DDEC phantom load?

[Iceni John]

Help!

This evening I found that one of my two 8D starting batteries is completely dead.   There is a mystery small-gauge wire surreptitiously attached to this battery's power cable, connected to what look like connectors that feed a loom running toward the engine.   Is this wire providing constant power to the DDEC II module, even when I turn off the Cole-Hersee battery master switch?   Can I disconnect this wire, or does DDEC always need power?   I don't want to disconnect it without checking with the DDEC gurus here first.   

Thanks, John   

[rv_safetyman]

John, I don't know all that much about DDEC II, but on later DDEC engines, the constant power draw is very little.  Unfortunately, this past year our bus sat a lot more than we wanted and the start batteries always stayed up to an acceptable level ( 3 ea 31 size).

I am lost as to how you would have only one battery down.  They should be wired in parallel and both batteries should be at the same level.  I suspect you have one bad battery.

Later DDEC engines (and I think DDEC II) have memories that probably last a long time without power.  I think most of the settable values are non-volatile.  Think about all the engines in wrecking yards that sit for months and still fire right up with the proper settings.

That said, I leave my DDEC IV powered up.

Jim

[Iceni John]

Jim,

This mystery wire is connected to only one battery's cable, before the Cole-Hersee main switch.   Even though I'm turning everything off at the main switch whenever I'm parked, this wire is constantly live, feeding I don't know what.   Both batteries are Dekas dated December 2008, and I'm fastidious at checking their electrolyte levels.   The full factory electrical schematic doesn't show any such wire, but a supplementary schematic for DDEC shows what appears to be a constant feed.   ABC Bus thinks that earlier DDECs like mine should draw at most a milliamp or two, assuming it needs constant power at all.   I have on each battery a SunForce 1.8 watt "battery maintainer" solar panel that should prevent batteries from self-discharging over a long time, but this is evidently not enough to keep up with the draw on this mystery wire.   If I disconnect this wire, and if it supplied the DDEC, would the DDEC throw out codes or otherwise malfunction?

The other possibility is that the dead battery simply died of natural causes unrelated to this mystery wire.   I will be changing over to Group 31 starting batteries soon, so I don't want phantom loads on a lower-capacity battery like a 31.

Thanks, John

[Cary and Don]

This happens on our Neoplan also.  It has ate two batteries now on the 12 volt side.  It hasn't been driven,  but we start it up while it's being stored.  Even with the disconnect off,  that 12 volt side goes down.

Don and Cary
1973 05 Eagle
GMC 4107
Neoplan AN340

[Ace]

I have the ddec 2 in our h3 and when we first got it w encountered the same issues. Screw contacting Prevost AND Featherlite coach, they both advised me to install a marine onboard 24v charger. The wire you mention is also on mine but mine has an inline fuse. It was told to me, don't know if its true but, that wire actually powers the ecm. The drain comes from what would be a light in a radio or monitor of some sort our even a bare wire that the previous owner may have left. Yes I found done of those too.
Before learning about the wire, I switched the wire from one battery to and that second battery went dead. Shut putting it back where it was, I installed new batteries and the charger only then my batteries would stay charged and read to start at any time there was still a drain. What I found was lights in the bay staying ON after the does were shut.
Now that all lights go off in the bays, charger stays on when parked, the batteries stay charged and have been in for a couple years now!
Also there are wires hard wired to the batteries that are fused that power the injectors. At least on mine there are and yours may be different!

[belfert]

I have enough parasitic loads on my bus that I need to keep a 24 volt Battery Tender in use all the time, or the batteries go dead in days or weeks.  The DDEC is one thing that sucks power constantly.  I have a Vanner Equalizer so the batteries discharge evenly.  I measured the parasitic draw at about 1.9 amps once.  Dina choose not to run the 12 volt stuff through the battery disconnect and I haven't decided if I should add a disconnect on the 12 volt or not.

I always plug in the battery charger the moment I get home now.  I learned my lesson the hard way last year when I didn't plug in the charger for a week or two after getting home and killed the batteries dead. 

[Ace]

Wow guess I should have spell checked first as using swype on my phone puts some words where they don't belong or what they mean! Sorry!

[Iceni John]

Thanks for your ideas.   My problem is that I cannot keep a charger on the batteries  -  my bus is in an RV yard without available power, so I absolutely have to minimize or eliminate any phantom loads.   The 1.8 W solar panels are not intended to compensate for any draw off the batteries, merely to maintain them against their own natural self-discharge.   One of my work colleagues had a 1992 Neoplan with a 8V92, and he used to completely turn off the batteries whenever it was parked;  he thinks his DDEC was completely switched off when he turned off the main battery switch.   I'm guessing his 1992 had DDEC II like my bus.   I know the later DDECs, like IV and V, have an internal battery, but I think the earlier ones don't.

Oh well, unless someone tells me I cannot deprive my DDEC of power, I'll disconnect that wire today.   If the bus doesn't start, I've got Good Sam to take it to ABC Bus just down the road from here.   Knowing my luck, I'll probably end up screwing up something expensive or irrepairable!   Darn, I wish I didn't have anything electronic to contend with  -  MUI would be fine with me.

John