Just Installed a new 12v Aux Battery in my 2006

Where did you find it for $155, please?

 

Last time I shopped for 12V battery, I went to Interstate Battery
Batteries - Interstate Batteries has every battery for every need


They sell refurbished battery for Prius, at $30
They only use the housing, and replaced everything inside battery.
You will need adapters for the poles, but that's about $15 or something...

That's a super deal for me.
So far, it has been on my Gen II Prius for 1.5 years, and 30K miles. No sign of degradation. I expect it to last same as regular batteries.

 

I now disagree with this voltage range, which seems tuned more to traditional non-hybrids. The Prius seems to run lower. I often saw 12.2-3V on my apparently healthy 2010, and saw numerous reports of others finding no symptoms yet even at 11.8-9V. Then someone posted a handy Charge-vs-V chart here: only 36-37 average mpg?

Cubbyg reported 11.7V before this swap. That wasn't dead yet, but according to this chart, it was near end of life. And far lower than the point where my non-hybrid failed to crank last month.

 

I had to add this note because some drivers in other threads may have been prodded to replace aux batteries that were perfectly fine. The 12.4V threshold in the post you copied is too high.

But I agree that yours, at 11.7V, was due for replacement.

 

My SmartKey system stopped working—had to insert fob in slot to start the car—so I used the procedure mentioned above to test. Voltage is around 10.3.

What's disappointing is I just installed a new Optima DS46B24R in February.

I'm going to charge it up and hope to get more life out of it. I'm not sure why it would go bad so quickly.

 

Hi cubbyg. Could you post the new voltages that you measure after a few days driving. Make sure to include both the Acc mode and Ig mode measurements.

 

14.0 is not the "Ig mode" measurement. That's READY mode. The states are OFF, ACC, IG-ON, READY.

 

I am no expert, but 12.1 is not that great IMO. Your battery is not fully charged. 11.9 should be higher also. 14.0 is normal and that is expected.

A fully charged battery should read 12.4 to 12.7 on the MFD or higher in the first part of the test. Your reading is 12.1 Note: The MFD does not always read the full voltage at a rest depending on loads being applied during the test. Try to minimize loads such as doors being open, fan blowing on A/C-heat, radio, etc.

Refer to this voltage chart to get an idea of State of Charge (SOC) on your 12 volt battery.

I understand you just replaced the battery with a new Optima, however there have been a lot of reports recently about the Optima's not being fully charged when being bought new. I would suggest you use a smart charger, and fully charge the battery then run the test again after letting the 12 volt rest for at least 8 hours. If you test right after the charge, the values will not be indicative of the true values after the battery has set for a resting period.

If you charge the battery, set your charger to AGM and choose 4 Amps for the best charge. Optima does suggest the battery can be charged at 10 Amps. If you choose to charge higher than 4 Amps, I would suggest you connect your charger directly to the battery rather than using the jump post underneath the hood in the fuse box. The Prius normally charges at 4 Amps, so my reasoning is that if you are using the jump post, you would want to simulate actual Prius normal operating conditions. I have no doubt other's will have their own opinion concerning charging methods, so I suggest you do some research before you follow the steps I mentioned.

FWIW, I maintain my Prius 12 volt battery (original OEM) with a smart charger and do keep it topped off at least once a month. I always use the jump post and set my charger on 4 Amps and AGM. By doing that I keep my battery fully charged at all times. I don't drive the car every day, and most Prius owners can attest that the 12 volts does run down quickly if the car sets due to the parasitic draw from the SKS and other electronics onboard.

My numbers are normally 12.3, 12.0 and 14.0 - borderline, but still doing the job. Have seen 12.4, 12.1 and 13.9 before. I will be changing my battery soon and will replace with a OEM battery rather than the Optima.

Ron

 

The internal tester in the Prius is not all that accurate. The real test is how does your car work?

 

Cubby,

If you are troubled by those numbers, I further suggest you do the following.

1. Check the resting voltage of the Prius with a digital meter that will measure DC voltage.
2. Check the voltage of the 12 volt battery while the car is completely off after the car has set overnight.
3. Check the voltage of the 12 volt battery while the car is in "Ready Mode".

Compare the value of the battery while the car is "off" to the volt chart in post #16 If the battery is not fully charged, charge the battery again and retest with the digital meter. Remember to allow the battery to rest before you take your readings. That will help to eliminate what is known as a surface charge.

If you find that you can not succesfully charge the battery to at least 90%, I would consider returning the battery under warranty and getting another one. As I stated earlier, there have been reports recently about the Optima batteries not being fully charged when being sold. I have also read that it seems the quality has gone down since the plant moved to Mexico. Note your date code.

In reference to the voltage in "Ready Mode". As long as the value is between 13.6 and 14.4 you should be Ok concerning the charging system of the car. Just make sure that the cables are clean and that all the connections in the back end are tight.

Ron