I'm not sure this doesn't belong in the towing forum, but here goes.
I try to use the DC mode on the refrigerator( in my 1999 16') to hopefully just maintain temperature while I'm on the road. This does work under ideal circumstances, however a couple of times, I found my trailer battery partly depleted at the end of the day. The refrigerator draws 10A, I've measured it. Would you expect that the tow vehicle's alternator could keep up with that? Is there a possibility that my alternator's output is low, and how would I check for that? The truck battery never goes down, at least not enough that I can tell.
Thanks for your thoughts.
The alternator can keep up. The wiring between it and the fridge can't. Easiest work around we've found is to start out cold with the fridge off, turn it on after your first stop (2-3 hours), off again at the next, repeat. The milk stays fresh, the beer cold, and the battery in reasonable condition.
Lynn and Pam
I run mine on 12vdc via an inverter, very inefficient I know, but that’s what I do because there is no provision to run it on 12 vdc directly. My f-150 will not keep the Scamp battery up, in 8 – 10 hours the Scamp battery is down to 12 volts. I'm thinking of running it on gas like every one else.
I've done a little more research on this. A typical automotive alternator is capable of around 60A output. Seems like that should be plenty, but, no, it can't all get to the trailer. I have 12 ga wire from my TV battery back to the trailer, which should be able to carry 20A that far. From there to the refrigerator, I'm not sure, but probably some of that wiring is 14ga. That should carry 15A. I have measured 10A at the refrigerator, so I know its wiring supports that (but at the time I measured that, I can't swear whether I was running off the battery or the shore power plugin). Altogether, it leaves me wondering why I can't get enough flow to the battery to keep up with the fridge drain. What am I missing?
Another point - in a Toyota forum I read that if you have the tow package (I don't), your alternator produces 130A. If that is the critical factor, I assume I can buy the alternator that's supplied with the tow package.
Randy in Paonia
Here's another nugget. I looked in the manual for my Tacoma. It has an entry in the specs section labeled "charging rate", under which it reads 5 A max. That seems like it matches the results I see. Is there any way to increase it?
Thanks again!
Randy in Paonia
The problem is voltage drop between the TV charging system and Trailer battery.
I wired our 2016 Tacoma with 4 (four) gauge battery cable. From the truck battery positive and negative all the way to the 7 pin tow connector.
We can run the fridge on 12v when towing and arrive with a cold fridge and a fully charged battery.
BUT, on 12v dc operation the fridge has no temperature control. It is always on. We have had food freeze in the fridge. It is a 2017 trailer with the small fridge, it does not have a freezer.
Eeberhrdt's suggestion works the best for us.
Oversize alternator? Heavier wires.
I doubt that either of those is the issue. With the alternator capable of 60A or more, and big, heavy wires to the battery already...
I think the charging rate is electronically limited so you don't boil the battery dry. I wonder if there's a way to bypass that and get more juice to the trailer.
I might add that over in TacomaWorld and the RV Forum, not everyone agrees with this. Some very knowledgeable-sounding people think that alternator capacity is not the limiter, but the length of run with too small gauge of wire is. There is discussion of running heavy gauge wire to a DC booster/charger in the trailer. I'm also wondering about solar.
I'll drop back in with an update if and when I get this figured out, but I'm mostly off on other things until we get closer to spring.
Randy in Paonia
I said I'd check back. Here's my status:
I've upgraded the pickup wiring to 10 ga. That's not the 4 ga that someone above reported, but it may help.
I've also purchased a portable solar panel - Renogy 100W suitcase with a Wanderer 30A PWM controller. It's not all hooked up yet. It won't help the refrigerator on the road. It will give me a way to recharge the battery w/o running the tow vehicle.
I have a wiring question that's probably dumb, but I'll ask anyway and risk the derision of my fellow RV'ers. Would it make any difference if the hot and ground wires from the tow harness went directly to the battery, and then a separate set of wires went from there to the terminal block inside? As it is, the vehicle hot goes to the terminal block, and a wire goes back out from there to the battery. I THINK the answer is, it doesn't make any difference. All the 12V+ cables are wired together, and the electrons go where they need to go. Please educate me if my ignorance is showing.
Thanks,
Randy
Randy in Paonia