Dual Battery Components?

[Old.Tony]

I'm not sure that there's a single magic box that does it. What I'm doing is this:

* 6mm double-insulated dual cable to run from the thermal fuse to the tub
* Inverter that can supply about 300 watts nominal like this one from Jaycar - see note
* Use a decent multistage charger (eg this one from Jaycar)

Note: the inverter needs to supply 6A @ 15V = 90Watts plus power to run the charger's onboard computer. Double the output power and you're safe, then double that so you don't stress the components. The inverter should be able to tolerate having its power yanked without it squealing too much - I have one I bought from Aldi that hates minor interruptions and squeals like a pig until you shut it down for 30 seconds.

 

[Aido]

I have heard that a ford starter solenoid is the way to go.
When there is no charge coming from the alternator it opens and splits the batteries. When there is charge it closes and both batteries get charged.
Sounds simple enough to me.
These blokes sell a plug and play solution for around $70 based on the aboveHi Tensile Engineering Supplies they are also the makers of Tyre pliers so they know their off road stuff.

 

[WIR35]

I agree with these Projectas however the one thing I will say is the 100 is more than enough. I understand that many people will disagree but if your running a standard alternator which is only about 90 Amps you can save yourself quite a bit of cash. The 100 is still capable of 125 Amp short term and and providing the battery is right will still be able to be used to crack the car over if the main fails.

When you consider that even at a full 90 Amps your vehicle is taking the majority of the Alternators output there is no need to go to the expense of a 150 and like cable. I'm running my system off a 100 and 10mm2 cable with a self resetting fuse and I've not had a problem since last Monday running the fridge in +35 heat on a cycle of +3 - -3 degrees and keeping the battery voltage above 12.5 even over night with the fridge running.

Considering I brought my Projecta100 for $54 it's a hell of a saving over the 150 which I'll never fully utilise. That's just my two bob's worth anyway, some may disagree but it's worked for me in the Nav and other utes before the Nav so I'm sticking with it.

Awesome, that's good to know - cheers. No substitute for tried and tested experience!

 

[KraftyPg]

There is a guy on ebay regularly selling the projectas (both 100 and 150) as a full kit with all the cables, plugs and wires needed to get the system working. When I was looking his price was about 60% of the price the retail shops were selling the stuff for. In the end I sourced mine from else where because I used different cables and I paid about 80% less than retail for the box by itself.

In all (excluding the second battery) I paid $68 for everything and still have about 6 meters of cable left over. The total job took me about 4 hours which included testing. Also I run my camera, cb, and other aux power off the same cable going from the front battery to the back battery so no matter which battery fails i still have aux power and cb power.

 

[maddogrc]

another Q...

with the aux battery fitted do i need to wire in all new 12v sockets/wires to my engel and accessories so that they work once the starter battery is disconnected, or will i still be able to use the factory sockets, etc when just the aux battery is active/live?

GEEZ this is confusing, there are so many bloody options! lol

my direct intent of use is to run my engel fridge throughout the night and maybe hook up my CB radio to it whilst i'm travelling from perth to uluru (going to see ayers rock and the kings something thats towards alice springs). all other trips will just be few day treks in WA...i'm starting tafe sometime next year with full time study so long touring will be a rarity.

i'm after something simple and reliable, and so far i've read many MIXED reviews about products with failures such as the redarc (all replaced with great customer service), the projecta series, and the piranha series (people have had circuit faults and some people had cars go ablaze due to them with the insurance company also saying it was the isolator systems fault).

 

[Old.Tony]

Your current in-car power outlets are all wired to the current vehicle battery. The only way to get them powered by the aux battery is to isolate the starter battery and hook the aux battery up to the main input (this is NOT my recommendation, it could be disastrous) or to just be really simple, run a fused line into the cabin and hook everything up to it in there.

If you want, say, two "cigarette lighter" outlets to run phone chargers and a separate direct line for your CB radio, this is really easy to do and won't be expensive, as long as you can bring BOTH positive and negative lines into the cabin.

Don't share the earth with the starter battery for this, just run that double-insulated cable in. If there's no grommet in the wall, put one there - vibration and movement will destroy the insulator otherwise, and cause not only a short, but possibly a fire.

 

[KraftyPg]

Given that you will have a second battery installed there is no reason not to remove all things that don't need to run off the main battery and put them on the second. I'm not going to have my fridge in the back all that often but I'll always have the power adapter for it, a volt meter and several cig lighter connections that are wired to the second battery. The majority of the time my second battery will only ever be used to power the camera screen and cb but making sure those plugs were on it and quickly accessible all the time was a priority.

