newb question

[lemming]

why do the diesel systems have two batteries?

[watrob]

I think it has to do with which country your in. Australian diesels are all 12 volt systems and as standard run one battery. In the US on these Toyota's they run 24 volts, also some owners then added more batteries and a converter or a 2nd altenator to get 12 volts to run other electrical systems.

I think the 24 volt thing is Military spec ?

[lemming]

Originally Posted by watrob

I think it has to do with which country your in. Australian diesels are all 12 volt systems and as standard run one battery. In the US on these Toyota's they run 24 volts, also some owners then added more batteries and a converter or a 2nd altenator to get 12 volts to run other electrical systems.

I think the 24 volt thing is Military spec ?

still kinda confused, but it helped. thanks.

[lostmarbles]

I agree with the previous explanation.

So being "diesel" doesn't necessarily require 2 batteries.

The 24V systems fitted to some diesels were designed for harsher conditions (like military). So the easiest way of getting 24V in "battery power" is to have two 12V batteries in series. (24V power means you get twice the power output - from a starter motor for instance - for any set current flow.)

Owners of some vehicles (whether petrol or diesel) often install a another "aftermarket" battery to run ancillary gear like refrigerators. (Because they fear being left stranded in the middle of no-where with a flat starting battery.)

[watrob]

There would be forum members who could shed further light on this but as I am in Australia and we use 12 volts , but one could assume some of the following:-

+ 12v - ____ + 12v - = 24volts

If you join 2 x 12 volt batteries in series you get 24 volts.

Because diesels have glowplugs and with your cold climate they draw a lot of power at start up and have two battery setup gives you a good reserve, rarther than one 24 volt battery.

The starter motor & alternator are 24 volts, so it requires 24 volts to start.

It is a lot cheaper to buy 12 volt batteries than a 24 volt ones and not many outlets I would assume would carry 24 volt batteries. They might be available in the US but you would have a lot of trouble going to your local outlet in Australia and buying one here.

A fellow forum member could also jump in here, but it well may be that they are using one 24 volt battery and a second 12 volt for other electrical systems that they have put on there vehicles, (but I doubt that) but this would certainetly require some specialised wiring in regards to charging.

But I have seen on the forum photo's of owners runing a extra 12 volt battery but they also have added a second 12 volt altenator, mainly because of the amount of electrical load they have placed on ther vehichle for all the extra add on's.

This is not standard but I have read on this forum of members draining their batteries when it has been very cold and unable to start their diesel's. Jump starting then fails as there is no battery power left to run the glowplugs to heat the diesel fuel. Now that would be scary if your out in the field and it's -20 deg's.

[watrob]

Thanks Lostmarbles, some of our fellow forum members that have diesel's have certainly made some major changes to their vehicles in regards to battery setup.

I wonder if any of them have gone and mistakenly put 2 x 24 volt batteries in, in series, now that would have certainetly made the wiring glow?

[lemming]

thanx everyone.

[M John Galt]

24 volts is the NATO standard. Most military equipment runs on 24 volts. Military organizations around the world are customers of Toyota 70 series diesels.