12/24 Volt Bus Battery System???

[0533]

Pam and I are now out on the road for the summer. We are in Henderson Harbor Ny. at Association Island Rv Resort. All, mostly all as been great.

Until this trip we mostly only spent overnights maybe 2 nights in the coach at any one location. At Association Island, we are here for 5 nights.

In my Prevost handbook it says to turn off both the 12/24 volt switch in the engine compartment when spending more than one overnight, actually it says to turn them off even for one night. I have done so to follow the protocol but wonder exactly why.

Prevost says that if these batteries get run (drained) done (?????) while sitting that when you start up the bus it might either not start at all or when it does the 270 amp regulator will fry the batteries????

I have all new batteries and have had no problems of any kind. Question here is what power source can possibly drain down the batteries while the bus is not operating??? Also is there some type of alarm that would come on if the batteries were being run down by a source.

Also the house and Bus battery systems are separate???? Correct?? If so then what Bus 12 volt 24 volt items can drain down batteries when not in use, little stuff, clocks etc, or again is all of this separate from the bus 12/24 system??

Thanks,

Bruce

[Jon Wehrenberg]

Bruce, There is no harm in abiding by that recommendation. However, as we learned on this forum a short while back, turning off those switches is no guarantee it will prevent your batteries from draining over time.

Your chassis batteries theoretically have no current drain when you do not have the bus running, unless you do things like turn on the lights. The recommendation to turn off the switches appears to be prompted by two concerns. First the stated reason is to prevent current draw on the batteries. It will certainly do that, especially if it is possible for you to accidently turn on a current drawing device such as lights. I think this recommendation is especially aimed at seated coach operators. If a driver follows this advice it doesn't matter if any passengers left on the overhead lights or if there are TV monitors still turned on. When the switches are off so is the current draw.

The second reason is by turning off the switch there is a minimal chance of an electrical problem or fire in an unattended coach.

But you can easily monitor your coach and you can make sure you have not left the parking lights on or the light in the engine bay on. So you can assume your battery will remain fully charged for the week you will be at your location. Your assumption might be wrong. As we learned CB19, 20 and 21 on your vintage coach is powered directly from the battery, and it by passes the master disconnect switches. Under certain conditions those circuit breakers which are for the 12V DDEC and transmission computers may still have current passing through them, gradually draining the batteries. Shutting those circuits off may cause you to lose some codes stored in the computers. If you have not issues that is no big deal, but if you are on the way to DD to have some codes checked you do not want to trip those breakers to completely kill all power to your chassis.

So the issue is for you to decide. The current draw through those breakers BTW is not consistent. Sometimes you can park for months with the main switches turned off and still have plenty of starting power in your chassis batteries, and sometimes on the same coach with the same switches turned off there will be enough current drawn by the DDEC and transmission computers to pull the batteries down in a short period of time like a few weeks.

Confused?

I do not ever turn my switches off in the rear, but I also monitor the battery charge and kick on my chassis battery charger on those very rare occasions when I think they need to be brought up to a full charge. In the last four years with this coach that has been two or three times, usually because I have not moved the coach for several months. But if I did not have my coach 50 feet from me I think I would kill all switches.

[0533]

Thanks Jon for the comments.

I really did not want to turn off these switches if I could avoid doing so. I do or was locking the door using the air lock switch at night, this of course uses some energy I guess. I am now just locking it with the manual switch. I will turn the 12/24 back on and keep an eye on things.

Thanks,

Bruce

[Jerry Winchester]

Bruce,

I just turned the 12 and 24 volt switches off for the first time ever on this trip. But I did it to reset the computer or logic systems on the bus. Seems the new busses are like a rolling computer. If your crap goes bad, just turn the whole thing off and start over.

Sad thing is that it worked. Go figure.

But I don't regularly turn them off and won't again until I get the glitches.

[MangoMike]

JDUB's right.

If you call Marathon with a house electrical issue the very first thing they tell you is "reboot".

I've done it twice in the last year and a half with good results.

Mike