Connecting solar and battery type

dogtubs · 12-29-2021, 11:42 AM

Hello, I recently purchased a Renogy solar panel suitcase with controller. I have a 2002 SMB with two lead-acid starting batteries and an AGM house battery.

I thought I’d be good to go by just connecting the controller to the starting battery under the hood, but then I couldn’t figure out which battery type to set the controller (AGM, flooded, etc.).

So, I called Renogy. They insisted that the controller be connected to the AGM house battery and set battery type to AGM.

As some of you know, connecting to the house battery is a pain because it’s mounted underneath the van.

Like most SMB’s mine is equipped with a battery isolater. I also have a SMB widget installed that cycles the charge to the weakest battery.

So, my questions are…

Does it really matter if I connect the controller to the starting battery or the house battery?

And, which battery type should I set the controller?

Many thanks for your time and suggestions,

Johnny C.

1der · 12-29-2021, 01:41 PM

Does your house battery connect to an inverter? If so, you can make your connections at the +/- big terminals where the battery cables connect. That will get the solar controller output to your house battery.

re The isolator - you would need to determine if the isolator is bidirectional. Post up which model isolator you have and one of us will know.

Where are you located? Please consider adding your location to your profile, makes it easier for us to know.

Also, do you have a 7.3 diesel? Those have two starter batteries. A gas engine second battery has an auxiliary battery on the frame rail.

dogtubs · 12-30-2021, 04:30 PM

Hello Ray,

Thanks for your response. Regarding your questions:

First, let me say - I have a solar panel on the roof that I have connected to a “big lug” that connects the house battery to the inverter. This solar panel has its own controller and works fine unless I have parked in the shade or the sun is at an oblique angle. Hence, the reason I bought a suitcase solar panel (portability!).

The isolater is a Sure Power 1315-200 | 12-Volt 200-Amp Bidirectional Battery Separator.

Yes, I have a 7.3 diesel with two starter batteries.

Again, I don’t see why I can’t just alligator clip the suitcase solar to the starting battery under the hood and be good to go.

Am I missing something?

Thanks,

Johnny C
Mt Pleasant, UT for 8 months and Beaver Dam, AZ for 4 months.
__________________

**daveb** · 12-31-2021, 10:51 PM

Quote:

Originally Posted by dogtubs

Hello Ray,

Thanks for your response. Regarding your questions:

First, let me say - I have a solar panel on the roof that I have connected to a “big lug” that connects the house battery to the inverter. This solar panel has its own controller and works fine unless I have parked in the shade or the sun is at an oblique angle. Hence, the reason I bought a suitcase solar panel (portability!).

The isolater is a Sure Power 1315-200 | 12-Volt 200-Amp Bidirectional Battery Separator.

Yes, I have a 7.3 diesel with two starter batteries.

Again, I don’t see why I can’t just alligator clip the suitcase solar to the starting battery under the hood and be good to go.

Am I missing something?

Thanks,

Johnny C
Mt Pleasant, UT for 8 months and Beaver Dam, AZ for 4 months.
__________________

You can do that if you wish. But the idea is to charge the house battery system whether or not the separator is open or closed.

"The BATTERY SEPARATOR monitors the battery system to determine if the batteries are being
charged. When the engine or auxiliary batteries (if 1315-200 is used), or the engine batteries (if
1314-200 is used) reach 13.2volts*, indicating charging is taking place, the BATTERY
SEPARATOR will engage, joining the two battery banks. If the drain on the charging system by the
auxiliary or main battery bank reduces the system voltage below 12.8volts*, the BATTERY
SEPARATOR will disconnect the battery banks from each other, thus protecting the respective
battery banks from excessive drain.
A delay function has been incorporated in the control circuit to prevent the BATTERY
SEPARATOR from reacting to momentary voltage fluctuations and chattering."

Scalf77 · 01-01-2022, 06:23 AM

There are four ways I would do this if it was my rig.

