12v battery maintenance, issues, etc.

[Graham47]

@Derek.w thank you for coming back to explain. 👍

[Cowgirl]

I would like some advice, I used to drive my car for 45 minutes morning and evening, due to a change of circumstances it’s now 10 minutes morning and evening. During the day I use a solar charger sunny or not.

Last weekend I drove it for approximately 2 x 25 minutes then put it in ready mode for an hour. Today it’s been solar charging all day (bright sunshine). Tonight my voltmeter in the cigarette lighter showed 14.5 when I turned it on but then dropped to 12.8 intermittently going up to 14.3. Is this because my Battery is fully charged or it’s knackered. Previously no Battery issues on original Battery at just over 2 years old.

[Roy124]

Perfectly normal. Fully charged as you surmised. 

[Derek.w]

3 hours ago, Cowgirl said:

I would like some advice, I used to drive my car for 45 minutes morning and evening, due to a change of circumstances it’s now 10 minutes morning and evening. During the day I use a solar charger sunny or not.

Last weekend I drove it for approximately 2 x 25 minutes then put it in ready mode for an hour. Today it’s been solar charging all day (bright sunshine). Tonight my voltmeter in the cigarette lighter showed 14.5 when I turned it on but then dropped to 12.8 intermittently going up to 14.3. Is this because my battery is fully charged or it’s knackered. Previously no battery issues on original battery at just over 2 years old.

Hi a reading of 12.8 just means Battery is fully charged so DC charger or altinator electronics has switched itself off when voltage again drops to 12.4 or 12.5 charging circuit will turn. 

[Cyker]

Yeah, a lot of newer Toyotas, even the ones with alternators, stop charging the Battery when it's full to save energy/reduce engine load - When that happens it drops to the normal Battery output of 12.whatever volts.

Then when it drops a bit it'll start charging it back up again - It's what's called cyclic-charging, rather than the more traditional float-charging, which just holds it at the 14.whatever charge voltage the whole time.

 

[Chas G]

100 pages in this thread.

Anyone would think there was a problem with Yaris Hybrid 12 volt batteries. 🤔

[hind]

How much of it are posts written by the people who actually have a problem? 😉

[RickyC]

58 minutes ago, Cyker said:

Yeah, a lot of newer Toyotas, even the ones with alternators, stop charging the battery when it's full to save energy/reduce engine load - When that happens it drops to the normal battery output of 12.whatever volts.

Then when it drops a bit it'll start charging it back up again - It's what's called cyclic-charging, rather than the more traditional float-charging, which just holds it at the 14.whatever charge voltage the whole time.

 

The only thing that is not clear to me is why the charging voltage drops of about a Volt moving gear from a drive position ( D, B, R ) to a stationary one ( N or P ) to regain a V when returning in a drive position.

[CPN]

14 minutes ago, RickyC said:

The only thing that is not clear to me is why the charging voltage drops of about a Volt moving gear from a drive position ( D, B, R ) to a stationary one ( N or P ) to regain a V when returning in a drive position.

That's simple. When you shift to N or P, the 12v Battery is immediately disconnected from the HV charging circuitry; hence the voltage drop...

[RickyC]

2 hours ago, CPN said:

That's simple. When you shift to N or P, the 12v battery is immediately disconnected from the HV charging circuitry; hence the voltage drop...

If 12V is disconnected from HV charging circuitry, why Toyota suggests to leave the car in P position to charge the Battery ?

[CPN]

29 minutes ago, RickyC said:

If 12V is disconnected from HV charging circuitry, why Toyota suggests to leave the car in P position to charge the battery ?

My mistake. Of course it remains connected in P.

[trashman1965]

I believe the 12v Battery is being charged all the time the car is in Ready mode. If the transmission is in neutral N then the HV Battery won't charge.

[Chas G]

Things could be a lot worse. 

I am quite happy with my Toyota Yaris Cross plug in self charging hybrid. Just plug in after every time I use the car and nothing to worry about and no inconvenience.

[HD2024]

Hi all, I’m sure the information I need is within this thread but it’s a bit overwhelming and, despite some searching, I haven’t found what I need (or at least all of what I need).

