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Title: What Gage cable Battery to Starter
Post by: ArtGill on June 05, 2010, 03:15:49 PM
I'm replacing the air starter with a 12 vdc starter on my NJT model 20 Eagle.  The battery box is beside the starter, so the cable run should be 5 ft or less.  I have two 8D batterys with each having positive cable running to the manual disconnect switch.  Should I connect the starter cable at this point, on the input side of the switch, not the load side?

Thanks,  Art


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 05, 2010, 03:29:33 PM
Starter cables should run directly from the battery positive terminal to the starter without passing through anything else first.  It is not uncommon to use the alternator lug, though, as an intermediate terminal.

For a 12v starter on a big diesel I would not use less than 4/0.  With a 24-volt starter you could go to 2/0.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: Lin on June 05, 2010, 03:35:48 PM
I thought that everything went through the main disconnect on my 5a.  Is the starter cable still hot when I shut that switch off?  I will have to test that when I get the bus back.  It could be very important to know.


Title: Re: What Gage cable Battery to Starter
Post by: Dreamscape on June 05, 2010, 03:36:28 PM
Sean, I'm having a hard time understanding your reasoning on having the battery positive running directly to the battery. My Eagle elec. schematics show the positive running to a battery disconnect then to the starter.

Our Eagle is wired according to the schematic and has always worked just fine.

Enlighten me please. ;)

Paul


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 05, 2010, 04:15:04 PM
Paul,

I confess I am not very familiar with Eagles and so I can not speak to how or why the factory would choose to wire that way.

What I can tell you, though, is that generally speaking, main starter cables are wired directly, and with good reason:

Starters can draw immense amounts of current while operating, particularly when first engaged and especially if the engine is cold.  Any extra resistance whatsoever in a main starter circuit can cause problems, including extreme heating of the connections, increased current draw, and heating of the starter motor.

A disconnect switch of any kind adds a minimum of three and usually four extra connections in-line with the starter, each of which is a potential increase in resistance and something else to heat up.  Manual switches left in a partially engaged position can also cause arcing and exacerbate the other problems.

Usually, when working on starters and alternators (which, BTW, should never be separated from the battery by a disconnect switch), safe practice is to first disconnect the battery ground cable, and then the battery positive cable, regardless of the presence of disconnect switches.

Note, BTW, that I am talking here about the main current path from the battery to the starter motor, and not the circuit to the starter solenoid, which may well be routed through a disconnect switch.  This would prevent the coach from being started when the disconnect is open.

Lastly, a main battery disconnect switch for most coaches would be tasked with carrying at most 300-400 amps of current under normal operation (and usually far less than that) and so a switch with that rating would be adequate.  However, starters can draw several times this amount of current, and so if the main starter feed is routed through such a switch, you'd need a switch with a (non-breaking) rating of perhaps 1,000 amps or more.  This, incidentally, is also the reason starter circuits are generally unfused as well.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: bobofthenorth on June 05, 2010, 04:22:39 PM
While I don't usually argue with Sean in this case I have to take issue.  The original equipment wiring on my 1981 Prevost takes the battery positive through the main chassis disconnect on its way to the starter.  Based on that single data point I'd say there's a lot of Prevosts wired that way.  We used to routinely put battery disconnects on older trucks and those went directly between the battery positive and the lead to the starter.  Older equipment tends to develop a variety of leakage paths due to years of amateur electricians working on it and the only reliable way we ever found to preserve the batteries was to put disconnects directly at the battery.  This is a fairly common practice on older equipment.


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 05, 2010, 04:31:20 PM
Bob,

Again, I am not a Prevost guy and so I can't speak to how they did it or why they made that decision, and I am sure you are more knowledgeable on that subject than I.

There is nothing inherently wrong with it, so long as the disconnect switch is properly rated for the starting load, and the size and nature of all connection points is adequate to ensure minimal resistance in the circuit.  I would assume that, if it was designed and installed by the factory, then such conditions should already be met.  I will say, though, that if you have such a setup, then tightening the connections on the switch, and cleaning corrosion, pitting, and deposits from the contacts, should be added to your PM routine.

