For those yes, but for trailer house battery (via the DC-DC charger) _and_ the trailer/tow vehicle ground being grounded all together?
DC to DC charger 12V to 24V battery....
- Thread starter southsouth
- Start date
outboard1196
Solar Addict
Your using the chassis as ground for the house battery? I don't see an issue with that
No I'm not, all of the interior lights/fridge/etc off the battery is isolated from the chassis. Which makes me hesitant to put that in the same GND as the chassis/tow vehicle. I don't know enough to understand the issues or ground loops or what not that that could produce, so I decided to go for isolated to be certain.
outboard1196
Solar Addict
I'm not sure what your asking to be honest. There's plenty of system with dual voltage systems using the same ground.
So having a ground connection with the connection point at the DC-DC charger between trailer/tow vehicle chassis & battery isn't a problem?
outboard1196
Solar Addict
As long as it can handle the current requirement.
Good to know, nice, thanks
HarryN
Solar Wizard
For a vehicle to trailer power connection of any significance, consider to use 120 vac instead of DC. Smaller wires and safer.
Hm, not sure what you mean. While in motion, driving down the road, you're saying get an inverter for the car, and then an AC charger in the trailer?! This is charging the battery while in motion from the alternator via the 7-pin trailer connection. Which is setup for DC from the tow vehicle, it would be extra, separate, 120VAC wiring that would need to be added, waterproof quick connect, etc.
outboard1196
Solar Addict
I'm confused by what was said too. Dc-dc charger is the simplest easiest way. No shock hazard compared to 120v
HarryN
Solar Wizard
Yes, correct. I am guessing that your trailer already has a 120 vac charger if the battery is of any significant size.
Let's assume that you want to charge at 1 kW from the vehicle to the trailer. That is easily done with 10 awg out door extension cord using 120 vac, but would take a wire pair, each wire the size of your thumb to do in 12 volt DC.
If something goes wrong, an ordinary breaker will almost instantly stop the flow and can be just re-set. Doing that with 12 volt, it will arc before shutting down.
If your goal is just to run some lights while driving, then that is different and can be done via trailer connection wiring, but not any serious amounts of charging. Maybe 50 - 100 watts tops.
Uh, there are 2 separate things when towing. 1) trailer turn signals, brake lights, electric brakes, etc, and 2) charging from tow vehicle alternator any house battery(ies).
We can essentially disregard #1, that all will run off of the dedicated pins on the 7-pin connector, totally separate from this discussion IMO.
#2 however is what we're discussing. And the 7-pin spec says up to 30a through the 7-pin for pulling accessory power (e.g. charging house battery or what not). So per the spec, you won't even think about trying to charge 1kW. Besides, you then need an _inverter_ to change the 12v the car alternator is producing to 120VAC, then add an appropriate spot that's weather sealed to run the wiring separate from the 7-pin, out to the trailer. And make it easy and quick to connect & disconnect. Plus more losses between going to AC just to go back to DC.
And anyone who has that large of a battery system (I don't consider my 280Ah to be very large) is going to have a large trailer, which means they probably have at least 600-1000W of solar on the roof, possibly more. So the tow vehicle charging can be a supplemental extra bit, rather than primary charging.
Likewise, for my trailer, with only 280Ah, my DC-DC charger is only a 18a max. And my AC charger for shore power is 15a, although I'm going to get MultiPlus 12/1200/50-120VAC eventually, which will be max 50a.
Tow vehicle charging is not intended to be a primary charging method. Or is intended to do things like keep a 3-way fridge on 12v running without depleting the house battery while in motion, because you shouldn't have it on propane while moving. For a van/RV it can be a significant one, but that's why you'd run multiple chargers in parallel with multiple conductors to get above 30-50a charging.
outboard1196
Solar Addict
Probably 10-15% in losses in double conversion to go 30'?
HarryN
Solar Wizard
Possibly, but even 1 kW is not much load on the engine while driving, so 100 - 200 watts of loss is negligible.
If you have a van that is close to 20 ft long, and then batteries in the trailer that are another 10 ft from the hitch, that is 30 ft, or 60 ft round trip wire length. Pushing 12 volt through 60 ft of wire is a big ask.
Next - think about your wife or kids connecting / disconnecting that 12 volt wire - live, vs disconnecting a 120 vac plug that they do every day.
The DC will always have a healthy arc, while AC quenches quickly and no one thinks twice about.
____________
Imagine that you are getting ready to leave for a trip, and realize that the 4 kW-hr trailer battery is low SOC, in a couple of hours of driving, it will be mostly charged up. Solar on the trailer can help to keep it charged during use.
It's not load on the engine, it's load on the alternator. Not all tow vehicles have a honking alternator. I tow with a Volvo station wagon, a small trailer. Not sure what size alternator is in there, but I doubt it's a 200+a like a F-150 or the like has. 1kW is call it ~80a, which I wouldn't be surprised is close to the same size as my car alternator. Your use case isn't the same as my use case isn't the same as OPs use case.
Although I'll agree he needs to choose different wiring setup if he wants the Victron Orion IP67 12/24-50A. Those are made more for RV/van alternator charging, which can have a lot shorter wiring runs and importantly don't ever get disconnected.
And like I said, the 7-pin is limited to 30a by the spec. Now I agree that 30a 12vDC is still more than I'd like for random connect/disconnect (for me, I actually have a shutoff switch I do), but also it's nowhere near 1kW or the like like you're saying. OP has a van setup he's doing. I'm the one that brought up tow vehicle & trailer setup.
outboard1196
Solar Addict
Also the Orion XS can be de-rated so it doesn't pull the full 50A.
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