12v battery maintenance, issues, etc.

[Sunflowers]

Hello, I am wondering if anyone might be able to give me some advice as I am really struggling at the moment. Please bear with me because I am by no means a car expert - and I won’t be offended if you suggest something to me that feels obvious to you, as it might have passed me by! 

I have a 2021 Toyota Yaris Hybrid Icon that I purchased earlier in the year from an approved used dealer. I have loved the car in general and had no issues with it. However, in October I was in hospital and was too unwell to drive the car or even go out to switch it on for a couple of weeks - the Battery then went flat and wouldn’t start (I understand that this was the result of me not using the car). After this, the car went for a service at a reputable dealer and they did an overnight charge of the Battery. The dealer tested the Battery and indicated that it was in a good condition after the overnight charge had been completed and that I shouldn’t expect any further problems. The car was then running fine but I have just gone to start my car today and it has a flat battery again and won’t start. It is strange to me because I only just used the car yesterday and it worked absolutely fine. I have read the threads here and understand that this might be a recurring issue for hybrid Yaris owners but I just wanted to ask for advice. My questions are as follows: 

In your opinion, what is the best course of action I can take to prevent the flat battery from recurring? Are my options to buy a charger and charge the car once a week, or turn the car on and leave it in ready mode on the driveway for 1 hour per week? 
If the best option is to use a charger, what sort of charger do you recommend? I have seen trickle chargers and CTEC chargers recommended here. 
In your opinion, when is the battery going flat not considered normal? I understand that the battery went flat after I was in hospital because I had not used it for many weeks. However, I was flabbergasted today when the battery was flat as it had been running fine all week. If I were to go away on holiday for a week and the car were not to be used, could I expected to come home to a car with a flat battery every time? Or if I had a week where I only did short journeys into town and back every day, would it be expected that the battery might go flat? 
Are there any kits you would recommend I keep so that I can jump start the car in an emergency or is this not recommended?
Thanks for any help you can provide, I really do appreciate it because I’m stuck in a very rural area with a tiny newborn baby and no public transport so am very keen to understand what I need to do to get it sorted. 

[Alan993]

Hi, the link doesn’t work!

[Chas G]

Yaris Cross - on Sunday afternoon I put Battery on charge until Monday morning. I left it for a few minutes after charging and checked the voltage which showed 12.97 volts which rather surprised me as i dont recall it ever showing more than 12.6 volts before.

I have checked it every day since then and the voltage had slowly dropped to 12.4 volts yesterday after sitting for 2 1/2 days and 1 trip to the doctor a mile away.

Just been to Watford 8.5 miles, did my shopping, drove home 8.5 miles, unloaded my shopping and then checked the voltage expecting to see it at about 12.3ish but it was 12.7 volts. Its never done that before.

Very odd. It's like something has woken up and decided to start behaving properly again.

[Chas G]

@Alan993 after all your repeated flat Battery issues I would get it replaced.

Its odd that your Battery loses so much charge overnight after being charged on a 100 mile run which presumably took a couple of hours.

I disabled the keyless entry, took out the dash cam and confirmed that my car is not connected to Mytoyota to minimise voltage loss when the car isn't being used.

[FROSTYBALLS]

2 hours ago, Alan993 said:

Hi, the link doesn’t work!

Toyota GB changed the link - OK now

[Dezzer21]

Bought one of these today quite a bit chunkier than I thought it would be and the leads very short.I went when Lidl opened they only had 4 went after dinner they had all gone spent a few hours charging hope it works ok🤞.

[Derek.w]

If the Battery going flat in just one day then its time for a New Battery!.

Use a smart Battery charger at least once a week if you do 2 or 3 short runs then recharge it when you arrive home.

Recharge when voltage is showing 50% that around 12.3 or 12.2 volts(it will still start at this voltage it just to stop the battery sulphurising & loosing capacity)

Battery for Yaris MK4 are but you can find others.