(option 1)I would purchase a suitcase without a controller, or disconnect the existing controller. Then I would connect the suitcase panels in parallel with the existing panels ( Note: they would have to be roughly the same voltage and controller should be able to handle current). I would then add a switch to the Surepower1315-200 to ground connection. When my goal was to charge my house batteries I would disconnect the 1315 using the ground switch. This would allow full solar resources to go to my house battery system. You would also not waste any power on the continuous duty solenoid of the Surepower1315-200.

(option 2)I would keep the controller, and add a auxiliary input to the house battery. The aux input would need to handle the current output of the controller, and the wire be appropriately sized for both current and voltage drop. I would then add a switch to the Surepower1315-200 to ground connection. When my goal was to charge my house batteries I would disconnect the 1315 using the ground switch. This would allow full solar resources to go to my house battery system. You would also not waste any power on the continuous duty solenoid of the Surepower1315-200.

(option 3)I would keep the controller and try to connect to the house battery with clips and charge the house batteries. Really I can't see myself doing this more than once before at least going to option 2. I would say add the switch also, but if your happy with this option you would probably not going to add the switch to the Surepower1315-200.

(option 4)My last option would be connect to the starters and use the Surepower1315-200 to make the connection to the house batteries. This is inefficient if your goal is to charge your house batteries.

Your charger setting should be set to the target battery. AGM and Wet are close so it wouldn't be a huge issue. You could also replace starters AGM at some time and then it would be moot. Being that were talking portable suitcase the impact of the mismatch wouldn't be high.

You can add the switch to the 1315-200 and get the benefit with your existing solar setup. The down fall of the switch is that you have to remember to use both when connecting solar and going back. I have documented drawings on how this can be done using a relay and the "run circuit" of the van. This would make it automatically disconnect when the van was off.

You could replace the 1315 with the 1314, this would be a unidirectional version. If I was replacing I would just go with the Blue Sea 762X ACR, they supply a switch for manual control.

-greg

**daveb** · 01-01-2022, 10:45 AM

You might also factor in the the starting battery health. If you're pushing part of the solar's charge current into the starting battery because it's not up to par, that is a bit more charge current that will never make it directly to the house. Overall (with respect to Greg's post) it's just less efficient hooking to the starting system. It doesn't take much to turn over an engine and many times you can't rely on knowing the starting batteries state of health just because the vehicle seems to start OK.
FWIW before I ditched the Surepower setup, I did the ground switch thing but used a key lock switch and the key was on my vehicle set of keys...to start the vehicle I had to pull the separator key. As shown there are a few ways of connecting your solar...some less efficient than others. I have a separate plug on the outside of my vehicle for my portable panel that runs to the main solar controller. My main solar controller output runs directly to the house side of the separator. YMMV.

dogtubs · 01-01-2022, 02:37 PM

Hello Greg and Dave,
Thank you very much for the great info. A couple questions:

I just replaced the 125 lb AGM house battery under the van. I really don’t want to, but I suppose I could, take it back out and connect wires. Instead, would it work if I connected the suitcase controller to the 200 amp fuse between the house battery and the inverter, and the negative to the inverter negative? Would this be similar enough to connecting directly to the house battery?

My goal is to charge the house and starting batteries with solar. If the solar is connected to the house batteries, and there is NO ground switch on the Surepower1315-200, would there be any charge going to the starting batteries? BTW, my Surepower is wired for Automatic operation (i.e., it only gets voltage when the ignition switch is in the start position).

If I need to add a ground switch to the Surepower1315-200 - could this be a simple toggle switch mounted on the dash? Or, is there a better approach?

I’d like to keep my existing solar setup (permanent mount 100 W on the roof with controller mounted inside van) and use (as needed) the 100 W suitcase/controller. Would there be any problems with running both solar panels with their respective controllers to the house battery? I’d like to keep the suitcase portable and use as needed.

All said, I’m still a bit confused, the Surepower1315-200 Manual says: “When the engine or auxiliary batteries reach 13.2 volts, the battery separator will engage, joining the two battery banks”. So, wouldn’t connecting solar to one of the starting batteries charge the house battery (after the starting battery reaches 13.2 volts)?

