3rd Leisure battery

hi folks

before i set off for my trip to Spain and maybe further a field (most of it to be wilding or off grid) I am in two minds whether to add a third leisure battery to my setup (I have a mountain of box sets to catch up when I am on the road and as it will be just me and the dog i might have a few empty hours to fill).

Just looking for a bit of reassurance here. My thoughts for adding the third battery in is that I won't ever have to worry about hooking up and I can stay in one place for a number of days if need be.

At present i have two 100watt solar panels (with 30amp Mppt controller) connected to 2 *110amp leisure batteries. The batteries are wired at present as per the bottom right diagram on this link Motts battery description Because the batteries are separated (one under the doorway entrance and another under the passenger seat I have had to wire them up as separated but in parallel.

Now if i add another battery (another 110amp leisure) its going to have to go in another location even further away. I understand that all the cables should be the same length and because of the longer distance they will need to be increased in size to reduce the voltage drop, and they should all be fused to 25amps. I will of course vent the new battery to atmosphere (through the van floor) as well.

My plan is to add the additional battery and change the wiring to conform with method 3 here Smartgauge Battery all positive leads to be fused again all cables to be the same length and thickness (16mm)

Any advice from the sparkies here?

Battery gas goes up so vent up not through floor if not sealed type,but they should be in a box in case of explosion and strapped down so they will not fly about in a crash.
Also use battery cable to link batts as if low the alt may be pushing 70 amps or more to them so thin wire is a no no.

Me neither, always through the floor. I guess when the gas builds up in the Battery it is forced out through the pipe which is turned down and out into the atmosphere.

Remember that multiple batteries must be identical (same size, same age, same brand).

As batteries age their internal resistance changes, it will also be different depending on size and band. Some say the batteries should be from the same production run to ensure the have identical resistance properties.
If batteries are not as near as possible identical all the different wiring options will make little difference, the output and charging rate will be concentrated on the one with the lowest internal resistance, leading to earlier failure of the others.

2 X 110amp batteries and 200 watts of solar with a good quality MPPT controller should be more than adequate in southern Europe. I am just back from 41°N and in the early November sun my 200w of solar panes were still pushing out up to 8 amps per hour on clear sunny days, going further south would improve on that figure.

In September we ran all the usual electrics including 2 TV's and a Sky box via an inverter and had no shortage of power during a 12 day stay without an EHU.

For maximum charging from the engine when on the move I have a 50amp Stirling B2B Charger fitted.