12v Battery, the Achilles heel

[Brechin Slate]

I was messing about with an OBD reader yesterday, trying to sort out which tyre pressure sensor was in which wheel.  I was working with the ignition on but not in the 'Ready' mode.  Less than an hour later when I came to move the car, the hybrid system wouldn't start because I'd flattened the 12v Battery.  I had no lights or radio on and no other systems were active when I was playing with the OBD.  Managed to get a jump start from a neighbour's Battery then hot footed it to Halfords where I bought a Noco Genius 5, (lovely bit of kit and nice to use the Gold Member discount).  All well now, the Battery is in good nick and I'll plug the charger in whenever I wont be using the car for a few days BUT...one of my hobbies is sailing and I sometimes go away for 3-4 weeks at a time leaving my car in a marina but without access to an external power source.  I guess others may leave their cars for extended periods too like in airport car parks etc.  Is the only answer to carry a jump starter?  Disconnecting the Battery would disable the alarm/immobiliser which would probably invalidate the insurance.  What do others do?  What is the best portable power pack?  If Lexus are aware of this weakness why don't they provide a standby?  A month into 300h ownership and the honeymoon period is over, I'm beginning to miss my IS250..

[Mincey]

I think the Lexus engineers need a word with their oppo's at Hyundai. My wife's Ioniq has one of these buttons:

 

If the 12v Battery goes flat for any reason (it hasn't yet and the car gets as much use as mine at the moment, which isn't much) a simple press pushes lots of volts from the hybrid Battery to the 12v Battery and off you go again. Or something like that. 

Following some fun with my late father's iQ ("Satan"), I bought one of these:

It has been used to start my IS300h a couple of times now and will remain in the boot. Just in case.

[PaulWhitt20]

Why not have a solar powered charger built into the parcel shelf to keep the Battery topped up.

[cruisermark]

1 hour ago, Mincey said:

I think the Lexus engineers need a word with their oppo's at Hyundai. My wife's Ioniq has one of these buttons:

 

If the 12v battery goes flat for any reason (it hasn't yet and the car gets as much use as mine at the moment, which isn't much) a simple press pushes lots of volts from the hybrid battery to the 12v battery and off you go again. Or something like that. 

Following some fun with my late father's iQ ("Satan"), I bought one of these:

It has been used to start my IS300h a couple of times now and will remain in the boot. Just in case.

I think that is simple but ingenious - In the event of a flat Battery you have all this power in form of a hybrid but no way to utilise this

[Brechin Slate]

30 minutes ago, PaulWhitt20 said:

Why not have a solar powered charger built into the parcel shelf to keep the battery topped up.

Nice idea. Have you got one? Pics?

[malcolmw]

I assume the Hyundai button just enables the DC/DC converter to supply the 12V system and charge the Battery a bit.

Apparently all-electric cars like the Taycan and the i-Pace are prone to 12V Battery flattening (i.e. a breakdown) as they also use DC/DC converters to  charge the vehicle system batteries.

[Herbie]

2 hours ago, Brechin Slate said:

If Lexus are aware of this weakness why don't they provide a standby?

It's not "a weakness" but a design 'feature'.

A conventional car needs a big beefy Battery to supply the starter motor with 300A or more to crank the engine.

Our hybrids don't have a starter motor. All the 12V Battery does is to boot the computers, pressurise the brakes and get the hybrid system up and running to READY mode, which is our equivalent of a conventional car with its engine running and just sat idling. This takes less than 20A to achieve rather than the 300A or more of a traditional car.

This benefits the manufacturer in a couple of ways:

• A smaller Battery costs less so there's an immediate financial gain there
• A smaller Battery weighs less, which helps to keep the overall weight of the car down, which in turn helps to keep emissions down to the ever-lowering limits set by various governments

It doesn't matter to us as the owners of an individual car but if you multiply it up by thousands of cars you can see their logic. The downside for us as the owners is that we have to be aware of this and either use the car more or take precautions. The owner's manual does inform you of this, I believe 

If you need to leave the car at, say, an airport carpark for a couple of weeks then you should carry a jump start Battery pack or jump leads etc., just in case.

There will always be a drain on the 12V Battery, even when you're fast asleep in bed at 3am, to feed the clock, the radio presets, keep the alarm armed and so on. I remember reading that it should be somewhere around 50mA or 0.05A.

My RX has a Battery of 51Ah and for the sake of this discussion we'll say that it's brand new and fully charged. 51Ah/0.05A = 1,020 hours (42.5 days or 6 weeks) to completely discharge. However, in reality it will not be brand new and fully charged so the age of it will play a part, and also, for the purposes of starting a car, it will effectively become useless well before that 6 weeks - so you may get 3 weeks out of it.

