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Old 07-21-2021, 08:59 PM   #1
Almost There
 
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Location: Melbourne, FL
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Year: 2003
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jumping dead battery precautions

My batteries are completely dead due to parasitic drain/neglect. I havent started bus in over a month but want to get it running tommorow.

my plan is to use a NOCO BoostPro GB150 jumpstarter that claims it will start a diesel. When i bought it it claimed to start up to maybe 8 litre, but i see the specs have been downgraded to 7 litre. I have a Cat C7 (7.3 litre IIRC). If needbe, can i hook up regular jumper cables in tandem with this?

What precautions do i need to take as far as ECU and TCU? do i need to remove those fuses? will the engine start (assuming appropriate amperage) without the ECU fuse?

Do I need to scrap the idea entirely and try to charge/replace instead of jump the batteries?

On a related topic, the Allison B300 trans TCU is wired directly to the batteries (attached photo, it is the parasitic drain in the first place). Can I disconnect that from the batteries and hook it up like the rest of the electronics in the fuse panel?
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Old 07-21-2021, 09:26 PM   #2
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charge the batteries first

this makes life for the alternator easier.

as big as those batteries are... one charger for each battery and several hours to charge.

william
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Old 07-21-2021, 10:16 PM   #3
Skoolie
 
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Quote:
Originally Posted by magnakansas View Post
this makes life for the alternator easier.

as big as those batteries are... one charger for each battery and several hours to charge.

william
I agree. Charge the batteries first. I ended up with a fried alternator on my fire truck. Being a 1970 model a replacement alternator was unobtanium and it cost a lot to rebuild the original.



Alternators are not "battery chargers" but designed to maintain batteries and keep up with normal usage of the electrical system. Large batteries that are low in charge can pull a bunch of current for a while. Normally, just after starting there will be a large charging current but that tapers off quickly.



A suggestion: get a small 20 watt solar charger that plugs into the cigarette lighter receptacle, plug it in and face it towards the south. the batteries will stay peaked up, even in the winter.


If you have parasitic current draw that seems excessive check the alternator. If one of the diodes has failed it may cause reverse current flow into the alternator.
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Old 07-21-2021, 11:16 PM   #4
Mini-Skoolie
 
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I'm former ASE certified brakes and electrical, former USMC motor transport mechanic and Maintenance Management Officer. Graduated top of class Sacramento College Auto ROP course.
Quote:
Originally Posted by flattracker View Post
I agree. Charge the batteries first. I ended up with a fried alternator on my fire truck.
100% correct....

Quote:
Originally Posted by flattracker View Post
Alternators are not "battery chargers" ......
Again, 100% correct. Charging a battery or batteries for these big diesels rather than replacing starting energy and providing ongoing needs will burn out an alternator.

Quote:
Originally Posted by flattracker View Post
A suggestion: get a small 20 watt solar charger that plugs into the cigarette lighter receptacle, plug it in and face it towards the south. the batteries will stay peaked up, even in the winter.
This is a viable solution but be sure that you plug it in to a lighter/power socket that is powered (i.e. connected to the battery) when the ignition is off. Many buses have solenoids that shut down electrical items when the ignition is off. I'm surprised yours doesn't.

Long term, installing a battery master switch at the battery box to isolate the batteries from the electrical system is another solution though it would require accessing the batteries to operate the switch.
Another option, install a solenoid in the offending circuit that only allows juice when the ignition is on.

The small maintenance panel is the better idea for those who are not comfortable and knowledgeable with circuitry as it solves the problem without introducing new potential problems. And, if the power socket isn't hot when the ignition is off, it's a very simple matter to add a constant hot socket or hardwire the small maintenance solar panel.
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