Battery charge when car not in use

[booke02]

We were on holiday recently - for 14 days - and on our return the Battery of our 2018 Yaris was dead. Dealer said that Battery would lose charge if car was not used for 3 days. Claimed that all the systems (like collision warning, etc) were still working even when the car was not is use - parked and locked. I suspect that the "3 days" was an exaggeration.

Does anyone have any experience/knowledge of this topic?

[Anthony Poli]

Hmm
A Battery shouldn't discharge that fast.
If a Battery only last 3 days, then you have an electrical problem.
The only thing that should be drawling power with the car switched off and the doors and boot properly, will be the alarm or remote central locking.

That applies to both hybrid and non hybrid cars.


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[Heidfirst]

2 minutes ago, Anthony Poli said:

The only thing that should be drawling power with the car switched off and the doors and boot properly, will be the alarm or remote central locking.

or possibly something else that has been hard-wired into the car e.g. a Dashcam or a bluetooth adapter into the OBD socket.

[booke02]

No bluetooth adapter in the ODBC socket. No extras hard-wired (as far as I am aware!). No lights left on, doors and boot properly closed.

We often don't use the car for over a week, so normal Battery life is at least a week or 10 days, The "3 day" story came from the Toyota dealer.

[Anthony Poli]

A Battery that is in a good state of health should last over 2 weeks without any problem.

Does the car only get used for short journeys?

If yes then it might the problem as the Battery never gets a full charge.


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[booke02]

Some journeys are short - about 20 minutes, but most journeys are closer to 1 hour.

Let me ask a different question: how long do I need to drive to recover the energy used to start the car?

[Bomber209]

I had a similar problem with wife's Honda Jazz (Hybrid) with stop/start keep draining the Battery. Solved it by fitting a 12v solar panel straight to */-  Battery terminals. 

[Graham47]

Am I correct in assuming that when you press the “start” button the 12v Battery only ‘boots’ the computer and the ICE starter motor is subsequently powered by the hybrid Battery?

if so, then the ‘start’ drain on the 12v Battery should be quite small and quickly recovered?

[Anthony Poli]

Toyota hybrids use the 12 volt Battery, for things like alarm/central locking, When shut down. When powering on it powers the basic systems

The downside is the charging rate is low, maybe you might consider a modern Battery charger that you can use while it's in the car.

A hybrid car charges at 4amps and if the Battery is low it could take 12 hours to charge.


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[booke02]

2 minutes ago, Anthony Poli said:

Toyota hybrids use the 12 volt battery, for things like alarm/central locking, When shut down. When powering on it powers the basic systems

The downside is the charging rate is low, maybe you might consider a modern battery charger that you can use while it's in the car.

A hybrid car charges at 4amps and if the battery is low it could take 12 hours to charge.


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My Yaris is not a hybrid ...

[Anthony Poli]

My Yaris is not a hybrid ...

Sorry I was going by another post and probably misread it.

An hours drive should put back what a standard starter motor takes out.

So it could be a faulty Battery.


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[Graham47]

4 hours ago, Anthony Poli said:

Sorry I was going by another post and probably misread it.

An hours drive should put back what a standard starter motor takes out.

So it could be a faulty battery.


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Unlikely....it’s a 2018 car...

[007matt]

Maybe 14 days in the cold is just too much for the Battery? 

[booke02]

Our local temperatures have been quite pleasant (between 15°C and 20°C), so don't think that cold is an issue.

I measured Battery voltage over a few days with the following results:

Battery voltage with the engine running : 14.1V

After full charge : 12.69V

After 24 hours : 12.36V

After 48 hours : 12.28V

My guess is that one cell is not holding charge (hence the large drop in first 24 hours), but the other cells are OK.

Make sense?

[Mick F]

Fully charged batteries should sit at 13v or nearly 13v. I reckon you've got a duff Battery and need a new one.

We had a Fiat500 up until a year or so ago and it had a Stop/Start system.  We bought the car out of warranty and I noticed after a while, that the SS system wasn't stopping the engine for the designed full three minutes.  I carried out many experiments to prove it.  I took the car to three separate independent garages and they all said that the Battery was fine ........... even though it would sit at 12.5v.  They all, to a man, said that that was a good Battery.  I knew different, and hoped they would back me up.