What I can not tell from the OP's question, given that he has an air-start coach, is whether any such switch that he already has on board is properly sized and constructed for a starting load, and so I stand by my original recommendation.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: luvrbus on June 05, 2010, 04:44:25 PM
Yep most Eagles have a cut off  for each battery.The NJT had a cutoff for each system as they had both 12 and 24 V.All  the Cat equipment is cut off at the batteries then goes to the starter.
All power leaves from the starter on Prevost and Eagles don't now about Seans bus 



good luck


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 05, 2010, 04:45:05 PM
Addendum to my previous:

Notwithstanding what I said about factory-designed and installed disconnects probably being fine, I would expect that they break only load circuits from the batteries (whether or not that includes the starter), and never the connection between the batteries and the alternator.

As I wrote two posts ago, the batteries and alternator should never be separated by a switch.  That's because inadvertently opening the switch while the alternator is running could, in fact, destroy the alternator.

So, while I understand the reasons why Bob says he used to routinely put disconnects at the batteries, I have to strongly advise against this particular practice.  At minimum, the battery to alternator path should be direct, continuous, and unswitched, and any switch should be installed between this pathway and the loads.

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 05, 2010, 04:50:13 PM
...
All power leaves from the starter on Prevost and Eagles don't now about Seans bus 


On my coach and, AFAIK, most Neoplans, the battery positive is wired to a terminal post, and from there one cable goes to the alternator, which in turn is wired to the starter (so both the alternator and starter lugs are always hot), and another cable goes to the main disconnect switch and from there to the loads.

So on Eagles is the alternator output also wired to the far side of the disconnect from the batteries?  That would seem like a poor choice.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: bobofthenorth on June 05, 2010, 05:10:11 PM
I understand the risk you are referring to Sean but given the application I think the risk of a completely discharged battery is likely quite a bit more serious on our older vehicles.  In the case of my coach I just had a look at the switch and the service manual and both indicate that the current situation is also the way it shipped from Prevost.  When the disconnect is off everything is disconnected - absolutely everything.

In the case of the field installed disconnects that we (and a large portion of the population of old truck users) used they are typically installed somewhere close to the battery case so that a short piece of cable can connect them to the positive post.  I guess in theory some idiot could walk by a running truck and disconnect one of them - and our staff complement always seemed to have its share of idiots.  All I can say is that we routinely lost batteries due to discharge and never to my knowledge lost an alternator due to an idiot performing that specific action.  Other idiot-induced actions .... all bets are off.


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 05, 2010, 07:50:05 PM
I understand the risk you are referring to Sean but given the application I think the risk of a completely discharged battery is likely quite a bit more serious on our older vehicles. ...


Absolutely agreed, Bob, and so long as there is a significant load present (for example, headlights on), opening the disconnect in such a circumstance is unlikely to do damage.

But can we all also agree that (1) replacement batteries, should they remain connected and discharge completely, would cost perhaps $200 while a replacement 50DN alternator would cost between five and ten times that amount and (2) since we're here discussing it, and people are asking how to do it, that we should be recommending "best practice" rather than "expedient"?

In which case, I will again stand by my recommendations:

1.  The alternator and the batteries should be directly connected, without an intervening disconnect switch.

2.  There should, indeed, be a disconnect and it should be used any time the coach is stored, but it should be "downstream" of this alternator-battery connection, and

3.  The starter should either be connected directly to the batteries without a switch, OR any such switch should be (a) sufficiently constructed to handle the load and (b) properly maintained on a regular basis.

And, just to be clear, as far as I can see, there should be no cost difference to having the disconnect after the alternator connection rather than before it.  It's a simple matter of on which side of the switch the alternator feed is connected.

As long as we are discussing it, I should point out that many of us have 50DN alternators with external Delco-Remy (or compatible) regulators.  These regulators have a "battery sense" lead, which, per manufacturer's recommendations, should be connected directly to battery positive.

