Amps Out at 7Way Charge Line on a 2019 Tacoma B

I’ve contacted Toyota but haven’t received an answer yet. Maybe a Toyota Tech member may know. I’m troubleshooting why my rv trailer refrigerator draws down its battery so much. The output on the trucks 7way must not provide enough amps to keep up. So what amount of amps is that output rated at?

Edit: title - Tacoma Dbcb Sport 4x4.

 

Don't have the number, but thinking that 7 way is only for Lights and Trailer Brakes. Not running the RV.

G.

 

Probably best to get out a multimeter and do some measurements. Even if you've got plenty of current capability at the connector, the voltage drop over small wires at that distance might be keeping the voltage too low to charge your RV battery.

 

Is the DC running only the circuit board for the fridge or are cooling the fridge with DC? If it's just the board there shouldn't be that much draw. If your actually cooling the fridge with DC that is a whole different thing.

 

Other than navigation lighting, the electrical system on the tow vehicle should be isolated from the electrical system of an rv travel trailer. "IF" the rv does have circuitry to charge it's battery while connected to a tow vehicle, it would be necessary for that system to have a low current design. Intended only for trickle charging the rv battery. The reason for this is because of the potential for a very high current spike just by simply connecting two different batteries together. When two different batteries are directly bolted together, their "state of charge" will balance instantaneously. And depending on the difference in charge, could cause an extremely high current spike. This spike could be large enough to destroy the small wiring of the tow vehicles trailer towing circuit. Or even reek havoc on the tow vehicles electrical system.

 

Wouldn't the tow vehicle have a fuse on that wire?

 

Sure. But, current "SPIKES" do wired things. I've worked in the electrical industry for many years. Even in my industry, circuit protection is staged in different steps from the distribution all the way down to the convenience outlets. I've seen current spikes skip over several breakers to ultimately take out a larger breaker. Never the less, if tow different batteries are going to be bolted, the correct size "large" wiring should be installed.

 

Ah yeah, fair enough. Fuses don't always blow quickly, but one would hope the fuse would blow faster than the insulation melts off the wire.

 

You should know that in a spike situation, you moving from a very low current situation to thousands of amps in less than 1 second. The fuse will most definitely blow. But so will other things too. I've seen large conductors melted all the way up to the breaker that opened the circuit. Electricity is NOT your friend.

 

The purpose of a fuse is to provide a full clear of the circuits fault duty to protect downstream devices, it would be unlikely that a properly selected fuse would allow for insulation melt before clearing in this application. If you are worried about a large inrush then you need to select the right fuse to clear the fault.

 

Oh I know. It does some crazy weird stuff, especially when you're playing with high voltage and current.

Capacitors the size of suitcases rated in the 10-20kV range scare me.

 

There is no real plan for circuit protection when your talking about an extreme spike situation like shunting two batteries together, phase to phase or phase to ground fault. Sure the circuit protection is designed to open as quickly as possible. But , things get damaged in these types of situations.

 

You are right that damage can occur but if you know what you're doing in an automotive application you can almost always mitigate faults with proper fusing and circuit planning, what is being discussed here is out of the scope of the designed protection so obviously it will fail in some instances. Cars are not substations or critical devices that require sub cycle tripping, proper fuse selection and knowing what you're doing will go a long way.

 

So, is this where I say “I told ya so”??

G.

 

ummm… travel trailers are designed to be charged from the tow vehicle.

 

2nd gen had a 30 amp fuse protecting the charging circuit on the trailer connector. There is a relay that opens the charging circuit when the engine is off.

So, lots of charging current available through the connector. I'd bet a cheeseburger that 3rd gens are the same.

Lots of misinformation in this thread. 12V refrigerators draw a significant amount of power, especially compressor types.

 

Agreed that I'm not a DC electrician. But I do have 30 years of experience in the electrical field. SO - to reiterate - the only "Plan" for mitigating the incorrect use of an electrical system is to: open the circuit as quickly as possible. There is no way to plan on what or even where damage will occur. This is true for any type of electrical device. Including CARS.

 

Yes but at what rate? There can be a big difference between a charging current and an accessory current.

 

I think you know what you're trying to say but its not coming out right, the way to plan on what and where damage occurs is the fundamental purpose of a fuse in any application.

 

according to the diagram the trailer battery charge wire is feed by a 40a fuse.