I have absolutely no doubt that if you hunt around hard enough you will find someone complaining about every system listed in this thread and those complaints may be varied but the one thing people rarely tell you about faults is whether it was their own fault. We've used Piranaha and Projectas now for about 15 years in different vehicles and never had a problem with either, the main reason I chose the Projecta was the price. Realistically if you wire it up as the manufacturer instructs and most of them are pretty straight forward you aren't going to have faults just because of a brand name.

As for insurance companies I think we all know that if those scummy bastards can get out of a pay out by suggesting you sleep with goats and it was goat urine that caused the problem they will. If you base your choice of setup by what insurance companies might pay out on you'd never do the job to begin with. They could just as easy try and blame something you had "professionally" installed on a fire and you'd still be as likely to get grief from them.

 

[maddogrc]

alright, i aint fussed about running wires through the dash and that, and i guess i'll just run two dedicated 12v cig sockets directly from the aux battery (one running to the tray and one inside the cabin, both fused).

at the moment i'm looking at a redarc smart start isolator and perhaps getting a version with an extended delay before it hooks up the aux in parallel and add on the 240v charger like you're recommending...how exactly do you have charger activate? i wouldn't mind running a manual switch to activate the 240v charger in-cab, but its just something that could be forgotten about...

 

[KraftyPg]

For starters you'd need a 240V outlet, you don't get many of those in modern cars

 

[WIR35]

The combinations and wiring/control methods you can use are virtually limitless. I would recommend speaking to an auto electrician, there are ways to do whatever you want and are only limited by how much you want to pay someone to do it. Luckily I am a qualified electrician (not automotive - but same deal) so I can do it all for the cost of components only and customise systems to suit my needs, but without the knowledge and training i would recommend going to an auto electrician or using proprietry systems with good instructions and a warranty (but be careful of warranty - may only be valid if installed by a qualified auto electrician). Have seen many dodgy setups on both vehicles and buildings done by people who have enough knowledge to "make it function" but not enough to "do it properly and safe." It would be worse with auto electrical because the voltage isn't directly dangerous, but fires can be....

 

[KraftyPg]

The combinations and wiring/control methods you can use are virtually limitless. I would recommend speaking to an auto electrician, there are ways to do whatever you want and are only limited by how much you want to pay someone to do it. Luckily I am a qualified electrician (not automotive - but same deal) so I can do it all for the cost of components only and customise systems to suit my needs, but without the knowledge and training i would recommend going to an auto electrician or using proprietry systems with good instructions and a warranty (but be careful of warranty - may only be valid if installed by a qualified auto electrician). Have seen many dodgy setups on both vehicles and buildings done by people who have enough knowledge to "make it function" but not enough to "do it properly and safe." It would be worse with auto electrical because the voltage isn't directly dangerous, but fires can be....

Dashboard fires are usually a lot more contained than house fires and I feel much safer with them. I don't use a "qualified" person for any of my electrical work but the bit of paper is only as good as the on the job experience allows it to be and while I'd never recommend anyone who was suss about doing sparky work themselves actually do it I'd never pass up the opportunity to play with a few volts.

Live chassis tv's and pc's used to make jobs a lot more fun and while 12V can still make a fire they usually aren't as spectacular (well mine weren't). The main rule of thumb always has to be confidence and attention to detail. If you have the confidence then go ahead and do the job if you don't pay someone who does however if you do it yourself it's always the stupid mistakes that will get you in the end. We all know red wire to red wire makes the right connection but that wont stop someone who's not paying attention try red to black and still expect it to work.

 

[WIR35]

For the most part - agreed. As long as you have an understanding of the principles of electricity, how to work out what size cable you need for the load, how relays and contactors work, and some basic good workmanship (using grommets, protecting cables from heat or mechanical damage, making sure your connections are good), everything should be fine.

 

[KraftyPg]

Yeah using ones brains isn't something that people should forget no matter what job they do but playing with electricity it's a definite rule to follow. I never do 240V work without having a full understanding of what I'm doing before me and I do have a sparky willing to check and sign off on my work when it's done (although he has found silly mistakes before). 12V electricity is no different, it might not always be as dangerous but if you don't have the brains don't attempt it.

*Disclaimer Electricity is a serious matter, just because I don't mind playing with it doesn't mean everyone should have the same outlook. Get someone like WIR35 to do the job properly because qualifications really do matter.

 

[maddogrc]

For starters you'd need a 240V outlet, you don't get many of those in modern cars

running an inverter lol

 

[SOLID D22]

This is some good info guys.

Cheers.

