Recharging boat battery's while towing....

[Casey]

George (Kerri On) is back on the road after a great visit here in Arizona. We finished making the "charging cables" for both Kerri On and Katmai, and George reports that his cable is working very well,and makes "boaterhoming" easier, and one battery is conveniently recharged while the boat is on the trailer.

As it turned-out we both have Ford F150 trucks. Both trucks have towing packages so are fit with both a 4-flat connector for a trailer as well as a round 7 connector RV-type plug.

George used #12 wire for his cable, since I already had #10 cable I chose to use it. #12 cable is sufficient, and somewhat easier to work with. If I was to redo the cable I'd use #12.

Both George and I had previously installed fused 12v sockets in the cockpit to power a small fan/light/laptop. Those 12v sockets are wired directly to one or both battery's (not through the Perko switch). The boat-end of the cable simply has a "male" 12v plug which connects to a 12v socket, and recharges the selected battery. The truck end of the cable uses a round connector which is only connected to the switched auxiliary connector, plus the ground. The trailer lights/turn signal wiring is completely separate.

That's the quick version of our project. There were a few changes of direction, and a couple of discovery's in both truck's wiring/fusing systems, a few blown fuses, and one errant 3/4" hole drilled in Katmai, but it finally worked out well. The lesson we learned is to rethink an original plan, an go with the simplest option available! I'll save the full version of the charging cable story for a campfire story somewhere/sometime.... With enough wine, it would be pretty humorous.

Casey
Lake Montezuma,AZ

 

[hardee]

Bringing this back for review. I'm interested in doing something like this. It makes for boaterhoming in comfort and practical --> you can use the boat's electrical store the same as you could if you were on the water.

I'm not interested in drilling a hole into my hull; I have a perfectly good hawse pipe on the fore deck that I will run the power supply cord into the cabin through. I have a 12VDC "cig" plug outlet that is live to at least one battery (I have 2 group 29's) even when the 1-2-Both-Off switch is in the "Off" position. I'm not sure I can charge both batteries through that plug (at all), or if I can do it with the switch in the "Off" or "Both" positions.

Wanted to bring this back and see if there are others who have done it and particularly anyone towing with a Tundra, just in case.

Harvey
SleepyC :moon

 

[DBBRanger]

I thought about this for a long time for my Ranger R25. I wanted it to be easy but be a quality installation and not cost an arm and a leg. The batteries on an R25 are in the aft so it's a long haul back there with decent size wires. My final installation doesn't perfectly match my desires as listed above, but is a good compromise.

I installed a 8-10GA wire from the truck battery to a 30A circuit breaker to a solenoid switch controlled by a switch in the truck cab and then to the truck rear end where I installed a male 30A 110V Marine connector. I then use my standard shore power cable and connect it to the connector on the truck. The shore power cable then runs along the topsides of the boat to the aft where I installed a pigtail with a female shore power connector and then another 30A circuit breaker and then to the house battery terminal block. When I'm running down the road, I flip the switch in the cab and charge the boat battery, but when I stop the truck engine, I flip the switch off in order to not charge the boat battery at the expense of the truck battery. This has worked to keep up with the load due to the refrigerator as I wished, however, it only charges at about a 5A rate so it will not bring up a severely discharged boat battery. The round trip length of the wires is more than 120' so the resistance of the wires plus the connector resistance tend to limit the current. I had worried that there might be too much current, but that didn't happen.

Some may be concerned that a 120V cable designed for shore power is being used for a 12V connection and that if the cable was mistakenly connected to shore power, I'd have big problems. That's a concern, but I've labeled them hopefully to insure that doesn't happen. The dual purpose cord helped keep the cost down. The 2 circuit breakers help protect both the boat battery and the truck battery.

My truck is a Duramax Chevy Diesel (2 batteries).

I wish I could get a higher charge rate, but I think that would take larger gauge cables (meaning big bucks!).

Hope that helps!

