Dead Battery

It's possible that the first time you drained it you left something on, a door ajar, or something - it does happen on occasion. And after a battery has been killed once, it's more likely to die (due to chemical reactions inside the battery) again.

If you have an amp meter handy, I'd give it a test when the car is off and see how much current is being drawn - it should be a very low number (for some reason 0.02 mA is sticking in my head). If it's high, then you have a problem somewhere and a Toyota tech should check it out.

If you do a search on here, you'll find the options for replacement batteries (don't know where the list is off hand, sorry)... they can be a little expensive (more so than for a regular car).

 

<div class='quotetop'>QUOTE(eagle33199 @ Nov 7 2006, 07:33 AM) [snapback]344965[/snapback]</div>

I think this is true if the battery is run completely down to nothing several times but I don't think Rick's was anywhere near that far discharged due to his comment about the map light being faintly on.

Unless you have a clamp-on Ampmeter the battery will need to be disconnected and an Ampmeter put in series with it to do that kind of test. But I think it is the best way to test it with this kind of problem because it will give you a good indication of rather it is a battery problem or something in the car. If the battery is OK you need to find out if something in the car is staying on when it shouldn't or if the charging circuits are bad. You could also take the battery out and put it on a charger, charge it up completely then just let it set over night out of the car then check the Voltage and see if it runs down on it's own.

If the car is still under warranty I would be tempted to take it in and let them test it, they have the proper equipment. The question is do they know how to interpret the results of their test and will they try to rip you off for a new battery even if you don't need one.

The battery should definitely last more than two years but they do fail prematurely sometimes. If it were mine I would go for a long drive (an hour or so) to charge it up and see if it goes down again..

 

<div class='quotetop'>QUOTE(Rick Grahn @ Nov 7 2006, 08:24 AM) [snapback]345006[/snapback]</div>

I didn't know about holding the shifter in neutral, guess I'll have to try that. Anyway it won't help charge the 12 Volt battery. It doesn't charge directly from the ICE, it charges from the HV battery through an inverter and a rectifier, when the car is turned on. There is no alternator on the ICE as there is on other cars.

If your car is still under warranty I would have Toyota check the charging circuits before buying a new battery. Being only two years old the odds are your battery is still good.

 

<div class='quotetop'>QUOTE(Rick Grahn @ Nov 8 2006, 07:21 AM) [snapback]345373[/snapback]</div>

As long as it starts some of the time.

Since the 12V (accessory, lead acid) battery charges from the traction (hybrid, NiMH) battery, I wonder if it is sufficient to keep the car turned on and in park. You could even lock the doors with the mechanical key and keep it turned on (as long as you feel safe that nobody will break a window and drive it away). The engine will run to charge the NiMH as needed. I'd guess that the NiMH will keep charging the lead acid battery as long as the hybrid system is turned on (pressing the Power button with a foot on the brake).

I've had car batteries fail like this before. I've never gotten more than a couple more months' use out of them, and even that has been unreliable. Of course those had to start the engine. Autozone will recharge and/or load test your 12V battery for free. If you are able to determine that a defect in the car is causing an electrical leak that drained the battery twice, I'd ask Toyota for a new 12V battery. If they replace the battery, I'd ask for a refund on its replacement if they later find an electrical problem that drained it. All that said, it's most likely that a light or some other power drain was left on.

 

<div class='quotetop'>QUOTE(theorist @ Nov 8 2006, 08:32 AM) [snapback]345412[/snapback]</div>

Yes, you could recharge it like that, but then you're mileage would be horrible much better to take an unplanned trip to visit that random family member who lives in the next state over.

 

A boost basically gives the battery enough charge to get the computers started so that the main relay can close and connect the hybrid battery, but the battery is still technically "dead" and unless it is actually recharged, will not stay "alive" for very long.

Now once the hybrid battery is connected, the converter will supply a 13.8 V nominal voltage and provide some charge to the 12V battery, but because this voltage is tightly controlled, the actual rate of charge coming from the converter to the 12V battery is actually *very* low; based on experience, it takes over 2 days of normal driving (about 2 hours a day: 50 min commute to/from home+ 10 minutes to/from lunch+5/10 minute to/from errands, with commensurate lengths of time in between drives sitting in the parking lot or the garage) to recharge a "low" 12V battery to a reasonable state.