[Herbie]

4 hours ago, Mincey said:

I think the Lexus engineers need a word with their oppo's at Hyundai. My wife's Ioniq has one of these buttons:

 

If the 12v battery goes flat for any reason (it hasn't yet and the car gets as much use as mine at the moment, which isn't much) a simple press pushes lots of volts from the hybrid battery to the 12v battery and off you go again. Or something like that.

I think it's the "something like that" option and nothing to do with the hybrid Battery or DC/DC converters at all.

Here's a screenshot from the owner's club showing a page from the owner's manual. The way I interpret this (and if I'm wrong I'm happy to be corrected) is that it's nothing more than a voltage sensing circuit and a relay.

A circuit monitors the state of charge of the 12V Battery and if it drops to a preset threshold a relay opens to prevent it dropping any further, to the point where it won't start the car. You get in and discover that the car won't start so you push the Battery reset button, which then closes the relay and the 12V Battery can then use its remaining power to start the car in the normal fashion.

The problem with this system (or at least the way that Hyundai have implemented it) is that it's a special 12V Battery that has been incorporated into the high voltage Battery, so no nipping down to Halfords or wherever to get a replacement if ever needed.

[Brechin Slate]

1 hour ago, Herbie said:

It's not "a weakness" but a design 'feature'.

Whichever way it's dressed up, it's a shortcoming.  The cost difference between a full size Battery which holds a usable charge for a month (a reasonable ask for any car owner) and one which after 2 weeks has the absent owner sweating like Fred West watching Groundforce is worth paying.  The list price of my car was over £42k, if I was asked to fork out another £100 for additional reliability it would be a no brainer.  If Hyundai have an effective solution then it has to be assumed that Lexus missed a trick.  As a marine engineer I agree with your figures regarding cranking and draining but it's a problem that's been handed from the designer to the consumer.

[Herbie]

2 minutes ago, Brechin Slate said:

Whichever way it's dressed up, it's a shortcoming.  The cost difference between a full size battery which holds a usable charge for a month (a reasonable ask for any car owner) and one which after 2 weeks has the absent owner sweating like Fred West watching Groundforce is worth paying.  The list price of my car was over £42k, if I was asked to fork out another £100 for additional reliability it would be a no brainer.  If Hyundai have an effective solution then it has to be assumed that Lexus missed a trick.  As a marine engineer I agree with your figures regarding cranking and draining but it's a problem that's been handed from the designer to the consumer.

I agree, it would be far better to have a solution from the factory.

But again, a simple reading of the owners manual - as we all should do when we get a new car - would prepare you for it. It's our responsibility to find out how our new machines work when we get them.

I'm not singling you out in any way but to be honest, I'm shocked at just how many people in this owners club and our 'sister' club on Facebook just get a hybrid and have no idea how they work or what they should do differently to owning a conventional car. I sometimes feel like giving them a good shake and shouting "RTFM"

[Brechin Slate]

I have personally read the manual, more than once, all 692 pages of it, I like manuals 😀  There are not many references to the 12v Battery, one is about the Battery saving function using the key fob, one is about how to recharge it and the one really relevant to this thread is:

"Auto power off function

If the vehicle is left in ACCESSORY mode for more than 20 minutes or ON mode (the

hybrid system is not operating) for more than an hour with the shift lever in P, the power

switch will automatically turn off. However, this function cannot entirely prevent 12-volt

Battery discharge. Do not leave the vehicle with the power switch in ACCESSORY or

ON mode for long periods of time when the hybrid system is not operating."

The brief to the manual writer must have been along the lines of "put a warning in but don't be too precise and make sure that 'power off' doesn't actually mean that.

I understand hybrid systems fully from concept to operation, I used to operate and maintain warships which were totally reliant on them.  The manual has one chapter missing and it's the one that explains why they fitted a part which made a car less reliable than it's predecessor.

[Mincey]

45 minutes ago, Herbie said:

I think it's the "something like that" option and nothing to do with the hybrid battery or DC/DC converters at all.

Here's a screenshot from the owner's club showing a page from the owner's manual. The way I interpret this (and if I'm wrong I'm happy to be corrected) is that it's nothing more than a voltage sensing circuit and a relay.

A circuit monitors the state of charge of the 12V battery and if it drops to a preset threshold a relay opens to prevent it dropping any further, to the point where it won't start the car. You get in and discover that the car won't start so you push the battery reset button, which then closes the relay and the 12V battery can then use its remaining power to start the car in the normal fashion.

The problem with this system (or at least the way that Hyundai have implemented it) is that it's a special 12V battery that has been incorporated into the high voltage battery, so no nipping down to Halfords or wherever to get a replacement if ever needed.