Doug

 

[Aurelia]

I don't have the need currently but a freezer installation this winter may change that (we can only make educated guesses at this point). I would personally look at using one of these:

http://www.yandina.com/c100InfoR3.htm

Combined with Dougs extension cord idea to have a simple and voltage regulated connection that I could connect and forget to keep the tow vehicle battery protected and charging active only when surplus power is available.

I would also not install anything to start with and test it to run simply from 12v socket in the cargo area of the tow vehicle to 12v socket on the boat. Think about what you are running and what the likely draw would be. For us is would be a freezer pulling .5-3amps so not much.

Greg

 

[Two Bears]

I replied to the first post in 2011 and have used that system since and it has worked well. In 4 years and more than 30,000 miles the only problem has been "operator error." Some thoughts after reading thoughts & comments above.
* I used a two prong Minn Kota plug designed for trolling motors. The plug will only go one way so no chance of changing polarity from a minute's inattention. Also, you need large wires to carry the power in a longer run like the 30 feet of wire I purchased. I used 10 gauge. My inlet receptacle is near the house battery at the back of the boat. I just googled "trolling motor plug" and the male/ female combo is less than $20.
* I visited with the mechanic at the Chev garage when setting it up. His comment was that having another battery just makes the car alternator think the new battery is part of the system and will bring it up to full charge. "Nothing special" was his implication. I was assured the truck system would shut off automatically. However, my last truck failed to turn off at least twice in 400+ nights with my camper. So I unplug when we are spending the night. As the wire runs from the Camper outlet in the side panel on the drivers side just behind the cab over the tail gate and then to the bow of the boat, I can't step over the hitch without getting my neck in the wire so I don't forget it. I have, however, forgotten to "replug" in the morning.

Chuck

 

[hardee]

For measuring the wire run for a #12 wire, am I right in thinking that lenget will be from the 7 pin plug at the back of the pickup to where it would plug into the Cig lighter plug at the help, where I am thinking I can plug this into charge the boat batteries. I am also thinking I can leave my 1-2-Off-Both switch in the "Both" position to charge both batteries equally.

Harvey
SleepyC :moon

 

[Will-C]

Maybe it's just me, but the idea of a solar panel with a controller would seem like a better option for us anyway. That way you can always reap the benefits. We travel on land we usually use campgrounds that have power available so like with shore power the battery charger can replace what the batteries lost during the eight or ten hours of driving per day. Then you still have the solar panel working for you if your out on the hook. I guess most of this need for constant charging is a result of refrigerator / freezers? We usually work out of a cooler while on the road and then once the boat gets back in the water we turn on the refrigerator/freezer. We always have at least one cooler on the boat anyway. Our fish guests need a place to chill out till I get a chance to clean them.
D.D.

 

[rogerbum]

For measuring the wire run for a #12 wire, am I right in thinking that lenget will be from the 7 pin plug at the back of the pickup to where it would plug into the Cig lighter plug at the help, where I am thinking I can plug this into charge the boat batteries. I am also thinking I can leave my 1-2-Off-Both switch in the "Both" position to charge both batteries equally.

Harvey
SleepyC :moon

I add in the length of the wire from that 7-pin plug to the battery/alternator of the truck (at least in terms of sizing the wire for amperage).

 

[hardee]

For measuring the wire run for a #12 wire, am I right in thinking that lenget will be from the 7 pin plug at the back of the pickup to where it would plug into the Cig lighter plug at the help, where I am thinking I can plug this into charge the boat batteries. I am also thinking I can leave my 1-2-Off-Both switch in the "Both" position to charge both batteries equally.

Harvey
SleepyC :moon

I add in the length of the wire from that 7-pin plug to the battery/alternator of the truck (at least in terms of sizing the wire for amperage).

On the Pickup Battery/Alternator to 7 pin plug 22 ft
7 Pin plug on truck to 12VDC Cig Plug at helm 18 ft
12VDC Cig plug at helm to Battery on Boat 14ft
Total length of run ================= 54 feet.

