hi all!

now my old 89 rocky has a standard car battery in it Sad

I was looking at it last night, and has anyone done this or found any problems with it?
basically, whats to stop me (apart from the battery tray, i will make a bigger one, and maybe its gone be tight on space) but whats to stop me putting in two car batteries wired up in parallel.
will the charging system cope?

I got an other car battery thats in good condition, and if they are both similar amp hours and are at a similar charge level, then would there be a problem?

Why? If you ran it with too m

Why? If you ran it with too much ampre im sure you could do some nice damage. Fry your ecu, or blow all your fuses...

Are you having any trouble? I mean... honestly, if there is enough charge to run the ECU and injectors and sparkplugs... there isnt a reason to do anything to it.

Go right ahead by all means, post some pic's and show us if it works, but the only thing i ever have done to a battery, is moved it to the back to make more room for a turbo... and larger intake...

*shrugs* the performance boost (if you wanna call it that) by having a tiny slight better currnt to the sparkplugs, would be FAR outweighed by replacing the wiring harness in my honest opinion, you will probably find, especially with a car that age, some duel core sparkplugs and nice good leads, would give you a much bigger boost, rewire all the earths with new (probably thicker gague) wire, and things like that which cost me aus$40 in total (i dont know whats that like 15 pound?) would do you much better good.

If you look at the electrical side ofyour car.

And a word of warning: your alternater probably wont be sufficent to charge BOTH batteries.

I agree but a lot of misinformation

I agree with skythra in that you should not put in a second battery. But you could replace your existing battery with a higher amperage one if you wanted to run equipment while the engine is not running. If the engine is running then the battery is not used anyway (unless there is a fault with the alternator circuit).

Batteries put out volts and equipment draws current (amps) so a bigger supply of amps will not affect the ECU of fuses. Also a bigger battery will not increase current to the spark plugs which in any case use an incredibly small amount as they need very high voltage for the spark to jump the gap. For any given load if you increase the voltage the current is decreased.

You haven't said why you want to increase the battery size, can you tell us? Smile

not sure what matey is talkin

not sure what matey is talking about regards spark plugs etc, its a diesel!

and also if the batteries are wired in parallel the voltage will be the same, the only difference is that it would double the amp hours of the battery, not the amperage it/they can put out! the same amount of amps would be drawn from what ever needs it, the setup would just hold lots more charge!
i want to put in a second battery to drastically increase the life of the battery charge when engine not running! so i can run my impact wrench, so i can jump start the engine on my hovercraft, so i can watch the telly, so my speakers dont make the battery flat! basically so i can make more cups of tea and watch hollyoaks while watching people race hovercaft lol! also with an inverter run power tools.
and i have got a genny but thats hassle lol!

i would put in a big big battery, but they are expensive and this would cost nothing as i have another battery in the workshop.

the main concern would be the alternator not putting out enough charge, but the voltage reg would only put in 14volts but this might over stretch the alternator and burn it out possibly????

any thoughts?

anyone wana ride in my hovercraft!

anyone wana ride in my hovercraft!


just had a thought, seen a kit in a caravan sales place, alows you to charge two batteries, for runninig fridges and tv,s, charges truck batt first then auxill batt, check them out

Edward (ews) '92 Fourtrak 2.8 TDX

Its not a problem. I have run

Its not a problem. I have run a dual battery set up in my Rocky for years.
Make your own battery tray up. I run 2 N70 size batteries, through a isolating solinoid, and havent had any problems. It allows you to run 12V accessories when camping, and still have a fully charged battery for starting.

Heres a pic of the tray set up.


Growing old is compulsary, growing up isnt, and MUD MAKES EXCELLENT TOOTHPASTE.
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All views and advice offered are my own, from my own experiences. Take such advice at your own risk.

Growing old is compulsary, growing up isnt.
I use billion dollar satellites, to find Tupperware.
Please visit
All views and advice offered are my own, from my ow

That's also a damn good idea

That's also a damn good idea if you have an electric winch. Say you've killed it in water, or rolled it and need to winch it out on it's side befor you can stand it up? Having the winch conected to an isolated second battery means if you totally flaten that battery, you are still going to have plenty of go to start the old girl once you finally get out of the stook you've caused youself. Works too as my sister in law can contest. Told her not to ge green laining on her own...

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.



Thought I would say, what I have fitted to my 91/92 2.8 TDX Fourtrak.
It is now on its third year,with no signs of loss of power,fired the girl last winter with dead glowplugs no problem,even spun her up to self bleed for weeks when I had a airleak in the fuel line.She's a dream to start,just let them glowplugs go click and fire her up.

After starting (as of now with new glow plugs) charge rate is 14.4 volts
dropping to 12.5 volts within minutes. Test may not scientific ,just a volt meter held onto the battery terminals.

Battery specs -: Type 644
Capacity 95Ahr
Cranking Amps 660

Hope this helps.

Edward (ews) '92 Fourtrak 2.8 TDX

Putting 2,3,4... batteries in

Putting 2,3,4... batteries in parolel basicly makes a bigger battery. IE it will last longer without any input from the engine, and it will take longer to charge up. It will not do any dammage to the car. Just DON'T put them in seiries, couse then you'll be putting out 24v (but I think you already knew that). She may be a truck, but she ain't no lorry.

Alternativly just put a tractor battery in her. Same diffrance.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.

Split Charge Batteries

just modified a people carrier (Citroen C8) to charge two leisure batteries (120AH each) in the boot when driving.

Use a split charge relay, effectively connects the batteries in parallel when a charge is available from the alternator. It disconnects the link between them at rest.

The relay has no volts drop when connected, diodes will drop 0.7V per diode, not much it would seem, but a lot when trying to get the most into the batteries.