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08-07-2019, 10:40 PM
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#1
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Bus Nut
Join Date: May 2018
Location: the Missouri Ozarks
Posts: 258
Year: 1997
Coachwork: BlueBird
Chassis: International 3800
Engine: 466e
Rated Cap: its Yuge
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How to hookup disconnect switch.
Batteries on my dt466e keep running down so I bought a disconnect switch. Had originally intended on switching the negative. But there is a cable running from each of the negative terminals as well as one that runs between them. Any recommendations on the best way to do this.
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08-07-2019, 10:41 PM
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#2
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Bus Nut
Join Date: May 2018
Location: the Missouri Ozarks
Posts: 258
Year: 1997
Coachwork: BlueBird
Chassis: International 3800
Engine: 466e
Rated Cap: its Yuge
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those clips are the charger i have hooked to it
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08-07-2019, 11:00 PM
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#3
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Bus Geek
Join Date: Sep 2015
Posts: 3,856
Year: 2002
Coachwork: Thomas Built Bus
Chassis: Freightliner FS65
Engine: Caterpillar 3126E Diesel
Rated Cap: 71 Passenger- 30,000 lbs.
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I can not really see the negative terminals from that picture. You may be able to install the disconnect between the grouding cable and the batteries.
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08-08-2019, 08:09 AM
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#4
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Bus Nut
Join Date: May 2018
Location: the Missouri Ozarks
Posts: 258
Year: 1997
Coachwork: BlueBird
Chassis: International 3800
Engine: 466e
Rated Cap: its Yuge
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Will try to get better pic. That was my original plan. But there is a wire running from each of the negative terminals to somewhere on the bus. Along with 1 between them
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08-08-2019, 09:13 AM
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#5
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Bus Geek
Join Date: May 2016
Location: Eastern WA
Posts: 6,401
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
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Question:
Every rig I have owned, that had a disconnect, had the disconnect on the positive side.
I never questioned it. What are the advantages and disadvantages of installing it on the positive Vs negative?
Thanks.
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08-08-2019, 09:40 AM
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#6
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Bus Geek
Join Date: Jan 2019
Location: Philadelphia
Posts: 7,000
Year: 2003
Coachwork: International
Chassis: CE 300
Engine: DT466e
Rated Cap: 65C-43A
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Quote:
Originally Posted by PNW_Steve
Question:
Every rig I have owned, that had a disconnect, had the disconnect on the positive side.
I never questioned it. What are the advantages and disadvantages of installing it on the positive Vs negative?
Thanks.
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It seems that the main concern with installing it on the positive side is that the switch itself (depending on the type) can significantly increase the amount of positive-wired exposed metal that is inside the battery box, increasing the chance of an accidental short.
I thought that the general guidance on removing batteries was to disconnect the negative and then the positive leads. If this is correct, I guess it would also make sense to attach the disconnect switch to the negative side.
I am sure of none of this, so I'll happily be corrected. I'm also wondering about what kind of switch has the necessary amperage rating for this, and whether the $6 Harbor Freight cheapie would work here (I'm guessing no).
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08-08-2019, 09:46 AM
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#7
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Bus Geek
Join Date: May 2016
Location: Eastern WA
Posts: 6,401
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
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The disconnects that I am familiar with are enclosed and don't have any exposed copper.
Like this one: https://www.amazon.com/Disconnect-Ve...54685735&psc=1
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08-08-2019, 09:49 AM
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#8
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Bus Geek
Join Date: Jan 2019
Location: Philadelphia
Posts: 7,000
Year: 2003
Coachwork: International
Chassis: CE 300
Engine: DT466e
Rated Cap: 65C-43A
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Quote:
Originally Posted by PNW_Steve
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That seems pretty clear that it's intended for the positive lead.
I was thinking more of this type: https://www.amazon.com/Battery-Disco.../dp/B07MTXDHNV which is intended for the negative post. I don't know why anyone would use this instead of the one you linked, except that it doesn't require any additional cables or splicing, I guess.
