There's a leak somewhere...

Jim Blackwood · September 20, 2021, 11:22:40 PM

I know there has to be, my volts are getting away.

I have a question. On my battery door it refers to there being both a 24v and a 12v cutoff switch. The 24v switch is pretty danged obvious, being that big stainless T handle but I'm just not seeing any 12v switch. Was that something optional?

Anyway, several new things here, and I'm showing a 2 amp parasitic load between the ground cable and the battery when the centertap cable is connected. It has a smaller cable coming off and going somewhere, I haven't tracked that down yet.

2 amps sounds about like what could be almost reasonable for a bus that is run every day. But it's enough to run down at least the left hand battery over a few days or weeks time. Does that sound like a fairly typical thing though? Is a 12v switch the answer, or is it reasonable to go after those parasites, root them out, and get rid of the worst offenders? I'd be curious to know what the most likely ones would be.

Jim

richard5933 · September 21, 2021, 03:49:32 AM

Can you just wire a latching relay on the 12v feed which is controlled by the 24v system? Shut off the 24v and everything goes off.

hogi6123 · September 21, 2021, 06:07:35 AM

Quote from: Jim Blackwood on September 20, 2021, 11:22:40 PM
I have a question. On my battery door it refers to there being both a 24v and a 12v cutoff switch. The 24v switch is pretty danged obvious, being that big stainless T handle but I'm just not seeing any 12v switch. Was that something optional?

On our 102DL3, the T handle had two sides switched at the same time, one disconnected the 12V and the other disconnected the 24V. There also was a battery equalizer mounted on a shelf above the batteries. I think usually the battery equalizer is wired directly to the batteries and the shutoff is connected after the equalizer.

My MC-9 main shutoff was for the 24V only. I added a separate disconnect switch for the 12V. The 12V in that bus pretty much just keeps the remaining headlight on if one burns out.

chessie4905 · September 21, 2021, 07:46:34 AM

don't know if you have an inverter, but they have a parasitic drain when off the pole. Not sure about equalizers. I'll have to check my manual when home.

luvrbus · September 21, 2021, 08:28:05 AM

Quote from: chessie4905 on September 21, 2021, 07:46:34 AM
don't know if you have an inverter, but they have a parasitic drain when off the pole. Not sure about equalizers. I'll have to check my manual when home.

The Vanner draws all the time, with 2 amps draw there is something else drawing but flooded batteries will discharge about a amp a day on there own,the DDEC draws all the time to which is not much and they have a clock battery that will go bad if you by pass that small draw

buswarrior · September 21, 2021, 10:23:03 AM

As noted, the 24 volt is on onide, 12 volt is on the other.

Every one of these buses has wires bypassing the battery switches, and a busnut who does not deal with these, gets to suffer.

PA system, a baggage bay light, the engine and transmission computers, are a few, for sure culprits.

I had no problems having the battery equalizer left attached, for months at a time in storage conditions, wired direct, outside the battery switch, but i had no parasites, and both batteries were healthy, and a matched pair. Others report issues?

Pay attention to the order in which you disconnect and connect the equalizer. The label on it, tells you.

Follow those subordinate battery cables, they go right to it.

Happy coaching!
Buswarrior

chessie4905 · September 21, 2021, 11:37:26 AM

most bus conversions, especially, have a phone hot line direct to batteries to bank loan dspartment.

Jim Blackwood · September 21, 2021, 06:42:07 PM

I got started on this today with mixed results. Pulled all the fuses there on the slanted board while measuring the voltage from the cable to the negative post and saw no change. Got inconsistent results on my current measurement so I've got to look more carefully at the meter.

On this bus I have the Vanner on that slanted board and whatever that other device is on the shelf above it with the three big heavy cables. Can't really see it well enough to read the label. Maybe with a mirror. I guess that would be the equalizer. What is special about the order in which the wires are connected? I guess since I've had the batteries out they've effectively been disconnected. But maybe it has to do with transferring charge between the batteries. I can see how you could get into trouble with that. All my wires are zip tied together so I guess I'll have to cut the zip ties and follow them out. Right now I'm keeping the battery disconnected to avoid discharging them. It's easy enough to hook them up when needed. For the 12v disconnect I'm sort of leaning towards the type used on race cars at the moment. Just as easy when throwing the big lever to twist that big red key also.

That business about the clock battery in the DDEC controller concerns me a bit. What is the symptom if it runs down, and how hard is it to change?

Oh, and BW, I'm making a determined effort to train myself to always insert the bay locking pins. The trick of course is to learn to remove them before trying to close the hatches.

Jim

hogi6123 · September 21, 2021, 07:33:51 PM

The large box on the shelf with 3 thick wires to it is the battery equalizer. Probably Vanner brand. On older models you had to disconnect the ground first (as I recall), for newer models the instructions say disconnect order doesn't matter. I don't know what the other Vanner device would be.

windtrader · September 21, 2021, 09:32:22 PM

Don't envy you searching for a phantom drain, no fun and hair-pulling exercise. The Vanner has a on/off switch. When all off, there is no drain. With it on but nothing drawing it still pulls about 50watts in idle.

The 24v-12v equalizer is connected directly to the battery but doesn't draw any current when not in use but since all the 12v stuff that is connected will draw current. check that circuit for any draw.

chessie4905 · September 22, 2021, 05:48:55 AM

How does a bad battery effect the equalizer when in standby state.
How about a bad diode in alternator?

Jim Blackwood · September 22, 2021, 10:13:42 AM

It's been raining for 3 days so I've been working inside the bus but Josh sent me a photo of the dual disconnect and my bus does have that. So it's just the cables that bypass the switch that I have to took at. I'm afraid there isn't much more I can do until it stops raining though.

I don't particularly mind working on the electrical. I've done a lot of that sort of thing. Hey, if I could troubleshoot B-52 nav systems I'm sure I can sort this out. Just bigger wires is all. More current of course. There were quite a few add-ons here, a significant part of which will go away and make room for yet more add-ons. For instance I just mounted the board for the leveler inverters. Three of them stacked on the wall behind the driver. The board is some of the marine plywood and sits edge-on in the side chair rail with a single screw attaching the top to the upper trim below the window. Dead easy to remove and reinstall that way. Has room at the forward end for the current limiters. By happy coincidence it seems my el-cheapo VFD units are wimpy enough to help protect the roll pins in the leveling jacks so the current limiters may be redundant but as much of a hassle as it is to replace the roll pins a belt/suspenders approach is fully justified. I found a limiter for model train controllers that may work but it looks like I will have to call the guy to find out.

Jim