2003 td battery managment

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Warrenpfo

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I am looking for advice please. I have a 2003 4.2 TD landcruiser which has the 2 12v batteries under the hood as standard.

I have been informed that on starting the batteries a switched to parallel to give me 24v cranking power and then switch back to 12v again. I am not sure if this is true as i have also read otherwise elsewhere.

What is the best way for me to establish what is going on under the hood and what is the best way to run a battery management system that will advise me on the capacity of each battery and stop either of the batteries running flat from a left on light or other electric accessory.

Lastly what is the best way to go about running other accessories off the system like fridges, inverters etc. Do i need to install a third battery?
 
Post a good picture of your engine compartment so we can see what is going on under the hood. You shouldnt need a third battery. Add a fuse panel and run it to the 2nd battery. Do a search on here and you will see some ways others have done this.
 
I found this on Toyota Owners Club website:

Hi there,
I had this explained to me recently by the foreman mechanic at the Toyota dealer.

I asked why my friends new Land Cruiser 3.0 had two batteries while my new Hilux double cab 3.0, with exactly the same engine, had only one battery. The answer is that the Land Cruiser has a 24 volt starter motor and the Hilux has a 12 volt starter motor. The only difference is the gearing in the starter motor which means the Land Cruiser needs more power to crank the engine over. All the other electrics on the Land Cruiser are 12 volts of course.
 
I can’t imagine how 2 batteries could be switched to series wiring (24 volt) for starting and back to parallel wiring (12 volt) for running? You could use a simple voltmeter across the battery(s) to see what’s going on. The advantage of 2 batteries is that either the volts are doubled (series wiring) or the amps are doubled (parallel wiring), but not both. Either way will supply much more power to the starter motor, assuming heavy enough wiring is used. Given it’s a 12 volt vehicle, the batteries are most likely in parallel, with very heavy wire and starter motor windings. I suppose someone may have figured out how to bring a second battery online when running the starter, but it seems way easier, cheaper, and more reliable to just use heavy wire/starter and keep it all 12 volt. I agree an underhood photo would help with explanations, in particular of any devices that connect the 2 batteries.
 
The aussie's will chime in soon but afaik, your 4.2TD runs on 12V all the time. Following both battery leads might help you verify. To run a dual battery system, you will probably want to run two larger batteries and separate the 2nd one for accessories.
 
I think someone is pulling your leg, mate. I have 2002TD and I haven't heard such thing.
It is 12V, and both batteries are in essence one big battery to crank the mighty engine.

In the land of Oz, 2 batteries can be separated without any dramas, as it is not cold enough to need 1 big battery. In the colds of Europe (and other cold regions) they require 2 batteries to start the engine.

If I'm not mistaking it is/maybe sufficient a single 600-650CCA battery to crank it up (in 15C+ ambient temp).


Assuming you dwell in a relatively mild climates, you can look into separating you batteries with a smart solenoid (like RedArc), which makes one of you batteries a dedicated starting battery and another battery - dedicated aux for all your aux devices.
Most smart solenoids have an override option, so you can connect your batteries again should you require big amps for crank the engine.


Also if you not doing long miles to keep you batteries fully charged, I would recommend into looking at good battery chargers (like Ctek MULTI XS 15000). *Keep in mind though, charging automotive batteries with more than 20A may damage them.

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With all due respects to this forum, but for more info and with questions on TD version you may be better going to LCOOL (Australian forums) at LCOOL.org :: Index
 
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