Battery charging whilst towing

[jamestaylor18]

Hi all

Total newbie here! I am a bit confused by my battery charger and the whole charging when towing. I have a 2005 Swift Fairway 460 2 berth van. My question is... how do i charge my battery when towing?

I have read a few topics on this, but i am still confused! My handbook doesn't really help either. So... when towing, i have the van/car switch in the centre? This will then activate the habitation relay and cut off the power to everything besides the fridge and battery? Is this correct? So, in theory this will charge my battery? (all be it very slowly). Do i need to have my charger turned on or not? I am guessing not, as there is no power to it, and the charge is coming from my car and not the charger?

I don't really plan on using my fridge while travelling, as i usually do a food shop once i get where i am going, by which point i plan to be hooked up the fridge should be on its was to cooling down. Therefore, will this create a better charge of my battery as all the power being supplied is going to my battery?

Any help would be greatly appreciated!

 

[colin-yorkshire]

it depends on how your plugs are wired up, one assumes they are just standard twin plugs or single 13 pin.
if so, you should have two power feeds one for the charge circuit and one for the fridge. everything after that should be automatic.
one permanent feed goes to the van. to supply the 12v electrics, this charges the van battery when plugged in and the engine is running as the habitation relay senses the power from the charge circuit, turns off the internal electrics and diverts it to the leisure battery for charging.
you can test this with a multimeter by taking a reading across the battery, before plugging in [should be around 12.5 volts] and then again while plugged in with the engine running, [should be around 14v] if you have similar readings to this it shows the van battery is being charged from the car and everything is fine.
note. it is surprising how quickly the car will charge or top up the van battery while running as there is plenty of spare capacity from the alternator, to not only run the car, charge the battery [after starting] but also charge the van battery and run the fridge all at the same time. it is how the system works.
there is no need to leave the fridge turned off while while travelling. it will cope just as well while under tow. [then it will be cool] when you arrive without waiting for it to start from scratch on the EHU.
I too carried very little in the fridge while travelling [to save weight] but found it useful to have enough provisions for a light meal and drink both while on the road and while setting up. before rushing off to the shops when on site.
you can either cool the fridge down before the start by running it on either a EHU or gas, or if that is not possible, a couple of cool packs out of the freezer, there is really no need to circumvent the van systems it works just fine the way it is supposed to.

EDIT, it should also be noted that the cooling element of the fridge is the same no matter what the fuel source is Gas, 230v or 12v , even if the fridge is empty it will cool down while under tow, makes sense to leave it on, even if there is nothing in it,so it is cold when you arrive, but I can tell you, you will be really happy for that coffee and snack out of the fridge, once you get on site, trust me.

 

[JTQ]

I have no knowledge of your specific van but all those I have had charge from the car irrespective of how any internal switch was left.
The internal switches on mine have only determined the source of 12 volt power within the van, from the van's battery or from the car's battery provided that was coupled up, or isolated from either.

To charge requires that the car's wiring is connected. There ought to be three 12 volt positive feeds from the car, one a sustained 12 volts whether the ignition is on or off , this feeds that van switch and via it can power the van's electrics. The other two are only live when the engine is running, one is to charge the van's battery the other power the fridge.

If using the twin 7 pin plugs the 12S, the grey one carries these connections; the 13 pin plug has similar provisions;
https://www.westerntowing.co.uk/acatalog/12S_Socket_Wiring.GIF

 

[colin-yorkshire]

I have no knowledge of your specific van but all those I have had charge from the car irrespective of how any internal switch was left.
The internal switches on mine have only determined the source of 12 volt power within the van, from the van's battery or from the car's battery provided that was coupled up, or isolated from either.

To charge requires that the car's wiring is connected. There ought to be three 12 volt positive feeds from the car, one a sustained 12 volts whether the ignition is on or off , this feeds that van switch and via it can power the van's electrics. The other two are only live when the engine is running, one is to charge the van's battery the other power the fridge.

not to confuse the OP, but mine had only two feeds one permanent live and one switched live,[fridge] the permanent one fed the van from the car but only went to the van electrics, the habitation relay [bailey] sensed the engine starting [through the fridge wire] and cut off the internal power and diverted it to the charge circuit.

 

[WoodlandsCamper]

So... when towing, i have the van/car switch in the centre? This will then activate the habitation relay and cut off the power to everything besides the fridge and battery? Is this correct?

When we had a van with a 3-position switch it was such:
Van - used when the van was uncoupled from the car, ie pitched up
Centre - everything OFF, all electrics isolated
Car - used when coupled to the car and towing to provide power to the battery and fridge

Our current van does not have a 3-position switch as the sensing when coupled is done automatically.

 

[jamestaylor18]

Thanks for all your help! I've had a read of the handbook and it say car mode will provide power to the van from the car battery to all 12v circuits. If I switch on the charger, it will provide power to all 12v circuits, but when car running, habitation relay kicks in.

I think I will just put the switch in the centre and switch my fridge onto battery mode when travelling. To be honest, I plan to get all of my charge from the EHU anyway once pitched. Am I right in thinking I can constantly have the charger switch on when pitched? Or do I need to switch off when charged?

Thanks for all your help

 

[Damian]

When on site leave the charger on as it provides a float to stop excessive draw from the PSU

 

[Gafferbill]

There ought to be three 12 volt positive feeds from the car, one a sustained 12 volts whether the ignition is on or off , this feeds that van switch and via it can power the van's electrics. The other two are only live when the engine is running, one is to charge the van's battery the other power the fridge.

.........you are describing the pre 1998 wiring standard.

The current standard uses only two positive 12 volt feeds........one permanently live and the other only live with the tow vehicle's engine running.

Colin's post 418954 describes how the two wire system works.

 

[BryanTheSnail]

When on EHU more recent vans will supply 12 volts from a separate part of the power unit, not from the battery, You would get 12 volts when on hookup even without a battery fitted. The charger will independently charge the battery at the same time. And if the battery is in a discharged state, you may hear the charger cooling fan running too..