Re: How do you know if your (12V) battery is on its last legs?
 

From the service manual:

Standard voltage:
11 to 14 V
If the voltage is below 11 V, recharge or replace the battery
before proceeding

Re: How do you know if your (12V) battery is on its last legs?
 

I don't know about that, mine read 11.5 volts for about 1 1/2 years and was working fine till I traded my car off. It may have been weak, but the car was almost 5 years old. The car was sold as certified used car by the dealer so they may have replaced it.

Testing for a going bad battery is usually 10% of it's normal voltage. A 12 volt battery less 10% would be 10.8 volts. Your right, toyota says 11 volts, time replace it.

Re: How do you know if your (12V) battery is on its last legs?
 

11V sounds great to me! My '07 reads 11.5 after sitting a day. It is the original Panasonic. Going in for my 75K service this morning, and will verify with them that 11V is the recommended replacement threshold.

-- Alan

Re: How do you know if your (12V) battery is on its last legs?
 

Just got back from the dealer. He told me my battery is below 300 A capacity, and needs to be replaced. I declined his $450 quote for the battery replacement. I picked up an Optima Yellow Top For $230, and have a $25 rebate to send in.

The battery swap was easy. However, now my car says "Service Hybrid System" with the red "!" warning light staying on. Does anyone know if this will clear itself once the settings recalibrate (assuming nothing else is wrong)? None of the nav screen diagnostics identify a problem or will reset this dash warning. Everything seems to be working fine.

For others doing the same swap, note that there is a thermistor over-temp sensor is under the original battery label. Just pull back on the label and the sensor pulls out easily, and then can be pressed snugly under the top clamp against the top of the new battery.

-- Alan

Re: How do you know if your (12V) battery is on its last legs?
 

Hey Alan,
Thanks for letting us know. Did you figure it out how to clear the errors?
What tipped you off that you need to replace the battery besides going to the dealer?
I have a 2007 camry hybrid made in japan and has about 108,000 miles on it. Do you think I need to replace it soon?

Re: How do you know if your (12V) battery is on its last legs?
 

Mine is also a first month, Japanese made TCH, and I live in the Sonoran Desert (Phoenix area).

The error finally cleared itself last night on my way home. Took about 30 miles of driving, and it just went away.

My clues that I may need a new battery were varied. First, many of my Toyota hybrid driving friends (Camry, Prius, Lexus) are replacing their AGM 12V in 4 to 5 years, and I know of nobody who lives out here who got more than 6 years. Second, the discussions here indicated the 12.6V battery should not fall to more than 11V after sitting a day or so. Mine was getting close to that. Third, the dealer said the cranking amps of the battery was about half its spec, and that it was probably only a short time to failure (he suggested weeks to maybe a few months).

I just decided to do it now, in part because my local AutoZone had the Optima Yellow Top at $10 off, and there was a $25 factory rebate, and I didn't want to wait until it wasn't my choice and it was 115 degrees!

-- Alan

Re: How do you know if your (12V) battery is on its last legs?
 

that's why you use back up battery, to feed power to the system, when swapping out those batteries. may be pain in too-too to do, but saves you headaches later down the road.
service light should go away after 3 consecutive startup/shut downs are performed.
when I'll be swapping mine, I'll have jumpers connected to cables and back up battery in the trunk. have not figured out yet how to connect them, but will.
yes, we do know about thermistor. it's pried off with a screwdriver and then placed onto a new battery.

Re: How do you know if your (12V) battery is on its last legs?
 

oh, and btw. Sam's has Optimas for around $170.

Re: How do you know if your (12V) battery is on its last legs?
 

I took a bench power supply I have and clipped it to the old battery. Then I lowered the voltage until the current was zero (matching the old battery voltage). Since the car was in use all morning (charging the battery), the then resting voltage was 12.1. I unclamped the terminals from the battery, with the power supply clips still on the car cables (and the power supply current jumped to around 100 ma). Then I attached the cables to the new battery. Not sure exactly when, but before I had both cables on the new battery, one of the power supply leads fell off! Oh, well.

-- Alan

Re: How do you know if your (12V) battery is on its last legs?
 

The 100 ma drain is really low and probably caused from the sleeping ECU. Makes it easy to see why you can let a toyota hybrid sit for a few weeks and it will still still start right up.