Engine battery is dead

I haven't used my RV since March due to Covid.  I'm getting it ready to use next weekend and discovered my engine battery is totally dead.  I know to run the generator from time to time, but didn't realize I had to also run the engine.  (The house batteries are fine - unit was plugged in entire time).  We jumped it 2 days ago and ran the engine for 20 minutes.  Today it is dead again.  What could be draining power from the engine battery?  I haven't used the radio and no lights were left on.  Is there something else?

Looks like it is time for a new battery!

Peg

Engine batteries in all vehicles made since the 80's (or maybe earlier) have parasitic drains on them, meaning even when parked there is some current being drawn from the battery.  In 6 months, that can draw the battery down badly.  Even 1/10th amp being drawn from a 400AmpH battery (typical vehicle battery is only about 100 amp hours) will totally drain that battery in 166 days.  And a 20 minute recharge from an idling engine is not nearly enough time to charge it up.   More like 24 hours or more using a 15 to 20 amp dedicated battery charger.   While draining a vehicle battery totally is very hard on the battery, it usually takes more than 1 full drain on it to wreck the battery.  I would give it a days charge and then see if it holds the charge.  It usually does.

Also, running the generator or even having the vehicle plugged in does NOT charge the engine battery.    You can add a device called a Trik-l-Start that will charge the engine battery at the same time the house batteries are being charged once the house batteries are mostly charged. I believe PC started making that a standard feature but don't know when.   But again, if you are not plugged in to shore power or running the generator often... that won't help much.  BTW... running the engine WILL charge the house batteries.. Just not the other way around.

The way I deal with those issues is to disconnect the negative cable on the engine battery whenever I park it in storage, even if it is only for a week or so.   I also disconnected the house batteries for winter storage.  In any case, what I use to disconnect the engine battery is a knife switch designed for that purpose.   This is an example of one:

https://www.wirthco.com/battery-doctor/battery-disconnect-switches/knife-blade-switches

Don

The way I deal with those issues is to disconnect the negative cable on the engine battery whenever I park it in storage, even if it is only for a week or so.   I also disconnected the house batteries for winter storage.  Don

Like Don, I disconnect the chassis battery for the very reasons discussed concerning parasitic power draining.  It is one of two ways to protect the chassis battery.  The other way would be to change that battery switch by the driver's left knee from spring-loaded temporary-on, to constant-on.  Then the chassis battery would be maintained with the house batteries.

Was parked 4 months hosting in a state park.  When time to leave, battery was dead.  Later found that light under step was always on.

Later found that light under step was always on.

That sounds familiar to me.  Those outside lights were on for me too but I caught it and got them to turn off.

As I recall, turning off the two front cab dome spot lights (reading lights) using the switches in the light fixture instead of turning them off using the headlight switch, keeps the step lights on by accident.

BUT I might have this wrong.  My memory on this is shady.  Maybe someone will confirm or correct me.

Thanks for all the responses.  I now have a new battery.  (I drive alone and husband didn't want to be called if I was stuck somewhere.  LOL).  Anyway, after he installed it, he measured the output.  1.5 amps seems like a lot of loss when nothing is on - or at least I can't find anything on.  Does that sound reasonable?  BTW, I'm still plugged into AC.

Peg

Your engine battery will not charge unless you hold the little switch on the left side of your steering wheel on. Replace it with and on-off switch and when parked for a while flip that switch on and charge the engine battery back up.

We will be in Brooksville at Silver Lake on 12/9.

I haven't used the radio and no lights were left on.  Is there something else?  Peg

1.5A does seem like a lot.  Just make sure the lights we mentioned in this thread are shut off, the ones that light up under the van doors.  I imagine it wouldn't hurt to turn the electric step off since it is powered by the chassis battery.  Power will still go to it, but maybe it draws less when turned off.

FWIW: I have to disconnect my van battery or it will suffer sitting idle for a month.  Maybe our rig draws 1.5A idle like yours does.  Our Saturn Sky isn't much different, but our Jeep Liberty and Nissan Altima can sit idle for a lot longer.