IF you choose to connect the alternator output to the non-battery side of a disconnect switch (contrary to my recommendations above), THEN you should also connect the sense lead to the same point.  Otherwise you risk, in the event the switch is inadvertently opened, the regulator not seeing what the alternator is doing at all, thus increasing the possibility of a "runaway" and alternator damage.

FWIW, YMMV, JMO, etc.

(BTW, to get back to the OP's question, again, absent specific information about the rating and construction of any existing disconnect switch, I would recommend direct connection between the battery and starter.)

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: Lin on June 05, 2010, 11:00:55 PM
Again, I do not have the 5a home to be able to test, but I do believe the starter goes through the main switch.  As I remember it though, the alternator is direct to the battery.  These are certainly things I will confirm.


Title: Re: What Gage cable Battery to Starter
Post by: Gary '79 5C on June 05, 2010, 11:25:02 PM
Lin,

On my 5C, both alternator & starter are downstream of the shutoff switch. Having replaced the alt. & rebuilt starter, I cut the power with the switch and not pulling a batt cable. IIRC.

Have a great day.



Title: Re: What Gage cable Battery to Starter
Post by: Dreamscape on June 06, 2010, 02:53:28 AM
Sean, Thanks for you explanation.

I'm leaving mine the original way, it's worked thus far.

Paul


Title: Re: What Gage cable Battery to Starter
Post by: bevans6 on June 06, 2010, 04:57:04 AM
On my MCI MC-5C, the master battery switch inside the luggage compartment interrupts the 24 volt  cable from the batteries to everything else.  Note to self - never throw that switch when the alternator is charging...   On race cars with alternators we use a battery master switch that has a subsidiary terminal with a resistor to ground the field terminal on the alternator, to force it to stop generating as soon as the switch is thrown.  I'd have to really think about how the field terminal on the 50DN is controlled to see if the same function exists, making the issue of throwing the switch while the alternator is charging moot, but easier to not throw the switch.

On my bus, 12 volts is connected to the center terminal of the battery pair, along with the Vanner.  Since the switch interrupts the 24 volt side, 12 volts continues to be present in the bus regardless.  Aside from disconnecting the battery or removing the fuse, there is no way to turn it off.

Brian


Title: Re: What Gage cable Battery to Starter
Post by: Jerry32 on June 06, 2010, 05:20:10 AM
I have two busses here ( GM 4905 & MCI 102A3 ) and both original have the batteries going through a cutoff switch of which I use when parked to avoid loading batteries and discharging them. Both start as soon as you hit the start swich so I don't see the problem as this also makes it so you can kill all power to the bus to work out wiring without dangwer of shorts . Jerry


Title: Re: What Gage cable Battery to Starter
Post by: JackConrad on June 06, 2010, 05:30:50 AM
On our MC-8, the OEM battery switch was located in the battery compartment (in front of front bay on passenger side) and, when disconnected, shut off everything. The switch had one cable from battery on one (input) terminal and 3 cables/wires on the other (output) terminal When I relocated the bus batteries to the engine compartment, we maintained this same wiring by relocating the switch with the batteries and connecting the 3 output cables/wires in the OEM battery compartment together with a 1/2" brass bolt and nut.  I try to  always shut off the bus batteries when we arrive at our destinations, although I sometime forget. So far, we have never had any starting problems.  Jack


Title: Re: What Gage cable Battery to Starter
Post by: Len Silva on June 06, 2010, 06:07:48 AM
I don't have the schematics in front of me but I believe the Eagle 15 used three group 31 batteries and had a disconnect switch for each of them, wired directly to the battery.  I particularly like this idea as you could easily isolate a bad battery and keep going.  IIRC they also had a switch selectable voltmeter right there in the battery compartment which could look at each battery individually (with the other two disconnected).  Were I to ever build another bus, that's how I would do it.


