How do you check 12V battery status on a 2011 Prius w/no NAV?

The right tool for the job:
http://www.amazon.com/dp/product/B000EVWDU0?tag=priuschatcom-20't even get me started on the poor choice of 12V battery for the Prii of the world...

 

Be aware that the product you purchased will only measure voltage when the power outlet in your Prius (under the flying bridge) is powered up. That only happens at two different times of a possibility of three options available to you.

When you use the product you ordered from Amazon and plug it in, you will notice different readings depending on how you "push the power button" on the Prius. When the Prius is in "Ready" mode, (normal driving) the voltage at the power outlet should measure in the 13.8 to 14.2 volt range. However, if you were to check the voltage at the power outlet while in "Accessory" mode (one push of power button WITHOUT the brake being held), you will notice that the voltage is much lower. Because of that fact you will need to be careful that you only check the voltage in accessory mode to get a "fairly" accurate idea of what the voltage is on the battery whereas you can determine it's amount of charge. Bare in mind that when you are in accessory mode, a small "load" will be applied to the battery, therefore the battery might measure slightly lower than you would expect. I would estimate you would read somewhere in the area of 12.2 minimum to 12.6 maximum while in accessory mode.

IF the power outlet were hot when the Prius is powered down (OFF), the item you purchased from Amazon would be great, but unfortunately the engineers who designed the Prius elected to have the power disconnected to the accessory outlet when the Prius is powered down. Because of that fact, the product you ordered is useless IF you want to measure the voltage of the 12 volt battery with NO load being applied. Concerning loads, various loads are applied even in OFF mode to the 12 volt battery. One example would be when you first open the drivers door. You will hear the brake accumulator pump running. That is one example of the many loads that can be applied during the time that the Prius is powered down. When checking voltage, be aware that loads being applied to the 12 volt will cause the voltage readings to vary.

If you want a better and truer way to measure the voltage of your 12 volt battery in your Prius, it would be better to purchase a digital multi meter which you can connect to the jump post under the hood and or directly to the battery while the Prius is completely powered down. (Power Off mode) On the Gen II Prius, we could use the MFD to test the voltage of the battery. However, the Gen III Prius appears to no longer have that opportunity available to us. I recommend you use a multi meter such as this.



The above unit is very inexpensive.

For those who prefer accuracy to the measurement of .000X (four places after the decimal point) I would suggest you purchase the more expensive Fluke.



The above unit is very high quality, but also is very expensive if you are on a limited budget.

For more information on what the voltage values truly represent, please refer to the following chart which demonstrates SOC (State of Charge) for the 12 volt battery under no load. The battery in the Prius is a AGM type battery, please refer to the AGM column when using the chart below.




Ron (dorunron)

 

FWIW- there have been quite a few 2010 and now some 2011 Prius owners who've replaced their 12v batteries by now.
Seems 3 years is the lower limit for them to start to fail... just keep that in mind, especially with a used vehicle where you don't know if the already fragile battery was abused (run down, etc..).

Even regular conventional batteries don't seem to hold up like they used to, I'm only 6 month in on a Walmart Maxx battery (3 year full replacement, 2 year pro rated) and I've noticed some reduced cranking capacity on our Honda CRV.

 

A couple of must-have items.

An analogue multimeter will do for most stuff, but to check 1/10's of a volt you need digital. You can use the multimeter for so many things besides the 12 volt status, too: just verify which of the batteries (D, AA, AAA, 9 volt etc) you have rattling around are viable, and which are duds. Troubleshooting broken appliance chords (resistance), making really really sure the voltage is off when opening up a 110 volt circuit box.

The CTEK 3300 (or something similar) is VERY handy for reviving a near-dead automotive 12 volt battery. It does "intelligent" charging, and and is low amperage, under 4 amp as recommended by Toyota.

 

you guys do realize this thread is over two years old, don't you?

 

Ah woops. Well, I'm going to blame the new website format: having the date at the bottom of the posting, small text, grey. And failing brain cells.

 

You got me too bisco
I didn't look at the post above "dorunron".

 

Beyond the old post date; the O.P presented voltmeter (post #1) is the best solution for any DIY at low cost and lowest risk of screw-up something.

 

OMG, all I can say is that I replied to the "Alerts" here on PC, I did not look at the OP's post date nor the last message post date. Since I was the first reply, all I can say is "OOOPS"! Sorry guys if I caused any confusion.

Ron (dorunron)

 

Never mind; to resuscitate this type of old post is good to have present the hardware that it's still available