12v battery maintenance, issues, etc.

[Corolly Poly]

Just taken mine in for a check over and service guy admitted there is an issue with under capacity batteries and said corolla not usually such a problem but mainly Yaris which they are now fitting uprated Battery to. He said if there is an issue with mine they will replace it but will check how Dashcam is wired first.

[badlywornroy]

So I parked up at 8 pm last night and the BM2 Battery monitor reported 12.48v 83%.  The car sat undisturbed until 09:20 this morning and the Battery monitor reports 12.34v 56%. Is this level of voltage decay to be expected or does it indicate poor Battery health ?

[Derek.w]

11 hours ago, badlywornroy said:

So I parked up at 8 pm last night and the BM2 battery monitor reported 12.48v 83%.  The car sat undisturbed until 09:20 this morning and the battery monitor reports 12.34v 56%. Is this level of voltage decay to be expected or does it indicate poor battery health ?

Hi Roy, I dont worry until it 12.3 volts or less then I connect a charger to it My car at 12.34 volts now so will charge it tomorrow as it be sitting all day.

Batterys degrade more under 12.3 volts but they will all still start at this voltage.

[badlywornroy]

8 minutes ago, Derek.w said:

Hi Roy, I dont worry until it 12.3 volts or less then I connect a charger to it My car at 12.34 volts now so will charge it tomorrow as it be sitting all day.

Batterys degrade more under 12.3 volts but they will all still start at this voltage.

Hmm, just checked mine again at 21:20 and it's now 12.27v =45% !

[Derek.w]

8 minutes ago, badlywornroy said:

Hmm, just checked mine again at 21:20 and it's now 12.27v =45% !

Hi Roy it will still start but I sugest you connect a mains charger to it sometime tomorow even if it after you return home from work.

[Derek.w]

I just checked my voltage it still at 12.34 volts

I am still using a solar charge controler but some days if it cloudy then it a added drain on the Battery as losses outway the gains over a 24 hour period.

[W1P30UT]

On 10/4/2024 at 9:46 PM, Chas G said:

All hybrids suffer the same problem if you use the car infrequently and for short journeys only. Some non hybrids do too. The 12 volt battery just doesn't have long enough to charge from the main battery. 

There are a number of options from using the car more often ie longer journeys, leaving in ready mode for at least 1+ hour per week, using a solar charger if appropriate, mains intelligent charger etc or sell the car and buy something else.

The Toyota magazine forum has 100's of complaints. 

All hybrids don’t suffer this problem. I rejected my Corolla and bought a Honda CR-V and I’ve not had one issue with the 12v despite sitting in the car park with the media system on for extended periods just on accessory mode. This is a Toyota issue and they need to fix it. 

[Chas G]

1 hour ago, W1P30UT said:

All hybrids don’t suffer this problem. I rejected my Corolla and bought a Honda CR-V and I’ve not had one issue with the 12v despite sitting in the car park with the media system on for extended periods just on accessory mode. This is a Toyota issue and they need to fix it. 

3 cheers for the CR-V, good to hear that there are hybrids out there that don't suffer from flat 12v batteries when left for extended periods or frequent very short journeys. 😁

3 boos for the HR-V.....and the Jazz and E honda and Lexus Lbx etc eg:-

https://uk.hondaownersclub.com/forums/topic/15185-2021-hr-v-dead-12v-battery/

[fred88]

Interesting, identical to the Toyota issue.