battery to battery charger

I started out running our 'fridge on 12v at first but after a few days I checked the electrical load and found it to be rather high, about 15amps. I have since only run it on propane when underway or dry camped. Can you use the propane option?

In my MH my fridge is huge. Not sure how large your fridge is. If my fridge operated off 12 volts it would draw about 30amps i. e about 300 watts. When I am towing my toad I measured the charging current. Never got over 10 amps. Usually about 7 amps. I am not surprised you had a dead battery when you stopped in the evening. You were pulling much more from your battery than you were putting back in. I haven't seen any of those 3 way fridges recently. My TC fridge never worked very well on 12 volts. JMHO

That 15 amps seem more accurate for a TC fridge. Still taking much more out than going in.

First, I would recommend that you not use your frig on 12v it draws to many amps. Just use the LP, you should have no problems driving with the LP

You need to do some math before you make any decisions. What is the expected increase in output to the batteries with a battery to battery charger? Will it be enough? Are you driving enough to justify the expense and to actually get a good charge on your batteries?

The good thing about solar is it charges whether the engine's running or not (assuming there's sun on the panels, of course). I would probably either switch the frig to LP or just add more solar panels to the roof, or both. How many watts do you have on the roof now?

My house batteries are charged only by solar and I never run short of power. No connection to the chassis charging system, and I don't own a jenny. But then again, I use LP for the frig.

First, I would recommend that you not use your frig on 12v it draws to many amps. Just use the LP, you should have no problems driving with the LP

For my unit, due to wind flow, my unit works better on 12V than LP at highway speeds. So on days I'm making infrequent stops, I use 12V. Even with the 10amp draw of the fridge, I can still charge the coach batteries at 20A/hr. I just pulled a 2 gauge wire from the vehicle battery to a heavy duty connector for the battery lines to the camper.

If you don't have a heavy enough cable to provide the recharge and frig, then suggest you use propane for the lp. I use LP on days when my interstate driving is limited. Below 52mph, my fridge works just as well on LP as battery.

I don't see how a battery-battery charger is going to help you out, since you will still need to charge the source battery. And if the source battery is the truck battery, you will still need to upgrade the wiring between the truck and camper.

Why complicate things with a "battery to battery charger" (whatever that is)?

Just install a nice heavy wire for charging the camper battery from the truck's alternator. 6ga minimum, preferably 4ga or even 2ga.

Even then it might not keep up if you insist on running the fridge off 12V.

Consider using propane for the fridge full-time. You're not going to blow yourself up or suffocate just from looking at the propane bottle wrong. The fridge does not use enough propane to significantly increase your travel costs, or shorten the length of time you can camp.

If you are having trouble keeping the fridge lit while driving, tape up the first few inches of vent in the access panel near the burner. I had to do this on my first camper, worked fine after that.

I am going through the charging exercise now. With the existing "camper charge" wiring in the 7 pin cable, I never saw more than about 10 amps charge, quickly reducing to less than 8. I have added a heavy charge cable and connectors and a charge controller (Balmar Digital Duo Charge). Now I can get up to about 16 amps charge initially, but again it quickly drops off. At 16 amps, there is about 0.2V drop in the cabling, another 0.4V through the charge controller. The Ford alternator set point seems to be 14.0V stone cold sagging to 13.8V as it gets warm. That leaves only about 13.2V to charge the AGM house batteries - not enough to get the job done in a reasonable time. 14.4V would be ideal. AGM batteries want to be fully charged periodically or they will die young.

So now I am thinking I might replace the charge controller with a voltage controlled relay (there is little danger of overcharging with the alternator set so low). That might help some. Or use a DC-to-DC battery charger. Mastervolt makes them, it is a boost-buck converter with a three stage charge controller built in. Expensive though. Another possibility is to add the second alternator (optional on a Ford Superduty) with a proper external regulator and use that just to charge the house batteries.

Thanks for all your replies-------I have been running the 'fridge (a big one for a t/camper) on LPG ------it does blow out sometimes--I will try taping up the bottom two slots on vent------for now, I will try a decent size cable from the truck battery to the leisure battery and see how we go-----we have 80w solar, not really enough space for more (we have two boxes on the roof)
Nigel & Pamala----Lakenheath--Suffolk

If your unit is old, it may not have the flame properly protected

The flame should be completely enclosed with sheet metal to reduce the heavy drafts. Usually just the gap around the burner tube and thermo couple line provides sufficient air for the flame.

kohldad wrote:
If your unit is old, it may not have the flame properly protected

The flame should be completely enclosed with sheet metal to reduce the heavy drafts. Usually just the gap around the burner tube and thermo couple line provides sufficient air for the flame.

I have moved the cover while sorting problems---maybe I should check I put it back right ???---1997 dometic RM3663
Nigel & Pamala