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pfitz94

Battery Charging

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Hi I have a Question Regarding Towcar Electrics.My Towcar is fitted with twin 12N/12S Sockets which I use for my 2005 Bailey Ranger, I also have a 18ft Boat With an Auxiliary Battery fitted,I would like to Charge the Boat Battery from the 12S Socket also,would this be possible to do?any suggestions?

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No reason at all why the 12S plug should not be wired into a 12v  battery in the boat when it is on the trailer.

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You would need to fit a habitation relay, as per the caravan wiring system, between the 12S socket and the boat battery. 

 

Web-Image-33-car-and-caravan-relays3-for-DS-use-onl2y.jpg

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Thanks for the Response,I was wondering if you could Recommend Correctly Rated Cabling for Plug?,Also,Would it Be Permissible to Use Pin 2 (Pre 1998 System) from the Split Charge Relay in the Boot to Switch Battery without Habitation Relay?

Edited by pfitz94

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Assuming your boat battery isn't wired to the permanent 12v car feed,, there is really no need for the Habitation relay IMO, as the boat effectively has no habitation connection. Do you have a 12v fridge?

 

Of course, you are discussing a non standard wiring configuration which some people would not be happy with.....

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what is a hibernation relay, how does it work?

 

I'd have suggested a split charge relay same as used in a caravan

 

macafee2

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6 minutes ago, macafee2 said:

what is a hibernation relay, how does it work?

 

I'd have suggested a split charge relay same as used in a caravan

The relay in the car is to ensure that the caravan battery is only connected to the car when there is charge to spare.

The habitation relay is in the caravan and prevents the caravan electrics, interiorlights etc, from taking the current which should be gong to charging the battery.

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18 hours ago, pfitz94 said:

Would it Be Permissible to Use Pin 2 (Pre 1998 System) from the Split Charge Relay in the Boot to Switch Battery without Habitation Relay?

No.  Because your car should be / is wired to the 1998-2008 standard to suit your 2005 caravan and pin 2 is 'sensing device' (probably not used?).  https://www.caravanclub.co.uk/media/1022790/towbar-wiring-mo.pdf

 

But the relay in your boot powers pin 6 & 7 for the caravan fridge (only when engine is running) and that circuit could be used to charge the boat battery when towing that trailer.

 

Cable size (sq mm) may depend on total cable length to the boat's battery to the 12S plug for minimising volt drop.  https://www.12voltplanet.co.uk/cable-sizing-selection.html may guide you?

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It depends on the car, if no stop/start then simple relay in the car will allow a little charging, if it has stop start then it needs an inverter to charge second battery.

 

I found a split charging relay will on starting car charge the second battery at around 15 to 20 amp, but within 15 to 20 minutes it's dropped to 2 or 3 amp, so with a 110 amp/hour battery half charged you would need to be towing for 12 hours to do much good.

 

Many boats have DC to DC inverters to charge the bow thruster battery so it may be possible to use that?

 

Main thing is:-

1) Some thing to stop drawing that much from car that car will not start.

2) Stop power going from aux battery to prime mover battery when cranking.

With a DC to DC inverter it will do that without the need for relays.

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