Solar Controller for 2 Isolated Battery Banks

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I'm running a Morningstar ProStar PS-30M solar charge controller with a Renogy 100w panel and am very happy with it. I only have one battery in the truck. I'm considering adding a 2nd battery in the rear of the truck for accessories only (full size deep cycle or motorcycle AGM). I CAN wire up the PS-30M controller to charge both batteries with my solar panel and Morningstar even has a White Paper how to do this with a couple of diodes but they don't recommend it.

I am looking at replacing the PS-30M with a Morningstar’s SunSaver-Duo charge controller. The Duo is designed for designed to charge 2 isolated battery banks with an adjustable charging priority and has a remote meter function as well which would be nice. Info here: https://www.morningstarcorp.com/products/sunsaver-duo/

Is anyone using or planning to use the Duo? It looks ideal solution for those with Solar over all the alternator dual battery setups out there but I can't find anything in the search function. Mind you, this use case is different as I won't be using this setup for a winch or any combining or high draw loads, just a fridge, LED lighting, charging phones and maybe a 12v electric blanket.
 
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I have 100 watt renogy panel. I'm using the renogy viewstar on a dual battery setup. Is there a reason why you would want to separate and charge the batteries individually?

You will be fine charging your aux battery off 1 panel. You are looking at almost a 5 amp peak charge at full sun.
That will be enough to maintain your battery for everything you listed except the electric blanket. At full sun you can link your battery off your dual battery controller and charge both batteries.

If you run a dual battery controller you will have to disconnect the voltage sensing wire on the solenoid or at cloudy days your Solenoid will link and unlink as the charge output from the solar panel will fluctuate. That's my experience.
 
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I'm pretty comfortable already with everything running off the truck but occasionally a cloudy day stops the solar charger dead in it's tracks so I have a Noco 1000 jump pack as well but I'd like to just offload the camping loads off the truck battery while retaining the solar ability to charge the truck and the 2nd battery when I'm out.
I don't have any alternator driven/solenoid based dual battery setup on the truck. Too expensive for what I need. I'm contemplating just building a portable battery box that the 2nd output of the solar charger would feed.
 

george_tlc

 
 
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Well, typically you would have all your engine-off loads running from the aux battery (fridge, external lighting, outlets for charging gadgets etc) so the main battery should be able to sit for many many days without being drained and needing charging. The whole point (at least the way I use an aux battery) is that the main battery should be essentially untouched while camped.

With the setup I have there's a marine switch that can select which battery (or both) feeds the winch, so I can just flick the switch to 'both' and the solar charger will be running to both batteries which at that point are in parallel) if the main needs topping up. Obviously that also means I can jump start the main from the aux.

I also plug the charge controller 'output' via anderson SB50 connectors and I have one on a pigtail on each battery, so I can also just plug directly into either battery. Maintaining flexibility of connecting things together in various combinations is a good thing :)

If I really need music (the only load on the main I can imagine when camped) then I just use a BT speaker box and run it from a phone etc.

The reason they don't recommend using a pair of diodes (isolator) is that it introduces a variable voltage drop between the charge controller and the batteries so detecting battery voltage (for bulk/absorb/float etc) becomes problematic.

cheers,
george.
 
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Well, typically you would have all your engine-off loads running from the aux battery (fridge, external lighting, outlets for charging gadgets etc) so the main battery should be able to sit for many many days without being drained and needing charging. The whole point (at least the way I use an aux battery) is that the main battery should be essentially untouched while camped.

With the setup I have there's a marine switch that can select which battery (or both) feeds the winch, so I can just flick the switch to 'both' and the solar charger will be running to both batteries which at that point are in parallel) if the main needs topping up. Obviously that also means I can jump start the main from the aux.

I also plug the charge controller 'output' via anderson SB50 connectors and I have one on a pigtail on each battery, so I can also just plug directly into either battery. Maintaining flexibility of connecting things together in various combinations is a good thing :)

If I really need music (the only load on the main I can imagine when camped) then I just use a BT speaker box and run it from a phone etc.

