Firstly welcome to the forum,

A few good questions there and I suspect there'll be plenty of good feedback.

I'll comment on just a couple of the issues raised as I believe these are important and you need to get it right.  As I have no knowledge of your technical background you'll excuse me if I assume you're not a technical person.

Firstly, the wiring from the vehicle needs to be sufficiently "heavy" enough to carry the charging current from the alternator to the van's battery without too much voltage drop. I would suggest  8mm ² (cross sectional area) or 8 gauge cable.  If using a DC-DC charger ordinary 6"mil"  cable would be adequate.  This will need to be wired via a "voltage sensitive relay" (goes under a number of other names too but does the same job) that gives priority charging to the vehicle's battery, and connects to the van via a separate "Anderson" plug or (better still) via a 12 pin trailer connector instead of the normal 7 pin connector.  This wiring will need to be separate to the 12v fridge wiring.

The second issue is the wiring of two batteries.  Apart from caravans and RVs and other non-critical situations,  you will almost never see batteries wired in parallel to increase the amp-hour or cranking capacity, especially in critical applications such as automatic starting back up generators or communications installations.  The normal (read "proper") way to do this is to use large low voltage series connected batteries.  eg it is much better to connect two 200 amp hour 6 volt batteries in series than two 100 amp hour 12 volt batteries in parallel to achieve a total capacity of 200 amp hours.

Many caravanners and RVers do have batteries parallel connected and claim this does not present a problem provided the batteries are identical in every respect including age and they are wired with very heavy interconnecting links to ensure the load is distributed evenly (?).  Their money, their batteries!

Parallel wiring means the two positive terminals are wired together and likewise the two negative terminals.  Series wiring means that the "load" (the stuff the battery's powering) is connected to the positive of one battery and the negative of the other battery and the two batteries are interconnected by connecting the remaining postive of one battery to the remaining negative of the other.

Hope this helps, no doubt there will be more contributions on other questions you raised.

Jim



-- Edited by jimricho on Monday 13th of December 2010 08:26:24 AM

peter and rose wrote:We are also looking at a solar setup .........

I am looking at a monitor that can tell me the charge on the batteries, the amount of input from solar and the amount of output at any given time.

---

Hi Peter & Rose.
For the solar you will need a solar regulator.
A good one will tell you everything that you need to know.
I suggest that there are 2 that you should consider.
1. A "Dingo" made by Plasmatronics. You would need to add a 240V charger and a DC-DC charger to this for a complete package.
2. A BMS1215 made by RedArc. This one also incorporates a DC to DC charger to properly charge your caravan batteries from the tug plus a 240V charger for when you have power available.
Both are quality products and are made in Australia and have excellent local support.

Cheers,
Peter

 

A further comment on the inverter issue....

Some 240v appliances draw significant wattage and this translates to very high current when connected to a 12v system via an inverter. A big saving on battery/inverter/solar capacity (and the cost thereof) can be made if you're prepared to forgo these items when free camping.

Such items are... microwaves, hair dryers, jugs, electric heaters, toasters, turbo ovens, bread machines, etc. in fact anything that heats. For most of these items there are alternatives that run on gas or other sources of heat (eg a good ol' campfire).

It is also not practical at all to run air conditioners except when 240v "ground" power is available. Likewise "electric-only" hot water systems.

Perhaps you could start out with your existing 100 amp hour battery and without an inverter and upgrade if/when the need arises. You'll have a better idea when you've been on the road for a while. If you later decide to add a further 100 amp hour battery to your existing battery you can do this by installing a changeover switch so that rather than having the batteries paralleled you run them alternately.


-- Edited by jimricho on Tuesday 14th of December 2010 06:37:33 AM

Thanks for that info Two Strays,

I use a large 7pin round on my rig and I assumed that the larger 5 pins on the 12 pin would be adequate especially as the fridge wiring and the charging circuit could use separate pins. Also the convenience of a single connector. However I take on board your comments as you have "hands on" experience with this connector.

If using Anderson plugs it would be necessary to provide some protection from the "elements" to prevent the little retaining springs from rusting, I've had this happen in the past. There are now rubber "boots" available for this purpose.

As I mostly camp in caravan parks these days I don't have a charging circuit from the tug to the van installed, I just rely on charging from "ground" power. I have bush camped for up to 4 days and found a 55 amp hour battery adequate as I only power the van's lights from the 12v system.

Jim

PS: I purchased an inverter several years ago and the only times I have used it is to power a 240v soldering iron when doing some "running" repairs.

-- Edited by jimricho on Tuesday 14th of December 2010 05:37:13 PM