[Ratman407]

i'm looking at putting a dual battery setup in my sierra
there so many different kits and stuff that I have no clue what to look for

Basically the sierras going to be a DD but with a camping/hunting trip every 2-3 months where i'm normally out for a week at a time
mostly only need to run the fridge and the spotlight while i'm out there and I do a far amount of low speed 4wd but the car can normally be parked up for 5-6 hours straight and I don't want the fridge to kill the battery and at some point I will end up getting panels just not as easy to do when you move around every few hours

i'm thinking deep cycle battery in the engine bay but other then that I really have no idea what way to go

[bumstein]

I don’t think a complicated dual battery charging system is necessary. A simple isolator and have your fridge etc hooked up to the auxiliary battery, this will save your cranking battery. Then if your cranking battery is knackered there should be a switch to start the motor off the aux battery if necessary.

I’d go for a simple redarc model like:

https://www.redarc.com.au/smart-start-sbi-12v-100a

eBay kits are likely fine, however I’d just want to make sure the wiring is up to scratch

[Gwagensteve]

I dislike dual battery systems in general, and especially dislike the added weight in a Sierra. If you absolutely must run a dual battery rather than a larger primary battery, I would avoid any controller that is "microprocessor controlled". This is code for "will fail at some random point and destroy one or both of your batteries"

I'd use one of these.



These are compact, cheap, and much more versatile than almost all "dual battery systems" They're available from Marine suppliers, but I got mine from Kar-Tek in the US, as these are used in offroad race cars due to their reliability. That image shows a single circuit isolator, but you can buy up to 4 position, with alternator field disconnect so throwing the switch to "OFF" will kill the engine. (part 9002e)

You can start/run charge from either or both batteries.

They have leading contacts so you don't lose radio presets etc when switching between batteries.

They have a true OFF position that completely isolates the batteries should you park the car up for periods to time.

Yes, you need to remember to switch it to do the job you want.

I continue to see dual battery systems kill batteries/discharge batteries with no rhyme or reason.

Oh, and remember, there's no point having dual batteries if the alternator can't deliver enough amps to charge them. Upgrade to a EL/EF alternator or your larger batteries are mostly a waste - you'll never recharge them fast enough.

[Gwagensteve]

Oh, The switch I pictured is from Blue Sea Systems.

[sideways]

You wont need anything special battery or isolator wise if you're only looking to run stuff for that sort of time. I'd just buy a cheapy commodore sized battery, it'l easily run a fridge and some lighting overnight.

There's basically 4 different ways of doing it.

Just link the 2 batteries together so it's like having one really big battery, obviously this is a bad idea if you don't want flat batteries.

Use a manually controlled solenoid/isolator switch/boat switch. The idea is you select when the batteries are linked or isolated but humans also make mistakes and forget sometimes. On the plus side, this can be done really cheaply and has no electronics to fail. I've seen a ride on mower starter solenoid used for this, they're like $10 on eBay.

Voltage sensitive relays. These are an electronically controlled relay that will automatically isolate the batteries when the starting battery hits a certain voltage (usually 12.4-12.7v) and reconnect them when the voltage comes back up to that level. They will normally have a wire that you ground to link the 2 batteries back together in case you get a flat starting battery and need to jump from your secondary. These are cheap, fully automatic and reliable. These are what I run.

DC to DC chargers. These are a smart charger that runs off your starting battery. These will get full charge into your secondary battery and get the longest life out of it. They can generally also have a solar panel plugged into them and control that. Also some models can be plugged into 240v and charge all your batteries. On the downside they're very expensive and they have limited charging ability. Cheaper ones may only be able to charge (for example) 6 amps. So if you had a 90AH battery that was discharged to 60ah you'd need to drive for 5 hours to recharge it (30ah divided by 6 amps), where as the above options are generally rated to over 100 amp so they will charge as fast as your alternator can keep up. More expensive models have higher charging rates. Also with a smart charger you can't use it to jump start off your second battery, you'l need jumper leads or a solenoid setup.

I bought one of these for my Sierra. I haven't fitted it yet but it seems quite good quality. It's pretty simple, the circuit just controls 2 conventional relays. It's a steel casing.

http://www.ebay.com.au/itm/VOLTAGE-SENS ... 2749.l2649

I've got one of these in my Landcruiser, it's been reliable and it was in my 4Runner before that. It's not actually a Jaycar branded one but it looks identical, there's lots of these with different brands stuck on them.

https://www.jaycar.com.au/140a-dual-bat ... g/p/MB3686

[pete_79]

Chuck a 50 amp fuse off the pos on battery, run pos and neg cables from battery to where ever you want your 2nd battery and terminate with Anderson plug.

