Start battery keeps going empty

[Mikeni]

Have recently started getting an anoying problem. The 12V start Battery keeps getting empty every night. What you do think is taking all the energy out?

This all started after I opened the car by using the manual key. All the alarms in the car got off and the next day I wasn't able to start the car before loading the 12V start Battery. Yesterday I drove about 100 miles but wasn't able to start it today either since the Battery was empty.

Tnx for help

[danowat]

Have you replaced the 12v Battery?

[TheProfessor]

If a lead acid Battery gets discharged completely, it's likely going to suffer hugely from the experience. Even if the Battery didn't need replacing before, it's probably best to now.

As a rule of thumb, 12V lead acid batteries would benefit from replacement after 3 years or so, depending on a lot of factors.

Assuming you haven't wired anything directly to a permanent hot fuse or Battery, it's most likely battery age. How old is it?

 

Sent from my Pixel 2 using Tapatalk

[Mikeni]

3 hours ago, TheProfessor said:

If a lead acid battery gets discharged completely, it's likely going to suffer hugely from the experience. Even if the battery didn't need replacing before, it's probably best to now.

As a rule of thumb, 12V lead acid batteries would benefit from replacement after 3 years or so, depending on a lot of factors.

Assuming you haven't wired anything directly to a permanent hot fuse or battery, it's most likely battery age. How old is it?

 

Sent from my Pixel 2 using Tapatalk

No idea actually. Just bought the car. Problably old. Shows 12.1V when I test it. 

[Starmans]

Is it a factory original Battery? If its from 2006 as your sig details that's lasted quite well 🙂

[kithmo]

12.1v should be enough to put the Prius into ready mode. I would charge the Battery with a Battery charger/conditioner (4 Amps max) overnight and see how it goes.