Dual Battery Set up

[AussieKane]

Ok guys, this is what I would like my set up to be able to do. Question is, what do I need to do that and what brands are recommended.

I currently have a caravan with one small solar panel, 2 batteries and an anderson plug at the towball. Also I am able to charge the van batteries by plugging into 240V.

On the Nav I want to have a aux battery which will be able to run the fridge (Waeco Cfx 50) for 24hours. I want this battery and the van batteries to be able to be charged by the alternator while travelling. Also would like the option of mounting a solar panel on the roof of the Nav at a later date which will charge the Navs aux battery as well as feed into the vans batteries when the hitch is connected but the Nav isnt running (no alt charge). Remember the vans batteries are already getting a charge from the vans solar.

Also would like to be able to keep the Navs aux battery charged when at van parks by plugging in to 240v.

So to all the experts out there, what will I need?

Cheers,

 

[happy john]

I would fit a Ctec or Redarc dc/dc charger to the Nav.Using the solar input on the unit it will regulate the solar and charge your aux battery when your not driving. Then you just need to wire your vans battery in parallel to your aux in the Nav via an Anderson plug. If the 240volt charger in the van charges those batteries it will also keep the tugs aux charged. If you do get a panel on the roof it will maintain everything. Do you have a 3way fridge in the van and if so is it run on 12 volt when you travel?.

 

[GunMentalGrey]

I'm not sure of the benefit of adding 240v charging to the car. If you have a solar panel on the roof and go for a drive every other day it shouldn't need it.

 

[happy john]

Yep I thought that too, I run 2 engels now one's a 23ltr as a frezzer. 120 watts of solar is ok but you can always have more if the weather turns foul. I'm putting 180watts up there then the portable 120 just plugs into an Anderson on the tray for a boost. The Ctek can only regulate 300 watts of solar so I'm ok.

 

[Old.Tony]

I've got a 60L Engel in my tub, powered by a 75Ah Optima D31A, charged by solar panel. There is an inverter in the tub too - but it's only there to provide power to the fridge while I'm driving so that the solar panel can have at the battery more efficiently.

Because I've got the inverter in there, it's a simple matter of running an extension lead from the outlet of my caravan into the tub and then hooking up the battery charger (which is in there, but isn't turned on or connected normally) and your requirements are met.

I too have an Anderson plug providing power to the caravan for charging the battery, but also supply power to the fridge. I have modified the fridge power - instead of running the fridge on 12V while driving, I've bought a 600W single outlet inverter and using a circuit that sees 12V and changes the 240V input from van-based to inverter-based, provides power to the fridge thus using the fridge's thermostat (which it doesn't do on 12V).

All of my cabling is 8Ga paired - I run both positive and negative. Protected by fuses up front, and relays to only allow power when the ignition is on.

 

[AussieKane]

I've got a 60L Engel in my tub, powered by a 75Ah Optima D31A, charged by solar panel. There is an inverter in the tub too - but it's only there to provide power to the fridge while I'm driving so that the solar panel can have at the battery more efficiently.

Because I've got the inverter in there, it's a simple matter of running an extension lead from the outlet of my caravan into the tub and then hooking up the battery charger (which is in there, but isn't turned on or connected normally) and your requirements are met.


I too have an Anderson plug providing power to the caravan for charging the battery, but also supply power to the fridge. I have modified the fridge power - instead of running the fridge on 12V while driving, I've bought a 600W single outlet inverter and using a circuit that sees 12V and changes the 240V input from van-based to inverter-based, provides power to the fridge thus using the fridge's thermostat (which it doesn't do on 12V).

All of my cabling is 8Ga paired - I run both positive and negative. Protected by fuses up front, and relays to only allow power when the ignition is on.

Thanks Tony,

How long do you get out of the Aux Battery in the Navara when the fridge is running.
Also what brand of inverter do you run in the Nav?

 

[AussieKane]

I would fit a Ctec or Redarc dc/dc charger to the Nav.Using the solar input on the unit it will regulate the solar and charge your aux battery when your not driving. Then you just need to wire your vans battery in parallel to your aux in the Nav via an Anderson plug. If the 240volt charger in the van charges those batteries it will also keep the tugs aux charged. If you do get a panel on the roof it will maintain everything. Do you have a 3way fridge in the van and if so is it run on 12 volt when you travel?.

Thanks John,

Thats the plan, to run the vans fridge on 12V while travelling.

 

[Old.Tony]

Thanks Tony,

How long do you get out of the Aux Battery in the Navara when the fridge is running.
Also what brand of inverter do you run in the Nav?

The inverter in the Nav at the moment is an Aldi one, it only needs to deliver about 50W tops so anything would do there. I was running an Aldi one to drive the caravan fridge but 380W was too much for the 600W inverter - I discovered, when I examined the circuit board inside, that the Aldi 600W inverter is actually TWO inverter circuits of 300W each. It was only a matter of time.

As for duration ... so far, indefinite. The solar panel up top has always replenished the battery. It's a monocrystalline 130W job. I guess I could put a 200W unit up there but since what I've got is doing fine, there's no need to spend any more just yet!

 

[happy john]

Thanks John,

Thats the plan, to run the vans fridge on 12V while travelling.

I'd run a direct connection from the alternator direct to the 12 volt input of the fridge via a VSR. You should never run a 3 way from the vans house batteries due to the fact it may draw up to 20 amps. Having a seperate charge for the aux in the tub and the vans batteries is a much better idea.

The inverted idea that Tony uses will give you better control anyway, on 12 volt the fridge has no thermostat so it basicly never knows when to stop. Always use the best quality cable you can afford, the voltage drop over that length is huge particularly for the fridge.

 

[AussieKane]

Thanks for your input guys. This is the great thing about these forums. I wouldve gone ahead with what I was planning earlier and been none the wiser until later on.

So this is the plan now:

Alternator goes to a Redarc battery charger (which also has the solar input) which charges the Navs battery and through the Anderson plug to the vans batteries. C/b under the bonnet for the battery cabling and ignition controlled relays under the canopy. Rest of the aux c/bs under the canopy.

Invertor installed in van connected straight to the van batteries on the 12V input side and 240v output side to the van fridge.

Questions: Will the two battery chargers work together if both sets of batteries are connected in parallel? Eg the charger in the Nav and the charger in the Van. Will they work?

Is it ok to run the Navs fridge on 12V or would I be better off getting a second invertor for that task only, to install in the Nav?

What size battery should I get for the Nav and does it have to match the Vans batteries.

What size battery charger should I get?

What size Invertor should I get for the Van and if I need a second invertor for the Nav, what size.

What size c/b do I need at the Navs start battery (alternator output) to protect the Aux circuit?

Sorry for all the questions but I feel like I get better info from here than I do from alot of auto sparkies!

Cheers

 

[happy john]

I'd run the fridge in the tub on 12volt making sure that it's power from the aux has heavy enough cable, Wacoe's will complain if there is any voltage drop from the battery. Your invertor is better off in the tug and run a lead to the 3 way in the van, this way you not getting as much voltage drop to that power hungry fridge. Also never use your chassis for the earth, you'll never get the same amps as a good cable, there's also more chance of a fault developing too.
The charger in the van should look after the aux in the tub as well, I'd look at 120a/h if you can fit it.
Cheers

 

[Old.Tony]

It looks a little complicated.

I'd run the tub electrics separate to the stuff heading to the van - don't make one system depend on the other. This also allows to you think about them completely separately, which makes things easier.

Is the fridge in the trailer a 3-way fridge? If so, I'd never consider running it from the batteries in the trailer. Ever. They just draw way too much power.