Make a simple battery box with another fuse on the pos, an Anderson plug and as many cig plugs as you like.
Make a short lead with Anderson plugs on both ends and your done.

I have this in both of my cars and haven't had the need for any fancy controllers or switches over the last 4 or 5 years.
I can move my second battery between either car or my camping trailer as required.
My fridge also has an Anderson plug, so I can run my fridge off the main battery or the second (portable) battery, depending on the situation.

This is my portable battery box in my trailer.
I have one battery hard wired into the trailer with the solar controller and use the portable battery to double my capacity on longer trips. It's just plug and play....




Edit;
Otherwise the switch that Steve posted would be the other solution if you go with the second battery permanently mounted under the bonnet...

[fordem]

Seeing as it's for "the occasional camping trip" I would go with something along the line of Pete's suggestion, a portable unit that can be removed when not required, and left connected to a trickle charger (or battery minder) when not in use.

You've been given several different options on how to interconnect but I feel one critical detail has not been fully covered, although Steve did touch on it briefly - charging. You say you can be parked for as long as 5~6 hours straight - what you really need to consider is the "drive time", because the system will only charge when the engine is running. You can expect a fridge to use an average of 20~30 Ah of stored energy in any given day (it varies with size, ambient temps, settings and how often you open it), so you need to put back as much charge every day. To put that into perspective, if you're going to be driving 5~6 hours a day, you would need to be able to charge the second battery at a rate of 5~6A, and as your drive time decreases, the required charge rate increases.

The typical vehicle charge system is very basic, the alternator output voltage is regulated to prevent it from rising too high and the alternator outputs as much current as it can until the regulator limits it - now read that again - the alternator outputs as much current (amps) as it can until it is limited by the voltage regulator - it sounds misleading because one piece is missing - the battery - the alternator feeds the vehicle electrical load and whatever current is not used by the vehicle goes to charge the battery, as the battery charges the system voltage rises until it is limited by the regulator, at which point the alternator starts to reduce it's output current.

The battery (or batteries) are charged by whatever current the alternator produces that is not required to operate the vehicle, and the vehicle manufacturer selects an alternator based on the electrical load expected whilst the vehicle is being operated, you are now adding electrical load which will be operating and consuming power whilst the vehicle is off, so you have to compensate for that by increasing the available charge current and you must take into consideration that that charge will only be available when the vehicle is operating.

That alternator upgrade that Steve mentioned is going to be the most critical part of the dual battery system.

[ZUZUKI]

My 2c worth, & I have a fair bit to do with this stuff, as I work at Piranha Offroad - not a plug, but I approach this topic with some bias (we all do) & experience.

Lucky we are talking Sierra's - a really basic animal, can't kill it with a stick stuff, so most of what has been said above won't hurt it, or matter in this case.
Some of the new fancy cars though, might object to some of the methods mentioned & I don't agree with some of what has been said.

Depends on how much stuff is otherwise packed into your car, as internal room might be at a premium.
There is a tray that fits under the bonnet - opposite the cranking battery, at the P/S/R. Takes a 10" case size. This will give an 82-86 amp hour storage capacity & weigh in the region of 20kg.
This sort of storage will run a fridge for the average camper for a weekend without starting the car or involving solar panels (more stuff to stuff into a Sierra) but like fordem says, it depends on a few variables as to how had the fridge has to work, as to how much amps it will consume.
As we all realise, Sierra panels are thin, they are now old & potentially a bit rusty. If you are going to belt the car on corrugations regularly, the under bonnet tray might be more than the car can hang onto. In which case a 'box in the back' is an option - just make sure if a battery is inside the car, that it is of AGM construction (or if a wet cell, vented to the outside, with a breather tube well away from hot, sparky things) & secured well & I mean properly held down, not with a strap over the lid, with the battery 'loose' inside the box.

Yes, more amps that an up-graded alternator can provide, over the stock unit (40-45amps isn't it?) is going to be good.

Of sideways 4 options, really 2 & 3 make the most sense here.
'Manual' connection / disconnection rely on you remembering to do something - up to you if you think that is going to work long term.
There are lots of VSR (voltage sensitive relay) products out there that will do the job fine, reliably, for years, automatically.

Charging current should be transferred by 10mm2 (or 6 B&S) sized cable, earth should be the same size, back to the engine block or chassis (checking that there is a decent sized engine to chassis earth somewhere else). Run sockets (Merrit is the best commonly available plug/socket combo - Andersons work ok, but are a bit big & clunky for a fridge) with 4mm2 or above cable.

Rgs, Michael

[Ratman407]

Thanks for the advice guys
I picked up a narava master switch today with the 4 postions so going to go that way

and yes the upgrade is on the list first I picked the pulleys up a few weeks ago and just need to get to the wreckers to get the alt but hopefully have that done within before my next trip in December