My last pickup truck developed a parasitic draw of almost half an amp.
It killed the two (it was a diesel) 12 volt starting batteries in about 2 weeks.
I found the problem by removing fuses one at a time with the ammeter connected until the draw stopped.
Turns out it was an issue with the instrument cluster.
So I just unplugged that fuse when not using the truck until I was able to find a place to repair the cluster.
Popped the rebuilt instrument cluster in and never had another battery problem.

Thanks for all the responses.  I now have a new battery.  (I drive alone and husband didn't want to be called if I was stuck somewhere.  LOL).  Anyway, after he installed it, he measured the output.  1.5 amps seems like a lot of loss when nothing is on - or at least I can't find anything on.  Does that sound reasonable?  BTW, I'm still plugged into AC.

Peg

Get a Trik-l-Start added, that will solve the issue.   Plugging in the RV does not charge the engine battery.   Replacing that switch to the left of the steering column is not a good idea as it removes the isolation between the two batteries (hous and coach) if you forget to turn it off. . 

Don

My last pickup truck developed a parasitic draw of almost half an amp.
It killed the two (it was a diesel) 12 volt starting batteries in about 2 weeks.
I found the problem by removing fuses one at a time with the ammeter connected until the draw stopped.
Turns out it was an issue with the instrument cluster.

2000's Chevy Blazer - Customer would have it go dead in 2 days at his house, sat in our shop several times overnight(s) and no draw...  until the night we parked it outside 'nose up' on an incline instead of inside on the flat concrete......BAM!  Dead battery. Customers driveway had uphill incline....

The weak spring on the passenger side sun visor would cause the visor to sag, and the 'makeup lights' by the mirror to come on. And drain the battery. But ONLY when the nose of the truck was uphill.  I chased over the course of WEEKS. Solved.


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A produce company with  Izuzu box trucks had one that the A/C compressor clutch would mysteriously lock up at night, overheat, and nearly caused a fire. 'Fixed' 3 times before it hit my bay.     I was warranty try #3 before the owner paid Izuzu to try.    

 LONG story short, it turned out that a piece of 'trash' metal in the A/C clutch control relay would shift and cause the A/C clutch to get power. Bump in the road, it would come back off. Operators never noticed the extra operation, as the cab stayed nice and cold.  Probably did it since new, wasnt that old.


BUT... if it happened that the debris would short out the relay, and then  NOT get that big bump before it was parked for the night, the clutch would keep heating until something gave way. The fuse would not blow, because the clutch wasnt pulling any more power than it should.... it was just keeping it on until the battery died or something overheated to failure.

Matter of fact, it the relay did short out, and you tilted the cab forward, it would dislodge the piece and by the time you tested the A/C clutch.. it was OFF??  You could check everything.... all works normal. You give it back...  And things would be fine until next time it went out for a days work, and the piece shifted.... The first mechanic was about to call a priest. 



Electronic diagnostics can be a mystery sometimes, and can take thinking and time.  Dont be frustrated if you dont find it first try. Keep notes, be logical, and you will find it. Even pro's can have a horrible time.

Just to add to the list:  once had a MH built on a dodge 350.  Over the key ignition there was a tiny green light to show the key hole when you open the door.  Battery kept dying.  Service determined that a bad door switch was not shutting off the little green light that was killing the battery.

Because Physics.
Trickle charger or battery disconnect.

We need the cab battery operational as the theft - tampering alarm is powered by that.  I've found that charging the battery for ~8 hours on a two amp charge -- about every three weeks -- is enough to keep it working.  As others have mentioned, any unexpected small current drain will be enough to cause problems.  We also carry a HB Battery Jump Starter.  And, as a last resort (since we do mostly dispersed camping) a package of aspirin in the glove box.   (A common trick from many years ago which still works).

And, as a last resort (since we do mostly dispersed camping) a package of aspirin in the glove box.   (A common trick from many years ago which still works).

I thought you were noting that the situation gives people a headache.  I googled "jump start aspirin" and now understand.  I learn something new every day.  Thanks for that tip.  I wonder if the aspirin contaminates the battery acid, requiring a new battery.