My Solar Charging Solution for Dual Batteries

[AZ Native]

After researching threads on solar charging I had trouble with a solution for dual batteries, so I thought I would post my solution I rigged up this weekend. I chose a 100 watt Monocrystalline solar panel and built a frame to mount it on using 2x4 pressure treated wood and a Rural Power Systems adjustable mounting kit. The solar panel feeds a Renogy 10 Amp PWM Dual Battery Charge Controller and the extension cables from the panel to the controller are 20Ft 10AWG MC4 Adpator cables. The MC4 connectors make great water proof connections. For the connections from the controller to the batteries I purchased WindyNation 8AWG stranded cable which came with the necessary terminals for a clean installation.

I learned two lessons during the installation. First 10AWG cable is plenty for this application and easier to fit into the terminals on the Renogy controller which is designed for 10 AWG. Second Solar Panels do have a Positive and Negative line feeding the controller. I hooked it up backwards and the controller indicated I had fully charged batteries (slow flashing lights). When I figured out what I did wrong then controller gave me steady lights on both batteries indicating they were charging properly. The controller was the cheapest component of my solution, but it's a perfect solution for charging two batteries simultaneously. It's programmable and includes an on board temp sensor that adjusts the charging current when it gets really hot to protect the batteries. That matters here in sunny Arizona.

Here are some pictures of the final solution:

 

[swatski]

After researching threads on solar charging I had trouble with a solution for dual batteries, so I thought I would post my solution I rigged up this weekend. I chose a 100 watt Monocrystalline solar panel and built a frame to mount it on using 2x4 pressure treated wood and a Rural Power Systems adjustable mounting kit. The solar panel feeds a Renogy 10 Amp PWM Dual Battery Charge Controller and the extension cables from the panel to the controller are 20Ft 10AWG MC4 Adpator cables. The MC4 connectors make great water proof connections. For the connections from the controller to the batteries I purchased WindyNation 8AWG stranded cable which came with the necessary terminals for a clean installation.

I learned two lessons during the installation. First 10AWG cable is plenty for this application and easier to fit into the terminals on the Renogy controller which is designed for 10 AWG. Second Solar Panels do have a Positive and Negative line feeding the controller. I hooked it up backwards and the controller indicated I had fully charged batteries (slow flashing lights). When I figured out what I did wrong then controller gave me steady lights on both batteries indicating they were charging properly. The controller was the cheapest component of my solution, but it's a perfect solution for charging two batteries simultaneously. It's programmable and includes an on board temp sensor that adjusts the charging current when it gets really hot to protect the batteries. That matters here in sunny Arizona.

Here are some pictures of the final solution:

View attachment 69458 View attachment 69459 View attachment 69461 View attachment 69462

Does that controller work similar to a shore-power connected "smart" multi (dual) battery charger?

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[Mainah]

Does that controller work similar to a shore-power connected "smart" multi (dual) battery charger?

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Almost identical.

@AZ Native nice set up. Have you done the dvsr mod? If not the dual bank feature of your controller is getting defeated by dvsr.

 

[adrianp89]

Do you have a list of parts? I could easily put the solar panel on the corner of my roof and run a plug down to the boat, would only be 20 feet or so.

 

[tim h]

That panel looks like it would fit nicely on my hard top.
What are the dimensions ?

 

[AZ Native]

I need to research the DSVR mod. I disconnect all batteries with the switches while charging. So each battery is being charged independently and directly from the controller.

All parts came from Amazon. The panel is 47” long by 22” wide and is UL listed for these applications. I probably have $200 in parts invested.

As for the charging, the controller has 9 settings to decide which batttery get’s charged first and how much before the second battery starts charging. I just set it at 50%/50%. It also can be programmed for 3 types of batteries including sealed, gel cell and flooded which I have.

I know I’m at risk of theft of the panel, but this is a pretty secure lot, with lots of cameras and access control.

 

[Mainah]

I need to research the DSVR mod. I disconnect all batteries with the switches while charging. So each battery is being charged independently and directly from the controller.

All parts came from Amazon. The panel is 47” long by 22” wide and is UL listed for these applications. I probably have $200 in parts invested.

As for the charging, the controller has 9 settings to decide which batttery get’s charged first and how much before the second battery starts charging. I just set it at 50%/50%. It also can be programmed for 3 types of batteries including sealed, gel cell and flooded which I have.

