2nd Battery

[Wayne_5133334]

We are off Rallying and want to take a 2nd battery to help support the main 100amp battery and 18amp solar panel over the period. Has any one come up with a simple, efficient and safe way of using the power from the second battery other than taking the prime one off and replacing it with the 2nd battery. Would be nice to be able to have a wired system to allow ease of connection

Regards

Wayne Seaborn

 

[JTQ]

The best way is to recharge your van's battery from the second battery.

That is easy to do with a product called a "Furnvo UniCharger"; this lovely device takes power from one battery, lifts the voltage and charges the vans battery. Its even smart enough not to take the donor battery too low to damage it.

More details can be found on this link:

http://www.ukcampsite.co.uk/chatter/display_topic_threads.asp?ForumID=8&TopicID=175264&SearchPagePosition=1&search=unicharger&searchMode=allwords&searchIn=Topic&forum=8&searchSort=dateDESC&ReturnPage=Search
The makers used to market them but now only make them to order.

I have made my own simply by using a very small [120 watt] inverter powering a CTEK 3600 smart charger and just leave this on over night. Road Pro now do a cut off device which would ensure the donor battery does not drop below 11.7 volts thus protecting that in the way the Unicharger does, but I have not yet got that.

On long stays I also recharge the donor battery in the car using exactly the same kit plugged into a 12 v outlet.

 

[oldievanner]

Ask the question on a Motor Caravan related Forum. Most Motor Caravans have a second battery, well all the people I know That have them have a 2nd battery.

 

[Gafferbill]

The best system is to have the second battery fitted on the tow car.

Use a sealed gel battery...no fumes and fix so the battery cannot physically move if you are fitting in the boot.

You can buy plastic battery boxes for this purpose..

http://www.towsure.com/product/2450-Battery_Holding_Box_-_Large
Wire the battery into the supply wire for the caravan battery charging feed and fit a 15-amp fuse.

Positive on 2nd battery to positive feed wire to caravan battery charge wire via a 15-amp fuse.

Negative on 2nd battery to earth on the tow car bodywork.

The beauty of this system is your second battery will be charged whenever the tow car's engine is running including when your caravan is sited and you are driving solo sightseeing etc.

To connect batteries together on site use a connector lead.

http://www.towsure.com/product/433-6m_S-Type_Extension_Lead
My second battery is under my 4x4 tucked between the chassis on a carrier frame.

I have used this system for a number of years.

You have to be up for some DIY...

 

[ChrisUK]

The best system is to have the second battery fitted on the tow car.

Use a sealed gel battery...no fumes and fix so the battery cannot physically move if you are fitting in the boot.

You can buy plastic battery boxes for this purpose..

http://www.towsure.com/product/2450-Battery_Holding_Box_-_Large
Wire the battery into the supply wire for the caravan battery charging feed and fit a 15-amp fuse.

Positive on 2nd battery to positive feed wire to caravan battery charge wire via a 15-amp fuse.

Negative on 2nd battery to earth on the tow car bodywork.

The beauty of this system is your second battery will be charged whenever the tow car's engine is running including when your caravan is sited and you are driving solo sightseeing etc.

To connect batteries together on site use a connector lead.

http://www.towsure.com/product/433-6m_S-Type_Extension_Lead
My second battery is under my 4x4 tucked between the chassis on a carrier frame.

I have used this system for a number of years.

You have to be up for some DIY...

I've got one of these same boxes but do not find it easy to fix securly. It is faily flimsy with slopy sides which I can not get a fixing to hold on. How did you do it?

 

[WilliamLX]

Gaffer, how do you connect the battery in the car to the one in the caravan while on site? The lead you give a link to looks like one end plugs into the grey socket in the car, but I am not sure what the other end is meant to connect to? Also how do you ensure that the second battery is not to fully discharged and that the actual car battery is not also being drained?

 

[Gafferbill]

I've got one of these same boxes but do not find it easy to fix securly. It is faily flimsy with slopy sides which I can not get a fixing to hold on. How did you do it?

Chris......... I did not use one of these boxes.

I suggested using such a box, as battery security in the set-up I was suggesting is very important for safety reasons.

Most people would have to fit the second battery in the boot or rear of the car.

All sorts of people read these posts and I wanted to emphasise this safety point.

My second battery is bolted to a purpose built steel carrier bolted to the chassis under my 4x4.

I would want such a box securely strapped or even bolted to the floor, depends what car you have and whether you want to drill holes in it!

 

[Gafferbill]

William...you connect the lead to the grey S socket of the Tow car and the other end to the caravan grey S plug. The connection is effectively an extension lead to allow you more freedom as to how you park your car on site.

As soon as you make the connection, your second battery on your car is electrically connected to you caravan battery in parallel.

If your caravan battery is 110amps and you second battery on your car is 110amps; you now effectively have a 220 amp leisure battery set up.

If the batteries are unequally charged, current will flow towards the lower charged battery and they will equalise.

The caravan battery charging circuit, to which you have connected your second battery is electrically isolated from your normal car battery until you start the engine.

This will prevent your car battery from draining whilst parked up on site.

Your second battery will only become fully discharged when using this set-up on a non EHU site if you do no drive you car on trips for sight seeing etc.

Running the engine and driving the car will charge your second battery.

My own set-up can also draw power via another circuit direct from my diesel car's 160amp car battery via a 'car' switch in the caravan. You have to be careful with this circuit to leave enough charge for engine starting. My caravan has a battery state of charge meter.

All this depends on the wiring on the car and caravan being done correctly and relays working properly.

If they are, then your car's starting battery will not run flat as a result of this set-up

 

[WilliamLX]

Thanks, Gaffer, it sounds like a good idea. Even without the second battery, the lead would be useful for allowing you to use your car to top the caravan battery up.

 

[ChrisUK]

I googled it but could not find a place to buy from. No longer made? I can see it might be the solution for our extended non EHUs in Scotland. I do have a small inverter and a Alidi CTEK equivalent but am a little wary of attaching a battery charger to the caravan battery whilst the caravan power supply unit (electronics) is attached. Wary of spikes and things. Any comments?

 

[bigbilly]

Before I had a solar panel I merely put a 110 amph battery in a plastic battery box and connected to a 12S socket on the outside of the box. This can be plugged into the 12S lead from the caravan and can be switched from Van to Car from inside the caravan.

Bill

 

[Wayne_5133334]

Before I had a solar panel I merely put a 110 amph battery in a plastic battery box and connected to a 12S socket on the outside of the box. This can be plugged into the 12S lead from the caravan and can be switched from Van to Car from inside the caravan.

Bill

Hi Bill,

Know you have a Solar Panel have you done away with the 2nd Battery and does the panel keep the battery topped up. What rating is the Solar panel

Wayne