Battery drained for no apparent reason

Perhaps () Toyota is following this thread and will be inspired to
catch up

 

The prius has that too. From what I understand, the OP had the door position switch overridden to be always on. It was an user problem.

 

No you can leave any light in the car on. The headlights do have the battery protection function. But not the ones inside the car

 

If this happened in a non-hybrid vehicle, it should not have been an issue as traditional 12 volt batteries have lots of cold-cranking amps and one dome light would not have made a difference - even if left on unnoticed for a day.

The Prius 12 volt battery does not need cold-cranking amps (no engine starting with that battery). All it has to do is run computers and the traditional 12 volt systems (lights). That is why it is more susceptible to drain-downs.

 

The 12V battery is small to save weight. Yes, it runs down alot faster than a conventionally-sized starting battery.

The hybrid battery is 200 VDC. You have to step that voltage down to the 13.6 that a "12V" battery runs at. The Prius has such a charger, but you can't just leave it charging all the time, because that would run down the hydrid battery, which is very bad for it.

That charger only comes on when the car is in READY, so the engine can run (to top it back off) if it has to. You need enough 12V power to boot the computers to get into ready. If not, then you're stuffed.

However, they should apply the 20-minute time-out to all interior lights (with the doors closed), even if they're in the manual-on state.

I hate to say it, but GM does it right on this one, and Toyota doesn't.

 

You are incorrect. If you have cabin lights in the door switch position and leave doors ajar, the lights will go off after some time. Only when the switch is left in always on position it will not work. I guess Toyota thought there were legitimate reasons to have illumination in cabin with ignition off and doors closed.

The part that should have been done is LED lighting. But it would cost $$. Good mod to do ourself.

 

My Prius is 1.5 years old and one morning I went to start the car but the battery was too weak. It was strong enough to run some of the acessories but too low to run the engine. It really freaked the rest of the car out. I jumped the car, and it started ,but the right side of my dispaly was black. I could see how fast I was going but I could not see any of the trip information. I looked for a light left on but nothing. I drove it to work with the display blank and tried restarting it. The car fired right up but still no display. At the end of the day I got in, the car started right up and the display was back as if nothing happened. When I took it to the Dealer they changed the battery(12v) and everything has been fine since. This was my first issue in the 1.5 years.

 

Need some advice:

i just reacently installed my fog lights yesterday, during the installation i had the door ajar for about 2-3 hours, would 2 -3 hours drain my battery where the car won't start? Everytime i try and start the car, i would press the brake and push the power button and wait for the ready to pop up, now i just see all the light lit up. Have i drain the battery to a point that it's still have enough juice to power the computer but not start the car? Right now i been starting the car using the accessory mode to start the car, is this bad, if done alot?

Thanks in advance.

 

3 hours may have been enough, especially if you had the radio or head/fog lights on as well. The car should recharge the 12V battery while in ready mode. check the voltage on the battery (should be ~13.2V), if it's low get the car in Ready and check again, the voltage should increase up while charging. if it's not charging, go to the dealer.

 

It has been cold (below 0 degrees Celsius) and I had not driven my 2010 Prius in 3-4 days. I was able to open the car and when I pushed the starter button the lights came on but not the ready light and I could not hear the motor. I did not know what to do so I switched the car off and only a triangular caution light stayed on. I tried starting again but the starter button LED was orange in colour and the vehicle would not start, so I called roadside assistance who tried to boost it as per the manual and then at the 12 volt battery with no response (no lights). I then had it towed as per manual instructions with dolly on the front tires and a back lift tow truck to the Toyota dealer.

I have a terrible feeling that the Prius 12 volt battery and electrical systems are useless in cold weather like -15 or -20 degrees Celsius. Does Toyota have anything to say about this issue regarding poor 12 volt battery? It would appear to be an achiles heel for hybrids and later for plug-in hybrids. The first question people ask me about the Prius is how well does the battery work in the cold? they are referring to the main HV battery, but it does give the Prius a bad reputation.

 

This issue seems to be cropping up rather frequently with the generation 3 cars. Some possibilities are:

1. Gen3 owners leave lights on and doors open more frequently than Gen2 owners. Not likely, especially if these lights are suppose to turn themselves off after 20 min. Has anyone tested this?

2. Maybe Toyota has received some defective 12V batteries that have internal problems causing them to discharge after a few days. Possible but someone needs to do some tests on a battery that goes dead. Measure it's capacity in Ampere hours and see how long it should last.

3. It could be that there is some kind of "sneak circuit" that draws to much current when the car is inactive. This is quite possible but it would also require some testing.

4. When these batteries are drawn down to the point that the car will no longer enter the Ready Mode it probably takes some time for them to recharge. The 12V charging system only supplies a limited amount of current and a short trip or two will most likely not recharge the battery sufficiently, it then goes dead again. I think this has happened to several who have reported this problem.

There are undoubtedly other possibilities but until we can do some definitive testing I don't think it will be solved. Of course maybe Toyota is busy solving the problem and will release a TSB any day now, but don't hold your breath.

