12V battery - how to test it?

From the 2010 Owner's Manual:

12.6 ⎯ 12.8 V Fully charged
12.2 ⎯ 12.4 V Half charged
11.5⎯ 11.9 V Discharged
(Voltage is checked 20 minutes after the hybrid
system and all lights are turned off.)

[SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial]According to this your battery is Half Charged but in OK condition. If you only drive for short distances it is not having time to completely charge. If you do not have a battery charger to complete the charging, you can leave the vehicle in Ready mode for a few hours and let the car's charging circuit complete the charging. [/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE]

[SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial][SIZE=3][FONT=Arial]The Prius battery charging system is very slow due to its' low current charging rate to keep from overheating the battery and causing it to gas off since the battery is located inside the cabin. [/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE][/FONT][/SIZE]

 

tomlondon,

If it were me, I would insist on a new battery.
Make sure it's new, not from another used Prius. I don't trust those blokes.

The issue is: when Lead Acid batteries are left in a discharged state for any length of time damage is done.
Look it up.
It's possible for a discharged Lead Acid battery to freeze and crack its case if it gets cold enough. The electrolyte has turned back to water,, or close to it...
It is possible to bring a totally discharged battery back to life, it may test fine, but it's life span will be shorter and its capacity will be much less. You might get a surprise if you leave your car at an airport for a few weeks.

Good luck with dealing with car dealers.... I try to avoid it... You know how to tell if a car sales man is lying?

 

If you have those same readings after sitting all night and the car is starting ok, then you may be alright for a while. But the battery is weaker than when new. If after sitting all night the readings are weaker then you might want to consider a new battery while you can chose when and where it will be replaced. Good luck getting the dealer to replace it now.

You might find this thread helpful.
Fitting mobility 12volt AGM battery. | PriusChat

 

Did you also try to check voltages in Diagnostic Mode with built-up self test?

 

Seems you don't have Nav/Camera display. My screenshots are attached.

I have the following results

• vehicle switched off - 11.3V
• engine off headlights on - 10.9V !!
• engine on - 14.2V

Obviously my battery needs to be replaced. For more than two months my car was unattended in cold garage, I was at sea and my wife neglected to turn on the car weekly as she was told before my sea time :/
I charged the accu for 10 hours with current approx. 2 A and the car is running fine, but next week I intend to buy the new 12v battery . It was too long fully discharged in cold conditions Anyhow it's 3 years old now and not a big headache.

 

1. Press "Power" button without pressing the brake pedal;
2. Press and hold "Info/Tel" button (see picture, possible you have different version of Nav unit);

3. Three times switch headlights on/off holding the "info/Tel" button;
4. Release the above button and voila...
5. ...the menu appears on the screen.

Be careful to fiddle with the settings about you are unsure!

 

Yeahh... better than mine anyway As for now I enjoy the ride having motorcycle battery + jump cables available... After Easter holidays I'll buy new 12V batt.

 

Definitely. Now time for some nap, can't wait till morning when I press the "Start" button again - like it soo much
Cheers!

 

Our's had been on the lot a long time, and the battery was deader-than-a-door-nail. Was more cut-and-dry: they acknowledge there was no hope, replaced it as part of Pre-Delivery Inspection. Sitting for months can kill the 12 volt.

 

As far as I know, a Midtronics tester is the only proper and industry-approved method of testing 12v batteries. I do not see how the methods mentioned previously are accurate.

 

In our shop (not a auto shop) the Techs use a 12 volt "Load Tester" on a battery ...It's not a complicated piece of equipment, and I don't see why every auto shop uses one for diagnostics.....
You simply connect it to a fully charged battery with large clamps similar to jumper cables, push a button for 5 seconds...
it will draw an instant load on the battery and tell you if the batter is healthy or not....will show a bad cell.....

 

Never heard - you sell them?
Mentioned previously method is a built-in facility in Toyota Prius for diagnostic purposes.

 

I picked up my Prius yesterday (2010, with 27,500 miles). The dealership had installed a new 12V when it first came to them for re-sale. Although not specifically stated, it appeared that this dealership tests all/most of the 12V batteries when they get used cars in and they automatically replace them if anything is "questionable".