12v battery maintenance, issues, etc.

[Mooly]

This is an old publication on sealed gel batteries although still a classic. Some might find it interesting.

Yuasa Little Red Book of Batteries.pdf

[anchorman]

1 hour ago, MCatPG said:

Mooly - I agree but I'm going to suggest a more complex causality, and solutions.

This will be a long post, those who aren't interested in getting to the root cause of the accessory battery failure problem and the possible solutions should skip it.

In another thread @anchorman kindly pointed out that Hybrid cars are not boats, presumably in case I hadn't noticed. But our boat is where I get my knowledge of 12V DC battery management from and it's directly relevant to the problem.

On the boat when we don't have shore power we use batteries of the same type as the accessory battery in the Toyota Yaris Cross, and many other hybrids:- 12V DC Absorbent Glass Mat/AGM. Our boat battery manufacturer provides data about anticipated lifetime cycles and battery damage caused by excessive discharge. The point is that the number of charge/discharge cycles and the actual energy in any cycle which you can extract from these batteries is limited, and greatly reduced if the batteries are mis-used. Here's a table I prepared myself:

The vital data is the note that the battery State of Charge (SoC) should NEVER fall below 50%, which on these batteries is indicated by 12.18V at rest. The Toyota accessory batteries will have different figures but not very much. If the batteries fall below this level and remain there for anything more than a few minutes there is a significant risk of bringing forward the bill for installing a new set of batteries. I manage the batteries when we are aboard so that they never fall into the red area and we have redundant warning systems to inform us if this happens when we are not on the boat. We aim to get 8 years from a set of batteries. The biggest problem we have had is the amount of electricity that is wasted by what we call parasitic (and others call quiescent or background) current drawn from the batteries. These are things which are always on and individually take only small amounts of current, but cumulatively they are a problem. Over the years I have got rid of a lot of them and I'm hopeful that I can get rid of more this year.

So how does this relate to the cars?

The accessory battery in the Yaris Cross is, I believe, 35Ah, so 35 x 12 = 420Wh, and assuming these batteries shouldn't go below 50% SoC that's 210Wh of available energy, from fully charged. Putting it another way a fully charged battery could run an old fashioned 100W light bulb for 2 hours, or for people my age with long memories a one bar electric fire for 12.6 minutes. The trouble is that current is being drawn from the accessory battery all the time, even when the car is idle, by parasitic devices.  If you search on the forums for "parasitic" and "quiescent" you'll find lots of posts and some very good technical analyses about the parasitic current being drawn from these batteries.

The accessory battery can only be charged by drawing current from the "Hybrid"/Propulsion battery (Toyota call it the High Voltage or HV battery) via the DC/DC converter, and only when the car is in READY mode. If the car is idle and locked there is no charge going into the accessory battery and the parasitic current will eventually discharge it below an acceptable SoC. How long this discharge takes will depend on the value of the parasitic draw AND the initial SoC of the battery AND the physical condition of the battery AND the ambient temperature.

With that as background, in my view the causes of the problem in the cars are deep-rooted in the design, and the solutions follow from the causes:-