I know I’m at risk of theft of the panel, but this is a pretty secure lot, with lots of cameras and access control.

Even with the batteries off once the start battery reaches a certain voltage the dvsr combines the batteries so then it is effectively one bank. Not a big deal in the short term but in the long term even with batteries of the same type and size it will have some impact on overall performance and life of the batteries. I am not familiar with the batteries you have or how much draw you have on them but can say that in most cases only 3 types of batteries should be used with a system like this. True deep cycle, AGM, or lithium ion.

At $200 you have a great system for your needs and I bet others will find this useful.

 

[Coheeba]

I have a solar charger integral on my boat but installed a similar system on my camper. I have two batteries in parallel and use it to keep batteries charged while hunting off the grid. Here is what I bought.

Solar Panel and Controller $167.99
Connectors 8.99
Cable 19.30

 

[AZ Native]

Even with the batteries off once the start battery reaches a certain voltage the dvsr combines the batteries so then it is effectively one bank.

Does my boat have this DSVR? It's a 2013 242LS and there is a 3rd switch you can see in the photo which is the only way to combine the batteries according to the manual. My understanding is that with that manual switch disengaged one battery handles the engine the the other the house duties, which is how they are actually labeled. I don't think there is any automatic switching going on is there?

 

[AZ Native]

Do you have a list of parts? I could easily put the solar panel on the corner of my roof and run a plug down to the boat, would only be 20 feet or so.

Here are all the Amazon Links.
HQST 100 Watt 12 Volt Monocrystalline Solar Panel (Slim Design)
HQST 20Ft 10AWG MC4 Solar Adaptor Cable
Renogy 10 Amp PWM Dual Battery Charge Controller
Solar Panel Adjustable Tilt Mount for Rv's, Roof and Ground Mounting (No Solar Panel)
WindyNation 8 Gauge AWG (8 Feet Black + 8 Feet Red) Power Inverter Battery Cable Wire Kit for DC to AC Inverters RV, Car, Solar, Marine, Off-Grid

 

[Coheeba]

Does my boat have this DSVR? It's a 2013 242LS and there is a 3rd switch you can see in the photo which is the only way to combine the batteries according to the manual. My understanding is that with that manual switch disengaged one battery handles the engine the the other the house duties, which is how they are actually labeled. I don't think there is any automatic switching going on is there?

Its hard to see in your pics but this is my boat and you can see the DVSR on the bottom left labeled "Digital BEP"

 

[Coheeba]

On my boat even with the switches off if you apply power (charger or solar) the DVSR will kick on and charge as follows.
This is from this Thread: I called BEP and they were very responsive (262)293-0600. The tech said that whenever 13.4v is sensed by the DVSR it will parallel (join) the two banks. So when the alternator is charging the batteries it will see 13.4v, when a shore charger is hooked up it will see 13.4v, if the solar panels are active it will see 13.4v. When the red LED is lit the banks are joined.

 

[Mainah]

Does my boat have this DSVR? It's a 2013 242LS and there is a 3rd switch you can see in the photo which is the only way to combine the batteries according to the manual. My understanding is that with that manual switch disengaged one battery handles the engine the the other the house duties, which is how they are actually labeled. I don't think there is any automatic switching going on is there?

From your photo at the top of the thread it appears as though you have a dvsr located directly below your house battery switch. Because of how this is wired behind the switches it does not matter what position the battery switches are in. Another option besides the engine on mod or in line switch mod would be to disconnect the small ground wire for the DVSR. This would mean that while running your engines it would not charge the house battery unless the combine switch was on. My preference is the engine on mod as it takes human interaction out of the equation and it is easy. Just T into the red loop wire behind the DVSR to the "Eng On" wire which is located nearby in the engine compartment.

 

[AZ Native]

I found another photo and I have an VSR Voltage Sensitive Relay Module under the House switch. This must be what you’re talking about. So basically what your saying is that I didn’t need a dual battery charging controller? I could have used a single and feed only one battery that would basically charge both when the VSR sensed voltage. What I doubt is that the charge controller puts out 13.4 volts, enough to trigger the VSR. And is the VSR looking for voltage from the alternator side or the battery side of the digital switch? If it only looks for voltage from the alternator side to switch, it will never see the voltage from the charging controller which is directly connected to the batteries. I guess my next call will be to BEP to see what how the voltage sensor works. And here I thought this would be simple.