Varta blue dynamic   544 401 042 or B 36 44AH 440 amps

Yuasa HSB202 Part no YBX5202  45AH cca 440 amps

Bosch S4 000  544 401 042  44Ah 420 amps.

You can also turn off follow me home lights.

If you always in & out of the boot with door open frequantly disconnect its boot light.

I(f you have auto-lights then turn the sensor setting town to its lowest (saves headlights comming on if you close to buildings in broad daylight. (No effect on night time driving.)

[Roy124]

@Sunflowers 

I don't think you have been answered directly:

After this, the car went for a service at a reputable dealer and they did an overnight charge of the Battery. The dealer tested the Battery and indicated that it was in a good condition after the overnight charge had been completed and that I shouldn’t expect any further problems.

He was being ingenuous as after the Battery had first gone flat there was already irrecoverable damage.  Not damage that would be immediately fatal.

The car was then running fine but I have just gone to start my car today and it has a flat battery again and won’t start. It is strange to me because I only just used the car yesterday and it worked absolutely fine.

While the car had been running fine you haven't said what journeys you had done.  The critical detail is time in Ready mode.  If, for instance, you did numerous short time journeys and switched off at each stop you will be using more power from the battery than the HV DCDC Converter puts back. 

In your opinion, what is the best course of action I can take to prevent the flat battery from recurring? Are my options to buy a charger and charge the car once a week, or turn the car on and leave it in ready mode on the driveway for 1 hour per week? 

You probably won't prevent the flat battery from recurring but it will need increasing care and may still fail when you least expect it.

If the best option is to use a charger, what sort of charger do you recommend? I have seen trickle chargers and CTEC chargers recommended here.

I use a CTEK charger, others use NoCo.  Either are good.  As far as these go, better than using a cheap Chinese knock off copy.

The 'no cost' option is indeed putting the car into Ready mode as you say.  Minimise other power consumers during this period, in particular switch of the Air Con.

I have read the threads here and understand that this might be a recurring issue for hybrid Yaris owners 

Not just Yaris, though other makes tackle the issue in different ways.

If I were to go away on holiday for a week and the car were not to be used, could I expected to come home to a car with a flat battery every time?

Every time, not at all, but with your current battery I suggest a near certainty as the damage has been done and your experience supports its imminent failure.

Or if I had a week where I only did short journeys into town and back every day, would it be expected that the battery might go flat? 

Probably, though it does depend on 'short', but every start sees the battery voltage drop by 1v before recovering.  Into town every day suggests 8 starts which require increasing time to allow the battery to be recharged.

Are there any kits you would recommend I keep so that I can jump start the car in an emergency or is this not recommended?

Yes, unlike the requirement for assured quality with the mains chargers, you can get an inexpensive jumper pack from Amazon or wherever.  All it has to do is provide sufficient power to operate the computers and switch the contactors for the HV battery to take over.  My pack has held an over 75% states of charge for several months.  

This link is for a typical inexpensive pack from Amazon.  It is not a recommendation but simply an illustration:

Amazon.co.uk : 12v 24v jumper pack

Or this one:

Portable 12V Car Battery Jump Starter Power Bank Pack Vehicle Charger 20000mAh ♘ | eBay

I have had a similar one, with was about £25 but over 2 years ago. 

[Derek.w]

Think of booster packs as peace of mind just to get you going its a situation you dont want to repeat to often or you be needing a new Battery.

If you do use a booster pack then its also time to connect a mains charger once you return home.

I use a bluetooth Battery Monitor it has short circuit protection built into it.

CTEK MXS 3.8 charger but some people use a 5amp version.

Regarding a jump starter that I can do from a spare batterys that I have at home.

[Roy124]

As @Derek.w says, these are all useful tools and are essentially one-off purchases that can last many years.  I changed my Battery charger after 60 years.  I still have a snow shovel bought 55 years ago for 10/-.  I have retired my jumper cables after 40 years.

Don't look on such purchases as needed for you Hybrid but as insurance for the future.

Oh, I also kept a jungle boot lace for 30 years before I used it to refit a side window in once car.  That has been retired too as car windows are different now.