The reason they don't recommend using a pair of diodes (isolator) is that it introduces a variable voltage drop between the charge controller and the batteries so detecting battery voltage (for bulk/absorb/float etc) becomes problematic.

cheers,
george.
Agreed on all points.

I really want to see if anyone has used the Morningstar Duo to charge 2 battery banks? I don't think anyone has on this forum.
 

bajaphile

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Why not just get the blue seas isolator (~$75) and keep your current charge controller. The isolator just opens up and allows the charge to both batteries from solar or when the vehicle is running.

Sounds like you have a different idea in mind though... I personally have not heard much about the dual battery bank controller.
 
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The isolator doesn't offer some of the specific features of the Duo like the dual voltage metering and variable charge rates. I'm just looking to do something different...as usual. :p
 

george_tlc

 
 
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Different often costs $$ for some minimal gain and more complexity :)

If you have a 400W or larger solar array I can possibly (no, actually I can't...) see some value in 2 channels for charging the 2 batteries. But for a 100W panel, not at all.

Makes sense for a boat etc where you may have 2 different sets of house batteries for running navigation etc on one bank and fridge, lighting etc on another. But in a vehicle that has a single main for starting and a single aux for the rest... doesn't seem to make sense, other than doing something 'different' as per above.

cheers,
george.
 
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I agree with George. Your only outputting a max of 5 amps on your panel. Your just adding more complexities for extra money and minimal gain.
 
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So, other than criticising my posts, goals and intentions, you don't have any experience with the Duo? :hmm:
 
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No experience with the Duo charge controller. It's a bit expensive and and a T-max dual battery kit is cheaper. Is there a reason why you are running a 30 amp charge controller? Are you planning to expand to more panels in the future?

What are your goals and intententions with the setup you want to run? Do you plan on running a winch?

I run a 100watt to my aux battery. I can camp the whole weekend running a engel 45, 24 watts of Led exterior lighting, shurflo 12v water pump, charging phones,etc and my aux is good to go. If your in Arizona you should be good to go.

I had to winch someone stuck on the beach last year. Even with the truck running and idle kicked up. My battery's took a big drain and I had to idle the truck at night to charge the battery's.
 

george_tlc

 
 
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Nope, no experience with it, since if I had, then I would have gone against my recommendations above.

I hope you don't think I'm criticizing for the sake of it, I'm offering my opinion based on my experience camping with solar. My first solar panel was purchased back in 1982 for camping use (40W panel was pretty impressive back then...), I have a bit of experience with charging dual battery setups in 4wd camping and consider 100W panel to be enough to deal with a fridge in warm climates with a bit left over for other camping duties (lights, electronic gadgets etc). In oz a short camping trip is 2 weeks, most more and some much more, so maintaining battery charge for weeks (with many days camped & not moving) is something I consider important. I've never needed to charge the main - if I did (e.g. the winching scenario above), then I would hook the charge controller directly to the main and let every amp it could provide go there until the main was back up to 100%. Then I'd worry about topping up the aux since it should last a couple of days with fridge load etc even in hot weather.

I can't see the point of trying to share a mere 100W panel between 2 batteries at the same time since it'll take just as long as just topping up the main first and then hooking to the aux...

Since you already have a decent charge controller, I'd spend the extra $100 on more solar versus a duo. That will speed up charging even more.

Anyhow, if you choose the path you appear to intend, please post back your findings so others can benefit from a 'different' approach.

cheers,
george.
 
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Dissent, I'm not criticizing your setup or future plans. I'm just trying to help you out with my experience and help you save some $$.
 

Cruiserdrew

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@Dissent

Just for sake of argument, you might consider a more efficient charge controller. You're running a large PWM controller now and the Duo is basically 2 PWM controllers in 1. Why not spend the $ on a more efficient MPPT controller since you have a very small panel and can use every bit of solar you can harvest?