Title: Re: What Gage cable Battery to Starter
Post by: roadrunnertex on June 06, 2010, 07:18:57 AM
According to the GMC wiring diagrams for intercity coaches (P8M4905A) and (P8M4108A). ;D
It shows the battery master disconnect system is in-line with the complete electrical system.
When you open the master switch the complete electrical system is "NOT" powered.
And yes I understand that if you were to open the switch while the engine is running the alternator will have a voltage spike and it will do damage to the components in the system. :'(
jlv
















Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 06, 2010, 09:07:25 AM
...  I'd have to really think about how the field terminal on the 50DN is controlled to see if the same function exists, making the issue of throwing the switch while the alternator is charging moot,


The field on the 50DN is controlled by an external regulator.  Some are P-type and some are N-type.  The regulator governs the field excitation based on input from a "battery sense" lead, which is intended to be connected directly to battery positive.  This will automatically compensate for any loss in the alternator to battery cabling, including, if present, a battery isolator.

This is the issue I was talking about earlier, when I said that you should be sure that the battery sense lead is on the same side of the disconnect as the alternator output.

Quote
On my bus, 12 volts is connected to the center terminal of the battery pair, along with the Vanner.  Since the switch interrupts the 24 volt side, 12 volts continues to be present in the bus regardless.


I have another word of caution regarding disconnect switches and Vanner equalizers.

If you have a Vanner it should be connected on the battery side of any disconnect switches, not on the opposite side.  And, yes, this does mean that the Vanner will be running all the time and that it's idle current will be depleting the batteries.

The problem with doing it otherwise, though, is that the Vanner needs to have the ground connection be the last one made and the first one broken.  Changing the connection or disconnection sequence can fry the equalizer.

Also, I recommend that you add a disconnect on the 12-volt tap if you have loads there.

Folks who have any 12-volt equipment on a 24-volt coach must exercise caution in the battery connection and disconnection sequence, whether or not an equalizer is present.  That's because a disconnected ground with connected 12- and 24-volt loads can apply a reverse 12-volt polarity to the 12-volt loads, possibly damaging any polarity-sensitive equipment such as stereos, GPS receivers, video screens, etc.

The complete disconnection sequence would be:
1. Open the 12-volt load disconnect.
2. Open the 24-volt load disconnect.
3. Remove the battery ground.
4. Remove the 24-volt positive connection(s)
5. Remove the 12-volt positive connection(s)

Connection is the reverse of the above steps.  This sequence assures that there is no possibility of reverse polarity, and also provides for the required ground-before-hot sequence for the Vanner (if any).

For the inquisitive, we used Intellitec latching disconnect solenoids on our chassis system, and connected them to a single toggle switch, so the 12- and 24-volt loads are disconnected or connected simultaneously with a simple flip of a single switch on the dashboard.  Our Vanner remains connected at all times, as does the alternator (and the starter, where this discussion began).

Our disconnects are only rated for 100 amps, but the loads and associated wiring are lower than that.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: cody on June 06, 2010, 09:13:30 AM
Let me see if I understand this correctly, ALL the other companies from GM thru Prevost are wired up wrong?  Somehow I find that not only unlikely but bordering on impossible to believe.


Title: Re: What Gage cable Battery to Starter
Post by: bevans6 on June 06, 2010, 09:20:19 AM
"If you have a Vanner it should be connected on the battery side of any disconnect switches, not on the opposite side.  And, yes, this does mean that the Vanner will be running all the time and that it's idle current will be depleting the batteries."

I really wondered about that, and considered changing it, since the ground is constant  and the 24 volt to the Vanner is definitely switched.  But it's the stock install by MCI lo those many years ago, and it seems to have survived just fine.  I decided if it's not broke, don't fix it, also known as the "let sleeping dogs lie" method...  ;)  The warnings by Vanner may be overly cautious, although another type of equalizer I have has the same warning.  Maybe the warning really is against switching the 24 volt off when drawing significant power from the 12 volt.  I can see that irritating it.

I did install a switchable breaker for the 12 volt feed to replace the in-line fuse, but I tend to leave it on most of the time so that the radio doesn't lose it's mind.  It's not a perfect scenario, but there only a couple of things powered by that 12 volt supply.


