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Author Topic: Battery question  (Read 2880 times)
Ace
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« on: September 07, 2006, 03:50:41 PM »

Today I went to start the bus, that is, after I exchanged two of the four 12v start batteries. There must be a problem somewhere as two batteries stay up and two are being drained after about 3 days. On the battery connections there are 2 small wires with 1 eyelet that go to one of the batteries that stay up. On these wires, there are two in-line fues holders with each holding a flat 15 amp clear blue fuse. With the batteries connected as they should be, and then hooking up this small eyelet, there is a VERY small arc. I decided to leave this pair of wires with the fuses OFF the positive post while attempting to start the bus. NO start! The motor turns over but doesn't start. After trying that twice, I decided to attach the eyelet. The bus started immediately. Could this be wires to the fuel pump? I'm not sure if this bus has an electric fuel pump or a mechanical fuel pump! Anyone have an idea? Anyway, somewhere in the system there is a very slow drain even with both the 12v and 24v  battery disconnect switchs turned OFF! I thought they eliminated all power to everything but maybe I'm wrong!

Thanks
Ace
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belfert
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« Reply #1 on: September 07, 2006, 04:23:55 PM »

My Webasto heater timer and such maintain power even with the disconnect turned off.  I suppose they want the Webasto to work for preheating even with the master switch off.  I also get a spark when connecting batteries with everything including disconnect off.  My batteries seem to stay up if I remember to turn the disconnect off even with the small loads.

Batteries usually should be replaced as a set or the older batteries may draw down the new ones.

Brian Elfert
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Sammy
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« Reply #2 on: September 07, 2006, 04:39:57 PM »

If your engine has electronic controls (DDEC), they could be the power wires to the DDEC ECM.  Cool
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Ace
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« Reply #3 on: September 07, 2006, 05:55:34 PM »

The OLD batteries show fully charged  and themeter moves very little when a load test is applied. The same thing with the 2 new batteries but if I check them in a couple 3 days from now without starting the bus, and having the main disconnects OFF for that period, the 2 inside NEW TODAY batteries will show weak if not completely dead when the same load test is applied! It only takes it about 3-5 days for the batteries to be weak enough to not start the bus! The 1 year old interstate batts never go down a bit. They are only 700 CCA's where as the new ones are 950 CCA's! Would this make a difference?

Ace
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NJT5047
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« Reply #4 on: September 07, 2006, 06:21:43 PM »

Ace, you have a battery drain.  Something's pulling them down.  Get a digital ammeter with a shunt and see which leads have a load.   If you have a Vanner, that may be the culprit...or as Sammy said, the DDEC wiring may be causing the problem.   The DDEC is probably 12V and would be tapped on a 12V post.   You can disconnect a Vanner without causing any problems to see if that solves the problem.  When disconnecting a Vanner equalizer, always unhook the ground lead first.  This assumes you have some sort of an Equalizer between your batts.
I suggest using a shunt to rule out large loads....you can use the low scale in series for a small drain without frying the meter.  Something's drawing your batts down.   
Finding the drain should be simple once you figure out which circuit has the load. 
A normally working Vanner will spark when the ground is hooked up.   However, a faulty Vanner will run batteries down. 
You are describing, from the failure to start, the DDEC leads.  My DDEC does not spark when re-attached to the battery. 
If you don't have access to a good quality ammeter, remove the leads from the center tap and see if the batts still go down.  You may have a tap off the hot side of the disconnect switch?  Does anything have power in bus chassis when the disconnects are off?  Can you easily access the backside of the disconnects?  If so see if there are any extra wires on the hot side of the disconnect.
Are your cranking batts powering anything else in the coach? 
Or if all else fails, unhook the battery ground.  That should solve the problem...albeit a temporary fix.  Unhooking the ground and checking the batteries a few days later would rule out the batteries.  You may have a new bad battery.  We get'em all the time.

JR

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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

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« Reply #5 on: September 07, 2006, 06:28:40 PM »

Its really pretty simple Ace. If there is an arc when you remove one or more of the small wires, then you have what is normally called a parasitic load. You must trace down where this goes to and get this load connected to a bus that is turned off when you turn the main disconnect off.
 
I had one and it was an electric clock. Would drain my batteries in about a week. Could be a light in a compartment, could be the excitation to the alternator.

You must absolutely get rid of that spark. Make yourself up a test light 12/24 volt and connect between the small lead and the battery terminal. It will be illuminated as long as there is something draining the battery. When you find the load and get it disconnected, the test light will go out.
Richard
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« Reply #6 on: September 07, 2006, 06:35:29 PM »

Ace, my batteries are set up the same as yours.

   My coach is a DDEC ll, and has the small wires hooked to the center tap on the batteries, it is the 12V to the DDECll. Yours is probably a DDEC lll or lV, and probably powered by 12V. That is why the bus wouldn't start.

Since only 2 batteries are going down, it sounds like you have a 12V load on them somewhere unless you have a Vanner (or other brand) equalizer.

Try pulling one of the small fuses and starting the bus, if it won't start put the fuse back in and pull the other fuse and try to start the bus, if it won't start put it back in. Both fuses go to the DDEC.