I’m okay with doing the engine on Mod if I need to, but I will need to figure out where the Engine On wire is located in the engine compartment. Mainah, you’re saying I have to disconnect the ground wire on the SVR and T wire into the engine on wire?

 

[Mainah]

Everything you need to know is in this FAQ linked post complete with diagram from BEP, and wire color to eng on (also labeled).

https://jetboaters.net/threads/making-dvsr-active-with-engines-on-only.9798/

I was mentioning an alternate option with removing the dvsr ground wire as a way to prevent charging as one bank with the panel but that would prevent charging from the engines. I am assuming you have a digital model that require power and ground for the internal electronics of the DVSR. The way that works is the digital brains for the DVSR require power to sense the voltage. They get power from the red loop wire which goes to and internal post connected to the start battery and the tiny ground wire to the battery. When the voltage is at 13.7 volts on the start battery in combines both as one bank when the voltage drops to 12.8 volts it disconnects. By cutting the red loop wire it no longer has +12vdc nominal going to the relay and it won't function. By connecting the proper end of the red loop once cut to the eng on wire which only has +12VDC nominal when the engines are running the relay will only operate when the engines are running. Charging both batteries as one bank is something to be avoided when it can. In large solar setups one bank is fine but all of the batteries should be the same and installed at the same time. That bank will also have the same draw across all of the batteries. In our boats the start battery is one bank with one load. The house battery is another bank with a different load. Additional batteries can be added to either bank to split the load. The emergency combine switch could be used to make the start and house one bank all of the time so they split the load but then the safety factor of having both is removed. I still keep a charged on board jump pack on board even though I keep as two separate banks and have high end batteries (Group 31 AGM for both house and start).

I do bet if you draw both batteries so that they need charged and then test the controller output while in direct sunlight you will find it outputting between 14 and 15v. In order to charge a battery electrons have to flow from the controller to the batteries and in order to flow the controller must be outputting a higher voltage than the battery. In fact this is exactly what the controller does. The solar panels could be outputting almost no voltage in very little sunlight or high teens to low thirites (depending on the panel) in direct sunlight. if directly connected to the batteries with no controller this would either draw them down over cause over voltage damage. The controller ensures that both don't happen.

All that said the way you have it now is ok and will work. Your total battery life between the two batteries will be a bit shorter and the top voltage/amp hours they will be capable of will slowly decrease over time more than if you had kept them as separate banks.

Sorry for the long post but I like to TRY and explain the principles behind everything so folks can understand and do what is right for them. Keep in mind I am just a guy on the internet with electronics and boating hobbies.

 

[Coheeba]

[So basically what your saying is that I didn’t need a dual battery charging controller?]
Right, you could have the same basic effect with a single bank charge controller, (you always need a controller for solar). I would check your specific model of VSR to ensure you understand how it works. The one @Mainah and in my previous posts is on my boat. It may work the same but it might not.

 

[AZ Native]

I’ve learned a lot from this conversation. I called BEP today and as stated in an earlier post the tech was extremely helpful and patient with a novice like me. What he determined is that I have the VSR (Voltage Sensitive Relay Module), not the DVSR. The VSR is a little older (2013) and doesn’t have the red wire or digital relay like most of yours. He also said that the dual controller I have should work fine to charge and maintain both batteries the way I have it hooked up. He doesn’t recommend any modification, unless I contact the solar controller manufacturer and find out that it can’t feed both batteries if they are banked together by the SVR. Frankly since the controller manages the voltage and turns it down when the batteries are full, he doesn’t think I have an issue.

What he did confirm is that, as stated in an earlier post, only charging by solar power (never shore power) will reduce the useful life of the battery, because unlike shore power it only charges for a few hours a day and drops off at night, so low batteries don’t get a chance to continuously charge to their full topped off status before the voltage drops. Over time the batteries loose their ability to hold a good charge. The best practice is to fully charge batteries with shore power and use solar for maintaining the charge. I don’t have that option. He did say that a battery that should last 4 years might only last 3. But, in Arizona due to the extreme heat we replace our batteries every two years like clock work. Especially car batteries. So I will be replacing them anyhow. I’ve been charging the gel cells in my skis with Battery Tender solar for a couple years and never had an issue.

I know this isn’t the last word on this, but I’m gettin more comfortable with my solution.