Warning signs the 12V battery is on life support

How old is your battery when you replaced it?


iPhone ?

 

very interesting. the last item totally makes sense. the first 4 not really, but i believe you. I totally agree, there should be some warning for the 12V battery. there is one for the 3V one!

 

Pick up a multimeter and maybe an electronic load tester, no more mystery.

 

What voltage should a Voltmeter display for a healthy battery?
I just checked mine, and it's a steady 12.75V after four years and 85K miles. I checked from the jump start plug, with the car fully off.

 

That's problematic. A healthy battery not being charged reads at or above 12v, but being under 12v (by a little) isn't odd.

The problem is that the Prius uses the big battery once things start up. This conceals the strength of the 12v battery.

In a normal vehicle, the sound of the starter straining or a long crank cycle to start is a sign of a weak battery. Likewise, if your headlights dim when the engine drops to idle, that means the 12v is weak.

Does the Prius headlamps work with the car off? That might be a way to see if the 12v is weak as I'd expect anything operating while the car is in OFF mode is running off the 12v battery.

 

That's very good. There's a chart of voltage here:

The 12volt Side of Life (Part 1)

Only thing, a battery showing decent voltage can still be getting on, somewhat weakened. The load testers (like the Solar BA5) test Cranking Amps electronically, are good for this. Most battery retailers will have a similar but professional level tester.

One other thing, a freshly recharged battery will show voltage higher than reality for a day or so, best to drive it a bit, let it rest overnight, then test.

 

battery should last 7 or 8 years, unless you've drained it, or don't drive much.

 

i don't think interstate makes a prius battery?

but anywho, we don't know your location of course. but i think interstate likes selling batteries. since my batteries have always lasted 8-10 years, in all my vehicles, i can only assume the ones not lasting as long have been abused in some way. but i could be wrong.

 

FYI:
Car and Truck Automotive Batteries - Buy a Vehicle Battery for Cars or Trucks | Interstate Batteries - Automotive / Truck 2013 Toyota Prius

 

thanks! looks just like an optima.

 

Click on the pic in the link and even more so:


For me the "view Canadian pricing" link is not much help: leads to a page with parts numbers, none of which correlate to the above. SaskBattery worked for me up here, free shipping and they charge GST only, no PST.

GST = Goods and Services Tax
PST = Provincial Sales Tax

(both are 6% in BC at least)

BC = British Columbia

 

At 4.5 years & 18,000 miles, my 2012 Prius c could not be started. The first Geico roadside assistance guy gave up on jumping my car and left me stranded (no kidding, he left in a nasty huff after trying to pull off the cover under the back seat). Another guy came out, and we still couldn't get it started; but he had a tow truck and took me to my dealer. My dealer replaced the 12V battery for $276 (plus $125 labor). 9 months later (and only 1,000 extra miles), my car again won't start (it's obviously the battery). I've now moved clear across the country, so I'm not able to return to the dealer who replaced my 12V battery. It's most unpleasant when the battery fails unexpectedly (my problems were not the result of leaving lights on), because a jump won't work. I can't believe I've had this twice in a year, I now see the great risk in having a hybrid car when they're still not well understood.

 

I wouldn't blame this on the battery, necessarily. You said the first/original battery lasted 54 months and 18,000 miles (333 miles/month) and next one 9 months and 1,000 miles (111 miles month). These are extremely low numbers, in my experience. I think you need to put your 12V on a maintainer/tender based on your low miles driven.

 

Ok, so my battery will be six years old soon. I sometimes put in on the charger, but haven't done that in months..

It's has been below 0 F in the past two weeks. The car is being driven every day, and sometimes every second. I've been unable to check the battery level because the damn hood is frozen.
The car starts just fine, but I know the battery is low on charge because it runs rough for some 40 minutes until it gets charged and then goes to EV and smoothens out. It runs high RPM even at the stop light and its annoying. Once the battery has enough juice, the car runs as its suppose to.

 

One problem with the Prius battery is it isn't a common battery. To my knowledge you can't get one from Walmart yet. At the first sign of strangeness on my 2008 I ordered a yellow top Optima on eBay and replaced it. The Optima was a lot cheaper than the OEM Toyota battery, and it was still fine at the ten year mark when I traded it in in November. The Optima was at that time the only manufacturer that had the place for the hose that vents the battery. I don't know if anyone else has made a replacement battery yet for the Gen 2.
At that time the Optima was a lot cheaper that the OEM Toyota, I just checked and it is not anymore.

 

Funny, I've noticed this particular behavior in my 2010 the last (very cold) couple of days.

You're doing a huge amount of speculation there, though, about why the car's control software is behaving that particular way. (Necessary disclaimer: the software is Toyota proprietary, I've never read it, but then neither have most other PriusChatters who write very positively about why it does a particular thing. The best information most of us have is what the manuals tell about what it does and why.)

There are some things we do know, though. First off (because this thread is about the 12 volt battery), it's worth remembering that the condition of that battery, whatever it is, becomes immaterial to the rest of the car as soon as the READY light comes on. The 12 volt bus, at that point, becomes powered by the car's DC/DC converter, and will have a stable voltage right around 13.8 to the low 14s. The only way a bad 12 volt battery could affect anything else voltage-sensitive in the car after that point would be if it is shorted, and drawing so much current that it loads down the DC/DC converter output. That's worth talking about as a possible scenario, even if only to remember how easy it would be to detect: watch the system voltage when in READY. I do (it's one of the values on my ScanGauge), and my voltage never wavers from the high-13-to-low-14 normal output range, so at least in my case, loading by a super-bad 12 volt battery is not among the possible explanations.

There is another battery in the car, though, and I suspect it might play a part in the cold-weather high revs we're seeing. The traction battery is monitored for temperature, and the car treats it extra delicately whenever the temperature is too high or too low. In Gen 1, there was even a turtle-shaped light on the dash to show you when that was happening. Later gens have no turtle light, but they still watch the battery temperature.

In my driving the last couple of days, I've noticed both: (a) more engine noise when moving off from a stop (because the engine is doing more of the work than usual, confirmed by the ScanGauge showing lower current from the traction battery than would be normal in milder weather), and (b) higher revving when slowing into a stop, lasting for some moments after stopping before coming back down to a normal idle speed. It sounds a lot like the B-mode use of the engine to burn off excess regen energy that the battery controller doesn't want to shove into the battery, and this is at least supported (I don't say confirmed) by the ScanGauge showing no more than 20 or 25 amps into the battery, during a deceleration/stop that would normally show 60 to 80. And this strange behavior happens less, further into a longer drive, which could well be a consequence, not of the battery's state of charge, but of it reaching a more suitable temperature.

I have not set one of the ScanGauge displays to show traction battery temperature, which would be a natural way to test whether that possible explanation has legs. But there is enough information already to strongly suggest looking in other directions than the 12 volt battery.

-Chap