Toyota: advice on 12v battery maintenance

[AEG]

On 1/31/2022 at 4:23 PM, Dala said:

12V for AGM?

I measured when the car was not running:
day 1: (second day): 12.4V - 12.5V
Day 2: 12.2V-12.4V
Day 3: 12.1V-12.2V
Day 4: 12.0 V - 12.1 V
Day 5: 11.9V - 12.0V
Day 6: 11.8V
day 7: 11.7V 

Isn't it possible that the car battery is being discharged by the Toyota MYT satellite system? 

I have the corolla 2022,   2.0 Hybrid.  Which suffers the same large voltage drop if left for a week uncharged.  Why is this ?  Well if I measure the Battery discharge current with the car locked and the alarm system on, the car system draws 0.6 Amp/hr.  So after a week it is not surprising the Battery is almost flat.  So what is draining the Battery ?

After looking into this a little deeper I found the alarm system is the main power consumer.  I proved this to be true by by switching off the movement sensor ( next to the mirror), and measured the discharge current again.  This had dropped to 0.065A. (65mAh). So I am clear, as to what is draining my 12v 45Ah battery down.

Obviously leaving the alarm system off is a risk, unless your car is securely locked away in a garage .     

     

[Roy124]

@AEG good thank you, though my Corolla sat in the garage unlocked during Covid and still suffered drain and flat Battery. 

[peter radford]

CAN YOU FIT A BIGGER Battery TO A TOYOTA YARIS CROSS FOR THE 12V SYSTEM

[Roy124]

On 2/22/2024 at 4:11 PM, peter radford said:

CAN YOU FIT A BIGGER BATTERY TO A TOYOTA YARIS CROSS FOR THE 12V SYSTEM

Yes

[Gren]

You could also fit a powered 12v socket directly to the Battery, like this poster did...

I fitted one to my car, quite an easy job, it provides a permanently-live socket that I can plug my trickle charger into (Noco, with the 12v socket adaptor)

 

[Auris Geezer]

Out of interest sake, what do you do when you park up at Manchester Airport to jet off to sunnier climes for a fortnight?

[Roy124]

1 hour ago, Auris Geezer said:

Out of interest sake, what do you do when you park up at Manchester Airport to jet off to sunnier climes for a fortnight?

In case you use a covered car park get a jumper pack.

If you know you will have a sky view rely on the jumper pack or get a solar charger.

Or rely on a breakdown service.

[Auris Geezer]

That's not ideal is it?  So what is it that actually runs the 12v Battery down please?

[Roy124]

12 hours ago, Auris Geezer said:

 

Trev, that was slightly tongue in cheek as it happens .but is not as frequent as you might suspect from this forum.  If it was 10% of all Toyota Hybrids per flight, or even 0.1%,it would hit the national press.

As for your question,  the answer would appear to be a combination of many things.  The Alarm system and possibly a dashcam; the remote key system listening for an unlock command; the Data Communication Module,  having uploaded the last trip data remains active should you want to check the status, heat the car, or flash the hazard warners.

Then you have normal voltage loss, common to all batteries. 

Clearly a small Battery, 35AHr, has a much lower starting capacity than a higher capacity one capable of driving a starter motor.