Charging house batteries while trailering.

MonacoMike

MonacoMike

Well-Known Member
Sep 15, 2009
14,721
Indiana lakes and Lake Michigan
Boat Info
2000 Cruisers 3870
8.2 Mercs
Engines
85 Sea Ray Monaco 197
260hp Alpha 1
It would be great to top off batteries as we travel. We often can't top them off before we leave, and trailer at least 2 hours and up to 6 hours. Has anyone ever set up a power feed from the truck to the boat batteries? Any potential issues? (Damage to either alternator or charger?). Two ideas come to mind to do this: one, run a wire pair the length of the trailer and add a plug line near the battery switch. Two: put a plug in the fore deck near the windlass and use the windlass wire to send the power back to the batteries. Thoughts? Thanks, MM
 
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I ve been thinking of some different ideas myself. I don't see why it would be an issue as camper trailers do it. Now I have some more ideas running through my head...
 
MonacoMike said:
It would be great to top off batteries as we travel. We often can't top them off before we leave, and trailer at least 2 hours and up to 6 hours. Has anyone ever set up a power feed from the truck to the boat batteries? Any potential issues? (Damage to either alternator or charger?). Two ideas come to mind to do this: one, run a wire pair the length of the trailer and add a plug line near the battery switch. Two: put a plug in the fore deck near the windlass and use the windlass wire to send the power back to the batteries. Thoughts? Thanks, MM
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how about installing some remote battery terminals like these in the anchor locker and direct wire them to the batteries....you could install another set of terminals under the rear bumper of the tow vehicle...these terminals would be wired directly to the tow vehicle battery...you then set up a 'jumper cable' of sorts to connect the two sets of remote battery terminals as you travel...the wire size is important to consider...as the distance to carry the DC current increases the need for a heavier gauge wire also increases...i ran into that when i installed my power inverter....


what about a solar powered charger (or two or three)?....i don't think they put out a lot of power but if your batteries are not drained too far down and you have a long trip planned they may could top off the charge....but if the weather is cloudy or you travel at night you would reduce or completely stop the amount of charge from the solar charger...

or possibly a rechargable 'jumper battery' could be charged over night and connected to the batteries with jumper cables when you start your trip...during the trip the charge from the jumper battery would charge the boat batteries (maybe not fully charged though)....
 
CliffA said:
how about installing some remote battery terminals like these in the anchor locker and direct wire them to the batteries....you could install another set of terminals under the rear bumper of the tow vehicle...these terminals would be wired directly to the tow vehicle battery...you then set up a 'jumper cable' of sorts to connect the two sets of remote battery terminals as you travel...the wire size is important to consider...as the distance to carry the DC current increases the need for a heavier gauge wire also increases...i ran into that when i installed my power inverter....


what about a solar powered charger (or two or three)?....i don't think they put out a lot of power but if your batteries are not drained too far down and you have a long trip planned they may could top off the charge....but if the weather is cloudy or you travel at night you would reduce or completely stop the amount of charge from the solar charger...

or possibly a rechargable 'jumper battery' could be charged over night and connected to the batteries with jumper cables when you start your trip...during the trip the charge from the jumper battery would charge the boat batteries (maybe not fully charged though)....
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This is a very hazardous solution. Keep in mind that when the trailer is connected to truck it is also grounded and if the hot "jumper" comes off and shorts to trailer there will be some arc damage before whatever circuit protection you use interrupts. There are insulated plugs specifically designed for this.....just sayin
 
floriduramax1 said:
This is a very hazardous solution. Keep in mind that when the trailer is connected to truck it is also grounded and if the hot "jumper" comes off and shorts to trailer there will be some arc damage before whatever circuit protection you use interrupts. There are insulated plugs specifically designed for this.....just sayin
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you are probably right...didn't think that one all the way through...thanks
 
Do camper trailers use the standard alternator on the truck? Or, do they upgrade the alt?

Without knowing for sure, I would lean towards thinking that the windlass wiring wouldn't be heavy enough? All I'm basing this on is that the alternator wire on my truck (charging two, big batteries) is larger than windlass wires - and it's only 2' long. Also, the alt on my truck works well for the two batteries (and I'm sure it's a bigger alt than what would be on a gasser), but I tend to think it wouldn't be good enough for 4 or 5 batteries.

How 'bout strapping a small generator to your swim platform?
 
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You might be able to run a dc to ac converter mounted in your tow rig and plug your shore power cord into it with a 120 pigtail. This might be safer and you wouldn't have all the dc amperage loss.
 
Lazy Daze said:
Do camper trailers use the standard alternator on the truck? Or, do they upgrade the alt?