 

[Old.Tony]

As for turning the charger off - the charger I pointed to on Jaycar's site has a 240V mains switch on it. Most inverters also have an on/off switch, so there are two ways to achieve that goal.

As for fires: they will ONLY start if the wire gets hot. The wire gets hot when there's too much current allowed in across a wire that's not capable of carrying that current. This means either you're using wire that is too small, or your fuse is too high (eg you're using a 50A fuse when you're using wire that's capable of carrying 20A).

Be very careful with the ratings on automotive cabling. Read what's on the label and HALVE it. If they say "30A", you know it will carry 30A over a short distance. But there's a couple of metres between your battery and the back of your dash (after you've run around the edge and through the firewall). Suddenly your 30A cable can truly only hold 15A or less without raising temperature.

I always use 6mm cable (50A) for long runs, and I always use 30 Amp fuses.

Your safety is not worth the couple of bucks you'd save on the better quality cable, or the fuse that you REALLY NEED to install right next to the battery.

I'll post a pic when I can remember to do it - I've got a pair of 30A thermal breakers mounted a few cm off the battery. One is for the brake controller (expected max draw 24A = 6A per wheel) and the other is for the aux power to the van (expected max draw 10A). My cable is that double-insulated 6mm stuff I've been carrying on about.

 

[WIR35]

As for turning the charger off - the charger I pointed to on Jaycar's site has a 240V mains switch on it. Most inverters also have an on/off switch, so there are two ways to achieve that goal.

As for fires: they will ONLY start if the wire gets hot. The wire gets hot when there's too much current allowed in across a wire that's not capable of carrying that current. This means either you're using wire that is too small, or your fuse is too high (eg you're using a 50A fuse when you're using wire that's capable of carrying 20A).

Be very careful with the ratings on automotive cabling. Read what's on the label and HALVE it. If they say "30A", you know it will carry 30A over a short distance. But there's a couple of metres between your battery and the back of your dash (after you've run around the edge and through the firewall). Suddenly your 30A cable can truly only hold 15A or less without raising temperature.

I always use 6mm cable (50A) for long runs, and I always use 30 Amp fuses.

Your safety is not worth the couple of bucks you'd save on the better quality cable, or the fuse that you REALLY NEED to install right next to the battery.

I'll post a pic when I can remember to do it - I've got a pair of 30A thermal breakers mounted a few cm off the battery. One is for the brake controller (expected max draw 24A = 6A per wheel) and the other is for the aux power to the van (expected max draw 10A). My cable is that double-insulated 6mm stuff I've been carrying on about.

And remember that your ground wire has to be equal size to your active wire, and the connection be bolted so that it won't vibrate loose. The ground wire carries the same current that your active wire does, and if it's too small, it WILL melt it clean off and/or start a fire. Have seen people run 6 gauge wire to an audio amplifier, and then use speaker wire to ground it. Melted the insulation off the wire, then melted the seat fabric and started a fire

 

[WIR35]

is that 6mm diameter, or 6mm2 cross sectional area? Because 6mm2 cable is only good for 32A, 40A max. I'm guessing it's 6mm diameter, because that would be about 19mm2 cross sectional area and good for up to around 70-80A (without taking volt drop into consideration).

 

[Old.Tony]

is that 6mm diameter, or 6mm2 cross sectional area? Because 6mm2 cable is only good for 32A, 40A max. I'm guessing it's 6mm diameter, because that would be about 19mm2 cross sectional area and good for up to around 70-80A (without taking volt drop into consideration).

6mm across the inner insulator, which is about 4mm across the actual multistrand conductor. The negative wire is identical - it's part of the reason why I use it. The other reason is that it's double-insulated, so it's automatically better protected.

You raise some other good points too, and reminded me of a few things.

1) Never be tempted to use household grade wiring. Household electrical wire is designed to be installed in a house, and in general houses don't move very far, or very fast, and certainly don't flex like Joshy's truck.

2) Never, ever solder your wires together. Always mechanically join them. It's okay to solder the end of the wire once it's been crimped, but CRIMP IT FIRST. The problem with solder is that it will eventually become brittle and will let go of the electrical join - your power won't get through.

3) Always, ALWAYS use screw-in wire connectors where possible. Those connectors that "cut" the shield so they can rub against the wire can actually cause more problems than they're worth. It might take longer, but cutting the wire and inserting it into a screw-connector will guarantee an electrical connection.

Enough preaching. Half the choir's out there already.

 

[WIR35]

yeah, those splice connectors you speak of are rubbish. So are scotch locks in my opinion. Interesting what you said about the solder issue, even I have never heard or experienced that... I have always soldered my joins with automotive wiring, but will keep that in mind from now on