How does your tow vehicle handle a second battery (which you need for solar)?

[Lisle]

I'm going to be using a 200W solar suitcase and am having a second battery installed in my 16' Casita next week. This may be overkill but I want to be able to boondock or dry camp for a week or two, even if it's cloudy or there are some trees. I'm not very electrical savvy, and am wondering how my TV (a Toyota Highlander Hybrid) will handle the second battery? Haven't seen anything about this on the forums or websites about adding solar. Should I be at all concerned? Will my Highlander just charge both batteries when I'm driving? Not going to pull too much juice from the car or its battery as long as the engine is running?
Thanks for your thoughts.

[David Tilston]

It is a good idea to isolate your vehicle starting battery from becoming drained by accessories. Adding an isolating relay between the starting battery and your accessory battery makes sense. When the vehicle is running the relay senses the additional charging voltage and connects the accessory battery so it charges as well. When the vehicle is shut off, the lower voltage causes the relay to open, preventing accessories from draining the starting battery:
https://www.amazon.com/Dual-Battery-.../dp/B08JYQHTRZ

[jaevans]

Also consider what current draw you may experience when charging your RV house batteries with your tow vehicle alternator/battery. Our 2018 Ridgeline 12v line to the 7-way connector is fused at 20 amps. My solar charge controller is also a dc-dc charger rated at 40 amps. My plan is to run a separate heavy gauge line to the TV rear end that could handle 40 amps if needed. I've already disconnected the 12v line from the 7-way connector inside the Casita and provided a standalone 12v gel cell battery for the breakaway circuit.

John - Colorado Springs

[WaltP]

I've had two batteries and solar on my trailers (Bigfoot and Escape) for about 7 years now and there's never been a problem with the battery and charging circuit on my 2013 Ridgeline.

Walt

[Thomas A Cronquist]

Originally Posted by Lisle

I'm going to be using a 200W solar suitcase and am having a second battery installed in my 16' Casita next week. This may be overkill but I want to be able to boondock or dry camp for a week or two, even if it's cloudy or there are some trees. I'm not very electrical savvy, and am wondering how my TV (a Toyota Highlander Hybrid) will handle the second battery? Haven't seen anything about this on the forums or websites about adding solar. Should I be at all concerned? Will my Highlander just charge both batteries when I'm driving? Not going to pull too much juice from the car or its battery as long as the engine is running?
Thanks for your thoughts.

I have a 2019 Casita Independence. I have 3 AGM batters in the Casita, and have 4-100 watt panels. I store these panels in the back of my truck bed, under a bed tray I made.
Tom C

[steve67]

I elected to mount my solar panel on my TV. As I'm driving that panel charges my RV battery via the charge controller in the RV. Owing to the distance between the alternator and the RV battery(s) it would required a very heavy gauge and expensive cable to do the charging as move than a light trickle charge.

When on site I can remove the solar panel or park near enough to remain plugged in.

[Lynn Eberhardt]

Short answer: It'll work just fine. No problem.

[Terry in Fowler]

Depending on the condition of the present battery you may need to replace both.

[Wayne Collins]

IMHO - Two 12volt batteries connected in parallel is just like one larger battery but would take twice as long to discharge under a given load. Likewise with charging.

[Raspy]

Originally Posted by Lynn Eberhardt

Short answer: It'll work just fine. No problem.

Yep. And you can add an Anderson plug to charge much faster than the seven pin wiring will do. And the Anderson can also be used to charge from solar, or run other 12 volt equipment.

Here's a pic of mine:

[Lisle]

Thanks everyone. Your responses are helpful, as they always are when I ask a question here.

[Terry in Fowler]

Raspy, I would like to know what gauge wire you used with your Anderson plug.
I am planning to install one on my next TV (yet to be determined) and trying to determine what gauge a wire would be best. I probably don't need one since my solar has worked for 3 years, but I would like to be able to charge the trailer battery on shorter runs. We sometimes camp in dense forest for a week or more and it would be nice to have another backup.

[parmm]

The charger instructions should tell you, but I'd say 6 gauge for less voltage loss.

[redbarron55]

I installed 300 watts of solar on the roof of my 16" Scamp and one reason was that it will charge the battery while traveling during the day's tow. The roof top is not the most efficient as they are flat and may be in the shade, but they are exposed all day on the highway. (well except for the tunnels and overpasses, etc.)
I did find an error in my planning, however. I found that the solar MPPT part of the controller generates 40 Khz signals on my ham radio system, so I installed a switch to disconnect the panels and that takes care of that issue, but I wired the Tow Vehicle into the buss on the PD power system. The issue is that I also ran the charger directly to the battery and the output of the charge controller to the distribution buss on the PD panel.
That part works well, but the TV will provide power to the trailer, but will not back up through the charge controller to charge the battery, A little more wiring will be necessary to directly charge the battery from the TV. ( When I forget to turn the solar panels back on...)

