If you wake up one morning out in the solitary dessert and find your milk is off because your fridge stopped working at night, it's not the worst thing in the world. Realising the chap from Wolf Creek is on the horizon but your engine won't start because your battery is flat...well, that's considerably worse. Trying to placate him with some UHT enriched cornflakes probably won't make the situation any better. It's time you thought about a battery management system! If you live, of course. Just putting that out there.

There are numerous types, but essentially it's a system that will enable your battery or more likely both of your batteries to stay up to full capacity as much as possible, ideally with the starting battery left unscathed whilst your secondary/auxiliary battery (or batteries) do the hard work of running your lights, laptop, mobile phones etc
A battery management system can be as simple as a switch between the two batteries that you manually turn on every time you park up for the night, or an isolator (will get to that) that sits between the two batteries so that whilst the secondary/auxiliary battery drains, the starting motor does not. Or it can be a $2000 system that actively monitors your batteries, solar and any devices plugged into it, providing real-time displays of drain rate and telling you next week's lottery numbers.

Erm...yes, moving on. Firstly, let's get the caveat out of the way: I am not an expert in Battery Management Systems, or indeed an expert in anything. The information listed here is from what I've read in various forums, articles and from my previous experiences of seeing my battery run flat a lot.
To answer the first question in this blog post: having a single battery run your car as well as a fridge and charge you mobile phone won't leave you with enough power in the battery to start your engine in the morning (unless you leave your engine running all night). Having two or more batteries is the key, and any way to manage those batteries is better than none.  Having the right battery type for the job also helps, and that's where our story begins.

Yeah there is always a boring bit. Ideally it seems you need two or more different types of batteries: the first or main battery which runs your engine needs to be a cranking engine, and they use the term CCA for Cold-Cranking Amperes. Why cold? Because when you start your car in the morning, it has to function in a cold environment e.g. zero degrees centigrade. Why Cranking? Because you 'crank' your engine to start. I thought Amperes were....nannies? Get out.

Basically starting batteries are designed to release a high burst of current, measured in amps, and then be quickly recharged. They're not designed to be run flat and if you do run them flat, they generally reduce their lifespan of the battery. Your secondary or auxiliary batteries need to be the opposite of that, pumping out current/amps for longer intervals and not impartial to being charged down to around 30% of its life. These are commonly called deep cycle batteries.

4x4 Australia has a good but slightly boring article here and Optima can tell you all about CCA here.

These batteries can be made of different materials (lead-acid, gels, lithium) but the most common are AGM, or absorbed glass mat. For me, I'll be going a solid standard lead-acid battery for my cranking (CCA of 700+ with 66 Amps per hour), and the best AGM battery I can get for about $250 to $300 dollars which should be in the region of 120-130Amp hours i.e. delivering more amps per hour.

Great question! The number of amps hours is the number of amps provided continuously per hour (don't hate me). Put it this way, every device you have such as a fridge or mobile phone or laptop, will consume energy to power itself - so you can measure the power drain through amps or power*. This can be measured in amps needed per hour. A good fridge for example could draw 3.5 to 4 Amps per hour/AH on 12V which your car batteries provide unlike the 240V in your home. A mobile phone battery is typically about 2 AH.
So if you're battery has a 100AH, it means it can supply 1 amps for 100 hours or more likely, supply 5 amps for 20 hours. Good enough for a night's rest.

(Trying not to make things complicated, you can work this out by an equation from your school days if you wanted: Power = Voltage * Current. So if you have something like an induction cooker that draws 2000 Watts and you're plugging in at home i.e. a 240V mains plug, it draws a current of 8Amps. However, in your little vehicle, these batteries work at 12V, so really that induction cooker will need 166Amps per hour). 