Brian


Title: Re: What Gage cable Battery to Starter
Post by: BG6 on June 06, 2010, 09:41:49 AM
What I can tell you, though, is that generally speaking, main starter cables are wired directly, and with good reason

My 1990 96A3 has a master disconnect in the battery bay, as shown in the factory schematics.  The cable from the hot terminal on the switch to 24VDC hot is the only connection to that end of the battery bank.

You can run a LOT of current through a switch for brief periods -- the rating on a switch is the OPERATING current, meaning how much it will make or break.  This is important, because switch arcing can weld and burn contacts.  That's why the starter is operated through a solenoid, with is a really-heavy-duty switch.

I agree with the 4/0 cable, even if the battery is only 2 feet from the starter.  Starting the engine is the most important job the battery can do, and the more power you send to the starter, the better. 





Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 06, 2010, 09:56:38 AM
I'd like to clarify some remarks I made earlier, because it occurs to me they could be misconstrued.

I am not necessarily advocating to anyone here who has a working configuration, whether that is factory-installed or otherwise, that they should go back and rewire their disconnect switches.  (Although I will suggest to those people that they at least check to see that their sense lead is connected in the right place.)

We started here with a question from someone who has no electric starter at all, and so is faced with the prospect of running new wire and making new connections for it, and my original advice was specifically targeted to that question.

And my numbered recommendations several posts ago were intended for anyone faced with adding or changing wiring, as so many of us have had to do in the course of our conversions.  If you are going to add or replace a disconnect switch, add a battery equalizer, or replace or change alternator wiring (as you would, for example, to implement a battery isolator system), then I strongly advise you to follow those recommendations.

If, OTOH, you have a working system wired differently that has not caused you any trouble, you might consider changing to these recommendations when and if you are able.  And, importantly, you should check any disconnect switches for corrosion, pitting, or loose contacts on a regular basis, and exercise caution when operating the switch so that an alternator is never separated from a battery while running.

Lastly, to clarify that when I said I advised against the practice of installing disconnects at the batteries, what I meant was not that disconnects should not be added.  Rather, that, if you are going to install a disconnect where none existed previously, it should not require any extra effort or materials to put it in the correct place: between the charging system and the loads.

I hope that clears up any confusion.

Let me see if I understand this correctly, ALL the other companies from GM thru Prevost are wired up wrong?  Somehow I find that not only unlikely but bordering on impossible to believe.


See above.

Also, don't forget that manufacturers have many competing objectives when they design and build vehicles.  A classic example is reusable fasteners vs. single-use fasteners: fastening a panel such as a dashboard with screws and washers will facilitate servicing anything behind the dash later, but having a single-piece molded dash with snap-fit plastic fasteners molded in will be much cheaper to build.  You will notice that almost all cars use this latter type of interior panel.  For those of us who work on our own vehicles and care about serviceability and access, it would be tempting to say "they did it wrong" but, in reality, they are trying to meet a price point.

Likewise heavy-duty manufacturers have the same trade-offs to make.  I can't speak to why any of the manufacturers you mentioned chose to put the disconnects ahead of the alternator connection, but what I can tell you is that it is contrary to the recommendation of the alternator manufacturers and it is not the optimal choice.

As I said above, the reason why I point it out here is because folks here are generally modifying these electrical systems.  Those modifications in many cases could not have been anticipated by the OEM and the OEM designs certainly do not account for them

For example, OEMs generally do not assume that there will be an entire second battery bank and that such a second bank might be interconnected to the chassis bank with a solenoid.  Or that there might be an isolator between the alternator and the chassis batteries.

So let me give you a scenario where a modification might cause a problem.  Let's say you have a disconnect between the chassis batteries and the alternator.  Let's further say that you've installed a solenoid between the chassis system and house system -- not an uncommon addition -- for the purpose of "emergency start" when there is a problem with the chassis batteries.

It is now possible to start the coach with the chassis disconnect switch open.  Then as soon as the "emergency start" button is released, the alternator will suddenly be working completely unloaded.  While the chances are small, this could, in fact, damage the alternator.

