How do you provide for charging a battery located in a trailer while your driving ?

[Red Monty]

I'm heading down to Expo West hauling an enclosed car hauling trailer. In it is a small living quarters up front. I'd like to bring an Engel refrigerator along in the trailer, so I don't have to always look for ice. I have 2 batteries that I've charged from a generator in the past, but now I'd like to charge them from the truck as I travel, because the Engel would always be left on. How do you do that ? I know my travel trailer does it, but this all new to the car hauler. I may be camped for a while in some locations while ridding motorcycles and will still need the generator when in remote areas for charging. Any help would be appreciated, Thanks.

George

 

[StayDirtyMyFriends]

If it has a 7 pin plug, one of the wires should be a heavier gauge (perhaps 10ga.) wire that goes to the vehicle battery. That should keep a charge on the trailer while driving if it is connected to the trailer batteries.

On my personal vehicle and offroad trailer I ran a wire off my alternator to an isolater, then to the back of the vehicle to a 150 amp anderson power plug. It's a bit of overkill though.

 

[mep1811]

I use a "TOAD" charger. http://www.lslproducts.net/ToadChargePage.html

This is a actual 10 Amp battery charger that runs off your main battery. I've hAD mine for several years and it works great.

 

[DiploStrat]

I use a "TOAD" charger. http://www.lslproducts.net/ToadChargePage.html

This is a actual 10 Amp battery charger that runs off your main battery. I've hAD mine for several years and it works great.

Appears that the TOAD charger is a simple, low amp, voltage booster to assure that you get at least 10A at 14v at the end of a long, small wire. Should work, but it is very limited.

If you need more, it may be worth investing in serious cabling and, if necessary, a serious battery to battery charger, such as one of those from Sterling Power or CTEK.

 

[IdaSHO]

Yeah, I find that system a bit suspect simply due to the 60' of 12 gauge conductor included.

Thats a LONG run for 12G

 

[sabconsulting]

I have a truck camper, not a trailer, but principal is the same - I use a DC to DC charger. It can adjust for voltage drop to give you the best charging possible on the remote battery (mount it near the trailer battery though). Yes, you want good thick wire from the alternator to the trailer, but even then you will get some voltage drop that will compromise the alternator's ability to fully charge the trailer battery. The DC to DC charger fixes that.

Mine is a CTEK D250S. It also has an input for a solar panel, so if you add a panel it will supply your battery from that when your truck isn't running. Your vehicle's trailer socket will probably have a charge relay to cut power to the trailer once the engine isn't running - so your fridge etc. doesn't flatten your starting battery and leave you stranded. With the CTEK you can remove that because it does the job for you, and once removed, if you have added a solar panel, it will use any spare charging power from the solar to charge your truck battery as well.

I've run mine for a few years now and very pleased with it. It is a bit pricey though.

Steve.

 

[DiploStrat]

...
Mine is a CTEK D250S. It also has an input for a solar panel, so if you add a panel it will supply your battery from that when your truck isn't running.

Steve,

Slap a SmartPass on that puppy and you will be amazed by the improved performance.

 

[LivinDaDream]

A key bit of information that would help offer a practical solution here is how much current the refrigerator draws when operating.

In my truck camper, my 3-way fridge draws around 12 amps when running off DC. When I originally wired the receptacle on the truck bed for the camper connector, I just used the factory +12V lead (#12 wire) in the factory wiring bundle to power the trailer. When driving with the fridge running on DC for 5-6 hours, the current draw would cause enough voltage drop through the factory wiring to eventually draw down the battery to about 60%...meaning that when I got to were I was going, my battery was down to 60% or so. With the smaller wire, the voltage at the battery with the fridge running was below full charge voltage (about 12.7V) so power was flowing both from the truck system AND the batteries until the batteries equalized at the same voltage as the feed coming from the truck, once losses in the cable had their effect.

I solved the problem by installing a #6 wire from the junction block under the hood where the factory wire came from, all the way back to the trailer plug in the bed. Voltage drop through the larger wire was minimal and the voltage at the battery was high enough to keep it at it's full-charge level.

My longer term and more flexible solution is going to be to put a 1000watt inverter under the hood of the truck and run 120VAC to an outlet in the truck bed and to the camper (with disconnect, of course) and then use the installed 30A charger/converter to run the refrigerator and charge the battery in a normal manner. The refrigerator works much more efficiently on 120V than 12V, especially if you haven't pre-cooled it before leaving on a trip. Of course I could always run it off propane, but I'd rather save that for cooking/hot water.

 

[4x4junkie]

#0 AWG cabling from under the hood going back to the trailer is all that should be needed here (this assuming your truck's charging system operates at 14.2-14.4V). Use a heavy duty Anderson PowerPole connector to make the power connection from the trailer to the truck. Fuse each end of the cable (under hood & at trailer battery) at whatever your alternator rating is (90-150 amps is typical range for stock electrical systems). You might also want to put a solenoid (relay) on the line (triggered by the ignition key) so your trailer loads can't draw down the truck's battery when you're parked (a nice simple isolator setup is described here)

Then enjoy your fully-charged battery.

A key bit of information that would help offer a practical solution here is how much current the refrigerator draws when operating.

1½-3 amps is average for freon-based fridges such as an Engel, depending on ambient temps.

 

[Red Monty]

Engel Fridge in car hauler.

Wow! thank you all for the response to my question. It's going to take me a little time to sort through it all, but thank you, I need all the help I can get, I'm like a fish out of water ! George

 

[rayra]

In the military they used to call it a 'slave' cable. Much like a 7-pin trailer connector in connection and use. Would serve as jumper cables between vehicles, or power to a bed mounted radio shack, etc. IIRC there's a couple such designs executed in the trailer subforum. Depending on the desired / required amp load, you could move up to a more robust wiring and connector. You can't put much thru a common trailer connector. Those big fat Anderson couplers sure seem nice. And they have rubber caps for the bigger variety. You'd have to consider the connection getting submerged, too, if you expect to cross streams etc.

 

[DiploStrat]

Should be clear from all of the chatter that a battery on a trailer is just like any other camper/house/leisure battery. The variables are:

-- Need for a disconnect - and a disconnect adds resistance.

-- Distance - which argues for larger cables and/or some form of voltage boost. It is just possible that a trailer might be that bit further and demand that smaller cable to the point that a battery to battery charger, on the trailer, might be worth it. (Whereas you could simply use a larger cable over a shorter distance on a single truck.)

The voltage and amount of current required are determined by the size of the battery, not the fact that it is on a trailer.