Disabling SKS drained battery?

[lordbah]

I haven't been able to drive my 2008 for the past two months. I have been starting it once/week and letting it run for a couple of minutes, thinking that might help keep it charged. (Appears to be a bad assumption - lately I read no charge for the 12V unless you actually move?) It always started fine. Last week it became evident that I would not be able to drive for several more months. So I figured I'd better turn off the SKS. Went to the garage today and it would not start. I've actually never started it without SKS before but it's just key fob in slot, foot on brake, press Power, right? The light in the Power button illuminates for a split second and then goes dark. The brake lights are lit, and the dome light works, though it flickers. Pressing Power without the brake does nothing. I tried re-enabling SKS by pushing the switch, didn't help.

How is it possible that disabling SKS made things worse?

I don't suppose there's any recovery short of a jump? (which I guess I don't really have to worry about for several months anyway)

[Hope I covered everything. I had this all typed up once before, then the board suggested a bunch of similar threads, and I clicked on one - and it erased what I had typed, the browser back button came back to an empty box :-(]

[richard schumacher]

Disabling SKS does not kill the 12V battery. You were trying to do all the right things, but it sounds as though something killed the 12V battery anyway.

Do you have any aftermarket electronics installed? They sometimes cause excessive drain.

Do you *always* lock the car? Always locking is an easy way to prevent many common battery-killing events.

[Oh crap, I overlooked "run for a couple of minutes". Yes, that will eventually kill it. In a cold climate it needs at least 20 minutes of "READY" once a week to keep the 12V battery charged.]

[Patrick Wong]

Originally Posted by lordbah

...I have been starting it once/week and letting it run for a couple of minutes, thinking that might help keep it charged. (Appears to be a bad assumption - lately I read no charge for the 12V unless you actually move?) It always started fine. Last week it became evident that I would not be able to drive for several more months...
I don't suppose there's any recovery short of a jump? (which I guess I don't really have to worry about for several months anyway)

The problem is that you only let the car run "for a couple of minutes" at a time. That does not help to keep the battery charged. You must leave the car READY for at least 30 minutes, every two weeks. (Not necessary to actually drive the car as long as it is READY with the gear selector in P.)

Turning off SKS did not hurt your situation. However it did not help because the 12V auxiliary battery is close to being dead now.

If you do not charge the battery up in the very near future, then expect that when you finally get around to it, the battery will not hold a charge and will need to be replaced. (It may already be permanently dead.)

If you must store the Prius for an extended period, then it would be best to either disconnect the 12V auxiliary battery (once it has been fully charged) or else hook up a battery tender (if you have AC power nearby and can leave the tender plugged in.)

[lordbah]

I think my bad assumption was helped along by always seeing 6 bars on the MFD and thinking that if the 12V needed anything then the traction battery would feed it. Oops.

I'll get my friend to jump it after work tomorrow. If it starts, would say 60 minutes be enough to fully charge it (and how would I know? is this something ScanGauge can monitor?)? I will then get on the 30 minutes every 2 weeks schedule.

[Patrick Wong]

I think that several hours may be required to recharge the 12V auxiliary battery if it is near dead now. If you have access to a digital voltmeter then you can measure the voltage across the battery after leaving the car IG-OFF for an hour or more. 12.6V or better is considered fully-charged. When the car is READY you should measure 13.8V, which is due to the DC to DC converter providing higher voltage on the DC bus to power the Prius electronics and charge the battery.

To give you a data point to consider, I don't drive my HiHy very much and don't bother to use a battery tender, so the battery voltage is usually around 12.2V (which is considered around 50% state of charge.) I recently drove 500 miles one-way, and brought along a meter to keep an eye on the battery. After driving ~5 hours, I stopped for lunch. After lunch I measured the voltage and it was 12.4V. I measured the voltage again after arriving in the evening and letting time pass, and the battery was finally up to 12.6V. The voltage dropped back down the next morning, probably because of the very cold weather at my destination, lows around 10 degrees F.

[JimN]

IMO you don't need a jump, you need the battery charged. I'd hook it up to a charger & let it charge for a day or two. If it has been discharged too long then you'll have to buy a new battery.

[andyprius]

It's pretty cold in upstate NY right now and batteries don't like cold, you may have to or want to bring it to the dealer for a total 12VDC aux battery check. Sometimes after total discharge, they are never the same. I think right now the tow is gratis because you are still under warranty. More trouble, but safer. If you jumper yourself, shut off the other cars engine, it's not needed. AND absolutely do not connect backwards!

[lordbah]

I don't own a charger or a tender. If I can get the Prius started, will the ICE run non-stop for as long as it takes to get the 12V charged?

If I had it towed to the dealer, I think they'd expect me to drive it back home after they charged or replaced the battery, and I'm not allowed to do that (license revoked). I could call on friends or family but I'm already calling on them for so many other things that I don't want to add one more unless it's absolutely necessary.

[Patrick Wong]

Originally Posted by lordbah

I don't own a charger or a tender. If I can get the Prius started, will the ICE run non-stop for as long as it takes to get the 12V charged?

If I had it towed to the dealer, I think they'd expect me to drive it back home after they charged or replaced the battery, and I'm not allowed to do that (license revoked)...

OK, now I see why the car is being stored. No, the ICE will only run as needed to warm up, and this is unrelated to charging the 12V battery. In fact, Prius does not appear to monitor the state of charge of the 12V battery in any meaningful way.

I think that the purchase of a decent battery charger (and if needed, the necessary tools so that you can disconnect the negative battery cable while you are charging the battery) would be reasonable and help you to be self-sufficient in dealing with this problem.

[andyprius]

Originally Posted by Patrick Wong

OK, now I see why the car is being stored. No, the ICE will only run as needed to warm up, and this is unrelated to charging the 12V battery. In fact, Prius does not appear to monitor the state of charge of the 12V battery in any meaningful way.

I think that the purchase of a decent battery charger (and if needed, the necessary tools so that you can disconnect the negative battery cable while you are charging the battery) would be reasonable and help you to be self-sufficient in dealing with this problem.

I agree with Pats comments, however the dealer for good customer relations "might" drive you and the car back home. After that you could still have a problem it's really a great shame that this car isn't being driven. There are probably many responsible men or women that would love to take responsibility for the car AND act as your taxi-driver when you have to go some place. If you know of none go to the nearest charity or Salvation Army. You might make a new friend.