There is no doubt the duo will work fine, but to what point? Morningstar makes excellent solar equipment so you can pretty much count on it running 100%.

The smart money I think in your set up, is to just buy another 100 watt panel. You have plenty of headroom in your existing controller and as you say, you're happy with it. Then you could join up your batteries by any means you like, ACR, Switch, Anderson plug etc.
 
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I'm pretty comfortable already with everything running off the truck but occasionally a cloudy day stops the solar charger dead in it's tracks so I have a Noco 1000 jump pack as well but I'd like to just offload the camping loads off the truck battery while retaining the solar ability to charge the truck and the 2nd battery when I'm out.
I don't have any alternator driven/solenoid based dual battery setup on the truck. Too expensive for what I need. I'm contemplating just building a portable battery box that the 2nd output of the solar charger would feed.


I don't know why this would be. I never loose output from my Renogy 100w and any of the three chargers I've had. For example it was cloudy drizzly all day today and when it got dark I checked and the battery was at 13.25V. It started the day at 12.85 or 9.

My controller is run to the house battery and connected to the start battery through a blue sea splitter.
 
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I don't know why this would be. I never loose output from my Renogy 100w and any of the three chargers I've had. For example it was cloudy drizzly all day today and when it got dark I checked and the battery was at 13.25V. It started the day at 12.85 or 9.
12.85-12.9 volts is almost fully charged battery. You will still see a small output on a cloudy day. Like .5-.75 amps so say 10 hours you will still get about 5-7 amps. Enough to top off your battery with no load.
 
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I don't have room for a second panel full time. I've seen a few guys with dual battery setups and isolators end up with 2 dead batteries. I just want to keep my potential house battery separate without diode or isolators. In shady camp spots, I don't get much output, on cloudy days it's very low, about .5A. As I start to use the house loads more, I'd really like to isolate thrm completely. I have a 30A because I thought I may do multiple panels, I have a Tee integrated but it's mainly for a rollup panel to run away from the truck once I deploy my roof platform which unfortunately covers the hard panel on the roof.

I appreciate sharing info to save money but I can repurpose the 30M at my home, so I'm not really out money, just looking to optimize. I have many different approaches to things on my truck and it doesn't bother me. The truck and it's add ons also act as a proving ground for future a RV when space allows. For now, this is it.
 
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12.85-12.9 volts is almost fully charged battery. You will still see a small output on a cloudy day. Like .5-.75 amps so say 10 hours you will still get about 5-7 amps. Enough to top off your battery with no load.

Are you sure? I've run the stereo on a cloudy day and while it takes longer than a sunny day the battery gets topped back up pretty quickly. This was with aftermarket HU and 100wpc amp.
 
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Are you sure? I've run the stereo on a cloudy day and while it takes longer than a sunny day the battery gets topped back up pretty quickly. This was with aftermarket HU and 100wpc amp.
OHMs law. The reserve capacity of your battery. How long you run the stereo, if you are running a sub woofer. If you like to listen to rap. Different variables. Also, what are you using to measure your voltage?
 

GeoRoss

 
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I'm pretty comfortable already with everything running off the truck but occasionally a cloudy day stops the solar charger dead in it's tracks so I have a Noco 1000 jump pack as well but I'd like to just offload the camping loads off the truck battery while retaining the solar ability to charge the truck and the 2nd battery when I'm out.
I don't have any alternator driven/solenoid based dual battery setup on the truck. Too expensive for what I need. I'm contemplating just building a portable battery box that the 2nd output of the solar charger would feed.

This is exactly what I did. I have a portable 100Ah battery box and a little portable Li jumper. I only worry about keeping the portable battery charged with solar. If my truck battery dies I can see if the portable Li will jump it or the portable 100Ah one. I try to always use K.I.S.S. when working this stuff out. It may be easier to just buy a little flex panel and charge controller to hook up to the main battery when you park to trickle charge it.
 
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