Weird Electronic issue after oil change

The car needs a new 12V battery. This has nothing to do with the engine oil change.

 

OTOH, it might be more than coincidence: how long did they have the car? Maybe they left some courtesy light on, due an ajar door? Something like that? Hard to prove though.

 

I agree 100% with Patrick's conclusion. I'd also like to recommend the Optima replacement, it's a much better battery for about the same cost, and you can even install it yourself if you have a few hand tools. There is a kit available that includes good instructions and all parts needed.

 

It is not normal for a 12V battery to wear out after only 2 years, given 44K miles on the odometer which implies the battery is getting plenty of charging time.

It is possible that the oil change place left the car IG-ON (where all instrument panel warning lights remain on) which places a very high drain on the 12V battery. Good luck proving that, however.

 

Typically these batteries last from 2-4 years, though depending on many factors the life can be shorter.

I would have suggested Mendel's idea that the battery could simply have been discharged if the Tech left the car in Ig-On mode or something, but because your wife has been driving the car, the battery would have had time to recharge by now.

What's happening is the voltage is sagging below 10v when the car is turned on, and the memory of things like the Fuel Gauge, Clock, MFD, etc, is being reset. Once the car goes ready, the DC/DC takes over and props the voltage back up to ~14, so all is good until you let the car sit and then try to turn it on again.

There are only a few other possibilities, one is a high parasitic load that's discharging the battery after letting the car sit, and the other would be a bad or high-resistance connection somewhere between the battery and the front of the car, which is causing this sag.

If you can find a competent place with a Midtronics battery tester, they will be able to confirm the bad battery. Some auto parts stores will test this for free, just be sure they use a midtronics-type transconductance tester. (older load types made for conventional car-starting batteries will falsely indicate the Prius battery is bad)

I'd bet you lunch though that it's your battery. The OEM 12v battery basically sucks, which is why I recommend the Optima as a replacement. It will last much longer.

 

Hi Peter. The life of the 12V battery is good if you keep it properly charged. But if you let it go fully flat then they often wont take a proper charge after that.

I agree that the workshop probably drained the battery, possibly even to the point where they had to jump started it. Again that's only a hunch and you probably cant prove it. We get a lot of stories here about people taking their Prius in for either mechanical or body work and while it's there the 12V battery getting drained, requiring a jump start.

You could try placing the existing battery on as charger and see if it comes back to life, but as I said they often don't take a charge so well after being completely drained.

 

On the problem Prius, try testing its voltage via http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html, esp. if the car has been left for 8+ hours or overnight.

It won't tell us if there's some parasitic loss causing a problem though...

 

That's to be expected. Your battery is weakened but not completely dead. Just don't leave the headlights on for 45 minutes while the car is off and it might be ok.

Whoops I spoke too soon.

Yes of course it's normal for the headlights to drain the battery. It might take more like 1.5 to 2 hours with a new battery but it could happen a lot faster with a battery that's already been weakened like this one has.

Yep. It points to a weak battery that has previously been flattened. But hang on, you already knew that!

Tell her to get over it. She has a weak 12V battery and if she replaces it (and doesn't leave the headlights on with with the new one) then problem solved. This is no big deal.

The warranty wont cover the 12V battery.

 

Even if the headlight switch was left in the on position, the exterior lights should automatically turn off if the driver's side door was opened and closed, after the car was made IG-OFF.

I would say that 1) the car still needs a new 12V battery, and 2) it would be good to connect a DMM set to read current, in series with the battery's negative cable to determine quiescent current draw when the car is IG-OFF with doors and hatch closed and locked.

 

Along the lines of what pEEf said before, if the battery was already weak, then you shut off the car, the battery voltage sags because the lights are on, and the body computer fails to auto shutoff the lights when the door opens. Does that make sense?

Put in your Optima asap. Your girlfriend will then start to love her car and you will be a superhero.

 

Here's the bottom line: The 12 Volt batteries in the Prius suck. Badly. If they're permitted to fully discharge even once, they won't hold a charge and you'll need a new one. It's one flaw in what is overall a really great car.

Buy the Optima and the conversion kit from elearnaid (Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 - 10), pop that bad boy in, and don't worry about it for years.

I bought my '07 new in April '07. Accidentally fully drained the 12V battery in Jan '08, had to replace (with Optima) and no worries since.

 

in a cold state like colorado, it is likely tha the battery could have been weak and pushed over the edge by the extreme cold.
normal size battery doenst like discharge and cold temps.
mini prius battery is even worse.
the prius is BAD at charging the aux battery, so it is very susceptible to being damaged from
1)weak charging cycle in prius
2)small size, no reserve
3)any accesory left on for 1/2 hour or more, lights, radio, door open,etc
4)cold temps

if it got damaged once it will never be the same, entirely possible that the shop did it, or your girl, or the previous owner.

 

1. What is your process to "turned off the Power"? How do you know the car is actually IG-OFF, after you have done this? Do you look at the combination meter (which contains the speedometer, odometer, fuel gauge, and shift indicator) and the MFD to see that all is dark?

2. What is your process to "popped out the key"?