Charging house batteries while trailering.

Just for the record this was not a major issue for me, rather a: I wonder how that might work? There have been several good ideas and concerns expressed. This question has often crossed my mind as I travel to the next adventure. Maybe this will give more insight ot my original thinking:

On our last trip out we loaded up on the trailer drove 5 hours home while running the refrigerator to keep our food cold. Arrived home unloaded and turned off everything, including the batteries that had ran the refrigerator (where we store I can't leave it plugged in all the time), salted the boat away in storage, and went home. Two weeks later we decide to go out last minute so topping the batteries off is not possible. Hence my worries and question. MM
 
Based on that information, just disconect the batteries comepletly. My dad used to do that when we left her in storage at a lake 6 hours from home every summer. That way nothing can take away from their charger while it sits for that couple weeks with no use. We used to go in about a month interval before we saw the bby again, and she always cranked right up. Just trying to elinmate the parasidic loads when disconnecting, Turning your battery switch off as you should know, wont eliminate all the possible parasidic loads from draining the batts. My 2 cents....you are worrying a little much :)

BBY
 
The the cable from the alternator as well as charging the battery has to provide for the electrics on the vehicle. eg two 90 watt headlamps (15 amps) two spot lamps (10amps), three brake lights (4amps) four markers/sidelights (2amps) heater blower (about 3 amps) wiper motor (3 amps) Radiator fan (4amps) stereo (1 amp) ABS pump, engine management/injection/ignition, fog lights etc. The alternator dependant, on spec, can bang out 40 or 50 amps but that current is not used charging the batteries. I'd use a cable plugged into the cigar lighter in the car and boat to charge the battery and fuse it at about 5amps and the cable needn't be that heavy. Just make sure everything is switched off on the boat and remember to run the blower before you try to start it (hydrogen from the batteries). The most likely issue is that when starting the vehicle current would be drawn from the boat battery but in most cars the cigar lighter plug is already fused at around 10 amps and isolated as the engine is cranked........easily checked.:smt001
 
All this sounds like way too much work and more parts to corrode/break. Get a jump pack. All you need to de is get the boat started and let the alternator do the recharging work while underway. If you have to monitor things that tightly then it sounds like you need a new battery...
 
I trailered two boats several hours and I charged my house batteries.
If you have a standard 7 prong setup as was shown in a previous thread, one of the wires is to charge batteries, usually on an RV.
There will be no problem using the windless wires. The wires do not have to be large. #10 is fine. I used # 12 wire. I put a plug right in the hull and just plugged it in when I trailered. If you have a windless it would be a great way.
This is common in the RV world and a trailered boat is no different.
If your tow vehicle came wired with the 7 wire setup the hot wire will be there. most likely it is unfused and you will have to find the fuse holder and add one.
Doug
 
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I have three batteries on my boat - two on the original system and added one for just the electronics that are isolated from the rest of the system; the charging system charges all three. I added a solar panel through a split charger; one side to the electronics battery and one side to the original system. The diodes in the split charger prevent 'intermingling' of the systems. The solar panel keeps enough of a 'trickle' on all the batteries to keep them from discharging. Since they are fully charged at the end of each trip, they pretty much stay that way.
 
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