Again, many thanks for you ideas and suggestions,

Johnny C
HAPPY NEW YEAR!

Scalf77 · 01-01-2022, 04:36 PM

Quote:

Originally Posted by dogtubs

Hello Greg and Dave,
Thank you very much for the great info. A couple questions:

I just replaced the 125 lb AGM house battery under the van. I really don’t want to, but I suppose I could, take it back out and connect wires. Instead, would it work if I connected the suitcase controller to the 200 amp fuse between the house battery and the inverter, and the negative to the inverter negative? Would this be similar enough to connecting directly to the house battery?

Sure, you don't need to connect directly to the battery, actual I prefer not to. Yes, the fuse would work, how many connections are on that at the moment, just one? You could also look where your existing solar controller connects.

Quote:

Originally Posted by dogtubs

My goal is to charge the house and starting batteries with solar. If the solar is connected to the house batteries, and there is NO ground switch on the Surepower1315-200, would there be any charge going to the starting batteries? BTW, my Surepower is wired for Automatic operation (i.e., it only gets voltage when the ignition switch is in the start position).

You are explaining the start assist function, the start assist tab should be connected to the start circuit "hot when key is in start". This will connect the two batteries while van is starting. After the van has started it should work as stated by Surepower Connect above 13.2 volts and disconnect below 12.8. SMB has occasionally connected the start assist tab to the run circuit "always hot when key is in run". It is my opinion that the start assist switch should not be used, other than possibly as a momentary switched function.

Quote:

Originally Posted by dogtubs

If I need to add a ground switch to the Surepower1315-200 - could this be a simple toggle switch mounted on the dash? Or, is there a better approach?

That would work, if the run is long I might use a relay, but probably not needed. This is also a good time to put a 10 amp fuse on the ground for the surepower.

Quote:

Originally Posted by dogtubs

I’d like to keep my existing solar setup (permanent mount 100 W on the roof with controller mounted inside van) and use (as needed) the 100 W suitcase/controller. Would there be any problems with running both solar panels with their respective controllers to the house battery? I’d like to keep the suitcase portable and use as needed.

Yes, this will work, I prefer one charge controller for both. This way they is no confusion on the controller side. You would want to make sure the controller charge settings are the same for both controllers.

Quote:

Originally Posted by dogtubs

All said, I’m still a bit confused, the Surepower1315-200 Manual says: “When the engine or auxiliary batteries reach 13.2 volts, the battery separator will engage, joining the two battery banks”. So, wouldn’t connecting solar to one of the starting batteries charge the house battery (after the starting battery reaches 13.2 volts)?

Yes, that would work, it is not efficient, your wasting time and power charging up starters. If your goal is to take care of your costly new 125 lb AGM battery. I am not sure what your camping power usage is, but 100 watt solar is not a lot of power I would use it wisely.

-greg

dogtubs · 01-01-2022, 06:06 PM

Hello Greg,

You are a master at this stuff, thanks for your reply. The main reason I want to connect the suitcase to the starting battery is because I like to listen to the radio. SMB installed a switch that allows me to turn on the radio powered by the starting batteries. It’s like having the key in acc, but it only powers the radio.

The problem is, I listen to the radio a lot. Too much at times and I have found myself not able to start the van. This was probably compounded by the fact that my AGM house battery was about dead.

Now that I have a new house battery, and soon to have new AGM starting batteries, I’m thinking the radio switch powered by the starting batteries may not be the best idea.

Do you think it would be better to power the radio from the house battery (where all the solar power is being sent)?

Again thanks,

Johnny C.

bigriver · 01-01-2022, 07:34 PM

Johnny - are you sure that switch is putting power from the starting batteries? In most of the SMB builds I've seen, and the three I've owned, the radio switch back in the living area is designed to allow the radio to be played from the house battery which would not otherwise be possible. Yours might have been rewired but if not that's where the power to that switch is most likely coming from.