1. Inadequate capacity of the accessory battery - the designers should have specified a higher capacity battery and accepted the additional weight and/or cost. 
2. Excessive parasitic current drawn from the accessory battery when the car is idle, together with insufficient control given to owners to enable them to reduce the parasitic current if necessary. Both these causes could be cured.
3. Lack of a warning system to inform owners that the accessory battery is being drained below an acceptable SoC. The owner needs some way of knowing that an accessory battery recharge is needed and that is why owners are buying voltmeters. Ideally there should be a warning light visible from inside and outside the vehicle and/or a text message. 
4. Very slow charging of the accessory battery via the system of engine generator > HV battery > DC/DC converter > accessory battery, so that numerous short journeys will result in the accessory battery never receiving a full charge. @Mooly questions whether the design of the DC/DC converter is part of the problem and I think it probably is. The manufacturer's solution is to tell owners to decide when to recharge the accessory battery (without telling them how they should know - cause 3) and then to engage READY mode and sit in or stay near to their cars for a lengthy period of time while the accessory battery is slowly charged by discharging the HV battery via the DC/DC converter, and the HV battery is itself recharged by occasional automatic engine runs. It should be possible for the owner to force the car to run its engine/generator when stationary and charge the accessory battery directly in the same way as a conventional car alternator does. I've seen comments that AGM batteries can't accept a high current inflow when they need it - this is incorrect. They do need a staged charge (bulk > absorption >  float) but a battery which is very depleted can accept a high initial charge. Alternatively the accessory battery should have a Lithium chemistry.
5. Lack of a convenient way to charge the accessory battery from an external source. This is what @Dala and others have installed and I will be installing myself. It should be a standard fitting and would cost the manufacturer very little. For the owner it would be no different to having a PHEV or BEV which needs to be plugged in.
6. Damage to batteries which have fallen below the minimum acceptable SoC at some time because of causes 1-5, and which now have a capacity to store energy which is far below the original capacity so that they "go flat" in just a day or two, as so many have reported. This could be solved by a better charging regime as explained above.

I know that Toyota don't read these forums so I've probably wasted my time typing this, bet never mind.

It seems to me that many other hybrids are similar. It's not just the yaris Cross and it's not just Toyota.

@MoolyPS: On my screen the figures for your car from 2003 to 2011 inclusive are missing

Very interesting.  I believe Toyota do read the forums but whether the right people for this subject do is another matter.  I’m not sure what you want to happen - getting Toyota to take responsibility for a design weakness might not be an easy task as they will have reams of calcs and test results to say the Battery is adequate.  It’s crossing that line between normal and abnormal use.  If you want to be sure, write to them.  I tend to guard against a flat Battery by leaving mine on charge while I’m away on holiday.  I think it’s easy but the car sits in the garage with easy access to a power supply.  I use the under bonnet connector and by feeding the wire out by the headlight I can close the bonnet.  I can operate the plug from an app on my phone and it shows the current draw which was 45 amps when the car was first connected (brand new) and dropped to 12 after an afternoon on charge.  What that equates to in terms of SoC I don’t know.  I also carry a jump pack for if I get problems away from home.  I sat in the car one day with it switched on waiting for somebody with the heater on.  It definitely came up on the dash to put the car in park in the ready mode to avoid flattening the Battery.  There have been accounts of people listening to the radio and not getting warned but I think they’ve missed or ignored it because mine was bottom of the range and mine warned me.  That’s me with the stuff to do it but it’s no help to someone with on street parking.  I only do all this because my use of the car is very sporadic so I expect it.   I come from an era of being a mechanic on cars with dynamos and you had to be mindful of using power because you could use it much quicker than you could make it.  I’ve not had the back seat out yet so I don’t know if the cradle will take a bigger battery.  What are you proposing?

[Mojo1010]

I have taken the back seat off my MK3 to clean the fan and check out placement of Battery. I think there is room for a very slightly bigger Battery say a 41ah. 

 

[Dala]

In the case of remote monitoring of the voltage or current consumption, the voltage of the microprocessor charger is recalibrated according to the temperature! Information for users so they don't get shocked 🙂

[AisinW]

35 minutes ago, Dala said:

In the case of remote monitoring of the voltage or current consumption, the voltage of the microprocessor charger is recalibrated according to the temperature! Information for users so they don't get shocked 🙂

 

 

 

In fact, the DCtoDC converter in the car does the best job. My past 12V Battery lasted more than 8y. The current one is 7y old and at 12.6V after 30 minutes drive. I rarely left the car more than 2 weeks. 

[Mooly]

Whenever I see the term 'float' charge I always relate that to the voltage that can be safely applied 24/7 such as in standby batteries and alarm systems and so. Also float charging of conventional lead acid batteries to maintain condition over time.

