Electrical Gremlin Stealing Chassis Battery Power :>(

[BornFree_n_Now]

We recently noticed we have apparently picked up a parasitic drain on our chassis battery ~~ At first we thought it was the battery ~~ the Optima we have been using, for the past two years, or so, had a bit lower than OEM CCA, so we replaced with the correct size with more than the original specifications ~~ At any rate, after we got the new battery all charged up, we noticed that we still have a considerable drop in available cranking power after the coach sits for 3 days, and after a week, we are dead. The alternator is putting out what it should, the battery is new. and there are no lights on, etc. Before we start digging into the system, has anyone else had a similar experience, and/or any helpful advice? We have a 2002 RSB (e450), with the gas V10.

[whemme]

Larry & Sharon,

Does your battery still go dead if you shut off your large rotary battery shut off switch?

[BornFree_n_Now]

Larry & Sharon,

Does your battery still go dead if you shut off your large rotary battery shut off switch?

Bill:

Thank you for your reply ~~ have not noticed a difference, irrespective of rotary switch position, and really thought that the chassis battery should be separate from the house battery circuit, except for charging when the engine is running ~~ I guess if the isolation circuit was defective in some fashion (really thought it is either on or off), then a drain on the house circuit could impact the chassis battery, as well as the house batteries ~~ In our case, however, the house batteries are fine, when the chassis battery is going dead or dead.

[whemme]

Larry and Sharon,

My mistake! I thought you were talking about your coach batteries going dead but I see that it is your chassis battery. Well obviously the coach battery rotary cutoff switch will not and should not have any effect on your chassis battery.

Evidently your Optima chassis battery is suffering some sort of parasitic drain on it or the battery itself has a partial internal short in it draining off its charge.

I would suggest you disconnect either the + cable or - cable from your chassis battery after it is once charged up and then reconnect it 3 days later and see if the battery is dead again by trying to start your coach. If it starts OK, then the problem must be a parasitic drain some where in the system. If it does not start or is very weak, I would say your battery is defective.

[tomdclark]

Larry,

I noticed on my 2005 E450 that the accessories remained powered for X minutes OR until I opened the door after I turned off the ignition and removed the key. (I haven't determined just what X is.) I suppose this is supposed to be a feature, but my first reaction was that it was potentially a good source of battery drain.

I don't know if you have the same feature but, if you do, you may want to check and make sure it isn't failing somehow.

[BornFree_n_Now]

Tom:

Thank you for the response ~~ yes, that delay is also in our unit, and caught my attention as well ~~ it does seem like that circuit is either on or off, and since we never see even a dim light after it goes off I think it is not the culprit ~~ I have fully recharged our new battery, and am now watching the rate of decay closely, to see what we have at the end of a week or so ~~ thanx again for the thought

[George Boley]

Larry,
You haven't been messing with the AM/FM radio have you? If so I have the answer. The problem today with all the electronics, we can no longer apply yesterday's diagnostic methods. Everything is tied into something else. I remember hearing about a case where a fellow could not start his Ford truck, it was like the battery was dead, but it was really OK. To make a long story short he had a short in his 5th wheel tail lights which blew the brake light fuse. This circuit also actuated the starter when you put your foot on the brake to start the engine. Years ago there was no relationship between these two items. George B

[BornFree_n_Now]

George:

Thank you for the response ~~ In answer to your question, there were no physical changes to anything on the coach prior to the initial drain occurring ~~ and while we don’t put a lot of miles on the unit each week, it is always driven at least 25 miles, or so, which, previous to this issue, always kept us charged enough to avoid problems ~~ If the new battery had not done the same thing the first one did, I would have assumed that it was at fault. As I indicated in my last post, we have now completely charged the battery and are watching it closely to note the rate of discharge ~~ Thank you again for your response.

[George Boley]

Larry'
Good we have eliminated one possibilty. A couple of more thoughts. A bad alternator in some cases, can actually REMOVE stored energy from a good battery. It happened to me in Oregon. But if the battery does not stay up during no run times, that possibility is also eliminated. Just because the battery is new does not mean it is good, I've had that happen as well. When ever a new part is bad you always question your diagnosis. A good volt/ohmn meter will tell you how many milli amps are being drawn out of your battery with the engine off and key out. The draw should be below 0.05 milli amps. Hope I have helped and not confused, I try to keep things as simple as possible. George B

[Mike Jean Bandfield]

George must have been in a hurry today. I think he meant to say either .05A or 50mA. If it is not start pulling fuses until it drops to normal or zero. That tells you the circuit with the drain. Put the fuse back in and start disconnecting devices or shrotening that circuit until it again drops to normal or zero. Keep doing this until you isolate the wire segment or device causing the excess load. This can get a bit tricky sometimes. A bad diode can back feed a circuit causing it to be on even when it appears to be turned off.

Mike

[BornFree_n_Now]

George & Mike:

Thank you both for the advice, it is what I was hoping to avoid, although I somehow knew it is where I would end up. Anyway, a-searching I will go, to see what I can find ~~ Thanx again for the thoughts.

[George Boley]

Mike, You are right. Thanks for setting me straight George B