I have a new to me FWC Eagle on a trailer. Trailer and tow vehicle connect through round 7 pin plug and receptacle. Trailer also has an exterior cord with a round male 3 pin plug that originates at the 12 volt fuse panel. Camper has a battery and battery separator. How do I integrate the 3 and 7 pin circuits so that the tow vehicle when running can provide power to the trailer?
Charging trailer battery
- Thread starter MDM54
- Start date
DiploStrat
Expedition Leader
The short, snarky answer is, "Don't bother." The wires are almost certainly too long and two small to ever deliver a decent charge.
Cobble up the cable and do a test with your engine running. If you do not see at least 14v at the trailer, then don't bother; you will need to so something else.
Cobble up the cable and do a test with your engine running. If you do not see at least 14v at the trailer, then don't bother; you will need to so something else.
4x4junkie
Explorer
Yep. Even a 0.5 volt drop can cut the charge current to your trailer battery by half or more (I'll bet the v-drop in the wiring going through a little trailer connector is many times that).
Your best bet is to run a separate wiring harness w/high-amp connector specifically to charge the camper battery while the engine is running. Depending on it's length, it's likely you'll need something around 1/0 or 2/0 AWG and a connector rated at whatever your alternator's output is (Anderson PowerPole connectors usually work well). Use of welding cables will maintain flexibility with that large of wire size (just make sure they're protected from chafing... Fuses for 100-150A circuits are not cheap, which you should have one at each end of your cable run).
Your best bet is to run a separate wiring harness w/high-amp connector specifically to charge the camper battery while the engine is running. Depending on it's length, it's likely you'll need something around 1/0 or 2/0 AWG and a connector rated at whatever your alternator's output is (Anderson PowerPole connectors usually work well). Use of welding cables will maintain flexibility with that large of wire size (just make sure they're protected from chafing... Fuses for 100-150A circuits are not cheap, which you should have one at each end of your cable run).
Borrego60
Rendezvous Conspiracy
Here is what I did and has been working very well.
http://www.expeditionportal.com/forum/threads/83874-12-volt-from-vehicle-to-trailers-battery
http://www.expeditionportal.com/forum/threads/83874-12-volt-from-vehicle-to-trailers-battery
Borrego60
Rendezvous Conspiracy
https://www.expeditionportal.com/fo...ailers-battery.83874/#lg=post-1184574&slide=2 older post but still working today.
4000lbsOfGoat
Well-known member
I use a BCDC1212T from Redarc to charge my trailer battery on the move. It is specifically designed to be used with a factory 7-pin connector and can operate on an input voltage down to 9v. No need to run expensive, heavy custom cables for this purpose - just buy a charger made for the job.
It isn't going to charge fast but it at least keeps up with the fridge, plus a bit extra.
Cheers.
It isn't going to charge fast but it at least keeps up with the fridge, plus a bit extra.
Cheers.
DiploStrat
Expedition Leader
I love, and use, REDARC toys. But let us be clear - The BCDC 1212 only charges at 12A. If that is enough, great. But do be sure that your 7- pin connector wire is rated for at least 15A or so over the distance of your wire run. The REDARC can't make electricity out of nothing.
shays4me
Willing Wanderer
I ran an eight gauge wire from my trailer connector through a forty amp relay and a forty amp circuit breaker at the battery. The relay comes on with the ignition switch so it doesn't drain my starting battery. I tried it first with twelve gauge wire and it didn't work due to current carrying capacities for long runs of wire. The eight gauge works though. If I hadn't sold my trailer I would have eventually bought one of the DC to DC chargers like the redarc unit. They step the voltage up and pulse the amps through the circuit. Deep cell batteries accept amps slower than a starting battery so the DC to Dc chargers are definitely the best way to go for peak charging your deep cell battery in a shorter time. Here's a handy chart I use for automotive circuit wiring. http://www.offroaders.com/technical/12-volt-wiring-tech-gauge-to-amps/
Towed Battery Charger Plus for flat towing
RVi Towed Battery Charger Plus, charge line replacement for flat towing a vehicle. Great peace of mind for the towed battery while towing a car behind a motorhome. Often used with RVibrake. TBC+
rvibrake.com