I would consider the operating conditions in the 12v Battery in Hybrids to be much more what is termed 'Cyclic' orientated where the Battery sees discharge for perhaps many hours or even days and then only gets a relatively short period of charging (when you are driving) and that type of use (to how I have always understood it) means a higher voltage charging regime can be usefully used.

I also wonder what the maximum charge rate is that the DC/DC convertor can supply when the Battery is discharged. A conventional alternator is limited only by its design capacity and the output can be as high as 70 or more amps. It is up to the condition of the battery how much it takes but the current is there if it can accept it.

I would expect the next generation Hybrids to address these issues as they have come to dominate the problems owners repeatedly seem to experience.

 

 

[Dala]

smart charging while driving

[RobertR]

I think if you connect hybrid car to the nonhybrid car Battery to "jump start"… it's possible but without starting the second car engine up, only put some energy to the dead Battery and then disconect the jump start cable before start. 

[anchorman]

That’s not according to the instructions…..

[Derek.w]

Don those instructions are in my manual, so is just leaving the vehicle in whats equivelent to the second key position before starting to give the hybrid Battery time to charge the 12 volt Battery before atempting starting with the brake depressed with a flat 12 volt Battery.

[anchorman]

10 hours ago, Derek.w said:

Don those instructions are in my manual, so is just leaving the vehicle in whats equivelent to the second key position before starting to give the hybrid battery time to charge the 12 volt battery before atempting starting with the brake depressed with a flat 12 volt battery.

That’s it Derek, that’s using the traction Battery to effectively jump start itself (12v battery).

[MCatPG]

15 hours ago, anchorman said:

(1) I’m not sure what you want to happen.....

(2) I tend to guard against a flat battery by leaving mine on charge while I’m away on holiday.....  I use the under bonnet connector and by feeding the wire out by the headlight I can close the bonnet.  

(3) I can operate the plug from an app on my phone and it shows the current draw which was 45 amps when the car was first connected (brand new) and dropped to 12 after an afternoon on charge.  What that equates to in terms of SoC I don’t know.    

(4) What are you proposing?

@anchorman I'm picking out the main points in your post:-

(1) What do I want to happen? Well I don't expect Toyota to be able to do anything for those of us with the current iteration of the car's design. We are on our own with this problem and self-help is needed. So the only things I want to happen are for owners like me to understand what typically goes wrong so we can (a) force a replacement of the accessory Battery if it is ruined while under warranty, and (b) know how to live with the problem.

(2) I would appreciate a photo of your charging arrangement. Is it the mains lead you feed out by the headlight or the charging leads from the charger? Also, I thought the accessory Battery had to be charged at the posts located close to it under the rear seat - I thought the under-bonnet connections were for "jump starting" only

(3) SoC in most batteries is usually measured by the voltage at rest (ie: when no current is being drawn). There is no isolation master switch for the accessory Battery and fitting one would require re-programming of accessories after it has been used, so it's difficult to put these batteries into a resting condition. However if one is confident that very little power is being drawn from the accessory battery a voltage measurement is a reasonably accurate to find out the SoC. Another way to measure SoC is indeed the input amperage from a charger and the manufacturer of our big batteries states that when the current demanded by the battery falls to 0.5% of its Amphour capacity at (from memory) 70 degrees Fahrenheit the battery is fully charged - in our big batteries that's 255Ahr x 0.005 = 1.275A

(4) My proposed solutions for owners are just what others have written about on these forums, and I'm grateful for all the useful comments, as follows:-

(a) Always carry a "jump start" battery pack (also I'm going to label the connection points and provide an instruction card on how to get the car mobile again if/when the accessory battery is over-discharged)

(b) buy a Voltmeter and keep an eye on the 12V system - never let it go below 12.2V. Learn how to manage the car's systems to maintain the accessory battery in good condition and accept the limitations on use which are required.

