Why are there two batteries?

[icsys]

Hi all,

Sorry. This could be the first of many questions from me.

I know the surf is a 12 volt machine so why are there two batteries?

Could it be because of all the electrics fitted? windows, sunroof, air con, adjustable suspension etc...
I assume the batteries are in parallel and so would provide twice the amps?

[Morr]

Hi all,

Sorry. This could be the first of many questions from me.

I know the surf is a 12 volt machine so why are there two batteries?

Could it be because of all the electrics fitted? windows, sunroof, air con, adjustable suspension etc...
I assume the batteries are in parallel and so would provide twice the amps?

The subject of much debate in the past.
Yes they are in parallel
Firstly, not all have two batteries fitted, and like many other items does not appear to be neccessarily based upon which spec you have.
From past posts it may be that it enables the supply of greater cranking power whilst using 2 cheaper batteries, rather than fitting one higher quality battery.
As I've said, its been the subject of debate before... so I'm open to correction on this!

[icsys]

Hi Morr,

I have borrowed a 4Runner owners manual that shows a picture of a 1KZ-T engine (described as a 4-cylinder in line, 4 cycle, diesel with turbocharger - 3 litre) It shows two batteries fitted but I cant find any info on why there are two. From this it would suggest that it is a factory fitted option.

They are mounted on proper carriers yet my engine is a 2L-T 2.4 litre which only shows one battery in the manual. Could be different for the UK spec I suppose.

Any way I was just wondering why there were two.

[Guest]

Hi Morr,

I have borrowed a 4Runner owners manual that shows a picture of a 1KZ-T engine (described as a 4-cylinder in line, 4 cycle, diesel with turbocharger - 3 litre) It shows two batteries fitted but I cant find any info on why there are two. From this it would suggest that it is a factory fitted option.

They are mounted on proper carriers yet my engine is a 2L-T 2.4 litre which only shows one battery in the manual. Could be different for the UK spec I suppose.

Any way I was just wondering why there were two.

As Maurice, said, it's a factory option and enables cheaper batteries to be used but still supply enough starting current. They are wired in parallell to double the Cold Start Cranking current.

Cheers

[da SLUG man]

this may have answered my question but... are they wired in parrallel i.e no relays etc between them as i'd like to add a second but didn't know if i'd bugger the alternator?

[icsys]

I found this info on fitting a second battery while browsing through the site for something else:
http://www.showmesome.info/hilux/workshop/battery.htm

btw which is the main battery? or does it not matter on factory fitted twins?

[hormygollop]

I found this info on fitting a second battery while browsing through the site for something else:
http://www.showmesome.info/hilux/workshop/battery.htm

btw which is the main battery? or does it not matter on factory fitted twins?

The main battery is the black one directly connected to the flux capacitor
Keith

[icsys]

The main battery is the black one directly connected to the flux capacitor

They are both identical batteries on mine so the main is the one on the drivers side?
Where/what is the flux capacitor?

I have also noticed they are paired, i.e. the poles are mirrored.
With both batteries facing the same way, both the +ve's are on the engine side and the -ve's are on the outsde nearest the chassis.

[Guest]

They are both identical batteries on mine so the main is the one on the drivers side?
Where/what is the flux capacitor?

I have also noticed they are paired, i.e. the poles are mirrored.
With both batteries facing the same way, both the +ve's are on the engine side and the -ve's are on the outsde nearest the chassis.

Flux capacitor is jokey reference to the delorean in Back to the future - it doesn't really exist.

Both Batteries are identical in function or though as you rightly pointed out they are handed.

They are a direct parallell connection, no relays in the circuit. You can add a second battery with no damage. Mind you if you are going to add a battery it might be worth putting in a split charging circuit and having one leisure battery and one starting battery.

Cheers

[icsys]

lol... i'll just go and dig out the pointed cap with a 'D' on it

Handed - thats the word I was looking for.

[Simon.O.]

Hi all, I came to this forum for a quick look and I think I'll stay for a while.
It is very simmilar to the one from Australia which is a wee bit closer to home for me,(NZ)
Anyway, with dual batteries the general idea is that two smaller ones will provide you with sufficient CCA to get the motor going, this is particularly important for Diesels.
Now some of us who think more is better have gone mad.
I have two 550 CCA main batteries that are setup with a charging /link system of my own design.
Under the passenger seat is a 6.5Ah 12Vdc Gell cell for powering the radios, yes plural radios=4 !!!
Add to the equation a 900CCA Jump-start pack in the back and link/charge the whole lot and we have POWER
Thats all for now I'm off for a surf

[valarius]

re batteries

in this thread it says that the main battery is on the drivers side and being in paralel so could you put two different ampage batteries on ? and mine is on the passanger side but all the wires are still there on the other side so i presume it had two fitted is there any way of checking as to whether there is a split charge circuit already fitted ?

[icsys]

If the wires are there and they are the same as the side with the battery then a good guess would be they are a factory fit.
If this is the case then it would be obvious to assume that either battery can be considered the main one. (Provided it has sufficient Ah)

As for the split charge, i have no idea. My original post was to discover why there are two batteries fitted. if yours is a factory fit (like mine) then I assume it wont matter if there is a split charger or not as if it did'nt work then why did Toyota fit them in this way??

Would I be right assuming the above?

[Guest]

It was a factory fit option, however like a lot of Toyota options they fit all the wiring whether the part is there or not.

On the Factory fit option both batteries are the same (except the terminals are left and right handed for the two sides).

A split charging system wasn't an option, it's just something that people do to allow them to fit different batteries so that one can be a good quality starting battery (Optima Red maybe) and the other a deep cycle leisure batter (optima Blue maybe). This allows you to use one battery to start the car and the other to run the fridge, telly etc etc when you go camping.

To be honest if you don't have 2 batteries then you don't need them as the single battery should be a higher Ah rating than either of the 2 batteries in the dual setup.

So basicall neither battery is the main one or either battery is the main one depending on how you look at it. In the Factory fit because they are wired in parallel with no active charging splitter, they basically act as on large battery (Basically one battery with the same number of plates but twice the plate area.

The only one advantage with the dual battery setup is that you met get away with one dodgy battery for a while whereas you don't have that luxury with only one battery. However again, the bad battery will eventually kill the good battery (because there is no charging splitter) so you end up having to buy two new batteries not one.

Cheers

[Just Cruzin]

Dual Batterys

Ian
In OZland the dual battery set up usually has 2 different CCA ratings.
One for starting the car only (Cranking) and the other being a Deep cycle battery for accessories like Car fridge, UHF-HF radios, GPS and extra lights etc where the current draw is rated for a period of time.

The set up usually has a protection system (Solenoid, Isolator switches etc) to ensure the batterys do not draw current off each other, and do not drop below a designated level.
They also have various systems to re-charge while driving the vehicle.
That way you should alwys be able to start the vehicle under most circumstances and if, for some reason there is not enough power to start the vehicle, they can be used together to get it going.

This gives us about 3 days in the outback camping or fishing on Fraser Island.
My vehicle (SSR-X) came stock standard with one battery and a BIG space for the second.
The 2nd Generation LN130 (2.4 TD) came with 2 batteries (I suspect) to run the electrics. We have tracked down unusual problems over here which were attributable to recent workshop work and where they did not affix both (2) earthing straps on completion.

HTH