I paid £100 for a new battery - Stop Start batteries are expensive!! - and the fault was immediately cleared.  Trouble is, unless you give the car a good run, the SS system stops being perfect, so I bought a battery charger with a plug connection (not croc clips) to the battery.  Each and every time I came home, I would pop the bonnet and connect up the charger on a long lead from the front porch, then lower the bonnet.  The job took less than a minute to do, and even quicker to disconnect before driving.  The SS system worked perfectly for years, and probably better than when the car was new.

The issue really, is that when they build cars, they are parked for months sometimes in a big carpark waiting to be sent out to be sold.  They then go to a main dealer by lorry and may sit on the forecourt for weeks before a punter wants to buy the car.  It then goes for a pre-delivery inspection, cleaned, battery charged, and then test driven.  The battery at that time could well have been flat .......... and that's the worst thing you can do to a battery.  If so, from then on, it's on its last legs.

Mick.

[hubrad]

I wouldn't worry too much about the Battery with those voltage readings.

With everything locked, put an ammeter in line, to see how much current is actually being drawn with 'everything off'. It might prove surprising. At least then you'll know your electrics' rest state. Battery capacity divided by rest current gives you maximum hours of rest before the battery's totally flat from full charge. Engine probably won't start quite some time before that.

Low Battery charge is pretty typical in the darker months, as on top of the energy to start the engine you probably have lights, blower, radio et al when running. This all increases the drive needed to get you back to full, and most people don't do the mileage. If it's that, a battery charger will get you sorted.

Edit: I just went out to check mine, which has been sat since about 0130 after a couple of 30 mins drives last night. Battery was new 3 months back. 12.56V and I'm totally confident in it all working as it should.

Edited December 2, 2018 by hubrad

[Mick F]

Voltage is only half of it.  You need to do a Drop Test to get a better idea.

How does the voltage hold up when under load?  Just coz it sits at what you think is a good voltage, doesn't mean it's got good regulation.  High internal resistance will kill voltage.

Aim for 13v on a Battery at rest, and you'd be more than likely fine.  12.56v is ok as you've not replenished the Battery after a couple of 30min drives.

Mick.

[hubrad]

True what you say about load, Mick.

One can buy load testers, but for the private motorist a new Battery is probably more cost effective.

I've just never had a Battery that stayed at 13V.

[Mick F]

14 minutes ago, hubrad said:

True what you say about load, Mick.

One can buy load testers, but for the private motorist a new battery is probably more cost effective.

I've just never had a battery that stayed at 13V.

If you charge your Battery fully with a Battery charger .................or go for a drive - in good weather not using electrics much - and make the drive a couple of hours or more -  your Battery will be fully charged.

Test the voltage after switching off and letting the battery relax.  Give it maybe an hour before testing the voltage.

It's difficult in real everyday use to have a fully charged car battery and generally it doesn't matter.  Eventually they fail through constant use or neglect.  Just coz a car is brand new, it doesn't mean that the battery is as good as new.  There is no substitute for a good strong battery.

Mick.

[booke02]

My gut feeling is the Battery is problematic. This is my wife's car, so she needs to be confident that it will start whenever she needs it. As the car has only been on the road for a few months, I will try and get Toyota to change the Battery under warranty.

Wish me luck!

[Bob110023]

Hi Keith. I think you are right. A fully charged Battery should be showing 12.80 volts. If it has been left for a while, say a couple of weeks it should not drop below 12.64 volts. Any readings below this would cause a on going problem especially during any cold weather if and when it arrives. Get your dealer to carry out a voltage resistance drop test, if they cannot do it there are lots of Battery sales companies that carry out a free check. Cheers.

[martswain]

My Yaris GRMN has just started after being left for 62 days, not even a flicker from the dashboard, it cranked normally and fired up within 2 seconds.

A 12V Battery should not discharge within 3 days unless lights or accessories have been left on by accident.

[booke02]

2 hours ago, martswain said:

My Yaris GRMN has just started after being left for 62 days

62 days - incredible!!!

[martswain]

I have also had a few hybrids, 2 Prius, one Yaris and a Lexus CT200.

They have all been left for 60 odd days, however, always pulled the fuse that runs the equipment that is live with the ignition off (immobiliser/alarm etc).

The cars were left in a locked garage which is integral with my house, so does not get too cold.

The 12V batteries have always provided enough power to start the electrics and the traction batteries only lose 1 or 2 bars over that time, so they always started first time too.

[martswain]

GRMN started first time once again after 61 days !