 

Hi there,

Well I have to say that I'm having the exact same issue (second time now) as detailed by Sakamura. I'm just a little north of Vancouver. It's cold, but still above 0ºC. The car is a Prius 2010 purchased in Seattle in October of last year.

Having read this entire thread, I'd have to agree completely with the comments thus far, and having that feeling that you don't if your car is going to start the next time you need to use it, just doesn't cut it. It's a brand new car, for crying out loud and we're in 2011!

No real solution that I can see so far, apart from getting some help from a neighbor to jump start the car, despite having been extra careful with all doors and lights, and any other way the car's 12v battery could have died.

Aaarggg!

 

If they weren't able to jump start it, then it doesn't sound like the electronics/battery to me. There are emergency starting instructions in the manual (Set parking brake; Press the Power switch to get to Accessory mode; Push and hold Power for 15 seconds while depressing the brake pedal) that might've done the trick, though. Of course, I tend to think that if they designed the car to not start in the condition it was in (whatever that may be - it sounds like it probably saved a code that can get scanned out and tell you what the problem is), then it's probably better to not start it, unless you have particularly good reason to do so.

 

Parasitic Drain on the Prius 12 Volt Battery

I was using my clip-on DC ammeter to measure parasitic battery drain on my 2010 and was surprised to find that the drain does not go away if a door is not completely closed.

If you leave the rear hatch wide open there is a continuous battery drain of about 0.50 amps on the 12 volt battery that does not go away after 20 minutes when the interior dome lights go out automatically. The drain is present even if the dome and rear hatch lights are manually shut off with the interior switches. Note that dropping the hatch lid over the catch (but not fully closed) is sufficient to turn off the dome light in my 2010 Prius and the parasitic drain will disappear.

If a single driver or passenger front door is left ajar, there will be a 0.9 amp drain on the 12 volt battery that will remain continuous regardless of whether the dome lights automatically time out or are manually shut off with the overhead switch. Part of the 0.9 amp drain goes to powering the interior light at the base of either front door. These door lights never shut off with the dome lights.

If a rear door is left ajar, the continuous drain on the 12 volt battery is 0.5 amps which is the same parasitic current draw as the rear hatch. The drain is less than an open front door since the rear doors do not have an interior lamp.

If one assumes that the amp-hour capacity of the Prius 12 volt battery is in the order of 25 to 30 AH, leaving a front door ajar will drain a fully charged battery to the point of "no start" in 24 hours. Leaving a rear door open will take a little less than 2 days.

It should be noted that the placement of the 12 volt battery in the Prius makes it difficult to recharge in cold weather. The Prius battery is stuck in a cold corner of the rear fender which might as well be a refrigerator in cold weather. Lead-acid batteries do not have nearly as good a charge acceptance when cold as in warm weather. If you run down this battery, don't drive the car for a few hours and expect it to be recharged. You need to use a battery charger and let it charge overnight at a minimum. The charger can be connected at the fuse center under the hood.

Note that the drain with the dome lights ON is about 2.5 amps which disappears after 20 minutes when the dome lights automatically shut off.

As a side note, I have left my Scan Gauge II plugged into the OBD2 port for weeks now for the purpose of tracking engine coolant temperature after adding lower grill blocking. After connecting my ammeter under the hood on the main (white) large gauge positive feed to the fuse center, I was surprised to see that there was a cyclic drain of 0.25 amps for 8.2 seconds followed by an 8.2 sec drain at 1.0 amps. This cycle repeated over a period of several hours. The car had been shut off in the garage over 15 hours prior to these measurements. The Scan Gauge display was off which is normal. This drain continued regardless of whether the doors were locked or unlocked. The key fob was not within range of the car.

When I disconnected the Scan Gauge II from the OBD2 port, the battery drain went away and the overall parasitic drain dropped to 0.02 amps which is probably normal. I have monitored the parasitic current draw over the last two weeks, and have not been able to duplicate the problem with the Scan Gauge. One thing is for sure, if the Scan Gauge display is illuminated and the Prius is not in Ready mode, the cyclic load on the battery is occurring. I am not going to leave my Scan Gauge plugged into the port if my car is to sit unused for an extended period of time.

 

Re: Parasitic Drain on the Prius 12 Volt Battery

Wow ! Great detective work. Thank you.

 

Im in Montreal and I do actually live with this same problem!!!!!!!! How annoying is that!

An no No light are left on the car......... This morning i had to jump start the car and i had no right side of the hybrid system screen on!

couple hour later, the car still wouldnt start!

I hope they will change the battery and will give me a bloc heater....but its 300$

 

Re: Parasitic Drain on the Prius 12 Volt Battery

 

Is this a sporadic issue or a real problem?

I keep my car in the garage, so it routinely starts up at about 35-40 degrees F when its really bad outside.

Next week I'm going to be leaving it outside for 8 hours when its like 25 degrees out. Do I have to sweat this? The car gets driven 76 miles round trip daily so the battery should be charged routinely and with enough time (I'd imagine).

2010 Prius built in August of this year.