24v operating voltage for BJ75

[Reinhardtius]

Hi Friends

What is your volt meter reading when your 24V truck is running? Please respond if you know in general, and especially if you have a 24V 3B.

It appears that my high side battery and to a lesser degree low side battery boiled over. I was having a difficult time starting the truck even after trickle charging the batteries. I thought that I had one or two bad batteries, so I made a trip to Interstate Batteries, who rejected my request for warranty replacement. They said that batteries had boiled over, and that boil over is caused by overcharging, and either a bad alternator or voltage regulator. They observed little to no water in the batteries. So, they added some water and some acid and they sent me on my way.

my next step was to remove the alternator and the voltage regulator for evaluation by an alternator repair expert near me.

I am *right now* in the process of removing the alternator and the voltage regulator. Upon removing the voltage regulator, I discovered a wiring harness placed between the voltage regulator and the wiring harness. That small wiring harness has a Hella change over relay installed, but it appears to be for a 12 V system. I am lucky that the relay was not spliced into the original wiring harness. Instead, I was able to remove the small piggyback wiring harness. I thought that I would reconnect everything and reinstall the batteries before continuing with the alternator removal.

Upon reinstalling the batteries and reconnecting the voltage regulator without this piggyback wiring harness and Hella relay, I started up the truck and I noticed that the operating voltage now sits at 27.3-27.5 steady. It does not climb like it used to, even when the engine is revved.

My high side battery appears to have one damage to a cell, but the truck still starts. I will have to replace at least that battery. Is it also safe to assume that I have resolved this overcharge problem? Please let me know what your operating voltage is.

 

[svsisu]

My 24v system is usually at 28.5 +/- a few tenths when charging, which is what I would expect. Most 12v systems with standard alternators/regulators put out 14.4v, so only seems natural that to charge 2 ,12v batteries one would need 14.4 or so going to each. If you were charging at 33v you were definitely cooking your batteries.

 

[jblueridge]

28v approx.

 

[george_tlc]

For a 24V system, you would typically see around 28V, maybe a few tenths above. If you have a battery that has a dead cell, it will screw up charging of the other battery. The bane of a 24V system is you need 2 matched batteries (capacity and age). You really need to replace the batteries as a pair and never draw from one battery to get 12V.

It would be a good idea to have a voltage display for each battery, or one of the dual battery displays and hook the main_sense to the 24V and the aux_sense to the 12V, then you can see what is going into each battery (mental subtract of the 24V from the aux to get the high side battery. Certainly with a 24V system and the expense of 2 batteries, seems prudent to monitor each of them...

Happiest ownership day of my diesel (other than initial purchase) in oz was scrapping the 24V junk and converting to a true 12V system.

Good luck.

cheers,
george.