Charging batteries while driving?
- Thread starter dawsonc61
- Start date
teotwaki
Excelsior!
In North American vehicles the battery positive terminal is hot and the negative terminal goes to the frame. If both trailer batteries are wired together with a good solid cable then you only have to pick one as your connection point.
The auto charge relay
would have one terminal connected to the Rubi's battery positive terminal and the other terminal will go to the cable to the trailer. You'd still want some inline fuses for safety
OlympiaFJ60
Adventurer
I have been using the Hellroaring battery isolator/combiner for years (http://www.hellroaring.com/rv.php). It can be mounted in the trailer or in the truck. If your trailer connector is already wired for the charge line, installing it in the trailer may be easier.
robert j. yates
Explorer
I took a different route as I did not want a constant hot lead running to the back of my Jeep when the trailer was not connected.
Essentially, I am using a constant rated solenoid along with a 100amp Buss fuse block underhood with the solenoid switched into my passenger compartment so that I can manually switch whether or not the trailer batteries are being charged. I also routed the charge wire into my 7 pin RV connector so I have a very clean trailer connection. I am powering this with a 220amp Mechman alternator and all of this is in addition to a Kodiack Industries dual battery (Odyssey pc1200's) conversion for my TJ. I think I have plenty of battery power :sombrero:
Essentially, I am using a constant rated solenoid along with a 100amp Buss fuse block underhood with the solenoid switched into my passenger compartment so that I can manually switch whether or not the trailer batteries are being charged. I also routed the charge wire into my 7 pin RV connector so I have a very clean trailer connection. I am powering this with a 220amp Mechman alternator and all of this is in addition to a Kodiack Industries dual battery (Odyssey pc1200's) conversion for my TJ. I think I have plenty of battery power :sombrero:
78Bronco
Explorer
How many amps can you run through your 7 pin connector...I would say 20 max unless you have made some upgrade to it.
If you don't plan on having to jump start your vehicle from the batteries in the trailer than that would work fine.
R_Lefebvre
Expedition Leader
Wow, was I horribly naive in thinking I was just going to run 10Ga wire back to my 7 pin connector and that's all there is to it?
I'd read somewhere that you *want* the battery to charge slower, as it's easier on the battery. If your battery is 50% discharged, and you hit it with 100Amps, that's not too good for it.
I'd read somewhere that you *want* the battery to charge slower, as it's easier on the battery. If your battery is 50% discharged, and you hit it with 100Amps, that's not too good for it.
Titanpat57
Expedition Leader
Totally agree Rob....start with a 30 amp inline fuse directly off the battery and head towards the rear...if you really want to get crazy throw another one before the battery(s) at the trailer.
R_Lefebvre
Expedition Leader
It was actually a question not a statement. 
I don't know, but I thought that's what was done, why there were 7 pins.
Heck, the power wire in the 7 conductor cable is only 10 Ga, so you wouldn't want to use 4Ga on the truck, to a big power connector, into 10Ga trailer wire.
I don't know, but I thought that's what was done, why there were 7 pins. Heck, the power wire in the 7 conductor cable is only 10 Ga, so you wouldn't want to use 4Ga on the truck, to a big power connector, into 10Ga trailer wire.
Mashurst
Adventurer
I'm not sure I wouldn't. With the circuit protected properly for the smallest wire I think it could work well. Voltage drop is a function of amps, wire size and length. So running a 4g to the back of the truck would keep the drop to a min for that run. Then you could drop down to the 10 in the plug and then maybe step back up a bit to say 8. The plug will be your 'hot' spot but keeping it short will minimize the loss of power while avoiding the complications of a dedicated power connection.
On second thought I think the way I would do it would be to run the 4 to the back with it's own fuse and hit some kind of distribution block. From there have a smaller fuse and a branch to the trailer plug. That way I could use that 4g for other stuff as well like back up/work lights or a fridge in the back.
