backup start battery options

i've never had any real need for a dual battery system, i travel fairly light, have no fridge etc.

although it would be handy to have a backup plan to start if i ever had a flat when out bush.

i spose the options are, dual battery, spare battery/power pack, generator with a charger.

i dont have any room under the bonnet so an aux battery would have to mount under the tub, probably not the most ideal place for a 4x4, would most likely cop a lot of mud/moisture under there.

what are your thoughts?

Under tub is fine, so are those portable power packs. Heed one warning with those: don't crank the engine for long from them. They're gel batteries and don't take too kindly to extended draws of 500A or more.

If you plan on putting it under tub, here are the boxes to tick:

1) VRLA battery only ("sealed and maintenance free")
2) Sturdy frame to carry the battery mounted securely to the car, preferably a mostly-closed one
3) Heavy cables running from the battery to a fuse first (right near the battery) then on to where they're needed
4) Once everything is connected, spray the battery terminals and all exposed connections with an electrical sealer.

thanks tony.

i'm undecided on what i'm going to do at this stage.

i had a quick look under the tub, there's not as much room as i thought. there's a bit of room but its not really in the ideal spots and would make mounting a battery awkward.

i'm not real keen on putting a battery in the tub, as i don't want to waste space.

to jump start off a rear mounted aux battery what thickness cabling, fuses etc would be required?

it would be easiest to just put a battery in a box, but it seems a waste to carry around a battery in the tub that may never get used. wouldn't be able to use it anyway without a way of recharging it, if it runs too low then it defeats the purpose of having it as a backup.

To jump start over that distance you'd want 0 gauge cables and hope that the cranking didn't go on too long. You're talking - from the rear of the cabin plus half a metre in a dual cab, with wiring passing under the car along the top of the chassis rail (to protect it) and up beside the steering column tight against the right hand guard (safest place) to the battery - about 3.5m, possibly 4m if you are mounting the battery higher (like in the tub, definitely 4m and that's with a custom hole into the tub).

Check this calculator out. Interesting that it's a 10% loss of voltage - if your surface voltage falls below (I think it's about) 9V your ECU may not start so your aux would have to be at 50% charge or better to crank the engine over.

You could always grab one of these. There's nothing left to think about. It's portable, has a built-in charger, built-in inverter, USB outlets, Anderson plug for higher power loads or charging from an isolator - you just about can't go wrong (unless you populate the interior with CR2025 button cells). The one I linked to comes with a quick-release mounting bracket kit too.

an ark pack would do the job.

maybe something more simple.
http://www.ebay.com.au/itm/POWER-BA...Caravan_Parts_Accessories&hash=item4ad0ddb6e1

maybe add a couple anderson plugs and connect it up to a dual battery isolator.