I knew you'd know! Thanks for putting me straight Herbie :-)

[paulrnx]

I think it’s a poor design. Ok I’ve never suffered from it and I’m on my 4th Lexus hybrid and the longest I’ve left one is I think the best part of 3 weeks and it started ok. Being able to leave a car unattended for a good number of weeks and have it start ok is I think a reasonable expectation for a modern vehicle. The battery should have been bigger in my opinion. I can now see from comments in the forum that this is a genuine problem. I’m making sure mine gets used at least one hour each week atm. When we finally get back to holidays I may well purchase something to give a dead Battery a boost. I’d hate to get back to my car in an airport or cruise terminal carpark after a holiday and find a dead 12v Battery. It would actually make me think about whether a Lexus hybrid was the right car for me to be honest. Some good tips on here though. Thanks everyone! 😀

[PaulWhitt20]

https://www.halfords.com/motoring/battery-maintenance/battery-accessories/halfords-solar-power-240-battery-charger-196471.html

how about something like this ?

I have not personally tried it but would seem to do the job. 
 

 

[Guest]

1 hour ago, paulrnx said:

I think it’s a poor design. Ok I’ve never suffered from it and I’m on my 4th Lexus hybrid and the longest I’ve left one is I think the best part of 3 weeks and it started ok. Being able to leave a car unattended for a good number of weeks and have it start ok is I think a reasonable expectation for a modern vehicle. The battery should have been bigger in my opinion. I can now see from comments in the forum that this is a genuine problem. I’m making sure mine gets used at least one hour each week atm. When we finally get back to holidays I may well purchase something to give a dead battery a boost. I’d hate to get back to my car in an airport or cruise terminal carpark after a holiday and find a dead 12v battery. It would actually make me think about whether a Lexus hybrid was the right car for me to be honest. Some good tips on here though. Thanks everyone! 😀

I agree, I visit relatives in Australia every few years, I have always left my car near Heathrow for 4 to 5 weeks and the last thing I would want is to get off a 24 hour flight to find a flat Battery, never had a problem in the past but never done it with the Lexus 

[Ala Larj]

With respect to these jump start packs how do they work? 

According to the manual, when jump starting I need to keep the donor vehicle running for five minutes at slightly higher than tickover revs before starting my car. Does that mean I need to keep the pack attached for five minutes before I try to start?

In the good old days before hybrid I could start my car straight away after attaching jump leads. 
 

During these lockdown days I’ve been running my car for 30 minutes every week but have still experienced a flat Battery! 
 

Is my Battery on its way out or do I have a voltage leak somewhere? If so, what’s the most obvious cause?

[Barry14UK]

The small electrical portable starters have been demonstrated to work and as a solution for a flat Battery are a way of getting you out of immediate trouble.  However, batteries should not be allowed to go flat as every time this is done it reduces its life.  In fact some manufacturers append a label saying that if the Battery drops below a certain voltage the Battery losses its warranty.  Zoom up on the top view of this one for the Prius as a case in point. https://www.ebay.co.uk/i/254088997428

I am sure I was not the only person who received a warning from Lexus to check the Battery every two weeks on my RX450h and to ensure it was adequately charged whist not in use during pandemic.  If its not connected up to the hybrid Battery you need a solar panel or keep up the voltage with an appropriate smart charger.  So Lexus are aware of the problem.  

I wonder whether when you leave the car at an airport for a few weeks you could take another suitable Battery (temporarily and properly secured)  and connect this in parallel to provide extra capacity.  

[Brechin Slate]

10 hours ago, Ala Larj said:

 

In the good old days before hybrid I could start my car straight away

The portable 'jump starters' have enough power to get the hybrid system started which is all you want.  There's no starter motor to spin so the power needed is nowhere near that for a conventional vehicle.  You don't need to wait five minutes, you can just connect it and start your car straight away.  If jumping from a donor car, they really don't have to rev their engines when jump starting a hybrid car.

Lexus recommend running your car for 60 minutes per week not 30 if it's not being used.  Leave it in P, no lights, radio, wipers etc, go to 'Ready' and sit there reading a book/newspaper/phone/laptop/Razzle for an hour.  The engine will cut in occasionally to charge the hybrid Battery and the hybrid Battery will charge the 12v auxiliary Battery.  If you're like me, you'll need to tell curious passers by that 'yes thanks, I'm ok'.

Or you could get a smart charger.  Many to choose from.  I bought this one and am pleased with it.  Discount with your Gold membership card!

https://www.halfords.com/motoring/battery-maintenance/battery-chargers/noco-genius5-5-amp-battery-charger-230278.html

 

[NemesisUK]

14 minutes ago, Brechin Slate said:

Lexus recommend running your car for 60 minutes per week not 30 if it's not being used.  Leave it in P, no lights, radio, wipers etc, go to 'Ready' and sit there reading a book/newspaper/phone/laptop/Razzle for an hour.  The engine will cut in occasionally to charge the hybrid battery and the hybrid battery will charge the 12v auxiliary battery.  If you're like me, you'll need to tell curious passers by that 'yes thanks, I'm ok'.

