Aux Battery Confusion

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Jaybird

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Loch Sport Victoria
I'm looking for an economical way of charging a 2nd battery in the tub of my ute.
I found a 100amp projector battery isolator kit on ebay that I thought might do the job at $139 but on querying the seller and after telling him I had a 2005 Navara STR he advised that it would not charge the secong battery to 100% and that I needed a DC to Dc charger at a cost of about $350 plus installation.
I want to put a 100amp auxillary battery in the tub that will have no draw on it during travel and hook up the 45ltr Engle fridge to it at night and be able to recharge the battery off the car during travel the next day. At any other time where we stay for any length of time I will have a 120w solar panel charging the battery.
The specs on the fridge are about a 3amp draw max so if im right that would pull about 30 amps from the battery if it ran for 10 hours, of course it cycles so this figure might not be this high.
So without getting to technical and confusing me more than I am already am I being given the right info or what do you suggest I do.
Thanks
 
I use the projecta 100 and don't have a problem with it and it's as simple to wire up as the kit suggests.

The 100% charge stuff is internet psycho babble led by a few to sell more over priced shit than is not required, but like all internet theories read up on them yourself and make your own decision. I've run dual batteries for over 15 years and never had an issue with the batteries.
 
It's not the info you wan't but simply use a marine switch when you travel turn it on when you pull up turn it off i have used this in 4 cars over 20years maximum volts will go to your tub if for some reason your starting batt failed you can start from the rear make sure you have a good earth to the chassis and e HEAVY fuse inline i run a waeco and engel overnight with a 120a/hr agm no problems if you can get welding cable it's as thick as your soft **** i have seen too many duel battery setup's fail but many do just my humble opinion
 
Not sure what is bull from your rude reply?can you start your rig from your auxillary batery if needed?do you have 100%control over what charge goes where and view with digital gauges perhaps go back and read the paper
 
Jaybird said:
am I being given the right info or what do you suggest I do.
Click to expand...

What if the BS comment was aimed at the above part of the OP's comment and you've just jumped to the wrong conclusion because the post appeared after yours, because after all the OP's been told a pile of bullshit in the hope of selling him a $350 extra he doesn't need.
 
What type of battery are you using for an aux? Depending on your type of battery may affect how you need to charge it. Old tony is a wealth of knowledge on different battery types, but I believe a spiral wound agm is the way to go for life and reliability. They're not cheap though, but some types like gel shouldn't be charged straight off the alternator as the charge rate is too high and you will cook the battery.

As for the isolator, if you are using a wet cell deep cycle or an agm just get the basic redarc or projecta one, they will work fine
 
Fair enough. What's your budget? Someone may be able to recommend one for you. Have you got a solar panel and/or regulator yet? If not, it would be worth looking at either c-tek or redarc as they both have dc-dc chargers with solar panel inputs and 12v battery input from your main battery. These will either charge from the alternator when the car is running or solar panel when the car is off
 
Technically speaking, the vehicle alternator never charges the cranker to 100% capacity and thus won't charge the auxiliary to capacity either, especially since it's on the end of a length of wire.

However, you'll still have plenty of capacity for the Engel fridge if you put a 100Ah+ in there. Don't use a gel, your alternator will kill it. With a 75% charged DC battery that you could drain to 20% before it's terminally damaged, that leaves you 55% or 66amphours. Your engel will probably use 3A for about 50% of the time, so in 24 hours it'll use 36A - you'll have plenty of capacity left if you do it with the Projecta kit or with a simple switch. Either way, make sure you put fuses on both ends of the cables going to the tub.

The way I do it is to run an inverter from the 12V going into the tub. This drives both the Engel fridge and the battery charger which is now charging an unloaded battery - and this method DOES charge to 100%. The D250S C-Tek unit is a good unit and so is the Redarc product, but they aren't needed to achieve your goal - you're on the right path.

Make sure you run both positive and negative to the tub. Relying on chassis connections could result in faults and frustrating failures. The cable should be quite heavy to avoid voltage drop too. Spend a little extra on the cable to make sure it'll be good and you won't regret it later. The charging system can be upgraded, swapped or whatever later, but if the basic carrier for the power isn't up to par, none of the solutions will be ideal.
 
OK Thanks for all your replies, I'll try to answer some questions.
Regards battery, I was looking at a 100amp/hr Sealed AGM Lead acid.
Regards cable, I was going to use 6B&S to Aux Bat, 1 for positive and 1 to run earth return, run through a Dual battery Isolator VSR. (sounds like I know what Im talking about)
As for securing Battery in tub I will manufacture a lightweight ply box with a removable top, I already have a Narva 3 point plug being 2 cig sockets and 1 engle socket that I will mount on top. The box will be manufactured and the the sides will have a series of 50mm holes to lighten box and provide ventilation to battery. I already have a portable 120w solar panel with external andersen plug on the outside of the tub canopy and this will also be able to be plugged into the battery via andersen when we are stopped for any length of time. The engle at the moment runs off the main battery so I figure that it could keep doing that when we are travelling and I was going to change it over to the Aux battery when we are stopped for the night, by doing it this way the Aux bat could be charged while travelling as it wouldnt have any load.
Clear as mud, but will it work. I'm on a pretty tight budget.
 
The short answer - yes.

6B&S cable is 7mm diameter or 13 sq mm - rated to handle 140A. It will cope nicely but will really need a fuse on each end to safeguard the car.

Providing ventilation for the battery is a reasonable idea but according to Australian standards, AGM (sealed and VRLA batteries as well) don't need to be in a ventilated enclosure and thus caravan manufacturers are installing these under seats in the middle of the van. I believe this is a dangerous practice and the battery manufacturers also recommend installing batteries in a ventilated enclosure.
 
Thank Old Tony
I should have added in my above post that a 100amp mega fuse will be added at 2 points in the positive cable. I have been looking at a web site called fridge and solar that seems to explain the setup fairly clearly. I think I will use the equipment he recommends, he seems to be up with it all. I also have a Ctek 240v 15amp staged type charger so if the battery get down I can always bring to up to full charge using the Honda generator or power when I can.

http://www.fridge-and-solar.net/dual_bat.htm
 
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