Hopefully you’ll be able to point me to the right places or summarise. Thanks

CONTEXT

Due to a medical situation I have been unable to drive my Mk4 Yaris 2022 for nearly 6 months. I know I should have done things to keep it working but, for a number of reasons, I didn’t. I now can drive again but the car isn’t working due to a flat Battery.

I’ve purchased a NOCO Boost Sport GB20 Battery pack and attempted to charge using the terminal in the fuse box. However, the alarm goes crazy and I am unable to switch it off. The car is NOT keyless entry, and all info I find about manually turning off the alarm doesn’t work as the bonnet is open and can’t be closed while the booster is connected. The second I disconnect the booster the car is dead.

As the horn is blaring, I can’t just sit in the car charging for 2 hours as it is because of my neighbours.

 

REQUEST

- Advice on how to charge the Battery (if what I’m doing isn’t right)

- Advice to shut off the alarm for non keyless entry or if I should/how to pull the horn fuse

 

Thanks in advance for any and all help

[Graham47]

Noco GB20 isn’t a charger … it’s a booster.

 It’s designed to allow you to immediately start the car, the alarm, I think, should then stop and you can run the car in ready mode to put some charge into the Battery.

[HD2024]

36 minutes ago, Graham47 said:

Noco GB20 isn’t a charger … it’s a booster.

 It’s designed to allow you to immediately start the car, the alarm, I think, should then stop and you can run the car in ready mode to put some charge into the battery.

Thanks for your fast response. I should have mentioned I tried starting the car and it wouldn’t.

From things I read this is because the Battery apparently needed to charge up to a certain level from the booster in the first place.

I have seen people use the GB40 for this but they didn’t experience the alarm issue.

[Dala]

The car Battery will  need to be removed from the vehicle and charged outside the car.

[Chas G]

@HD2024 - maybe the immobiliser is stopping engine from starting.

I would phone the Rac or Aa and get them to fit a new Battery

or close the bonnet, turn alarm off and lift the rear seat.....there are two catches under the front lip of the cushion and you have to give them a serious snatch to get them to release then connect your Noco booster direct to the 12 volt Battery. Not sure whether it will start though if the traction Battery is also flat.

Good luck.

 

[jthspace]

Think if the traction Battery goes flat, that's serious sh*t and dealer visit is the only solution.

Booster can also connect under the bonnet to the Battery connection point and a good earth.  Connection point goes direct to the 12v Battery.

[Cyker]

Did you try hitting the unlock button on the remote fob? Even the normal key should have one of those and that's usually enough to stop the car freaking out.

I'm surprised you weren't able to start the car after powering up the jump-starter though - I would have thought that would be easily enough to power the car on

I suppose it's possible the 12v Battery is so flat it's sucking up too much power out of the jump starter so the ECU and HV contactors can't be activated properly, but given the alarm works that seems unlikely...!

 

Also when you tried to start the car, did you hold down the brake pedal before twisting the key to the ignition position?

[Cowgirl]

20 hours ago, Chas G said:

100 pages in this thread.

Anyone would think there was a problem with Yaris Hybrid 12 volt batteries. 🤔

Chas, I don’t have a Battery problem but with the change of use I want to avoid one!

[HD2024]

Thanks everyone for your help.

I accessed the Battery directly under the rear seat and connected the GB20 pack. This allowed it to charge the Battery with the door and bonnet closed, avoiding the alarm.

I was able to start the car (brake pressed) and it unexpected started in EV mode with 3/4 on the traction Battery which was a relief. However the electric doors and key fob still wasn’t working, I assume because it was prioritising power to more important functions.

Drove it for 2 hours and 60 miles in a mix of local streets and 70mph roads. Turned it off and it seems to be working as it should, key fob and all. I suspect the 12v was absolutely, completely dead and am hoping it will now hold a charge.

I’ll see if it starts up on its own tomorrow and book it in for a service too (which it needs anyway).

Appreciate all the help and support.

[Cyker]

Glad you got it working! Surprised you had to connect it directly to the Battery but the main thing is you got it going.

It might still hold a charge, but 12v lead-acid batteries deteriorate a lot when they're discharged, so even it it's working it will likely be at significantly reduced capacity, esp.  if it was a factory 12v Battery which were a bit ropey to begin with.

Keep the Noco charged and handy and get the dealer to check it when you take it in for servicing, as I suspect it will need replacing...!