Electrical System Shutdown after recharging and reconnecting battery

subaru
outback

#1

Our car seems to be running fine now but I’m trying to make sense of an electrical anomaly that shut down most of the car’s systems for a few minutes last night.

History: after 3-4 days of non-use we found our 2008 LL Bean Outback’s battery completely flat for the first time, ~ 100mv. (26mo. old Interstate battery, no heavy drains, no cold winters, charging system is healthy). The only item obviously amiss was the rear hatch being in the half-latch position which activates a door open warning light at the dash, but the rear dome light doesn’t come on unless the hatch is actively lifted against the half-latch and which did not appear to have occurred, though it’s plausible…

After recharging fully followed by sitting awhile the battery measured ~ 13.4vt. open circuit (it was isolated while charging to avoid fighting a potential drain). The negative terminal was reconnected and as the key was advanced the dash panel illuminated, bells chimed, and all seemed normal. Immediately upon turning to the starter position the electrical system went dead, no solenoid click, all dash lights off, door locks didn’t work, seemingly nothing. I took the key out and tried again, nothing. I did find the reading light over the windshield would turn on with its switch, but not the headlights, dash lights, nor cigar lighter socket (which comes on only with the key). The battery still measured > 13V and connections were tight. I was beginning to think about master links but tried the key once more and all came on and the car cranked and started normally. It held charge overnight and started properly again this morning. Previously the car has started normally after disconnecting the battery for a day or more while performing mechanical work.

Parasitic drain was measured after the battery was charged and before reconnecting the negative terminal. Initially ~ 500ma, it gradually dropped over about a half minute to ~ 125ma. While drainage seems somewhat higher than desired (and probably includes the hatch open warning light) it isn’t sufficient to drain a healthy battery over just a few days. Has anyone else experienced this or have an explanation?


#2

Correction, it’s a 2006 Outback (typo).


#3

Some strange data. A healthy battery (charger disconnected) should measure 12.4-12.6 volts, not >13 volts.

How did you measure parasitic drain with the battery disconnected? It should read zero with no battery.

Skipping that, I’d suspect the battery first. Yes, it’s relatively new, but they can have internal faults. Second, I’d check the cables between the battery and starter and ground for corrosion. Take off the cable and clean the male and female parts. Both ends of both cables.

Remember that if you totally discharge a battery, it is a bit damaged. Do that a few times and you need a new battery.

“Immediately upon turning to the starter position the electrical system went dead, no solenoid click, all dash lights off, door locks didn’t work, seemingly nothing” That indicates a bad battery or bad connections. The battery has enough power to handle the lights but not the starter.


#4

Yeah I think you either have a bad battery or connection. When you put a load on it, like with the starter, it arced and failed. Some things aren’t worth trying to understand but just need fixing.


#5

Most electrical turning off as you move the switch to Start may be normal - to keep the electrics safe and to let the starter motor take all the power it needs. A look at a schematic will tell you what is powered in each position of the ignition switch.

Bad battery or connections? That seems the most likely explanation. Starter solenoid becoming erratic? It happens. I don’t like coincidences, but you may have one. Do you have another battery you could swap in - or a good warrantee on this one, so you can get it replaced at a fair price?


#6

Useful points, thanks. Battery connections are clean and tight but I should check the other ends of the cables to be sure. Regarding connections, it occurs that an intermittent starter switch or a relay are possibilities, too. I was taken with how quickly and absolutely things went dead, no sound from solenoid or starter, dash lights and accessories completely off, etc. Nothing came on dimly, or groaned, etc.

The seemingly high terminal voltage is something of a puzzle, I may have measured too soon after charging, and should check my meter’s calibration - the engine did crank briskly both after charging and the next morning suggesting both a good charge and low resistances internally and to the starter.

Deep discharging does affect plate integrity of batteries not made for deep discharge service so I make it a habit to have the battery tested after an “event” and replace before the next winter if it has been deeply discharged, especially when over several days - cheap insurance.

Parasitic drain measured with a DVM in 10A mode connected in series between the negative battery post and its respective cable (before the cable was reattached) with nothing knowingly turned on, except the rear hatch was half latched activating the dash warning).

If the problem is mechanical my money is on the starter switch, but also wonder whether there is any way the computer could have done this. Will need to check a wiring diagram.


#7

Actually what happened to you may be perfectly normal. Some vehicles today monitor the battery voltage with the PCM. If the PCM detects the voltage dropping, it shuts down circuits in an attempt to extend the battery life. I found this feature in the owners manual of my 07 Silverado.

Now for some speculation, it may have taken a few minutes for the PCM to realize that the battery was OK and all circuits were restored, or the PCM had to reboot and that took a couple of minutes, or you have to turn the key from off to on two times and back to off before you can start it.

I kind of suspect the latter as my daughters 14 Toyota battery went dead and it did not engage the starter until the third try and just the other day, I put a new battery in the Silverado, same thing. But that was not in the owners manual so I’m just speculating. It may also be that if it is the computer had to reboot, it finished it’s reboot as I completed the third try.


#8

I had my diesel with two batteries in the garage parking at work. I went to start the car and I heard a snap sound and then nothing. Everything had been fine before. Jumpers did nothing. Went and bought two new batteries and everything was fine. What can it hurt?


#9

It could measure that much soon after disconnection from the battery charger. Eventually it would return to around 12.6 volts, but that might take several hours.


#10

You’re wrong about that

125 milliamps IS enough to drain a health battery over just a few days

So even though what I just told you may not solve your problem, you may want to file away the information I just gave you


#11

That’s a 3 amp-hours per day phantom drain. Batteries tend to hold a total charge of around 35 amp hours. So a 3 day drain of 9 amp hours wouldn’t totally drain a good, fully charged battery; but an iffy battery, or one that wasn’t fully charged, who knows. If the battery was fully charged and in good condition, there must have been a larger drain than than 125 ma.

I’ve experienced similar symptoms on my Corolla one time – cranking didn’t turn the engine & caused all the dash lights to go out or go dim – and that was caused by a poor connection between the battery posts and the connectors. Right after a battery is charged with a battery charger, especially if started from totally discharged, sometimes an effect called “surface charge” can take place, and that requires some time before it eventually goes away and allows the battery to properly function. That’s another idea.


#12

Good point.