If the bus will run with one of the fuses out then leave it out and see if the batteries go down.  

  Have you added anything to the coach lately that would cause the battery drainage.

  Usually, when I have a problem it is the last thing I worked on.

I'm curious as to the outcome of your problem, since I'm having the same problem.
I leave my batteries unhooked because I only start the coach about every 2 or 3 months and still have some old, not used, coach wiring to remove.

I'm hoping that once I get all of the unused stuff removed my problem will disappear.

HTH  Ed.
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Ace
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« Reply #7 on: September 07, 2006, 06:59:55 PM »

My bus has a Vanner but I'm not sure it goes to the batteries. It's on the complete opposite side of the bus and very small!

I will try removing one fuse at a time to see if it will start and go from there! That's fairly easy!

Another question is, I see a lot of replies referring to CENTER TAP, where is this at?  Undecided

Ace
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NJT5047
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« Reply #8 on: September 07, 2006, 07:24:17 PM »

A 12V center tap is point between the batteries that will supply 12V.   Often headlight backups are wired here as are DDEC units and some 12V accessories such as radio equipment. 
If you have four cranking batteries and a 24V system, you'll have two 12V batts wired in parallel, which will make 12V, and they will be wired in series with another set of two 12V batteries.  The center lead that connects the series batteries will be 12V (12V potential).  The above 'splaining assumes you are not using 6 V batteries...but the center tap would still provide 12V...but all batts would be in series and the concept remains the same.
A Vanner isn't a large item...about 12" long, 10" wide, by 4" deep.   That would be a 50 or 60A size.  Vanner makes various product other than equalizers.  You may have another accessory of some sort.
It should remain connected to the batteries ahead of disconnect switches.  Improperly disconnecting them may damage the units.  If your "box" you refer to has 3 terminals...one ground, one 12V, and one 24V terminal, It's probably an equalizer.  It could be anywhere a 10 or 12G wire could be run from the batts.   You can verify whether it's wired directly to the batts by checking for 12V at the 12V post, and 24V at the 24V post.  Use a chassis  ground or the ground stud on the Vanner.  If they have read 12V and 24V respectively with the battery disconects off, the Vanner is hooked up direct to the batteries...which is as it should be.  Still the Vanner may be your problem.  If you find this situation, unhook the ground, 12v and 24 leads from the Vanner and monitor the batts for discharge.  If no discharge...you problem is found.
When unhooking these leads, be sure that they are protected from shorting to ground.  That'll fry something. 
By removing one fuse at a time, you will isolate what does what...DDEC etc.   The trans will have a fuse  that should display some sort of CEL and perhaps a "Do Not Shift" light.  I'm not familier with what engine and trans you have.
JR 
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
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« Reply #9 on: September 08, 2006, 08:21:09 AM »

Ace - Email me your fax # and Monday I'll send you the info from DaBook
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« Reply #10 on: September 08, 2006, 08:44:06 AM »

Ace you still haven't answered the question of wether or not yer bus is a DDEC controled engine but, from your description of the wires and what happens I'd say the 2 little fused wires are the 12volt power to the fuel injection (1) for each bank! I've had some problems in the past with those getting corroded and losing contact creating the crank but no start syndrome, then pull the fuse stick it back in and VROOM! So that is what I believe those wirse are to ! But I don't believe they are whats draining your batteries my Setra had been "HACKED" by a previous owner and now has no battery shut off at all! I can let it sit 3 at least 3 weeks and it starts fine! Now we had a dead spell a little while back and it sat a month to the day and wouldn't start (but since then I found out one of the 2 8D's was bad! I replaced it and it's back to normal! BK  Grin
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belfert
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« Reply #11 on: September 08, 2006, 09:14:01 AM »

I'm almost certain Ace has DDEC as I don't think the H3s haven't been out long enough to have a mechanical engine.

Brian Elfert
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NJT5047
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« Reply #12 on: September 08, 2006, 09:32:15 AM »

Ace doesn't have a non-start issue...he disconnected the 12V taps and then the bus wouldn't start..probably disconnected the DDEC power leads?  Hooked the wires back up and it fired right up. 
As has been stated, his coach isn't an MUI per the year model.
His primary complaint is battery discharge over a period of less than a week. 
JR
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
belfert
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« Reply #13 on: September 08, 2006, 10:28:01 AM »

Ace doesn't have a non-start issue...he disconnected the 12V taps and then the bus wouldn't start..probably disconnected the DDEC power leads?  Hooked the wires back up and it fired right up. 
As has been stated, his coach isn't an MUI per the year model.
His primary complaint is battery discharge over a period of less than a week. 

I think some are asking about DDEC as they figure that could draw down the batteries.  The DDEC is not the issue if this just started.

My Series 60 bus has some battery draw no matter if the disconnect is on or off, but the batteries seem to stay up IF I remember to tuirn off the disconnect.

Brian Elfert
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Sammy
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« Reply #14 on: September 08, 2006, 12:37:20 PM »

Hello all, only mentioned DDEC wiring for the no start problem Ace had.
Did not mean to imply it could be his draw on the batterys.
Sorry if it caused any confusion.
Sammy  Cool
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