12/24V Questions

[kfouad]

Hi Diesel guys , I'm converting from 1FZ-F to 1HD-T soon, and i needed some info as I'm new in the 12/24V thing.
What i know is that the 1HD-T i'm getting has a 24V starter and 12V charger. My 80 has already dual batt + IBS monitoring system.
So my questions are:

1-as far as i read both batt are 12V and the switchover relay coverts them to a series config, so does this mean that I'll get 24V on one of them during engine start????

2- If yes then any idea how can i use the 2nd batt as aux batt ?? or i will get 24V at starting and blow off all my 12V accessories (Lights, fridge, IBS monitoring system, inverter)?

3-wouldn't it be better to get a 12V starter?

 

[lostmarbles]

..What i know is that the 1HD-T i'm getting has a 24V starter and 12V charger....

Really? So it has a 24V starter yet the alternator is only 12V?

I'm not really familiar with any post 1980's engines but it surprises me to hear that Toyota would make an engine with mixed voltages like this.

 

[canucksafari]

HI81s are connected in series for a 24V start. Not sure if all 81s have a 24V starter. Might just be cold weather models. The HJ60 series here are all 24V except for 12V headlights (the evil centre tap).

As for the Qs:
1) yes, you will have 24V coming off of your high battery on start-up - but just to the starter.
2) Don't know enough on how it works on the 81s, but I assume that it sues a solenoid that creates the series circuit. If you run a 3rd battery it will be hooked up in parallel and you will use a battery isolator to protect it and your starting batteries.
3) If you don't need 24V start (cold climate), then there is nothing wrong with just using a 12V alternator. You'll need someone who knows what they are doing to rewire so you don't get 24Vs going to the 12V alternator.

 

[danakittilsen]

The 24v starting system on the HDJ81 uses a series/parallel switch. The very first thing I had to do when I bought mine was replace that solenoid; mine was stuck in 24 so it would start, but then not switch back 12v to charge both batteries. After a few starts the second battery would be dead.
I called a local auto parts shop that carried tractor truck parts and got the switch. Sorry i cant find the paperwork in my records; i think it was a Denso part.

 

[fitzmooney]

Because it uses a series/parallel relay, you will get 12v across each battery and also across both batteries in ignition off or run positions, as they are in parallel.
In the start position, you will still get 12v across each battery, but 24v across both batteries, because they are in series.

 

[kfouad]

Because it uses a series/parallel relay, you will get 12v across each battery and also across both batteries in ignition off or run positions, as they are in parallel.
In the start position, you will still get 12v across each battery, but 24v across both batteries, because they are in series.

great Fitzmooney, how come? does the change-over relay has diodes?
so this might answer my next question; i have an IBS dual bat monitoring system (12V version). i guess it won't burn up , right?
in other words, my dual batt setup will not be affected/changed.