[Sunflowers]

Thank you @Derek.w and @Roy124, I really appreciate the advice

[hind]

11 hours ago, Roy124 said:

If, for instance, you did numerous short time journeys and switched off at each stop you will be using more power from the battery than the HV DCDC Converter puts back. 

11 hours ago, Roy124 said:

but every start sees the battery voltage drop by 1v before recovering

Do you have diagrams for that? Can't find it in this huge thread 😄 The drop from what you say seems huge and I guess it's rather short lasting - should be the time between pushing the Start button / turning on Ignition and the DC/DC kicking in. I don't think it takes more than a minute of Ready state to compensate for that. Of course we don't know the charge rate unless we monitor the current too and count the balance. 

[Roy124]

57 minutes ago, hind said:

Do you have diagrams for that? Can't find it in this huge thread 😄 The drop from what you say seems huge and I guess it's rather short lasting - should be the time between pushing the Start button / turning on Ignition and the DC/DC kicking in. I don't think it takes more than a minute of Ready state to compensate for that. Of course we don't know the charge rate unless we monitor the current too and count the balance. 

Dala has posted several BM screen shots that demonstrate the effect.  The BM only records data at 2 minute intervals. You are right it is a momentary dip.

It does not need much imagination to think what might happen if the prestart voltage is 'ok' but minimal,

E2A

Checked this week's data.  Haven't caught the data dip but noted a 5 point drop in state of charge and a 1.6v increase in the following 2 minutes after start and a further 0.3v in the following 2 minutes.

I looked at about 5 start points and the graph clearly shows this drop, the data gathering has not captured it from which we might surmise the drop is definitely less than 2 minutes duration and is probably much less than even one minute.

 

[G L J]

In case anybody is after a portable power pack there is one al Lidl at the moment.https://www.lidl.co.uk/p/ultimate-speed-portable-jump-starter-with-power-bank/p10010233

[Roy124]

Further to the voltage drops shown on my BM6.  I checked with the OBD meter plugged in.  The voltage reading 12.25v.  When I pressed the brake pedal the voltage dropped to 12.09v (brake lights).  Pressing Start it dropped immediately to 11.75v before jumping up over 13v as the HV energised.

From my earlier BM6 data, voltage measured from 30 minutes after last use (about 1730) and pre-start on the following morning at 0700 gave the following drops 0.21v, 0.31v and 0.3v.  

This appears to show an alarming 6v drop in 10 days but in practice the rate of voltage drop tails off significantly over time.

All these figures are over 4 days this week with the car being used for short 10 minute journeys morning and evening with some longer runs during the days.

[hind]

5 hours ago, Roy124 said:

It does not need much imagination to think what might happen if the prestart voltage is 'ok' but minimal,

You are right, just wanted to point out that the start/stop (or rather ready off/ready on) cycle in hybrid engine is not that much of an issue as with regular non-hybrid ICU engine when the starter takes hundreds of amps and it takes a fair amount of time to recharge.

I did some calculations, based on Dala's data from the clamp meter and calculated, that the first 2 minutes prior to kicking in the DC/DC consumes around 221 As (ampere-seconds) of power = 0.06Ah. Almost half of it is covered in the next 12 seconds (when the provided log ends) but assuming (maybe wrong) that the DC/DC would continue delivering 6 amps to the Battery, it should be replenished with the next 50 seconds. 

So this isn't that bad, doing 2 minute drive should cover the 2 minute preparation to drive time.

Of course you have to recharge what was wasted during earlier parking phase but that's a separate story.

[Roy124]

Here is today's graph from BM6

 

[Chas G]

Toyota Yaris Cross - had a long Ctek 5 charge on Sunday and it seems to have kicked my Battery up the Harris. It's charging properly now even on short runs. To say I am pleased is an understatement.

After standing idle over 4 nights, 1 local trip to doctor, 1 trip to Watford and local trip to Asda the Battery is showing fully charged at 12.76 volts.

