Tow vehicle alternator/7 pin connector

[Rembee]

If I pulled the aux fuse on my tow vehicle for the alternator power supply to the 7 pin connector, would that cause any problems with my travel trailer while towing?

 

[TacomaJoe]

No problem as long as your battery has a good charge to handle the parasites and keep a level to run the breakaway brakes. I have solar on my trailer with lithium battery so I have my 7 pin circuit disconnected to save my alternator.

 

[Rembee]

No problem as long as your battery has a good charge to handle the parasites and keep a level to run the breakaway brakes. I have solar on my trailer with lithium battery so I have my 7 pin circuit disconnected to save my alternator.

Thanks ToacomaJoe. I will have solar and a lithium battery bank also. I'm presently in the stage of designing a power system for my t/t.
Where did you disconnect your 7 pin circuit at?

 

[Pappion]

It can be disconnected at the Travel Trailer. I would put a switch on it.

 

[TacomaJoe]

I put a switch in at the trailer end. In my plan I had the original FLA and added LiFePO4 so I put a 3 way switch on the truck 12V so I could direct it the FLA or to the sense of the DC/DC charger or to just neither. The alternative would be to just pull the fuse/relay in the truck to kill it completely.

 

[Rembee]

It can be disconnected at the Travel Trailer. I would put a switch on it.

A switch at the Travel Trailer is a good idea. I plan on rerouting the breakaway electricawire to the battery bank bus bars anyway. I will be doing away with stock deep cycle battery off the T/T tongue also. So tracing down the 7 pin 12v wire shouldn't be a problem.

 

[Rembee]

I put a switch in at the trailer end. In my plan I had the original FLA and added LiFePO4 so I put a 3 way switch on the truck 12V so I could direct it the FLA or to the sense of the DC/DC charger or to just neither. The alternative would be to just pull the fuse/relay in the truck to kill it completely.

As I'm in the process of designing my system, I'm trying to incorporate any issues that I see as I brainstorm through the design. I would prefer to stay away from a dc to dc charger and not even have to deal with any problems with my alternator or a dead truck battery.

 

[Pappion]

I kept one FLA on the tongue and the original breakaway switch wiring. The wiring has no fuse or breaker (this appears to be common). Sticker indicates FLA legally required. The LiFeP04 does not have the low temperature rating. I use a 2-Bank battery switch to separate the systems.
2 bank battery switch

 

[Pappion]

On my prior A-Frame camper I used a 15A 13.8v DC-DC boost to charge. Used fuses on input and output. Used 12v automotive relay to connect when the 4-Runner was supplying power. The 4-Runner will cut the power when the ignition is off. Many vehicles do not and need a relay added.

 

[Rembee]

I kept one FLA on the tongue and the original breakaway switch wiring. The wiring has no fuse or breaker (this appears to be common). Sticker indicates FLA legally required. The LiFeP04 does not have the low temperature rating. I use a 2-Bank battery switch to separate the systems.
2 bank battery switch

What sticker are you referring too?

 

[12VoltInstalls]

would that cause any problems with my travel trailer while towing

You need to have the vehicle charging circuit connected to keep your breakaway battery charged.
If the charging circuit doesn’t disconnect key-off use a relay as suggested.

 

[Rembee]

You need to have the vehicle charging circuit connected to keep your breakaway battery charged.
If the charging circuit doesn’t disconnect key-off use a relay as suggested.

I was going to rewire the breakaway to the Lithium battery bus bars in the pass through.
Would that be a problem that I'm aware of?

 

[Pappion]

What sticker are you referring too?

"SAFETY BREAK-AWAY SWITCH WILL NOT OPERATE
unless connected to a power source equivalent to or greater than an automotive type 12 volt, 12 amp hour wet cell battery."
IMHO: An LiFePO4 at 20F cutoff is not equivalent.
The switch wiring is typically not fused and does not run near flammable material. Any modification can cause legal liability.
I wish I knew what the RVIA required, but you need to spend hundreds and get training to see their codes.
IMHO: Recreational Vehicle Industry Association engages in an unsafe practice by restricting access to their codes.

 

[Rembee]

"SAFETY BREAK-AWAY SWITCH WILL NOT OPERATE
unless connected to a power source equivalent to or greater than an automotive type 12 volt, 12 amp hour wet cell battery."
IMHO: An LiFePO4 at 20F cutoff is not equivalent.
The switch wiring is typically not fused and does not run near flammable material. Any modification can add to liability.
I wish I knew what the RVIA required, but you need to spend hundreds and get training to see their codes.
IMHO: Recreational Vehicle Industry Association engages in an unsafe practice by restricting access to their codes.

If I keep the 12v LFA Deep cycle on the trailer tongue for the breakaway, can I run a dc/dc charger from the same bus bar that the solar will be on after the mppt ties in?
Will this keep the LFA battery charged?
If not, then I will have to find another way to keep it charged.

 

[Pappion]

If I keep the 12v LFA Deep cycle on the trailer tongue for the breakaway, can I run a dc/dc charger from the same bus bar that the solar will be on after the mppt the in?
Will this keep the LFA battery charged?
If not, then I will have to find another way to keep it charged.

I don't worry about keeping the FLA charged. The only load is the Tongue Jack. My 2020 Rams adaptive charging runs up to 14v sometimes. My Victron Smart Shunt reports the "Starter Battery" (Tongue Battery) is 12.77v. Good enough.

 

[Rembee]

You need to have the vehicle charging circuit connected to keep your breakaway battery charged.
If the charging circuit doesn’t disconnect key-off use a relay as suggested.

I want to take the tow vehicle charging circuit out of the picture. My plans are to either;
A) rewire the breakaway power source to the 12v bus bar in the Travel Trailers pass through where the multiplus II will be. Or;
B) keep the breakaway power source wired to the stock FLA battery and charge that battery with a dc/dc charger from the bus bar that the solar mppt outlet goes to.

 

[Pappion]

I want to take the tow vehicle charging circuit out of the picture. My plans are to either;
A) rewire the breakaway power source to the 12v bus bar in the Travel Trailers pass through where the multiplus II will be. Or;
B) keep the breakaway power source wired to the stock FLA battery and charge that battery with a dc/dc charger from the bus bar that the solar mppt outlet goes to.

When I am settled down for the winter, not towing, I can rotate my A-B bank switch to both, long enough to level up the FLA battery. I retained it's 30A self-reset circuit breaker.

I also have a small 10W solar panel charger combo. Next dead weight to get rid of.

 

[12VoltInstalls]

want to take the tow vehicle charging circuit out of the picture.

I don’t understand that. Just charge the brake battery with the vehicle- not the rest. You’re making something quite complex out of a very simple thing.

 

[Rembee]

I don’t understand that. Just charge the brake battery with the vehicle- not the rest. You’re making something quite complex out of a very simple thing.

Maybe I'm missing something here. Does the 12v wire coming from the tow vehicle by way of the 7 pin go straight to the FLA brake battery on the trailer tongue?

 

[Pappion]

Electrically it does on mine. Mechanically it goes to a junction box and joins the battery wire and the tongue jack at one terminal of a 30A self-reset breaker. Other terminal has the 12v system connection and slide out 20A self-reset circuit breaker.