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08-08-2019, 10:13 AM
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#9
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Bus Nut
Join Date: May 2018
Location: the Missouri Ozarks
Posts: 258
Year: 1997
Coachwork: BlueBird
Chassis: International 3800
Engine: 466e
Rated Cap: its Yuge
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Quote:
Originally Posted by PNW_Steve
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This is actually the one that I purchased.
Think i will just put it on the positive lead. May have to figure out where the 2 additional small fused wires on the positive terminals go. They may be the source of my drain.
Thanks guys!
dave
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08-08-2019, 11:43 AM
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#10
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Bus Geek
Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,482
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
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Quote:
Originally Posted by MambaJack
This is actually the one that I purchased.
Think i will just put it on the positive lead. May have to figure out where the 2 additional small fused wires on the positive terminals go. They may be the source of my drain.
Thanks guys!
dave
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The fused wires go to the negative. That switch is designed for the neg terminal and the added wires also go to ground. I would not hook them to ground and hook it to the pos lead.
The only disadvantage to being hooked to the pos. is in the event of and accident or shift of the batteries, the terminal ends could contact the body or frame and short the circuit. NHRA requires cutoffs on the Pos.. Use one that has covered terminals.
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08-08-2019, 02:25 PM
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#11
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Bus Crazy
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 1,956
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
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Quote:
Originally Posted by PNW_Steve
Question:
Every rig I have owned, that had a disconnect, had the disconnect on the positive side.
I never questioned it. What are the advantages and disadvantages of installing it on the positive Vs negative?
Thanks.
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Strange but every vehicle I have is disconnected from the battery on the negative side. Done by a habit I have got used to since trade school.
Not really remembering those classes much no I searched direction of current in a dc circuit.
Seems the dc electrons flow in one direction, from high potential to low potential.
Now I am positive of why I placed the disconnect switch on the negative post of the battery. This may seem unconventional to many but is the way dc current works with regards to batteries.
Don't believe me, do the search I just did as above.
John
__________________
Question everything!
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08-08-2019, 03:04 PM
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#12
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Bus Crazy
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,362
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
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My bus has a Cole-Hersee M-705 battery isolator/selector for the two start batteries, connected to their positives and directly to the starter motor. That's how Crown did it, and I have no reason to doubt their rationale. The M-705 has now been replaced by the essentially-similar M-750, and they work well; if you don't have space for one, the Blue Sea 9001 and 9002 are also very good quality and take less space than the C-H. I recommend not buying some cheapo generic switch for something that can briefly pass hundreds of amps.
John
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08-11-2019, 02:40 PM
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#13
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Bus Geek
Join Date: May 2016
Location: Eastern WA
Posts: 6,401
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
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Quote:
Originally Posted by musigenesis
That seems pretty clear that it's intended for the positive lead.
I was thinking more of this type: https://www.amazon.com/Battery-Disco.../dp/B07MTXDHNV which is intended for the negative post. I don't know why anyone would use this instead of the one you linked, except that it doesn't require any additional cables or splicing, I guess.
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I would have some concern about the current rating on that one. Looks like 750 amps surge. I suspect that your starter may exceed that. I would get that question answered before pulling the trigger.
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08-17-2019, 06:31 PM
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#14
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Site Team
Join Date: Apr 2015
Location: Nanaimo, British Columbia
Posts: 429
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Someone mentioned NHRA... if it’s good enough for race cars, it’s good enough for me...
No direct bus experience here, but I have wired off-road winches through Blue Sea manual marine disconnects (the big red ones that let you connect one, two, or no batteries) with great results. Check the current ratings; they’re higher than the automatic charging relays, generally.
I’ve also used those ACRs, and they’re great for dual battery systems in a 4x4.. For winching current levels, I always thought the manual ones were more appropriate, so I used them for that.
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08-18-2019, 05:23 AM
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#15
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Mini-Skoolie
Join Date: Aug 2018
Location: Keene NH
Posts: 33
Year: 2004
Coachwork: Corbeil
Chassis: GMC 3500 Cutaway
Engine: 4.8 V8
Rated Cap: 14 passengers
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I think the concept of disconnecting the negative side first (on negative ground vehicles) was simply practical, if your tool on the terminal accidentally hit the chassis you get no short. Other than that I don’t see why it matters which side you disconnect.
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