Is the amps figured on the amount of amp out put from the truck alternator? 100 amp I think. Or the amount of charge I want into the battery 5 amp I think to go to the Cig lighter? My on board charger is 10 amp, a 5/5 Guest, if that makes any difference.

Harvey
SleepyC:moon

 

[hardee]

Maybe it's just me, but the idea of a solar panel with a controller would seem like a better option for us anyway. That way you can always reap the benefits. We travel on land we usually use campgrounds that have power available so like with shore power the battery charger can replace what the batteries lost during the eight or ten hours of driving per day. Then you still have the solar panel working for you if your out on the hook. I guess most of this need for constant charging is a result of refrigerator / freezers? We usually work out of a cooler while on the road and then once the boat gets back in the water we turn on the refrigerator/freezer. We always have at least one cooler on the boat anyway. Our fish guests need a place to chill out till I get a chance to clean them.
D.D.

I like the idea of solar too, but I can get along with just having a charge day by day. I use a CPAP at night, other than that, I use very little electricity on the boat when towing, (only a very low draw camera for watching the cockpit and aft.) When on the water, I don't use a cooler or fridge, and running the OB's about 30 min a day will charge enough for the CPAP.

The Solar would be a plus for at anchor times, and help power the CPAP and my tiny Garmon GPS for anchor watch.

Harvey
SleepyC :moon

 

[texasair]

I used 12 gage wire from the charging circuit at the trailer connector.

At first charged the boat batteries through a cigarette lighter plug near the helm.

After I later installed a trolling motor, I was able to shorten the charging wire by connecting through the trolling motor plug located on the front deck.

Works well, keeps boat batteries charged, Engel cold.

No discharging of truck battery when parked overnight.

 

[DBBRanger]

On the Pickup Battery/Alternator to 7 pin plug 22 ft
7 Pin plug on truck to 12VDC Cig Plug at helm 18 ft
12VDC Cig plug at helm to Battery on Boat 14ft
Total length of run ================= 54 feet.

Is the amps figured on the amount of amp out put from the truck alternator? 100 amp I think. Or the amount of charge I want into the battery 5 amp I think to go to the Cig lighter? My on board charger is 10 amp, a 5/5 Guest, if that makes any difference.

Harvey

When calculating the size of a wire needed for a given current, you must use the round trip length, ie there and back. In your example, it would be 2 x54 or 108 total feet. Then use the resistance for the size and type of wire you expect to use (can get that online). Once you have that, then use Ohm's Law to calculate the expected current. So using V=IR, V is actually the voltage drop. So if the truck is charging at 14.5V, say, and the boat battery is at 12.2V, the drop is 2.3V. If 12 gauge wire has a resistance of .00162 Ohms per foot (total of .175 ohms in your case), then expected current is 2.3V/.175 = 13 amps. That's the most you can expect - I got a lot less. Your alternator will supply what ever is possible (it's not a constant current generator so it will not supply 100 amps unless the resistance allows it).

I'd be careful about using a cigarette lighter to pass that amperage - I'm not sure the wires to the lighter are adequate.

Hope that helps!

Doug

 

[colbysmith]

Ok, something I've wondered, but have not tried. What would happen if you plug a 110 vt. inverter into your 12 vdc accessory plug, and plugged your shore power battery charger into the inverter? I'm assuming the battery charger doesn't draw much amperage, and that if you have enough battery voltage to power the inverter, it would recharge the battery. (I'm thinking of a 100 watt inverter.) Maybe a stupid idea, but still, something I keep forgetting to try just to see. Colby

 

[Captain Bella]

This is a little off track, and others have probably done the same...

We occasionally run our Honda EU1000i from the storage site to the boat ramp. This allows us to begin warming the cabin for a long weekend, or cools the fridge, and charges the batteries. It also keeps our generator exercised.

We secure the generator with a dock line, and connect to the boat via the 30amp - 15 amp adapter...no traditional power cord.