(c) Buy a good quality charger and find a way of routing the mains power supply cable to the charger - either your under-bonnet arrangement or fit a convenient socket like @Dalahas done with power to the charger coming into the car somewhere else. But that only works for people who can run a mains supply cable safely to the car. For everyone else I think a high capacity battery pack+inverter ("power station") like @Dala is using is the best solution for routine use, taking it indoors to recharge it when necessary. Possible also have a PV panel + controller when the car is standing idle for lengthy periods of time, if there is enough sunlight and the panel can be mounted correctly. Be vigilant about charging the accessory battery when necessary.

(d) Be aware that if the accessory battery is discharged for any lengthy period below (probably) 12.2V, and certainly 11V (for example in an airport car park) and has to be "jump started" you probably need to buy a replacement because it will not regain its full capacity. It will "go flat" much quicker than when it was new because the period of excessive discharge will probably have caused sulphating of the plates. The caveat to this is that the modern chargers which have a setting specifically for AGM batteries usually have a reconditioning mode and it will be worth trying that because it won't cause any additional damage.

(e) This one's a bit of an outlier. I'd say that owners like Veronica who started this thread could consider claiming that they were mis-sold the car by the dealer on the ground that the car is not fit for her purposes and the dealer ought to have established what her purposes are before selling the car. An accusation of mis-selling strikes fear into the heart of the legal department of any consumer-facing business. However there is a caveat to this - if Veronica's purposes have altered because she became ill after she bought the car I think such a claim would have much less weight.

 

 

[anchorman]

1 hour ago, MCatPG said:

@anchorman I'm picking out the main points in your post:-

(1) What do I want to happen? Well I don't expect Toyota to be able to do anything for those of us with the current iteration of the car's design. We are on our own with this problem and self-help is needed. So the only things I want to happen are for owners like me to understand what typically goes wrong so we can (a) force a replacement of the accessory battery if it is ruined while under warranty, and (b) know how to live with the problem.

Part b will be easier than part a.  The nature of forums is that they attract people with problems.  It’s hard to quantify just how much of a problem this is so is ignoring the advice in the handbook considered self inflicted.  It would take a lot of evidence that Toyota have and we don’t for a test of reasonableness to be applied in court.   The dealers could do more in advising people OR making gestures towards or covering replacement batteries if they failed to advise the customer adequately.

(2) I would appreciate a photo of your charging arrangement. Is it the mains lead you feed out by the headlight or the charging leads from the charger? Also, I thought the accessory battery had to be charged at the posts located close to it under the rear seat - I thought the under-bonnet connections were for "jump starting" only

I wouldn’t advise anyone to trap the mains lead by the headlight or anywhere else on a metal car.  As you suggest, I just put the trailing leads through which on a Ctek are protected against short circuit or incorrect polarity.  I leave the unit up on the side where I can see the display.

(3) SoC in most batteries is usually measured by the voltage at rest (ie: when no current is being drawn). There is no isolation master switch for the accessory battery and fitting one would require re-programming of accessories after it has been used, so it's difficult to put these batteries into a resting condition. However if one is confident that very little power is being drawn from the accessory battery a voltage measurement is a reasonably accurate to find out the SoC. Another way to measure SoC is indeed the input amperage from a charger and the manufacturer of our big batteries states that when the current demanded by the battery falls to 0.5% of its Amphour capacity at (from memory) 70 degrees Fahrenheit the battery is fully charged - in our big batteries that's 255Ahr x 0.005 = 1.275A

(4) My proposed solutions for owners are just what others have written about on these forums, and I'm grateful for all the useful comments, as follows:-

(a) Always carry a "jump start" battery pack (also I'm going to label the connection points and provide an instruction card on how to get the car mobile again if/when the accessory battery is over-discharged)

Yes, perhaps we should have a tutorial pinned in the tech section showing advice for low usage users.

(b) buy a Voltmeter and keep an eye on the 12V system - never let it go below 12.2V. Learn how to manage the car's systems to maintain the accessory battery in good condition and accept the limitations on use which are required.

Ctek make a number of plug in traffic light led’s that show battery condition.  I guess the useful one would be the one that plugs into the accessory socket because although no use for charging, it does get isolated and would stop any parasitic draw.