[Raspy]

Originally Posted by Terry in Fowler

Raspy, I would like to know what gauge wire you used with your Anderson plug.
I am planning to install one on my next TV (yet to be determined) and trying to determine what gauge a wire would be best. I probably don't need one since my solar has worked for 3 years, but I would like to be able to charge the trailer battery on shorter runs. We sometimes camp in dense forest for a week or more and it would be nice to have another backup.

I've done this on two different trucks I've had.

My Black Series had a 50 amp style Anderson plug installed from the factory. It had #6 fine stranded and tinned wires, with a 50 amp breaker next to the batteries. So, in the truck I ran #6 wire, 2 conductor, and a 50 amp breaker next to the truck battery.

I got a new truck and installed #4 marine fine stranded and tinned romex, 2 conductor, with an 80 amp breaker. I changed the Anderson plugs to the 120 amp style, but kept the trailer wiring as it was. I was going to increase the size of the trailer wiring, but I decided to sell the trailer before I got it done.

This system has worked very well on both trucks. The trailer had four 100 AH AGM batteries. The Ram was reading a charge of 14 volts until the batteries were up and then switched to a float charge of 13 volts indicated. The Ford seems to have a different strategy and never goes to float. It is always reading about 14.1 to 14.5 volts. This system brought the batteries up fast, but I'm not sure how many amps it was delivering, other than it never tripped the 50 amp breaker and I measured it once with the batteries nearly at full charge and it was delivering 24 amps.

One of the first mods to my new trailer will be to install an Anderson plug on it, but this one has lithium batteries, so I'll likely install a dc-dc charger. Not sure on that yet.

If the need arises to charge the batteries while camped, I would rather plug into the truck and idle it, than run a generator. The truck is quieter, it produces a lot of amps at idle and I don't want to bring my generator along on trips.

I didn't bother to unplug the truck when stopped, unless we were going to be there for a few days. I had no isolator and I like the idea of using the Anderson to plug in a suitcase, run my compressor after airing down, or run my jack. Those things can plug directly into either the trailer or the truck, because the Anderson is not male or female, it is the same plug, turned over to plug into an identical plug. You don't buy male ones and female ones, they are all the same. You not only get to run equipment, but power can go in or out to charge or draw power.

We always arrive at the destination, night or day, good weather or bad, with fully charged batteries.

[ThomasC]

Originally Posted by Raspy

I got a new truck and installed #4 marine fine stranded and tinned romex, 2 conductor, with an 80 amp breaker. I changed the Anderson plugs to the 120 amp style, but kept the trailer wiring as it was. I was going to increase the size of the trailer wiring, but I decided to sell the trailer before I got it done.

We always arrive at the destination, night or day, good weather or bad, with fully charged batteries.

Why are you running 2 conductors? A good chassis ground will save on wire and work exactly the same.

[denswaer]

I put a second 12V in my TV p/u bed near the tailgate. I removed the clamps from a set of jumper cables and put eyelets that would attach to the batteries and hooked the battery in the p/u to the battery on my Scamp 16 tongue in parallel. Then I installed an Anderson plug in the cable near the Scamp battery. Works great.

[Raspy]

Originally Posted by ThomasC

Why are you running 2 conductors? A good chassis ground will save on wire and work exactly the same.

It seems to me that a lot of current running through 20 feet or more of steel parts, connected with steel bolts, will have a lot more resistance than fine stranded copper wire. There also seems to be some concern about welding on the frame, not only because of affecting the temper of the steel, but just running a lot of current through it that can affect the computer. Am I wrong? Is running that current through the frame better?

[ThomasC]

Originally Posted by Raspy

It seems to me that a lot of current running through 20 feet or more of steel parts, connected with steel bolts, will have a lot more resistance than fine stranded copper wire. There also seems to be some concern about welding on the frame, not only because of affecting the temper of the steel, but just running a lot of current through it that can affect the computer. Am I wrong? Is running that current through the frame better?

You're over thinking things. Sure copper is a better conductor per square inch but look at how large the cross sectional area of the frame is. Besides you are only dealing with 50 amps or so. There are vehicles that have the battery far away from the motor and the starter has no problem drawing a couple a hundred amps through the chassis.

[parmm]

Originally Posted by ThomasC

You're over thinking things. Sure copper is a better conductor per square inch but look at how large the cross sectional area of the frame is. Besides you are only dealing with 50 amps or so. There are vehicles that have the battery far away from the motor and the starter has no problem drawing a couple a hundred amps through the chassis.

I remember vehicles of yesteryear which had their battery located under the back seat. But those were old style vehicles which did not have computerized components. Today's vehicles are a whole new ballgame! Just like the "smart alternators" which may, or may not, charge lithium type batteries!