R_Lefebvre
Expedition Leader
My understanding about using 10g the whole way, is that it is a self-regulating circuit. You *need* the resistance of the 10g wire to lower the amps to something manageable. If you run 4 Ga to the back, your total circuit resistance will drop, and maybe cause the amperage to be too high for the 7 pin connector.
charging on the road
I have 2 deep cycle batteries in my trailer. They are charged thru the 7 conductor jack (I think it is the black wire). My truck is a F-250 which has a trailer charge circuit protected by a fuse in the panel. I think it is a 20a . THe charge circuit only works when the engine is on. If your vehicle has a similar circuit you should be in business. If your tow vehicle does not have such a circuit, check with companies that provide battery chargers for trolling motors. There are several products that are made for this application.
Most trailer wiring is 14g, but that provides sufficient current to charge the batteries in a few hours of drive time. You would only need heavier wire in between the batteries and a large load (ie a fridge, or a jump start condition) That wiring would not necessarily need to connect the truck battery to the trailer battery.
I made up charging cables for the batteries out of 10g wire, that plug into a marine type jack in floor of the trailer. The charging cables are protected by a 30a inline fuse in case they come loose while driving and short to something.
I have 2 deep cycle batteries in my trailer. They are charged thru the 7 conductor jack (I think it is the black wire). My truck is a F-250 which has a trailer charge circuit protected by a fuse in the panel. I think it is a 20a . THe charge circuit only works when the engine is on. If your vehicle has a similar circuit you should be in business. If your tow vehicle does not have such a circuit, check with companies that provide battery chargers for trolling motors. There are several products that are made for this application.
Most trailer wiring is 14g, but that provides sufficient current to charge the batteries in a few hours of drive time. You would only need heavier wire in between the batteries and a large load (ie a fridge, or a jump start condition) That wiring would not necessarily need to connect the truck battery to the trailer battery.
I made up charging cables for the batteries out of 10g wire, that plug into a marine type jack in floor of the trailer. The charging cables are protected by a 30a inline fuse in case they come loose while driving and short to something.
Mashurst
Adventurer
The problem here is that it will not lower the amps. It will only lower the volts and the difference is simply made into heat. This is a wast of power. Amps is a mater of how much the devise pulls. You need the volts to charge the bat. If you try to charge a bat at to low a voltage it is hard on it. Aside from cost and with the proper fuse/breaker, bigger wire is always better.
That said there can be a problem charging a bat too fast. If it gets too hot it can be damaged. I wonder if there is a heat sensing charging regulator on the market. I know the later XJs (and other new cars) have a temp sensor under the bat for this reason.
ntsqd
Heretic Car Camper
Large current alternators don't necessarily dump their full output into charging the starting battery. Most of that capacity is there to support the vehicle's loads. Since at least the late 70's the trend has been to size the battery for starting only, the alternator carries all of the vehicle loads. That is why late models have such tiny batteries and 100+ amp alternators where older stuff have larger batteries and smaller capacity alternators.
If you poke around the marine world in particular you'll find some very nice battery charge controller/regulators. They don't come cheap, but compared to a whole bank of 8D's they're not all that bad.
In the roughly 20 years that I camped with my grandparents in their succession of Airstreams we never had any of the fancy connectors or large charge cables. A 10 gauge wire was strung back down the frame rail to the trailer light receptacle. In the engine bay there was a 20 amp breaker and that was all that there was to the system. Granddad made a point of unplugging the trailer lights every time we stopped overnight or longer, and reconnecting them when we moved on.
If you poke around the marine world in particular you'll find some very nice battery charge controller/regulators. They don't come cheap, but compared to a whole bank of 8D's they're not all that bad.
In the roughly 20 years that I camped with my grandparents in their succession of Airstreams we never had any of the fancy connectors or large charge cables. A 10 gauge wire was strung back down the frame rail to the trailer light receptacle. In the engine bay there was a 20 amp breaker and that was all that there was to the system. Granddad made a point of unplugging the trailer lights every time we stopped overnight or longer, and reconnecting them when we moved on.