Charging batteries while on the road

[knotflying]

Has anyone thought about tying in the house batteries to the power from your vehicle while towing so the batteries will be topped off? While trailering the boat we keep the refrigerator on and as long as we pull into a site that we can get shore power there is no problem, but I am sure the day will come when we won’t be able to get power and I figure having the batteries topped off while driving will prevent a battery drain after a 24 hour period without power. Anyone have thoughts or information on how you did it?

 

[RProffer]

I have been wondering about that for my 5th wheel camper. On the road or at a primitive campsite, I would not have a way to charge the campers battery. As a quick workaround I connect an inverter to my truck battery and plug my campers power cable into the inverter. I would have to have the trucks engine running to keep the trucks battery charged so I would not end up with a dead battery on my truck. This will work, but is not practical.

At this link http://www.etrailer.com/faq-wiring.aspx, they show the wiring for 4, 5, 6, and 7 pin trailer connectors. On 6 and 7 pin connectors, there is a black wire to be used for "Break away kit, interior lights and battery charger". Most trucks with a trailer kit have a 7 pin connector. My boat trailer has a 5 pin connector. The 5 pin connector does not have a black wire. You would have to put a 7 pin connector on your trailer, then run wires to your boat. I would not run the wires directly to the boat's battery's because your truck would need a battery isolator to properly charge the second battery. I don't think the black wire is powered by a battery isolator - I could be wrong. Don't forget to use marine wire for any new wiring on the boat. I hope this makes sense.

If someone knows a better way, please let me know.

 

[HRowland]

You could use something like the Xantrex Echo Charge. This provides charging current to the target only when the source is a high enough voltage to indicate a charge source is present. It also limits charge current to 15A. If you used automatic charge relays as used by Ranger between the batteries there would be no limiting, you would need to install extremely heavy gauge wire.

http://www.xantrex.com/power-products/p ... arger.aspx

You would have a very long round trip wire distance (positive and ground) between the truck battery and the tugs battery and would need to use large gauge wire to prevent excessive voltage drop, probably 8 gauge or even more, I would have to refer to a table to check.

Howard

 

[Levitation]

Mike, I have on-the-road charging for my power winch battery on the trailer...
It charges off the +12v aux pin (PIN #4, Black Wire - a 10 ga. wire and usually a 20 amp fuse) at the truck's bumper socket... You should be able to pick off #4 up on your trailer's wiring harness...
#4 is only hot when the vehicle is running... When the truck is shut off the relay is open and no current can be drawn from it to prevent discharging the truck batteries overnight...
If you wire it to your house set (not the start and thruster batteries) and if you don't let the house set get heavily discharged likely the initial in-rush current will be less than 20 amps...
I would do a quick and dirty test/trial by wiring it direct to the battery and if it blows the fuse then you can put a 50 watt bulb in series with the lead to the battery to limit the current until the battery charge rises enough for the current to drop off...
You will need to also supply a negative return from the battery to the plug (PIN #1, White Wire)
10 ga. wire will work for both leads... Smaller wire will limit the current in-rush to a discharged battery but the wires may get excessively hot... I would use the series bulb to control current to 5 or 6 amps if you have fuse blowing... Or a pair of 50 watt bulbs wired together in parallel will limit in-rush current to roughly 10 amps...
If any questions give me a call...

 

[Levitation]

Oh yeah, we will also need to block the Blue Seas relays from putting all the batteries in parallel when it senses 13.6 volts... I converted my relay control to manual so I tend to forget that... Anyway, that is just a simple SPST switch in the Blue Seas ground line...
I know this whole thing sounds complicated but it is not and once you see it done you won't be intimidated...

 

[tedwhit]

I admit I don't even know what language you guys are talking but shouldn't the solar panel give you enough of a charge to keep the refrigerator running?

 

[knotflying]

The solar panel will send a charge to the batteries, but not enough to keep up with the amperage that the refrigerator uses. It will take longer to discharge than with no solar panel, but over time you will discharge. Add in a cloudy day or so and you will be well discharged. Under normal circumstances with running the engine during the day and then anchoring out there is no problem. However if you are trailering the boat and have a cloudy day and stay at a place without power and then trailer the following day, I would say you are really pushing your luck.

 

[Levitation]

Ted, like a Three Dog Night, it is probably a Two Panel day to keep up with the frig given the hours of darkness and some dim days... Another panel is ~$500...
Mike found by experiment that the stock battery set is good for 3 days running the frig without the charger/solar being on...
Or, you can start the engine and run it in neutral at a fast idle for an hour or so, every day... Less than a gallon of fuel with only the alternator as a load...
Or open the frig only once a day in the morning to get out the days food and turn off the frig at night to save power...
Or go to the proven sailors method of the centuries, oak casks with salted pork and fish and no refrigeration :mrgreen:

 

[JamesTXSD]

We bought one of these...

http://www.cabelas.com/trailer-accessor ... er-1.shtml

It fits in the second 7 pin connector in our truck (where we plug in the 5th wheel when we're hauling it). I wired a 12v cigarette lighter end on a wire, run that wire back to the house batteries on the boat, put in a 30 amp fuse, then connect that to the batteries. Anytime the truck is running, it is charging the boat batteries.

