My turn for a new 12v battery?

I drove for about an hour and did a battery status check right after. Stayed at 11.9V - 12.0V while in accessory mode. I then watched it fall off the map after 30 seconds of watching it. Feel down to 9.9-9.8V.

 

Getting less than 12.0V under a small load (such as ACC) means the battery is dying. At less than 10V yours is nearly dead. Replace it now before you get stuck somewhere.

 

Called toyota dealer, they want about $190 for new battery and installation. Is this reasonable? How are the batteries they use? Should I buy my own and just pay for installation? Any input on this would be great. Thanks!

 

I agree that you definitely need a new battery given the voltage readings that you posted.

The Toyota dealer price for a 12V battery ranges from $130 to $160. Installation is extra. So $190 incl installation is a good price unless you can DIY.

 

ditto, ditto. regular voltage readings in the 9's means you are in great danger (if it has not already happened) of reverse polarity.

your battery is actually made of 6 cells at about 2.2 volts each. they rarely discharge at the same rate. so what has most likely happened is that one cell has reversed its polarity. after that happens once, the cell will tend to stay that way.

iow, its working against the other 5 cells. now it will swap back over to the correct polarity when fully charged, but all it need is to be discharged slightly to reverse again causing the 9 volt readings you are seeing.

when that happens, you need to change it or trickle charge it 24/7. the latter option is extremely inconvenient.

 

I plan on getting a new battery within a week. Is this current battery going to do any damage in the meantime? I was thinking optima yellowtop with the prius mod it comes with. Also, am I significantly losing fuel efficiency with this current battery?

 

nope. 12 volt battery does little to affect your mileage. it will drain the traction battery somewhat more for recharging but it will an insignificant amount

 

No damage. The danger is being stuck somewhere unable to start. Note that if a jump start is attempted and the polarity is reversed even for a moment it can do many hundreds of $ of damage.

 

Cool, so should i stick with the oem battery and have a toyota dealership install it or get the optima yellowtop and do it my self. It is around the same price for either.

 

Why not buy the battery from the Toyota dealer parts dept and install it yourself?

 

I have an interesting symptom in my '04 with NAV, and I suspect the 12V aux battery.

I've had my car for 3 years, and the battery is not best but it's been working ok. I was running a small inverter / LED lights when we were camping 3 weeks ago, I only ever drew it down to 12.1V. But I have measured some time ago that when I start the car, the current spike could bring it down to 10.5V.

After we came back the car went to the shop for paint work. After we got it back, we noticed the usual way we quickly start the car (jump in, brake, power button) would lead it to IGN-ON and not READY. If I then power down and do brake-power button, the car would go to ready. It's happening all the time now.

I wonder if the paint work and the high temp exposure has stressed the battery. Even though the system closes the main traction contactors, it may not be going to ready because the Aux batt voltage is failing or something.

I guess I've been living on borrowed time... I'll get some help to measure aux battery voltage during start.

 

From what I heard, the yellow top is a good battery, even better than OEM. I was just wondering if anyone had an opinion on the quality of the OEM 12V and a optima yellowtop. I wouldn't mind paying a lil more to install the yellowtop vs the OEM if its a quality battery that will last longer. Any opinions on this battery or non OEM 12V?

 

Judging from the design the Yellowtop ought to last longer, but I expect that too few have been in use in Priuses long enough for a comparison. Side-by-side the Toyota battery looks like a precision instrument and the Yellowtop looks kinda crude, like a typical USA car battery.

gwfung, note that the self-test given and referenced above includes a load test. No tools or second person are required.

 

I see and have done the voltage test on the display check. However, the lowest voltage I've seen previously occurs when you are trying to power up the computer. In order to measure that, I have to use a volt meter and observe the battery V just when the computers turn on.

So no one has seen the power-on behaviour I described?
It may be an issue of battery internal resistance, or current surge capability.

 

I went ahead and bought a SGII. It doesn't detect either the airbag code or the transmission power supply code. Not sure why that is. When I drive with it, says the voltage is 13.7. That seems okay I guess but the ACC voltage was bad to begin with, plus I already have a battery on its way.

 

The ScanGauge is a generic device intended to work with just about any OBD-II equipped vehicle. Prius has multiple ECUs, many of which can produce DTC. A generic OBD-II reader will ignore most of those DTC. You and other SG owners have proved that SG is similar to other generic code readers.

A reading of 13.7V when the car is READY means that the DC to DC converter within the inverter is working properly. This says nothing about the health of the 12V battery.

A voltage measurement when the car is first turned on, in the ACC-ON and IG-ON (not READY) positions will show you battery voltage under light load and slightly heavier load. If that voltage is low then this shows the battery is either discharged or (if it had adequate opportunity to be charged) needs to be replaced.

 

Your post helped me to finally figure out what was draining my traction battery every night. It would drain 3-6 points or so each night sometimes more the longer that it sat. I ordered a replacement last week and installed it on Saturday. The traction battery hasn't had any significant drain since then.

My experience is that my 12v battery would drain up to 10% of the traction battery depending on how long it sat. The car started fine and ran fine. The only sign was the traction battery drain and I'd never have noticed that if I didn't have a scangauge that I paid close attention to.

Given the significant drain that my 12v battery put on my traction battery I'd say that it does have an affect on mileage given that the ICE would have to run longer because of the low SOC on the traction battery. Probably not much but it does make some difference.

 

I just got through using the dealer to replace the 12v aux battery on my 2004 Salsa Red Pearl Prius. It had the original battery and 135 000 miles on it so the battery was well overdue to go. If only my son-in-law had mentioned that he had trouble starting the car 3 weeks ago and unlocking doors since then. I could have saved the tow job to the dealer on a Thursday night!

I am wondering if the 2007 Prius I have will need a change soon. It has only 55 000 miles on it and is charged everyday with a commute across NJ to work. I have no mechanical ability and take both cars in for regular maintenance every 3500 miles.

 

Quite possibly it will last for a couple more years. Use the battery selftest to check it out.

3500 miles is really more frequent than is needed, unless that's every six months for you (and I gather it isn't). If not you can safely save some bother and expense by using the recommended 6 months/5K interval.

 

3 to 6 points!! OMG... how did your battery get soooo dead??

as far as SOC on the traction battery affecting your mileage. look at my post "short tripping" for effects of mileage with changes in SOC