(c) Buy a good quality charger and find a way of routing the mains power supply cable to the charger - either your under-bonnet arrangement or fit a convenient socket like @Dalahas done with power to the charger coming into the car somewhere else. But that only works for people who can run a mains supply cable safely to the car. For everyone else I think a high capacity battery pack+inverter ("power station") like @Dala is using is the best solution for routine use, taking it indoors to recharge it when necessary. Possible also have a PV panel + controller when the car is standing idle for lengthy periods of time, if there is enough sunlight and the panel can be mounted correctly. Be vigilant about charging the accessory battery when necessary.

That is why I don’t see any benefit in adding the remote socket by the seat.   Toyota have added a wire to the fuse box which is heavy enough gauge to carry the current without noticeable drop.  That’s what it’s there for.

(d) Be aware that if the accessory battery is discharged for any lengthy period below (probably) 12.2V, and certainly 11V (for example in an airport car park) and has to be "jump started" you probably need to buy a replacement because it will not regain its full capacity. It will "go flat" much quicker than when it was new because the period of excessive discharge will probably have caused sulphating of the plates. The caveat to this is that the modern chargers which have a setting specifically for AGM batteries usually have a reconditioning mode and it will be worth trying that because it won't cause any additional damage.

Thats why I’d urge the use of a decent brand charger. I bought the one recommended for stop/start batteries and is optimised for AGM batteries.

(e) This one's a bit of an outlier. I'd say that owners like Veronica who started this thread could consider claiming that they were mis-sold the car by the dealer on the ground that the car is not fit for her purposes and the dealer ought to have established what her purposes are before selling the car. An accusation of mis-selling strikes fear into the heart of the legal department of any consumer-facing business. However there is a caveat to this - if Veronica's purposes have altered because she became ill after she bought the car I think such a claim would have much less weight.

I would suggest that her illness wouldn’t come into it.  There are plenty of low use users but again, I think the dealer should be the interface in determining what is the requirement of the customer just by asking a few questions.  They could also either recommend or provide at a cost, either a jump pack and or a charger if their property permitted it.  Using it is no different to dealing with a flat tyre.

 

I’ve replied within the text above.  
 

I notice the charger is down to 2amps after 24 hours.  

[FROSTYBALLS]

8 hours ago, MCatPG said:

I'd say that owners like Veronica who started this thread could consider claiming that they were mis-sold the car by the dealer on the ground that the car is not fit for her purposes and the dealer ought to have established what her purposes are before selling the car.

In the OP's case, the dealer who sold her the car has moved out of the area, and she was advised that if she wanted to reject the car, she would need to approach that dealer rather than her current local one.

Topics on 12 volt Battery maintenance have been  pinned in each of the main forums (Yaris & Yaris Cross, Corolla, Rav4, etc) since February 2021.

[AisinW]

On 1/8/2023 at 10:58 PM, RobertR said:

I think if you connect hybrid car to the nonhybrid car battery to "jump start"… it's possible but without starting the second car engine up, only put some energy to the dead battery and then disconect the jump start cable before start. 

That's right. But our Battery 34b20r  only have 270 CCA (ideal new fully charged).   Typical regular cars have at least 500CCA for starting the car.  It may work but I will not do that either because of our AGM Battery is not design for such heavy lifting.  you can do that for desperate  emergency situation and it is for your friend and family.  There is no point to waste $200 good Battery just to help stranger who can ask other drivers around without sacrificing anything. 

[RobertR]

I don't say you should jump start the other car. Just used your car to charge a little the dead Battery, just enough to start the other car. Not starting dead car when connecting to hybrid car. Only use our hybrid car like a charger...30 min should do the thing. When no other options are avaliable. 🙂

[Roy124]

Robert true, but you would have to watch the other driver like a Hawk.  Perhaps hold their keys while yours is the master. 

You also need cables that are long enough, and if your Battery is inside the car, a positive clamp that can grip the positive blade on the fuse box. 

Best advice I suspect is make your apologies and leave. 