Might be worth a try for those of you already hauling around a generator.

 

[hardee]

Ok, something I've wondered, but have not tried. What would happen if you plug a 110 vt. inverter into your 12 vdc accessory plug, and plugged your shore power battery charger into the inverter? I'm assuming the battery charger doesn't draw much amperage, and that if you have enough battery voltage to power the inverter, it would recharge the battery. (I'm thinking of a 100 watt inverter.) Maybe a stupid idea, but still, something I keep forgetting to try just to see. Colby

Colby, I'm not sure if I get what you are wanting to charge `shore power battery charger` into an inverter. I routinely run a 300watt inverter off my 12VDC Cig plug to charge a camera battery and have charged a lap top battery off that inverter.

I am wanting to charge my #1 and 2 batteries as I am towing though, so I can use off them at night.

If you are thinking of running the shore power charger off the inverter in the truck while I am towing, I don't think the 300 watt inverter is up to that.

Harvey
SleepyC :moon

 

[hardee]

Jeff, I don't carry a portable generator with me, well not a dedicated one anyway. If I need to (and I have on some occasions,) I will run one of the twin 40's for a bit.

Harvey
SleepyC :moon

 

[colbysmith]

Harvey, I think you sort of followed my thought, but I'm speaking of running a closed circuit, plugging an inverter into the boats 12 vt accessory plug, and then hooking the boats shore power up to that inverter, so that it would be driving the boat's charger... I don't know if my 100 watt inverter would handle it, but it handles my cpap without the humidifier at night. I think I do have a larger, 300 watt, inverter as well I could try out. I just wonder if running a "closed" circuit like that would work... I'm assuming that the electronics inside the inverter and battery charger are putting out more current than they take in. (I'm only thinking about doing this when dry camping on the boat while it's on the trailer, without AC power available to recharge the boat's batteries after a night of cpap use (and some cabin lighting.) On the lake, no problem, as I can just run the engine for a while to charge the batteries.

I also have a 2000 watt Honda Generator I sometimes travel with, that I have used to recharge my boats batteries when dry camping without electricity available. Colby

 

[JamesTXSD]

So, if I am understanding this right (and I'm probably not), you are going to run the inverter off the boat's 12v plug, then use that inverter to charge the boat's batteries??

:?: :crook :?:

You'd be using the boat's batteries to charge the boat's batteries? Yeah, I am sure I am missing something in that explanation.

 

[colbysmith]

I said it might be a crazy thought James! I think there is a lot of PFM going on inside that inverter, but maybe I'm giving it a lot more credit for what it can do... (Even I come up with some off thoughts... :roll: )

 

[thataway]

Sounds like the perpetual motion machine--and none of those work! No, do not run a battery charger off an inverter either using the truck or boat 12 volt charter.

It is easy to hook up a the batteries to the truck circuit. See my post on page one, where we use #10 wire. Ours from the RV is shorter than most trucks. We use simple connectors, inside of the boat--and run the wire thru the anchor deck pipe--no need for external hull fittings.

We use a version of this on our Yukon, which has a platform for a second battery under the hood. We run #8 wire (fused) from the start battery to a Voltage Sensitive Relay, on a bracket I fabricated out of sheet metal next to the second battery (Group 29) There is also an "on and off" switch, there to take this all out of the circuit. This second battery has a single output (fused) to # 12 wire to a cig lighter plug under the driver's seat of the truck--and this powers our refer/freezer.

This same concept (using a VSR on the start battery) to power a circuit going to the boat works very well. You don't have to worry about running down the trucks battery over night, but will charge the boat battery when you run the truck engine.

I am not sure I am keen on running an EU 1000 on the boat, when unattended going down the road! Where do you put the EU 1000? What about CO? Fire hazard, power issues--what do you use to "heat the boat" with--small electric heater? I won't leave a boat with a generator running--I have seen too many bad issues, ranging from run-away generator, to cooling issues, short circuits etc which can happen with any type of generator...let alone on the road.