This is *unlike* a conventional vehicle with an alternator, where the battery and the regulator function in tandem to regulate system voltage and by driving at high revs, you can actually push a *lot* of current to the battery without any noticable impact to the rest of the electrical system. Thus, for a Prius, if your 12V battery dies, your best bet is to get out the 120VAC charger and hook it up to the battery overnight, don't rely on the converter and the hybrid system being able to recharge the 12V battery to any significant extent from just a brief drive.

 

<div class='quotetop'>QUOTE(eagle33199 @ Nov 8 2006, 09:57 AM) [snapback]345432[/snapback]</div>

As long as we're concerned about our MPG and not the amount of gasoline consumed or greenhouse gases emitted. If you're really concerned about any of these, take the battery to Autozone and let them charge it for free or use your own plug in charger.

I expect that the engine would only run a small fraction of the time that the hybrid system is left on (after it warms up.)

 

FYI, if you have JBL, you may have a bad amp with a draw in it. There's a TSB on this issue; it causes a dead battery.

Nate

 

<div class='quotetop'>QUOTE(Rick Grahn @ Nov 7 2006, 10:03 AM) [snapback]344939[/snapback]</div>

This weekend I just had our battery drain and we had no lights on in the car. However...

My wife is in education so she brings home class materials and supplies in the trunk. She developed the habit of leaving the trunk open over night so she could unload to work at home and reload in the mornings. With our Honda Civic and with the trunk light in the off position, the lamp would never be on, so this was never a problem. We assumed that this would be the case with the Prius, although the "door open" indicator on the dash does stay on, it's just a little LED.

Well, I measured the 12V battery current using my Fluke multimeter and DC current clamp to check for any high leakage current that may have caused the battery to drain. Would you believe that even with the trunk light switched off, a current draw of ~0.4 - 0.5 amps exists. In fact, if you do turn the light switch on, it only draws maybe 0.2A more. So there must be some ECU function that stays alive due to having the hatch open on the Prius and eventually drained our battery over the weekend.

glen

 

<div class='quotetop'>QUOTE(Tideland Prius @ Nov 9 2006, 01:05 AM) [snapback]346115[/snapback]</div>

It could be that the hatch latch is still being powered but I don't know why that would be necessary once it's been released.

No other lights are on except the Door Open Warning light on the instrument panel. This is easy to verify in a completely dark garage!

gk

 

First thing I'd do is to make sure that the the cables, etc. are tight and in good working order.

Second thing I'd do is put the battery under a load test to see if it's any good or not. It sounds to me like it *was* drawn down pretty low, since even just a teensy map light emitted just "a faint yellow glow." So, yes, the odds of it being damaged by that are probably pretty good.

I'd doubt that 0.5 amps draw over the course of an evening would be enough to kill the battery, unless it was in pretty bad shape to begin with.

My best guess would be some sort of failure within the battery itself; I wouldn't be comfortable with its 'deciding' to work again.

Could leave you stranded when you least expect.

 

<div class='quotetop'>QUOTE(glenk @ Nov 8 2006, 10:48 PM) [snapback]346110[/snapback]</div>

Glen I'm going to have to ask that you recheck that. Using a less sophisticated current shunt, I have found parasitic current drain of about 40 milliamps in the NHW11 Prius and others reported about 30 ma in the new model, but I don't know if that is with the SKS switched on or off. This load is very briefly higher upon making the connection (a few meter fuses have been lost from that) but that's where it settles down. If anyone's Prius draws much more than that, something needs fixing. The OEM 12 v battery is spec-ed at about 30 amp hours so one can estimate how long it can (ideally) keep the car alive.

 

<div class='quotetop'>QUOTE(tochatihu @ Nov 11 2006, 11:27 AM) [snapback]347462[/snapback]</div>

I thought Glen measured the 400-500 mA current with the hatch open. I assumed that it was normal with the hatch closed.