International 4300 DT466 Battery issues !

What does this truck require for Batteries, and alternator! The company I work for, does everything on the cheap, and the people in charge do not really know ( expletive ) about repair work. They have been screwing around with this truck for a while, mostly jumpstarting it when they need to use it, and then blaming the drivers for leaving the key on as excuse for Batts being dead. I haven't been there long but since I'm the only one in the shop with Electrical education, and 30 years working on copy machines
I told the boss that I can fix the problem. He looked at me like I was stupid. I said the connections are horrible, the whole mess needs to be taken apart and cleaned, the batteries checked ( even though less
than a year old ) charged up and checked to make sure they can hold a charge. Later he told me go ahead, do what you you think you gotta do. So I did, Pulled the batts, cleaned the poles, put a meter on them 12 volts on one, 11 on the other. Told him they gotta be 13V . Put them on the 100 Amp fast charge. In the meantime I cleaned all other connections. However neither batt recovered. So I told him
Batts probably no longer any good, and since they are dated Feb 2020 take them back to Interstate. Then I told him, look you cant just toss a couple good batteries in there and expect it to work. You have to meet the power requirements of the vehicle. Its going to need batteries with required Amps, and an alternator
capable of keeping them charged. And we have the additional problem of all the "added equipment"
thats been "rigged in" and whether or not that its causing a drain. ( which it likely is ). I said I can fix this,
but not in 15 minutes, or even a day. I have to do some research.
SO ! My questions are ? How many ? and of what capacity of Batts do these trucks require? Current wiring configuration is for two Batts, I've seen pics with 3. And What Amp Alternator is required?
Also , I should state that the truck is used a "Crash Truck" or "Attenuator Truck" for Highway
maintainence , in case that makes a difference.
Thanks in advance !

 

Thanks, I hadn't thought of that, I have a multimeter test meter, so I shouldn't have any problem checking that. Boss got 2 new 950 Amp Batts, that one of the foremen reinstalled the other day.
I was busy doing the normal part of my job, so I dont know how it turned out yet. The winch that
is used to raise the "Crash Box" on the back of it, I believe is hard wired to the batteries and has an off and on switch of its own. There is also a breaker at the Batts that I believe is part of that circuit.
The arrow board is my suspected culprit. The wiring there looks like what a 16 year old would do when wiring a stereo and speakers in his car. In fact they have to unplug one of the wires to get
the arrow to turn off. So I suspect it is falsely wired into Battery accessory, instead of ignition
accessory.

 

.l..

 

That makes sense, the extra battery to run the liftgate motor.