Again, I am not suggesting anyone run out and change a working OEM system.  But if you are making modifications to your chassis electrical system, even if that is as simple as cross-connecting it to the house system, it's best if you are aware of the potential dangers ahead of time.  When you are planning these sorts of additions and modifications, it is usually a simple and inexpensive matter to make sure the disconnects are in the proper place, which may not be where the OEM put them.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: cody on June 06, 2010, 10:05:49 AM
I guess if a person felt the urge they could also wire a welder into the kitchen circuit, what I'm asking is, are the companies that manufacture buses all wiring them wrong by putting the disconnect switch where the factory put it, clearly somebody here is wrong, incidentally, my eagle also has the disconnect and it's factory installed.


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 06, 2010, 10:08:31 AM
You can run a LOT of current through a switch for brief periods -- the rating on a switch is the OPERATING current, meaning how much it will make or break.

Actually, heavy-duty battery switches should carry both kinds of ratings, which is why I said that you'd need a switch with a "non-breaking rating" sufficient to carry the starter current.

You are correct that a switch which could make or break that much current would be much different.

Again, if your coach builder put the starter across a switch from the batteries, that switch is probably properly rated for starting current, or at least we would hope that the coach builder used the right switch.  But that does not mean that the switch used in the OP's air-start coach is so rated.  Also, as Bob wrote earlier, older coaches can have all manner of "amateur" wiring modifications, and disconnects that have been installed by other than the coach builder might not be properly rated.  I have personally seen cases where switches have been replaced by sometimes well-meaning but usually rushed technicians with items that did not meet the required specifications.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: BG6 on June 06, 2010, 10:19:42 AM

If you have a Vanner it should be connected on the battery side of any disconnect switches, not on the opposite side.  And, yes, this does mean that the Vanner will be running all the time and that it's idle current will be depleting the batteries.

The problem with doing it otherwise, though, is that the Vanner needs to have the ground connection be the last one made and the first one broken.  Changing the connection or disconnection sequence can fry the equalizer.


Sounds like it would be a good idea to put a switch into the Vanner ground line, labeled "Disconnect FIRST, Connect LAST"

Looking at the MCI schematics, I have to sit corrected -- all Vanner connections are on the battery side of the main disconnect.  That means for long-term parking, it will need to be disconnected.  I'm thinking of a SPST for the ground and a DPST to cut the other two, so it would be:

1)  Cut Vanner ground
2)  Cut Vanner hots
3)  Main disconnect

Then the other way around when it's time to roll.



Title: Re: What Gage cable Battery to Starter
Post by: Gary '79 5C on June 06, 2010, 10:31:25 AM
Good Points brought up for discussion,

I like the master sw killing everything for two reasons, One the batt's are then protected from any drains etc.etc.

Second, God forbid any of us get a engine fire, I would try to shut off the master on my way to the back.

Have a great day.


Title: Re: What Gage cable Battery to Starter
Post by: bobofthenorth on June 06, 2010, 10:44:05 AM
It has been a very interesting discussion and I have to agree with Gary, I like the idea of everything being clearly and absolutely cut off when I throw the disco.  Pretty well everything we do is a compromise and it is good to know what the trade offs are.  I personally wouldn't have thought of this one.  Sean raised a good point and I understand the risk but I still think the risk of a battery drain is several orders of magnitude higher than the risk of destroying an alternator.  That, in my mind anyway, justifies the "risk" that I am taking.  I don't know much about risk theory but it is the product of cost times probability that matters.  Looking at cost or probability alone is not adequate.  We dealt with a lot of older equipment over the years and I know for a fact that battery drains were a huge cost that could easily be controlled by the addition of cut off switches.  It took us a while to figure that out but once we had it figured the first thing we did whenever we added some antique to our fleet was to add a battery shut off.


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 06, 2010, 10:53:36 AM
I guess if a person felt the urge they could also wire a welder into the kitchen circuit, what I'm asking is, are the companies that manufacture buses all wiring them wrong by putting the disconnect switch where the factory put it, clearly somebody here is wrong, incidentally, my eagle also has the disconnect and it's factory installed.


Cody, the world is not that black and white, where someone has to be right and someone else has to be wrong in every instance.