Worth noting in addition to the above, in colder weather, the engine will cut in to provide heat to the cabin and in warmer weather the hybrid Battery will be additionally drained to power the a/c, unless one switches off the climate control.

[Brechin Slate]

6 minutes ago, NemesisUK said:

Worth noting in addition to the above, in colder weather, the engine will cut in to provide heat to the cabin and in warmer weather the hybrid battery will be additionally drained to power the a/c, unless one switches off the climate control.

👍

[ColinBarber]

53 minutes ago, Brechin Slate said:

Lexus recommend running your car for 60 minutes per week not 30 if it's not being used.  Leave it in P, no lights, radio, wipers etc, go to 'Ready' and sit there reading a book/newspaper/phone/laptop/Razzle for an hour. 

Not sure there is an hour's reading material in that last option 😉 

[ColinBarber]

12 hours ago, PaulWhitt20 said:

https://www.halfords.com/motoring/battery-maintenance/battery-accessories/halfords-solar-power-240-battery-charger-196471.html

how about something like this ?

I have not personally tried it but would seem to do the job. 
 

 

They don't provide nearly enough power. The 2.4w quoted would be at midday in the summer with the panel directly aligned to the sun.

Sitting on a dashboard with glass in the way, only directly aligned to the sun for an hour or so every day (if any due to cloud), and with the amount of daylight hours during our winter months it would probably slow the discharge to give you an extra a couple of days at best. It certainly wouldn't be able to maintain the Battery at a fully charged state.

You also need one that attaches to the OBD port as the 12v socket isn't permanently live.

[ColinBarber]

1 hour ago, Brechin Slate said:

Or you could get a smart charger.  Many to choose from.  I bought this one and am pleased with it.  Discount with your Gold membership card!

https://www.halfords.com/motoring/battery-maintenance/battery-chargers/noco-genius5-5-amp-battery-charger-230278.html

I've a Genius 5 I use for charging, but I keep my car connected to a Genius 1 to keep it fully charged - cheaper option.

https://www.halfords.com/motoring/battery-maintenance/battery-chargers/noco-genius1-1-amp-battery-charger-230262.html

[Herbie]

16 hours ago, paulrnx said:

I think it’s a poor design. Ok I’ve never suffered from it and I’m on my 4th Lexus hybrid and the longest I’ve left one is I think the best part of 3 weeks and it started ok. Being able to leave a car unattended for a good number of weeks and have it start ok is I think a reasonable expectation for a modern vehicle. The battery should have been bigger in my opinion. I can now see from comments in the forum that this is a genuine problem. I’m making sure mine gets used at least one hour each week atm. When we finally get back to holidays I may well purchase something to give a dead battery a boost. I’d hate to get back to my car in an airport or cruise terminal carpark after a holiday and find a dead 12v battery. It would actually make me think about whether a Lexus hybrid was the right car for me to be honest. Some good tips on here though. Thanks everyone! 😀

Agreed - it is a poor design.

Agreed - you should be able to leave a modern car for a good number of weeks.

The text in red is the most important.

Hybrids are a 'relatively' new technology and they are very complex and they are certainly not the right car for some people and/or situations. Just because I can get a decent sound out of my home hifi doesn't mean I can walk in and operate the mixing desk at a live Rolling Stones gig tomorrow!

It never ceases to amaze me that people squirt thousands, even tens of thousands of pounds at a car without doing research first, and expect it to operate and be like just any other car they've ever owned. Google (other search engines are available) makes it easier than ever before to find out a widget's strengths, abilities, downsides, and anything else you could ever wish to know about a given widget before buying it.

Hardly a day goes by without someone in this club or the 'other' club on Facebook bleating about leaving their car for a couple of weeks and now the 12V Battery is flat. It's just so unnecessary and could easily be avoided if they did a bit of research before buying the car.

I passed my driving test in June 1975 and since that day I have never, ever, ever, bought a car 'unprepared'. In fact, my wife gets annoyed with me because when it's time for a change I usually have an idea of which make and model I'd like, so for about three or four months beforehand I get every book, magazine, search the Internet, join the Owners Clubs and basically drive her mad with constant talk of it until I either go ahead and get one or decide it's not for me after all and move on to some other make/model and start the process again.

Instead of blaming someone or something else, people need to take responsibility for their own actions.

There you go - rant over Oh and Paul, I'm not having a go at you mate, it's just that your post had all the salient points in it

[Brechin Slate]

2 hours ago, ColinBarber said:

They don't provide nearly enough power. The 2.4w quoted would be at midday in the summer with the panel directly aligned to the sun.

Agreed, and if you already carry a portable power pack type jump starter it renders this surplus to requirements.  I've also joined LRA, more for my wife's benefit but at least I have belt and braces