We generally stay at RV parks while towing the boat to other cruising areas; plugging in each night couldn't keep up with what the fridge used for power. This cord fixed that.

I don't know what Ranger uses for an onboard battery charger in their boats, but the Guest that came in our C-Dory only puts 5 amps back into the batteries. Our fridge uses about 4 amps/hr. So, if the fridge is running 24 hours per day, but the boat is only plugged in 12 hours, you are losing ground. It's not a problem with the fridge or the charger, just a matter of power used vs power regenerated.

Best wishes,
Jim B.

 

[walldog]

In the Ranger 27 with the Mariner ProTech charger with separate inverter, expect the 30amp fuse to the house batteries to blow if you run the house batteries down and connect the charger without turning off the loads first. I found out the hard way to turn off ALL the 12volt breakers before connecting the shore power to the charger. Guess I have been lucky to have enough sun to keep the batteries up while trailering. Our solar panels put out near 10 amps in full sun....probably average about 5 during the day. We keep our temp control around 4 to keep the lettuce and eggs from freezing.

Herb, running out of 30amp fuses......20amp does not work.

 

[Levitation]

Herb, I found a real penny on the sidewalk the other day... I'll send it to ya... That'll solve the fuse problem - that's how my dad did it...

 

[walldog]

Herb, I found a real penny on the sidewalk the other day... I'll send it to ya... That'll solve the fuse problem - that's how my dad did it...

I tried a penny in that fuse holder, but could not make it work. :cry:

 

[knotflying]

If you run a straight line of power from the truck to the batteries on the boat without a regulator isn't there a posibility of overcharging the batteries?

 

[Levitation]

Nope...
The alternator controls it's output voltage (and therefore current) based on the voltage it sees looking into the battery(s)... Once ALL the battery(s) are up to charge and pushing back against the alternator it will taper off the voltage to 13.7 which is a safe level for all the battery(s)

 

[knotflying]

Okay then. My plan will be to run a pair of #8's (negative and positive) directly off the truck Battery straight back to the rear bumper of the truck with a female plug. Then I will run a pair of # 8's that will plug into the truck bumper socket to the back of the trailer with another female plug. Then I will fabricate a lead with battery clips ( like a charger has) that I can clip to the house batterys on one end and then a male plug on the other end to plug into the rear female trailer plug. I will install a 30 amp inline on the positive terminal. A lot of wire because bumper to rear of boat is 58 feet add approximately another 12 feet from trailer to battery compartment and you are talking about a 70 foot run. I assume the # 8's can handle that run.

 

[Levitation]

Yup... #8 is good, a bit overkill but good
To avoid a hot spark right at the battery (to avoid lighting off any hydrogen gas coming from the battery(s)) connect the alligator clips to the battery first, then plug it together at the bumper plug, THEN start the truck... Hooking up from the batteries forward eliminates any sparks in the battery compartment...

Remember, the voltage from the truck can be high enough to activate your Blue Seas ACR relays that put all the batteries in parallel - right as the truck starts charging the boat (just like it does when you start the Yanmar and the alternator comes on line)
This might be a problem - as it adds two more batteries to the charging load and increases the chance you will pop a fuse...
Or it may not be a problem - if the two batteries (engine and thruster) are well charged they will actually help to provide current to the more discharged (lower voltage) house batteries and reduce the initial immediate current on the truck circuit...

Of course, the only way to work it out for sure is to try it... If you pop the truck fuse, then we will have to put a cut out switch on the Blue Seas ACR relays (simple job)
This is fun... Wish I was there to help...

 

[Levitation]

Darn - I really MUST learn to read someday... You said directly off the truck battery

Everything I said stands except for starting the truck last... Have the truck running when you make the final connection at the bumper to avoid have the truck battery pulled down by the low batteries in the boat....

And, if plugging into the connector at the bumper makes to much spark too close to your fingers for comfort you can safely hook to the battery with the truck wires hot by hooking the alligator clip to the battery positive while the negative alligator is disconnected... Then close the battery compartment, open the engine cover and make the negative connection somewhere on the engine ground line so that the spark is not right over the battery...

 

[GulfSailor]

I will install a 30 amp inline on the positive terminal. A lot of wire because bumper to rear of boat is 58 feet add approximately another 12 feet from trailer to battery compartment and you are talking about a 70 foot run. I assume the # 8's can handle that run.

It depends on how much voltage drop will be acceptable. Looking at the these graphs and assuming a 70' round trip and a charge rate of 30A, it appears that if you're accepting a 10% drop you can use #6 and for 3% you'll need #2.

http://www.westmarine.com/webapp/wc...toreId=11151&catalogId=10001&page=Marine-Wire

 

[Levitation]

The issue here is not a minor voltage drop under normal charging conditions of, say ten amps or so, rather it is the initial current surge into discharged batteries blowing fuses and this is where a bit of resistance in the wiring loop can actually be helpful...