Long may this continue.

[Chas G]

I think my car had probably been sitting on the forecourt for a few weeks before I bought it and was jump started for my test drive and delivery.

It then took a really good long charge to kick it back up to full capacity despite showing 12.6 volts after shorter charges.

I had pondered the question whether Toyota would have produced a car with a charging system which wasn't capable of keeping the 12 volt Battery charged after relatively short journeys and I think the answer is no otherwise they would be inundated with complaints and a disappearing customer base.

[skidlid]

8 hours ago, G L J said:

In case anybody is after a portable power pack there is one al Lidl at the moment.https://www.lidl.co.uk/p/ultimate-speed-portable-jump-starter-with-power-bank/p10010233

Thanks for the heads up, been and picked one up.

Been considering one for a while now and the new Yaris is due in March and do not want to end up with a non-starting anything blocking the other 2 in (too old to push them about). One is the 6 year old Fabia with original Battery (that goes when the Fabia arrives), a Superb PHEV but still has a 3.5 year old 12v Battery that could let us down and finally a 31 year old with a Battery that is almost 7 years old (never got more than that out of one) and its inevitable that will let us down this year.

Hopefully we are covered now with the smart charger as well.

[Roy124]

49 minutes ago, Chas G said:

It then took a really good long charge to kick it back up to full capacity despite showing 12.6 volts after shorter charges.

12.6v is my normal.  However, I want to make a point.   It is not the absolute value that is important but the change from your norm.

The BM6 gives a steadier value than the OBD but is slightly lower.   A hand held voltmeter gives a slightly less precise reading but differs from both.  The different readings are probably within the individual specs. 

It is the rate of change from a particular device that will give you a better indication of your Battery performance. 

[Chas G]

1 hour ago, Roy124 said:

12.6v is my normal.  However, I want to make a point.   It is not the absolute value that is important but the change from your norm.

The BM6 gives a steadier value than the OBD but is slightly lower.   A hand held voltmeter gives a slightly less precise reading but differs from both.  The different readings are probably within the individual specs. 

It is the rate of change from a particular device that will give you a better indication of your battery performance. 

I am using the same voltmeter on the jump terminal and aluminium bracket under the bonnet each time.

[Roy124]

Chas, that eliminates some potential variances, but my point was don't compare my set of readings with yours and think them better or worse.  Look at how your readings compare, one with another over a period.

My 'shocking' drain measured over half a day was I significant when calculated after 2 weeks out of use.

[Chas G]

47 minutes ago, Roy124 said:

Chas, that eliminates some potential variances, but my point was don't compare my set of readings with yours and think them better or worse.  Look at how your readings compare, one with another over a period.

My 'shocking' drain measured over half a day was I significant when calculated after 2 weeks out of use.

Roy, I understand what you are saying.

I am only comparing my own readings taken in exactly the same way and since a long charge last Sunday they are all significantly better. Its like the Battery has woken up. I just hope it stays that way.

[Cyker]

4 hours ago, Chas G said:

I think my car had probably been sitting on the forecourt for a few weeks before I bought it and was jump started for my test drive and delivery.

It then took a really good long charge to kick it back up to full capacity despite showing 12.6 volts after shorter charges.

I had pondered the question whether Toyota would have produced a car with a charging system which wasn't capable of keeping the 12 volt battery charged after relatively short journeys and I think the answer is no otherwise they would be inundated with complaints and a disappearing customer base.

My personal theory is the Mutley batteries suffer excessive degradation if they're discharged too low, and as you say it's likely that's happened once or twice while it was in storage, so the Battery starts off degraded when it gets to the customer. Customer then doesn't use the car so much and Battery degradation accelerates.

That's why I reckon the Yuasa seems to solve the problem, as it seems to be much more resistant to degradation from partial charge and doesn't just drop all its capacity off a cliff so readily.

My Mk4 is a workhorse so it gets heavy use, but I think that's staved off the degradation in the OE Battery (Which still hasn't died on me!)