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partsman_ba
Administrator
United States
377 Posts |
 Posted - 09/12/2013 : 4:59:16 PM
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| Does 260mA sound like too high a parasitic draw on a 2012 (sorry, had wrong year initially) BB D3FE? That's as low as I could get it after shutting down the 2-way radio and DVR and closing the door to de-energize the brake interlock. We do have a GPS unit, but it should have been asleep at the point we were testing. |
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Tb4020
Senior Member
United States
82 Posts |
Posted - 09/13/2013 : 03:55:20 AM
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| Be sure that the master switch for the overhead flasher system is off, we have some that if that switch isn't turned off they'll be dead in five days. |
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partsman_ba
Administrator
United States
377 Posts |
Posted - 09/13/2013 : 08:14:47 AM
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Oregon law prohibits a master switch for 8-ways. We got some Visions equipped that way, as our dealer also serves S. Washington, and had to have the switches changed out.
My thinking is that, considering all the modules (ECM, TCM, ABS, Actia dash) and other electronics on these units, 260mA is about par for the course. Perhaps if we waited for everything to go to sleep that draw would drop? |
"Growing old is mandatory. Growing up is optional." |
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IBTMech
Top Member
USA
973 Posts |
Posted - 09/13/2013 : 5:57:22 PM
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| What is the voltage draw? That's the biggest factor. |
If it doesn't fit, FORCE it.
If it breaks, well, it needed replacing anyway.
Pullin' wrenches for 45 years. |
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partsman_ba
Administrator
United States
377 Posts |
Posted - 09/13/2013 : 10:59:57 PM
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| I'm not following you. Power draw is measured in amps - any circuit will draw as many volts as you put into it until it burns up. |
"Growing old is mandatory. Growing up is optional." |
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bluebirdvision
Top Member
USA
1081 Posts |
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bwest
Administrator
United States
3820 Posts |
Posted - 09/14/2013 : 06:16:13 AM
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quote:
Originally posted by bluebirdvision
The draw will drop once it goes to sleep.
That's what I was thinking. Maybe something's going on there. |
Bryan |
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IBTMech
Top Member
USA
973 Posts |
Posted - 09/14/2013 : 3:46:08 PM
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Anytime you diagnose a battery drain, the voltage of the drain is important. A full static voltage drain is considered major. A less than static voltage drain is considered minor.
Just curious. Sometimes even a digital clock will show up as a full voltage drain. |
If it doesn't fit, FORCE it.
If it breaks, well, it needed replacing anyway.
Pullin' wrenches for 45 years. |
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bluebirdvision
Top Member
USA
1081 Posts |
Posted - 09/14/2013 : 7:00:53 PM
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I had one mechanics throw an old basic Custom Radio (Black with a LCD you can hardly read) out of a 2000 or so BB TC into one of our EFs. It works okay, but with the key off the clock is always on. Believe it or not, over the weekend, that will drain the battery down low enough that the bus will hesitate to start. I start it once a week if its not on a run.
This goes to show you, something small can really drain the battery fast. |
Facebook Page: Blue Bird Corporation Fans
https://www.facebook.com/home.php?sk=group_212311114614&ap=1
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sambrutay
Advanced Member
United States
271 Posts |
Posted - 09/16/2013 : 04:33:22 AM
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Bruce |
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Brad Barker
Administrator
USA
874 Posts |
Posted - 09/16/2013 : 5:59:22 PM
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260mA is only .26 amps. My cut point is 1.0 amp. The new units we sell will normally draw .95 amps. Under normal driving conditions this should give you a good start after two weeks of sitting. If sitting for longer periods I recommend disconnecting the batteries.
And yes, I always check for parasitic draw initially with an ampmeter. If I find more than 1.0 amp draw I then go to the fuse panel and start checking circuits with a voltmeter. Those which are showing battery power I then check across the fuse with an ampmeter to measure exact circuit draw. |
Brad A. Barker |
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BJ Henderson
Advanced Member
USA
280 Posts |
Posted - 09/17/2013 : 05:36:58 AM
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Parasitic draw is usually measured in amps. It depends on the equipment and the amount of draw. If you have a bus with two group 31 batteries with a .02 amp draw, it probably won't be a problem unless the buses are shut down for three months and not moved. Increase this to a 1.0 Amp draw and you will know it over the weekend, Monday AM when the driver comes out of their home 50 miles from the shop, you will definetly want to find the problem before this takes place.