Without knowing for sure, I would lean towards thinking that the windlass wiring wouldn't be heavy enough? All I'm basing this on is that the alternator wire on my truck (charging two, big batteries) is larger than windlass wires - and it's only 2' long. Also, the alt on my truck works well for the two batteries (and I'm sure it's a bigger alt than what would be on a gasser), but I tend to think it wouldn't be good enough for 4 or 5 batteries.

How 'bout strapping a small generator to your swim platform?
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Thanks Dennis,

If this was for me I have a generator but I like to start with fully topped off batteries.

The windlass wires are 4 gauge on my boat. The RV charge wire is like 12 gauge on my travel trailer. The alternator on my truck is for trailering and heavy loads. I would be charging 2 group 31 and, possibly one group 27 in addition to the truck battery. This load may over-pull on the alternator. I was thinking like a trickle charge, not a full recharge from a badly discharged state. If the wire was too small would that reduce the pull the alternator but still give a little bit of charge? MM
 
With large RVs there is a solinoid that comes on with the igintion. It is used to supply power to the house batteries when you are driving. I am not an electrian but you might concider this sort of wiring off your truck alternator. I do this on my boat to charge the house batteries. Wire size I think is 10 gauge.
 
Do you have an issue getting to the launch with low batteries?
 
MonacoMike said:
Thanks Dennis,

If this was for me I have a generator but I like to start with fully topped off batteries.

The windlass wires are 4 gauge on my boat. The RV charge wire is like 12 gauge on my travel trailer. The alternator on my truck is for trailering and heavy loads. I would be charging 2 group 31 and, possibly one group 27 in addition to the truck battery. This load may over-pull on the alternator. I was thinking like a trickle charge, not a full recharge from a badly discharged state. If the wire was too small would that reduce the pull the alternator but still give a little bit of charge? MM
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I was thinking (seriously) that you could strap the generator to the swim platform while you're trailering. Plug it right into the boat and use the onboard charger.

I guess there's something different done with regards to the RV charge wire - as opposed to what I was envisioning for a charging lead. That's right - you put in the windlass yourself, right? That's why you have 4-ga for the windlass? I think my alternator wire on my truck is 4 gauge.

If the wire is too small, it can burn up - too much juice trying to flow through a small straw.
 
firecadet613 said:
Do you have an issue getting to the launch with low batteries?
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No. Just overly ana! about details and having fully topped off batteries. Probably something to do with a bad experience I once had with a generator issue and the batteries were not fully charged when the adventure started. I was behind the power curve the whole trip. It is also why I watch my voltage levels so compulsively, I been surprised on two occasions, once as above and another more recently where I was in a slip on shore power, turned off the Garmin voltage monitor screen, ran power like crazy, (we are on shore power for gosh sakes), and low voltage alarms start going off at 1 AM.

I now am ana! and watch power like a hawk. MM
 
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How about using a 7 prong trailer plug? Red wire to charge. Should provide enough to keep batteries topped off

http://www.etrailer.com/faq-wiring.aspx
 
As long as your are just maintaining a charge on the boat batteries, and not trying to recharge them from will say.. 50% Your alternator isn't going to burn up. Its a charge circuit, maintaining a charge, which is why if you could find a way to route it back to the batteries usuing your RV trailering circuit, from a 7 pin connector....this idea would work. My buddy has 2 group 27 batteries on the front of his camper that tie into his 7 pin wiring harness and it maintains the charge on the two batts plus the truck...Done it for years. no issues.
 
BlewByYou88 said:
As long as your are just maintaining a charge on the boat batteries, and not trying to recharge them from will say.. 50% Your alternator isn't going to burn up. Its a charge circuit, maintaining a charge, which is why if you could find a way to route it back to the batteries usuing your RV trailering circuit, from a 7 pin connector....this idea would work. My buddy has 2 group 27 batteries on the front of his camper that tie into his 7 pin wiring harness and it maintains the charge on the two batts plus the truck...Done it for years. no issues.
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I have pulled the travel trailer with it's group 27 connected via the red wire on the 7 pin, while also topping off another group 27 on the lighter connection in the truck. Seems the same to me. MM
 
I haven't had a chance to look at the other threads, but low voltage alarms while on shorepower would make me look at the on board battery charger...
 
Well, if the charge wire doesn't need to be that big, then it sounds like your idea of using the windlass wires would do the job. Just install a plug up on the bow of the boat, route the wires securely out of the way of the windlass and the rode - plenty of room to do that around the inside, outer perimeter of the anchor locker.
 
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