Switching between car & van battery

wasn_me · Guru

Switching between car & van battery

oldtrack123 · Guru

wasn_me wrote:
I have bought a van that doesn't have a battery in the van. 12 volt is from the car via an anderson plug. I want to install a battery in the van & be able to switch between car & van. I have been told the van-car switch in vans is a 240 volt two way light switch. Is this correct? If so will it handle the current draw from the 3 way fridge when travelling?
Cheers Pete

Hi Pete

Answering you questions in reverse

[a]A 3way fridge SHOULD NOT be run on12V from the VAN battery

Only direct from the tug battery via it's own totally independent HEAVY wiring[ as all 3way fridge makers recommend]

An automatic system of switching the fridge "OFF " should be used to prevent flattening the tug battery when the engine is not running

The VAN Battery SHOULD have IT"S OWN independent CHARGING circuit fron the tug

Again with an automatic isolator to prevent VAN loads discharging the tug battery

[c]The currents involved are much heavy than what a typical light switch can handle

Who ever gave that info does not know what he is talking about

-- Edited by oldtrack123 on Wednesday 20th of August 2014 07:00:04 PM

Murraman · Senior Member

Oldtrack looks like your spell checker wasn't working. I understand what you are saying but the OP may have trouble with it. To the OP if you intend putting a battery in the Van then I would advise that you look into installing a solar panel or 2 on the roof to maintain that battery.

If no room on the roof maybe a portable folding panels and put in a decent regulator/charger to run between the panels and battery.

Some say that a 240v switch can be used to control 12v dc but to only use half its rating which if a light switch would only be 5 amps as they are rated at 10 amps. But I would get a proper 12v dc switch and double the amp rating you need.

Allan

-- Edited by Murraman on Wednesday 20th of August 2014 12:14:12 PM

wasn_me · Guru

Thanks for the replies. This is the set up I have seen. It seems to be common in production vans. This one is a millard. The front switch selects electric or battery. The rear switch selects car or van.

I will only be charging the van battery with solar. I agree with your comment Murraman re current draw. I believe the 3 way fridge draws around 15 amps on 12 volt?????

Can anyone suggest a selector switch that would be rated 20 amp or better. I have found some that select batt 1, batt 2 or both. I don't want to connect both batteries.

Cheers Pete

Murraman · Senior Member

This relay will handle 20 amps. Mini Relay 0332209158 - Single

You have 2 inputs running a fridge, I have 2 of these relays setup that run my fridge when engine running off Alternator and when engine stops it runs off Battery that you designate. It works well for me. Not sure if this is what you are exactly trying to do.
So it automatically changes the source, In your case Tug to Van.

au.bosch-automotive-shop.com/en/products/details/-/productdetails/0332209158/mini-relay-0332209158-single

oldtrack123 · Guru

wasn_me wrote:
s. This is the set up I have seen. It seems to be common in production vans. This one is a millard. The front switch selects electric or battery. The rear switch selects car or van.
I will only be charging the van battery with solar. I agree with your comment Murraman re current draw. I believe the 3 way fridge draws around 15 amps on 12 volt?????
Can anyone suggest a selector switch that would be rated 20 amp or better. I have found some that select batt 1, batt 2 or both. I don't want to connect both batteries.
Cheers Pete

HI Pete

Clipsal do have 20A 2WAY 240v AC mechanism

So I would imagine that is the ones shown in the pics

You have not given the model number for the fridge [always a good idea when seeking help]

But depending on model ,the fridge could draw uo to 20A on it's own.

That would be pushing those switches to the limit .

Even a small 3way , one drawing 15A will very quickly flatten the house battery

4hrs & a fully charged 100Ahr LA battery will be down to the recommended max discharge level

To do that safely, you would need around 400W of solar & 400Ahrs of battery capacity

You would also need some other means of charging for poor weather when the solar was not putting in much charge

Unless you have large battery capacity & fast high rate charging ,running a 3way fridge off 12V is very bad idea.

When not being run from the tug battery, with the engine running ,& no 240V available, they should only be run on GAS

Of course , you have not given any indication other loads you would hope to use from the house battery

or is the switching only intended for the fridge

If so forget ,do it correctly, run a separate set of HEAVY cables for the fridge from the tug battery with a simple IGNITION controlled 40A relay for isolation when engine is not running

PeterQ

-- Edited by oldtrack123 on Wednesday 20th of August 2014 07:33:20 PM

Aus-Kiwi · Guru

In our Winnebago the 12v only works when engine is running and no thermostat control..
So I assume it pulls some load ..

wasn_me · Guru

HI Pete
Clipsal do have 20A 2WAY 240v AC mechanism
So I would imagine that is the ones shown in the pics
You have not given the model number for the fridge [always a good idea when seeking help]
But depending on model ,the fridge could draw uo to 20A on it's own.
That would be pushing those switches to the limit .
Even a small 3way , one drawing 15A will very quickly flatten the house battery
4hrs & a fully charged 100Ahr LA battery will be down to the recommended max discharge level
To do that safely, you would need around 400W of solar & 400Ahrs of battery capacity
You would also need some other means of charging for poor weather when the solar was not putting in much charge
Unless you have large battery capacity & fast high rate charging ,running a 3way fridge off 12V is very bad idea.

When not being run from the tug battery, with the engine running ,& no 240V available, they should only be run on GAS
Of course , you have not given any indication other loads you would hope to use from the house battery
or is the switching only intended for the fridge
If so forget ,do it correctly, run a separate set of HEAVY cables for the fridge from the tug battery with a simple IGNITION controlled 40A relay for isolation when engine is not running

PeterQ

-- Edited by oldtrack123 on Wednesday 20th of August 2014 07:33:20 PM

Thanks for the reply. I found the clipsal switch online. I was unaware they were available with 20 amp rating. I rarely use the van fridge, usually on gas, never from the van battery. I only run lights, charge phone, laptop, & watch tv occasionally. I mostly use an engel in the tug for fridge.

Cheers Pete