Get a current probe, inductive pickup type, and experiment as soon as you have time, if you don't know about parasitic draws.
The same rules apply as when trying to locate a short to ground. Catch the problem as it happens, isolate the circuits. With modern buses we are looking at now, training is a critical part of this business. Never ceases to amaze me how the school systems can find megabucks to do training for teachers, but none for mechanics and drivers. Our buses share the road with the administrators and their families. |
CMTT,CMAT,CMBT |
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Wolf0r
Top Member
USA
2181 Posts |
Posted - 09/18/2013 : 1:49:51 PM
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You guys are saying a 1.0 (one amp) draw is acceptable?  I have a small battery charger ammeter I use first, that way I don't blow my meter fuse. It's reads from 0-6 amps. 260mA is a little more than 1/4 amp right? I would say that is excessive. |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
Edited by - Wolf0r on 09/18/2013 1:57:56 PM |
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Matt Towns
Active Member
24 Posts |
Posted - 09/23/2013 : 09:29:03 AM
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HAVING draw problems with an 04 model blue bird 3800 t44e has a 4.3ma draw at batteries will kill both batteries overnight any ideas where to look basic bus no cameras with two way radio
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partsman_ba
Administrator
United States
377 Posts |
Posted - 09/23/2013 : 12:26:12 PM
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Matt, are you sure that isn't a 4.3 AMP draw? 4.3mA is about what one of my Seon DVRs draws when it is shut down. Two way radio draws about 1A in receive, 400mA in standby. Do you have a brake interlock? That'll draw 800mA if it's triggered.
Probably the best thing to do is to start pulling fuses/relays one at a time and watch your meter. You should be able to find the super-sucker circuit that way. |
"Growing old is mandatory. Growing up is optional." |
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Matt Towns
Active Member
24 Posts |
Posted - 09/23/2013 : 1:48:21 PM
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| not sure bout brake interlock with doors closed pulled all fuses out and the draw was down to a 2.7ma draw also have alternator unhooked to rule out bad diodes in it |
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partsman_ba
Administrator
United States
377 Posts |
Posted - 09/24/2013 : 09:51:04 AM
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| There is no way that kind of draw would drain your batteries - I mean, the LCD screen on a radio draws more than 4.3mA! Are you testing the drain by pulling one of your battery cables and hooking your ammeter inline with it? |
"Growing old is mandatory. Growing up is optional." |
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Matt Towns
Active Member
24 Posts |
Posted - 09/25/2013 : 11:07:42 AM
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YES I am with fully charged batteries and alt disconnected from monday midday til tues morning batteries were dead before i hooked it back up I rechecked the amp draw and it was at 2.8 mA all the bus would do tues morning was click bat voltage was 9.3 volt gonna double check and make sure one battery is not bleeding the other
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Wolf0r
Top Member
USA
2181 Posts |
Posted - 09/25/2013 : 11:19:14 AM
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| When in doubt do a cell check with a hydrometer. |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
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Matt Towns
Active Member
24 Posts |
Posted - 09/26/2013 : 06:39:54 AM
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| well load tested both batteries they are good now what gonna start disconnecting relays and see where it goes from there |
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partsman_ba
Administrator
United States
377 Posts |
Posted - 09/26/2013 : 08:35:03 AM
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| Matt, all I can think of is something is turning on and sucking those batteries flat that you're not seeing when you are testing (you know, buses never act up when you are working on them...) My buses will make it at least 24 hours with a 400mA draw (driver leaves the 2-way radio on.) Now, if that was a 2.8A draw you were seeing, that would be a horse of a different feather. |
"Growing old is mandatory. Growing up is optional." |
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Parasitic draw