What I said was that, for our purposes, where the coach builder put the switch may not be the "preferred" location, which does not make them "wrong."

Again, there are competing objectives.  For fleet vehicles such as seated coaches, I am sure there is a cost advantage to having the disconnects ahead of the alternator (and starter).  For example, service technicians can simply open the disconnects before working near these parts of the engine, whereas with them directly connected it will first be necessary to disconnect the battery ground before working near these items.

I was taught to always disconnect the battery ground before working around starters and alternators anyway, regardless of what switches may or may not be present.  And I would expect that for most of us here, the extra few minutes to properly disconnect and reconnect batteries before working on those items is probably not an undue burden.   For most of us, disconnect switches serve mostly to protect batteries from discharge due to phantom loads, and secondly to facilitate working on electrical components elsewhere in the coach -- how many times, really, are you swinging a wrench near the starter?

OTOH, for fleets, where mechanics may do this very thing dozens or hundreds of times in a week, saving the extra 2-3 minutes it takes to physically disconnect the batteries would be a good reason to wire it that way.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: luvrbus on June 06, 2010, 10:58:17 AM
I can not speak about any other bus on a Eagle it is like Len describes a cut off for each battery and the switches are rated for 1200 amps intermittent service and 300 amp continuous service for each switch maybe a overkill but I never saw one fail yet have seen a bunch of lost handles lol


good luck


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 06, 2010, 11:07:15 AM
Sounds like it would be a good idea to put a switch into the Vanner ground line, labeled "Disconnect FIRST, Connect LAST"
...
That means for long-term parking, it will need to be disconnected.  I'm thinking of a SPST for the ground and a DPST to cut the other two, so it would be:

1)  Cut Vanner ground
2)  Cut Vanner hots
3)  Main disconnect

Then the other way around when it's time to roll.


You know, we thought long and hard about this when we redid the bus, and decided to just hard-wire the Vanner.  So long as the batteries are already equalized, the idle current is so minimal as to be almost irrelevant.  If the batteries are unequal for any reason, you want the Vanner to be doing its job.  And, lastly, if you hook up any kind of trickle charger to top the batteries up during storage, you'll want the Vanner in the circuit.

If you store long enough, the batteries' self-discharge rate will cause you to have to top them up periodically anyway, whether that's by starting the bus, or using a charger.  The Vanner does not really decrease the period for this all that much.

JMO and FWIW.

If you do decide to use switches to disconnect the Vanner in storage, then, yes, that's the right way to do it, or, alternatively, you can get (for a price) sequentially broken/made multi-pole manual switches.  Just remember to use switches with the proper ratings -- some of those Vanners go up to 100 amps, which is a pretty big switch (one of the reasons we decided against it).

Quote
Looking at the MCI schematics, I have to sit corrected -- all Vanner connections are on the battery side of the main disconnect.


That makes more sense.  I was surprised when you said MCI had wired it the other way, because I know Vanner will not stand behind the units that way, and MCI was an OEM customer.

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: BG6 on June 06, 2010, 12:16:46 PM
Sounds like it would be a good idea to put a switch into the Vanner ground line, labeled "Disconnect FIRST, Connect LAST"
...
That means for long-term parking, it will need to be disconnected.  I'm thinking of a SPST for the ground and a DPST to cut the other two, so it would be:

1)  Cut Vanner ground
2)  Cut Vanner hots
3)  Main disconnect

Then the other way around when it's time to roll.

You know, we thought long and hard about this when we redid the bus, and decided to just hard-wire the Vanner.  So long as the batteries are already equalized, the idle current is so minimal as to be almost irrelevant.  If the batteries are unequal for any reason, you want the Vanner to be doing its job.  And, lastly, if you hook up any kind of trickle charger to top the batteries up during storage, you'll want the Vanner in the circuit.

If you store long enough, the batteries' self-discharge rate will cause you to have to top them up periodically anyway, whether that's by starting the bus, or using a charger.  The Vanner does not really decrease the period for this all that much.

What is the idle current on the Vanner?  Any more than half an amp can cause long-term problems on a coach which isn't run much.

