 PM   #17
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Thanks. Here are the clamps. I plan to use for my one panel and controller to trickle charge the batteries while my motor home is in storage . I add distilled water to my batteries. Are these batteries Flooded, type batteries or acid?

Thanks
Which batteries are you referring to?

The premise of your question is flawed. The batteries in your picture are Flooded Lead Acid (FLA) which have a liquid acid electrolyte.

Other common battery types include:

AGM which have the same lead-acid chemistry but the electrolyte is in a glass matt material.

SLA (Sealed Lead Acid" same chemistry but in a sealed maintenance-free package.

Lithium Iron Phosphate (LiFePO4) - most suitable for RV applications

Other Lithium-Ion batteries - not normally used in RV applications.
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Old 09-28-2021, 07:50 PM   #18
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Sorry for the confusion. My controller can use four types of batteries. I just want to be sure I set it up with the right setting.
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Old 09-28-2021, 07:52 PM   #19
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This should be better picture.
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Old 09-28-2021, 08:00 PM   #20
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This should be better picture.
All batteries have acid (electrolyte) in them. Gel batteries are pretty non-existent anymore. The picture is waaaaay too simplistic and technically inaccurate. I hope the manual is more accurate.
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