Powering internal electrics from second battery?

[kenbw2]

I've fitted a second leisure battery to my '96 Synergie and would like to power all the internal electrics - lights, cigarette lighter, radio to the leisure battery, so that I can use them without draining the starting battery.

Is this something I should do at the fuse box? Is it a simple case of replacing the feed for each fuse as I find it, or is there some other way?

[ekjdm14]

The easiest way I can think of doing this is rather than power just the interior from the second battery, is to get a basic split-charge kit with a diode pack, and use the "primary" battery only for the starter circuit. Even the cheapest kit should allow you to do this.

[kenbw2]

Yea that's what I've got set up, the leisure battery is in the car. I wanna suss out how to rearrange the cables so that the internal electrics drain the leisure battery rather than the starting one

[ekjdm14]

All you need to do, is swap all the wires from the positive terminal of the original battery onto the positive of the secondary, except for the thick ones that run to the starter solenoid and glow plug relay. That will leave the secondary battery only needing to activate the stop solenoid & low-power sides of the starter solenoid & GP relay, which as long as it's not completely drained, should be fine as they only need a few amps between them.

That's how I'd do it, but I'm sure there'd be a way to rewire the ignition switch so that the ACC position was powered from the secondary battery, just can't get my brain in electrics mode ATM so I'll leave that to someone else to chew over. (it could be as easy as adding an extra feed to the ACC terminal on the ignition switch from a fused & switched + wire run from the secondary battery, but depends how the switch itself works).

[kenbw2]

Interesting, I hadn't thought of doing such an en-masse switchover. Ideally I'd like to keep crucial car-related electrics (pump solenoid, dashboard lights, headlights etc) on the starter battery, and internal comforts on the leisure battery. But I'll give some consideration to such a simple solution.

[wheeler]

I've done this on a van I've converted to a camper so I could have the interior lights, radio & 12v sockets etc running off the leisure battery. the easiest way is to remove the fuses of the circuits you want on the 2nd battery, I have a small separate fuse box running wires into the original outlet side of the fuse slots with male spade terminals. This way no original wiring is butchered & can easily be put back to standard. The 2nd battery must be earthed to the chassis of course.

[kenbw2]

I always like not butchering things, so that's perfect! I'll get that sorted, thanks! Only question I have is how do I suss which side of the fuse is the outlet?

[Stickyfinger]

Why not just do a direct feed to the radio from battery No2, and a line to a fuse box to wire in some small extra LED light fittings and a 3 set of 12volt sockets. Your running wires anyway ?

[kenbw2]

I don't see much point reinventing the wheel, when the lights and wiring are already in place. It's duplication of effort, and will end up being messy too

[ekjdm14]

I always like not butchering things, so that's perfect! I'll get that sorted, thanks! Only question I have is how do I suss which side of the fuse is the outlet?

Multimeter set to 20vdc, one probe to earth & use the other to see which side of the fuse holder is live, the opposite side will be the output

I like the thinking behind the removing fuses & feeding acc's from a separate box, my efforts are generally on vehicles which are "keepers", or at least "keep till it fails the MoT on anything drastic" lol but having the ability to return to standard spec without rewiring anything is good for selling on in future.

[BX]

Most of what you are talking about are fed off the accessories position off the ignition switch or off a relay controlled by the acc position. Normally there is also 2 ignition positions. One which switches off to conserve battery drain whilst starting and the other one which remains live. If you want these supplies to remain controlled by the key just use a 70 amp relay for whichever supply you want switched. Other items are permanently live and you need to do these individually. Glow plugs, the starter motor, road lighting, wipers and supplies essential to the driving of the vehicle should remain on the engine battery. This is because if your leisure accessories run down the leisure battery and the state of charge is somewhat low in the engine battery these items may not work until the engine battery is charged first. For example you do not want to drive off without brake lights or wipers for example. An extra trick is that you can join the positive poles of both batteries with a heavy cable through a battery isolator switch such as the ones with the red plastic keys shown in the attached link. This switch is left in the off position with its key removed. However if the engine battery is low you have a built in jumps start system with no risk of sparks or wrong connections.
https://www.google.ie/search?q=battery+ ... d=0CDUQsAQ.
Most leisure batteries now are well capable of handling starting currents.

[ekjdm14]

More thinking that I like with the built in jump start setup Just be sure to remove the fuse or you could inadvertently drain both batteries (the type that mount directly to a battery terminal usually have a small fuse to allow accessories to be used with the switch in the off position, but not allow the engine to be started). The panel mounted "inline" type used on race cars don't have this feature as they are a complete cut-off so should be fine. Just something to remember if you get a battery mounted one.

[Hell Razor5543]

On narrow boats with several batteries the 'cranking' battery has a key switch in line, so that when you have finished with the engine for the day you rotate this to the off position and then remove and hang it up. This is to prevent you from inadvertently draining it. As long as you can start the engine, and the electrics are in good shape, you can charge the batteries when the engine is running. Mum has 6 batteries on her boat; 1 cranking battery, 2 for the general services, and 3 for the freezer.

[kenbw2]

I actually have a voltage switched relay for that, so no problems with that. I know I'd end up forgetting a switch and killing the starting battery

[old-un77]

there is always the option of using a fairly powerful diode, to allow recharging, but to prevent the leisure battery draining back to the car electrics..
Bob