Some battery disconnect switches

If you want to put in a very simple split charge system, you'll ideally want to use some decent sized wire between the 2 batteries, but in doing so you need to use a switch that can handle the current the wire can, a normal light switch wont be able to carry more than about 20 amps, so your a little stuck for choice, luckily there's a product sold under a few different names,  a battery kill switch, battery isolator, battery disconnect and so on, they come in all sorts of different styles, prices and current ratings, here's a few:

This type is the cheapest, but not really suitable for our use as a split charge connector due to the key being removable, more suited to a security disconnect switch for the starter battery, these can handle about 150 amps. This type is a lot more suitable for the use we want it for, the handle is fixed to the body, again it can handle about 150 amps, but looks a lot neater when mounted on a panel inside the van.
Battery Master Disconnect SwitchThis is another version of the last switch, just has a different type of handle that's probably easier to see whether it's in the connected or disconnected position. This type is found at boat chandlers, and usually commands a premium price, you twist the know like the others to select connect or disconnect, this type the knob can be removed if you want to, may look a bit bulky due to it's surface mount design tho.

Now these are quite expensive, they are almost exclusively marine switches, this type switches both the positive and negative wires, which is a pain to wire in on a motorhome, (boats use isolated earth returns as their usually made of wood or fibreglass, so can't use chassis earth like we can)

And another marine type battery switch, again twist to select on or off, but this has a highly visible marker to show if it's on or off.
BLU9001E.jpg

Some more almost totally boat type switches, these are actually battery selector switches, you can just see you have a selection of: OFF, battery one, battery 2 or both, boat people tend to have more than one leisure battery bank, and so want a way to select between the banks of batteries when one gets drained, this is really of no use to motorhomers, as we are quite happy with a single leisure battery bank, and don't want to use the starter battery to supply power to the living area (what's the point of having a separate leisure battery system if you can drain the starter battery too at the flick of a switch)

To wire these in you will need to modify the wiring a little bit, all the power you draw from the leisure battery has to go through this switch, it does give you a way to turn all the power off to the van from this switch by placing it in the off position, but in reality that's something you will do anyway from the distribution panel.

With some of these switches you also need the bring the wire from the alternator output terminal to the switch, this is so that the alternator only charges the battery bank the switch is set to, otherwise it needs to be in the 'both' position to charge both  battery banks, when it's in 'battery 1' position, no charge will go to the leisure battery bank, or it is possible to wire just the alternator output through one of these switches and so on.

It gets quite complicated, and i've never fitted one of these my self, I'd personally recommend you leave a battery selector switch to the boaty types, where they're kinda normal, or use it if you for some reason have 2 leisure battery banks that need to be kept separate.

Some caravan type distribution panels come with a selector switch to enable you to draw power from the starter battery or the leisure battery, I have always disconnected this feature, all it takes is a kid who likes pressing buttons, or someone to accidentally lean against the panel to change the switch from leisure battery to starter battery position, and you'll be running all the loads in the living area of the van from the starter battery by mistake, and you can guess what'll happen in the morning when you come to start the van.

I will do an article on a separate page on putting in an emergency start switch, to enable you to start the engine with a flat starter battery on the leisure battery, but the way i've always done things.. if the leisure battery dies, you make do with out power.. start the engine up and put some charge back in it if it's not 3 in the morning on a crowded camp site, but I always leave the starter battery alone to do it's job.. i.e. start the engine and run the vehicle electrics only, I wont switch over to the starter battery to run the living area's loads if i've drained the leisure battery, as you'll only do the same with the starter battery then be in trouble.