Providing the vehicle I buy doesn't already have one installed, I'll be going for a CTEK Battery Management System which includes an isolator to protect your main battery and negates the requirement of a solar regulator. So it will consist of three things:

• CTEK D250S Dual to enable me to charge from both solar and leisure batteries
• CTEK Smartpass will manage the batteries themselves ensuring they don't go flat
• CTEK Battery Sense monitor will mean I can relay the status of all that to my mobile phone - yet to work out if this is inspired or a pain in the bum

​All of that above should cost less than $600 if I'm hunting around on ebay and various discount or second hand sites. Additional things to consider:

• Before I go off an buy a solar panel, I want to make sure of my actual needs first i.e. how long will my vehicle last on dual batteries without the addition of solar
• I'm also going to double check the alternator: if you have an alternator of 120A and a charging current of 100A, the battery will only receive 100A. Only upgrade the alternator if the systems that will benefit from it can handle the increased capacity.
• Buy cables that will suit the job. All cabling must be rated for a minimum of 20-25 amps. CTEK recommend wire is sized for 3-4 AWG ( 5-6 mm dia copper area), and thicker if lengths extend beyond 5 meters.
• Built in fuses on the positive wires of each battery and Solar-panel array (25 amp fuses for example). Fit fuses right at the positive terminal of each battery and put them all together in a fuse box that you can easily access.
• Having an Inverter is an interesting one. Initially I had thought of getting an inverter for the laptop, but in reading one forum very wise human pointed out that to actually do that would be ineffective: you're transitioning a 12V supply to a 240V supply with the inverter only for the laptop cabling to reduce back to a required 17-19V which most laptops require. Your several hundred dollars may be better spent on a 12V cigarette lighter fort $30 example link (although not great reviews). 

Let it go....there is something even better though. This fantastic chap at campertrailer.org put together spreadsheet to calculate your energy drain when running fridges, TV, lights etc and even includes solar.  The best bit is it's free! You can find the link right here, and if Richard ever reads this, thank you Richard!

http://www.campertrailers.org/solar_spreadsheet.htm

Other references:
http://search.supercheapauto.com.au/search?w=cable has red and black 25Amp cabling
https://www.youtube.com/watch?v=TjqcOAjT4W4
https://www.4x4australia.com.au/gear/1602/dual-battery-systems-explained
http://www.projecta.com.au/Products/DualBattery/DualBatteryKits.aspx#!prettyPhoto
http://www.outbacktravelaustralia.com.au/4wd-mods-electrics/dual-battery-systems
https://www.campertraileraustralia.com.au/features/technical/1310/battery-systems-for-camping

The intervening period betwixt my last missive and this, encompassing solely the pursuance of my vehicular transportation, has been nothing but a baleful, everlasting treadmill of utter wretchedness and acerbic disappointment! But hey ho, could be worse eh?

There have been vehicles dotted the length and breadth of the country, both measurements of staggering proportion in this fair country. Every sniff of a chance has been snuffed, but with such exacting requirements for this travelling extravaganza, it isn't quite as easy as it seems.
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There is a requirement for any vehicles travelling to America (for permanent importation) to be at least 25 years old or face the scrupulous testing of EPA and DOT requirements, which my intended vehicle would miss in spectacular fashion. Picture a 50-a-day, emphysemic, chain-smoking pensioner stepping into the ring for 15 rounds with Mike Tyson, and you'd be somewhere close. 

So along with being over 25 years of age, the vehicle has to have its original engine. The 1HZ engine I'm searching for was manufactured from 1990 onwards, which means I have a 3 year window before that 25 year embargo hits. In addition, the engine cannot be modified in any fashion i.e. since these old machines don't boast a great deal of torque, the temptation for many is to turbo them, making them instantly better whilst at the same time instantly null and void.

In addition, since I am a complete princess and have lived in Australia for ten years, I do require air conditioning. This is a luxury, but a necessary one, as many a country strewn with my desperate perspiration can testify. The countries don't want my sweat; I don't want my sweat. Ideally I'd also like these extras: duel battery; duel tanks; bull-bar; roof-rack; side-ladder; duel-rear-wheel carrier; non-tinted windows (apparently used by local polizia as an excuse for bribery in some South American countries) and some bucket swivel seats. Rear draws, fridges etc can all be fitted out by myself, but some or all of the above will be most welcome. Oh, and little to no rust, which almost crosses off almost the entire upper half of the country, which is exactly the type of area that the famed Troopies like to roost!
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So the hunt continues...will keep you posted!