Andrew & Jen (Melb) replied:

I have always thought that something like that sounds sensible but have thought that it was somewhat inefficient to change from 12 to 240 with the inverter only to change it back to 12 again. The other issue is that the Deep Cycle batteries seem to take ages to charge fully and you might have to drive around for 15 hours per day. Also if you use a bigger charger, you might need a bigger inverter. Have never done the sums to work out how it would go.
Andrew

Lone Wolf replied:

Did I miss the bit about the really really looooooong extension cord?

Peter replied:

Have a look here at the twin charge battery charge controller

http://www.12volt.com.au/webcat2003/daulbatt.html

Seems like a good idea just connect to relay to ignition and away you go.

Peter replied:

Have a look here at the twin charge battery charge controller

http://www.12volt.com.au/webcat2003/daulbatt.html

Seems like a good idea just connect to relay to ignition and away you go.

Dave from Fraser Coast 4WD Club replied:

THe inverter and charger will take more juice to run than they will put out, I guess that if you have a really high out put alternator, this will be fine.

COnsider also that whe the car is running (and charger is charging the batteries) there will always be some drain on the 2nd battery (you say that everything is running off it) therefore your charger will be outputing at max output all the time, this is not good for the charger.

By making this simple system with "no solenoids getting stuck" and no "fancy circuits" you have made a much more complicated and extremely inefficient system.

Talk to your auto electrician about making a diode pack that will allow you to 'trick' the alternotr (or regulator more precisely) into a higher output voltage if you really want to be able to "cook" the DC.

or do what more and more people are doing and forget the DC and go for a hybrid like the exide extreme.

Is your car diesel?? if so, have you considered that you will be trying to glow the motor off the 2nd battery, not a great idea.

Seriously DB setups aren't hard to do, mine works a treat and is very simple to operate (TJM IBS) it wasn't that expensive and I've only had to replace 1 solenoid (last year) in 6 years. In my books, with the treatment that my truck recieves, that's pretty good!

I know that you are trying to think outside the box, but in all seriousness, I think that you'll end up with dramas and will then spend the money on a DB anyway.

Cheers

Member - Pesty (SA) replied:

If Batt b is flat and you drive for an hour you could expect a 100 amp alt to put in 30-40amps , but a 10amp 240 charger ( physical size will restict you) will only put in about 6-8 amps in the same time.
Forget all the crap and buy yourself a 80 amp relay and wire it in to come on when ignition is activated and put an 80 amp lead to the batt b and presto less than $60. jobs done.
As an added back up if it breaks down while away you can put a jump lead across batterys during the day and unclip at night to keep yourself going.

Cruisergxl replied:

I have my set up wired to a second oil pressure switch so that in addition to being wired through the ignition so it will only come on when the engine is actually turning over.

I actually use two 30 amp relays in parallel, not an ideal solution but I happened to have them and they are voltage spike protected witha couple of zener diodes across their coils.

Whole thing seems to work fine thus far, have never actually got out the hydrometer to check if the battery is fully charged.

As said before in the rare situation that you need to use your auxillary to assist starting then get out your jump leads!

Cheers,

Chris

Member - Jeff M (WA) replied:

Ineffeciant is the key here I think, not to mention that you should turn your inverter off before doing any serious water crossings (zzzap!) hee hee.
There are much simpler ways to go about it (mentioned above), my little Jaycar (silicone chip) system works great, give me less than a 0.05v voltage drop through the isolater, diodes are great but they can have a 0.5v voltage drop!
My whole system cost me $60 bucks (already had dual bats in paralell) and it charges the deep cycle pretty damn good, it'll show 14v on the display while charging without the headlights on.
I still whip out the 240v charger and give it a good fry before we go away on a trip though, just to make sure.

Truckster (Vic) replied:

LMAO with all the confusion, I just went a piranha system.. it works, 30mins to fit, wasnt cheapest on earth, but ... WORKS.

Magnus replied:

Fat,

The other posts have address the charging while going issue. What about when you are stopped in one place for a week because the fishing is good or the scenery is great etc.

You will need to top up the second battery if it running all the camp gear with a generator, running the vehicle or a solar panel.

Good gen sets will set you back about $1k and a decent solar panel to put out 2 amps about $400 or so.

If you are staying put for any length of time you need to calculate your daily amp draw and arrange a way to replace that daily draw down or let your battery go flat.

Cheers

Magnus

Mrs Diamond replied:

are you confused yet lol.

Jimbo replied:

Lardarse,

Be very wary about Pirahna, they are EXPENSIVE. Talk to a few auto elecs about a simple or smart solenoid. Also consider an AGM battery as they can absorb a huge charge in a short time. Conventional deep cycles batteries dont like to absorb more than about 5 A/h regardless of what your alternator is putting out.

Regards,

Jim.