Quote
If you do decide to use switches to disconnect the Vanner in storage, then, yes, that's the right way to do it, or, alternatively, you can get (for a price) sequentially broken/made multi-pole manual switches.  Just remember to use switches with the proper ratings -- some of those Vanners go up to 100 amps, which is a pretty big switch (one of the reasons we decided against it).

If you check around, you can find manually-operable circuit breakers up to 140 amps in the $25 range, and I've bought them by the boxful from wrecking yards for a couple of bucks each (go where they put the rice rockets and other too-damn-loud-stereo cars).



Title: Re: What Gage cable Battery to Starter
Post by: cody on June 06, 2010, 12:45:04 PM
I don't recall saying 'they" were wrong.  I believe that was another poster other than me.  My fear would be that somebody unfamilier with coach wiring or wiring in general would take the gospel and look and find out that their coach appeared to be wired differently and not knowing that the gospel may in fact be wrong proceed to rewire their factory coach to the new schematic and get hurt or damage their equipment, it doesn't matter who the gospel is according too.  My point being that there are thousands of coaches on the road from several different companies and I still cannot believe they are all wired wrong because one individual has declared that to be the case.  Many far more experienced engineers would have picked up on the mistake long ago if it had been in fact an error.  I do agree that some people change their wiring aftermarket and that could be wrong but when factory schematics agree with how the switch is wired in, I'll take that as my gospel.


Title: Re: What Gage cable Battery to Starter
Post by: luvrbus on June 06, 2010, 12:49:34 PM
Guys we were a big help to Art he knows how to wire everything except his Eagle LOL


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 06, 2010, 04:04:24 PM
What is the idle current on the Vanner?  Any more than half an amp can cause long-term problems on a coach which isn't run much.


17 milliamps (0.017 amp)

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: BG6 on June 06, 2010, 04:27:01 PM
What is the idle current on the Vanner? 

17 milliamps (0.017 amp)


Yeah, that's pretty much equivalent to built-in voltage loss.

Speaking of which, I'm looking for a used Vanner . . .


Title: Re: What Gage cable Battery to Starter
Post by: Lee Bradley on June 08, 2010, 09:59:41 AM
As Sean said most Neoplans, mine is a Colorado built Neoplan. I am installing my leveling system with 24 volt air valves and needed 24 volts to check their operation and the easiest 24 volt source is the start batteries. Because of this discussion, I checked my disconnect switch. The starter and alternator are connected to the switched post with the batteries on the other post. The disconnect also has a small spring loaded switch to power the regulator, it is spring loaded to power so a failure will be no power to the regulator. Something to remember if the charging system stops charging. The Vanner is hard wired to the batteries.


Title: Re: What Gage cable Battery to Starter
Post by: Sean on June 08, 2010, 11:56:06 AM
I probably should have mentioned it in my first post on the subject, and of course Brian pointed it out in relation to race cars, but this is the other "safe" way to implement a disconnect switch between the batteries and the alternator.

Disconnect switches, such as the one Lee has, are available with a second set of contacts to control the alternator, and these switches have a sequential break/make sequence.  The alternator contacts are broken first and made last, so that the alternator is never running when the batteries are disconnected.

The alternator contacts can either be in the field wiring (between regulator and alternator) or in the regulator power (between "ignition" and the regulator).  The latter is preferred, when possible, to keep the regulator from working at exciting an alternator that is no longer in the circuit.

Of course, none of that is applicable if you have a "one-wire" type alternator, in which case, once again, my recommendation is to stick with wiring the alternator on the battery side of the switch.  Fortunately, most of us have externally regulated alternators.

That said, few manufacturers likely go to the extra expense of the fancy switch with the extra contacts like Lee has.  I'd be curious to know if any of the Prevost or MCI folks have such a switch installed from the factory?

-Sean
http://OurOdyssey.BlogSpot.com (http://OurOdyssey.BlogSpot.com)


Title: Re: What Gage cable Battery to Starter
Post by: muddog16 on June 09, 2010, 05:03:11 PM
I love these threads!  LOL........more is learned in threads like these than any other!