[anchorman]

25 minutes ago, RobertR said:

I don't say you should jump start the other car. Just used your car to charge a little the dead battery, just enough to start the other car. Not starting dead car when connecting to hybrid car. Only use our hybrid car like a charger...30 min should do the thing. When no other options are avaliable. 🙂

You can’t do it.  To do what you suggest would take hours. It’s a notion that simply won’t work and you shouldn’t suggest it to other uninformed people.  It’s going to end in disaster.  

[nadca]

Hi everyone,

Just one question to those who have had concerns with the 12v battery:

Do you ever leave the car parked in the N or D position of the shift switch?

This could be the reason for unexplained flat batteries!

[RobertR]

It will work, I'm sure it does but not recommended for anyone who dont know what they doing as you said. My first car have manual lights and i forgoting turn them off after trip or over night numerous time, it was old VW polo 1.4 petrol, Battery was dead...deaply under 12V and i just put my garage lab power supply, put voltage to 14.4V and current limiter to 5A and after 15 to 20 minutes Battery have enough charge to crank up the engine. Toyota hybrid dc to dc converter is charging 8A into the Battery and if you connect discharged battery to your battery, the current will flow into battery with lower voltage, into the dead one, even your good battery will be putting some current to weaker battery. Yes its risky if you dont know what are you doing but if no other choice, somewhere in wildness, I will do it without hassitation. But as you said, not recommended as commod advice.

[Roy124]

Let's face it, to many motorists an ICE to ICE is scary enough.  Indeed opening the bonnet, if they know how, is pushing the competence of many. 

I recall a driver asked for the something to be topped up.  Whatever, but it was oil or water in the wrong place. 

[Cyker]

I once spoke to someone who genuinely thought you had to take a car to a garage to have air put in the tyres, when they found they had a flat...

These are the sort of people who the DVLA saw fit to grant a driving license, and that we share the road with...  

I can see why they introduced things like the show me/tell me part of the test...!

 

[Rhymes with Paris]

9 minutes ago, Cyker said:

I once spoke to someone who genuinely thought you had to take a car to a garage to have air put in the tyres, when they found they had a flat...

These are the sort of people who the DVLA saw fit to grant a driving license, and that we share the road with...  

I can see why they introduced things like the show me/tell me part of the test...!

 

Show me/tell me? 

What kind of new horror is this?

Joking aside, I don't know what this is.

Unless it is like the bike instructor's training at Cardington where the trainer falls off the bike when you have forgotten to tell him to put a leg down when the bike stops.

Apparently some people are so stupid that they don't understand this, so you have to teach them basic physics.

[Roy124]

At 18 I could drive but we had a lecture on petrol engines with the instructor talking of manifolds.  Lots of heads nodding until I help up my hand and asked what was a manifold. 

He was incredulous that I had no knowledge what ever of engines.  

How many people in ordinary life have had lectures on engines?  

We buy petrol in litres and consume it in miles per gallon. How many people can convert one to another using mental arithmetic?  Or compare US to Imperial? 

[Cyker]

So, two new things that I suspect you didn't have to deal with when you learned is the hazard perception test, which basically involves watching a bunch of videos and pressing a button when you spot a hazard (Usually a cyclist or pedestrian about to pull in front of you).

The show me/tell me stuff are questions like Show me how you'd clean the windscreen, or Tell me how you'd check the oil. When I did mine these were asked before you got in the car and started the practical test proper, but I'm told they're now done while you're driving?!

For the morbidly curious the official allowed questions are handily provided by the DVSA (Not the DVLA as it turns out, which I wrote at first ) :

https://www.gov.uk/government/publications/car-show-me-tell-me-vehicle-safety-questions/car-show-me-tell-me-vehicle-safety-questions

 

There have been some weird changes, like removing classic manoeuvres like turn in the road (aka 3 point turn), but they've added this bizarre one that involves pulling over to the wrong side of the road and parking up facing oncoming traffic, then reversing and moving off again. I still don't understand what the idea behind that one is!