Half of the Volts, and "name that thing"

[MihiT]

1990 TD42, LWB cut down...
I'm installing an alarm, central locking and radio, all 12v.

One of my bateries is sitting at 14.4 ish across the terminals, the other is 13.7, both 530cca Exides. I dont like the imbalance, but it's what I've got. (1 - Is it worth swapping the batteries over to exercise the other one?)
So i'm tapping off the one at 13.7v To ground, running a dual-battery isolator to a third batt which i'm going to shoehorn behind the passenger seat.
I want to screw the isolator on the passenger side engine wall - there was a "thing" screwed to it, between the diesel primer/filter and the battery tray on the LHS, looks to be something to do with vacuum boosters, it is a plastic cylinder about 3" dia x 4" long, one inlet, one outlet, and apparently nothing in it..
It has 1/4" ish piping from the back of the alternator?? through a check valve, into this thing and then tubing over to the booster. I've unscrewed it and cut the pipes so it now hangs out of the way.
2 - What is it?? It seems to be a ballast tank or something? Can I chuck it out altogether?

Anyway, I will post some pictures when it's daylight. I expect that running it this way will give me good 12v in the cab without forking out $150 for a 24-12 converter.

[keithal]

Running it the way you are will f*&k your batteries real quick assuming it's a 24v truck

[MihiT]

Running it the way you are will f*&k your batteries real quick assuming it's a 24v truck

It is 24v.

The battery isolator stops current to the third if the primary drops below ~12.8...
Also, I should think having a third batt, rather than just drawing off 1, would be a good enough buffer?

[3VILC]

You will still draw off one to charge the 3rd one, better to run a 12v reducer to the charger for the 3rd or even better a separate 12v alternator.
Re the 'thing' its a vacuum tank stores extra vacuum for the brake booster, and clutch booster if its manual.

[Swamped]

I run a redarc charge equaliser to manage the batteries individually and just run 12v stuff off one battery in the 24v system. Been working well for the last 5 years.

[MihiT]

I run a redarc charge equaliser to manage the batteries individually and just run 12v stuff off one battery in the 24v system. Been working well for the last 5 years.

I saw those. But at $600, I was hoping to make use of things I have lying around already!
I see 20A 24-12v units for $130 so that may end up being the way I go, if not alternator

[MihiT]

You will still draw off one to charge the 3rd one, better to run a 12v reducer to the charger for the 3rd or even better a separate 12v alternator.
Re the 'thing' its a vacuum tank stores extra vacuum for the brake booster, and clutch booster if its manual.

Thanks, I figuired it was something like that.
And I'm now considering a 12v alternator, (again, I have a few lying around) I just wouldnt think it would be THAT bad tapping off...

[skidmark]

You will still draw off one to charge the 3rd one, better to run a 12v reducer to the charger for the 3rd or even better a separate 12v alternator.
Re the 'thing' its a vacuum tank stores extra vacuum for the brake booster, and clutch booster if its manual.

Thanks, I figuired it was something like that.
And I'm now considering a 12v alternator, (again, I have a few lying around) I just wouldnt think it would be THAT bad tapping off...

Yes it is THAT bad. Consider batteries as buckets of water. As the alternator is in series both battery's get equal current when charging. So as buckets of water they have Equal 15 liters going in per minute.yet if your drawing 20 liters from. One and 12 liters from the 24 battery, one will slowly be drained and empty yet the other will be overflowing. You will #### both battery's.. see it all the time mate.dont do it. As has been said,charge equalizer or reducer.

[MihiT]

Thanks, I figuired it was something like that.
And I'm now considering a 12v alternator, (again, I have a few lying around) I just wouldnt think it would be THAT bad tapping off...

Yes it is THAT bad. Consider batteries as buckets of water. As the alternator is in series both battery's get equal current when charging. So as buckets of water they have Equal 15 liters going in per minute.yet if your drawing 20 liters from. One and 12 liters from the 24 battery, one will slowly be drained and empty yet the other will be overflowing. You will #### both battery's.. see it all the time mate.dont do it. As has been said,charge equalizer or reducer.

OK OK!

I do understand the theory, thought I had it under control. Don't. Wont.

So I have a 12v alternator in my hand... and I'm thinking "where the hell is this going to fit??"

Moderators, I am going to start one thread for my "build", to save starting heaps of newbie threads. If you'd like to merge them all that would be cool:
viewtopic.php?f=18&t=43487&p=441663

[DieselBoy]

That "thing" you cut the pipes off is the vacum reservoir for the brake booster.

There is a vacum pump on the back of the alternator that supplies the brake booster with vacum to provide you with assistance pushing the pedal down during braking.

I suggest you reconnect that and put it back where it was ASAP!!!!!!

[3VILC]

Ultimately I think the best and possibly cheapest way esp if you have one laying around is to fit a dedicated 12v alt and fusebox. If you can find a place to mount it haha. A safari prob has more spare room than anything, just getting the pulley lined up and the right length belt will be the fun part