charging problem or not

[ALAW]

10 hours ago, Herbie said:

In theory it should be fine Brent, but the caveat is that I don't know the current state of your battery so I can't guarantee it.

To remove all anxiety and give peace of mind I always carry a unit similar to this one. Never had to use it on my own car yet but it's started at least a dozen others and works first time, every time.

Thanks ever so much Herb I think ill get one of these. Reading what Para says if the 12v Battery is flat you can only open the doors with the emergency key that's a pain isn't it then some resetting to do Mmmm. Think i will when i have time look at the manual and see where you do this jump starting and how. Been discussed on other threads if I remember as well  thanks for your input and para for the thread. PS i reckon the bat will be ok after 10 Days.

[GSLV6]

I have had this twice with my RX.  As long as you can access the auxiliary Battery (presumably it's in the boot as with other hybrid models?) the test procedure is as follows.  Using a multi meter set to voltage, your Battery should read at around 14.6V with the engine running and the hybrid Battery charging it via the charging circuit.  With the engine off and the ignition off, a healthy Battery should maintain around 12.4 to 12.6V.  If it dips lower then there may be a chance a cell has been compromised.  One major difference between engine cranking high torque batteries and leisure batteries (such as the auxiliary battery) is that the latter should never be allowed to drop below 50% charge as this can damage the Battery cells and they won't be able to recover.  You may get away with it a few times.  These days, I always have  Battery tender wires attached to the terminals permanently so if the car is going to sit longer than say 2 weeks without use, I simply hook it up to a CTek Battery charger on trickle charge.  Most Battery chargers come with the wiring and connectors needed for exactly this purpose.  The Battery can remain insitu as it won't damage the electronics doing this (I checked with Lexus).

[RONNIE W HODGEKINSON]

On 1/17/2023 at 10:48 AM, Moleman said:

As far as I am aware, the answer is no, there is no way of telling the state of the start battery (from within the car). Other third party equipment can be added to measure this.

If you are not using the car at least weekly, Lexus recommend running the car in park for at least one hour, to ensure the start battery is charged. During this time the hybrid battery will charge the start battery.

If you cannot trickle charge, then the car needs to be used as described above as minimum.

Spot on.......................................................................................................................................................

[GSLV6]

But it is easy enough to diagnose with a Battery tester such as the Duratool tester (which I have) or to do a quick check on voltage across the terminals.  

[ALAW]

Well I have to be honest and say I really had 12v Battery anxiety on finding the car flat on my return from holiday and further anxiety by the fact I will be using the meet n greet service at the airport and if they found it flat and jumped it incorrectly and it caused damage. Firstly the correct procedure should you need to do this as in the manual is remove the fuse cover and expose positive terminal then remove engine cover to reveal negative terminal. After reading all the posts on this thread I decided to ring a few dealers up to gauge opinion hopefully to put my mind at rest. I got mixed responses. One said couldn't guarantee it would start it depends on condition of Battery. On starting with a jumper one said they do it all the time and connect the jumper to the positive and negative terminals directly onto the 12v Battery in the boot, they also said come down and will show me. Another dealer when I mentioned this said its not advisable can damage the system always jump on the terminals under the bonnet. Another said about the solar charger as mentioned by @Lent and @Steppy how this works they said you plug it into the diagnostics port which is inside the car front right i think he said (anyone confirm) put panel on window dash and it puts a trickle into12v Battery the OP @para999  I would say this is your best option. However overwhelmingly most said I shouldn't have a problem especially having over an hours drive to the airport the 12v will be well charged. A pal has an RX and he has left his for 3 weeks once no problem. So you will all be pleased to know my anxiety has now eased greatly after ringing round. Hope this helps others. 

[Herbie]

57 minutes ago, ALAW said:

Firstly the correct procedure should you need to do this as in the manual is remove the fuse cover and expose positive terminal then remove engine cover to reveal negative terminal. [...] On starting with a jumper one said they do it all the time and connect the jumper to the positive and negative terminals directly onto the 12v battery in the boot [...] Another dealer when I mentioned this said its not advisable can damage the system always jump on the terminals under the bonnet.

This comes up often and never fails to make me incandescant because dealers really should know better 

If you take a multimeter and put the positive probe on the "special" jump start post in the engine bay fuse box and put the negative probe to any unpainted nut, screw, bolt, or bodywork, it will show 12V.

There is no hidden or 'special' 12V source in that fuse box, or in the engine bay, or anywhere else for that matter. The 12V you're measuring is coming from one source and one source only, and that is the 12V Battery at the back of the car, in the boot.

That Battery and that 'special' jump start post in the engine bay fuse box are directly connected to each other by a big cable. Ergo, 12V at the front is exactly the same as 12V at the back and it makes not one iota of difference whatsoever, which you choose to connect your jump leads to.

The one and only reason not to connect directly to the Battery is that the Battery can generate hydrogen gas and there is a very small risk of ignition and an explosion if the jump leads spark when being disconnected.

After more than 45 years of driving and 'hobby mechanic-ing' and after asking family, friends, workmates and others, not a single person has had personal experience of this, nor have they ever heard of it happening to anyone else, so it would appear to be more of a theoretical risk than a practical one.

In conclusion, both the Battery at the back and the jump post at the front are absolutely identical and equally viable places to connect jump leads/battery pack to from an electrical point of view.

[LenT]

On 1/27/2023 at 12:41 PM, GSLV6 said:

These days, I always have  battery tender wires attached to the terminals permanently so if the car is going to sit longer than say 2 weeks without use, I simply hook it up to a CTek battery charger on trickle charge.  Most battery chargers come with the wiring and connectors needed for exactly this purpose.  The battery can remain insitu as it won't damage the electronics doing this (I checked with Lexus).

Precisely so, Paul.  

I have these CTEK cables permanently connected to the Battery posts of both our cars.  It means that the connection to the trickle charger is a simple plug that’s distant from the Battery.  As Herbie has patiently explained on several occasions, this enables the Battery to be charged without the risk of causing a spark near the Battery itself.

I also have a NOCO Power Pack - having once seen an AA guy use one very effectively.  They come with their own spark prevention procedure clearly explained.

 

[hamfam]

do you know Lexus fix for it - L-SB-0036-20     DCM Reset and Firmware Update (LG)

Some 2020-2021 ux250h vehicles may exhibit one or more of  the following conditions

DTC B15A804 is present in current of history

Red sos LED stays on after bulb check

Unable to subscribe to remote services

Unable to activate Wi-Fi

*Depleted 12v vehicle Battery when in IG-OFF

 

[ALAW]

Evening folks well i can happily report after been left at the east midlands airport meet n greet for 11 days on my return the car started no problem at all. So @Herbiewas right shouldn't be a problem. Should anyone use this airport the Meet n greet service is good.

[UX250h]

I use this, 

Car Cigarette Lighter Power Socket Charger Adapter 120W USB Port Chargers with Voltage & Touch Switch Cigarette Lighter Splitter Adapter for Iphone, Smart phone, Tablet, GPS, Dash cam etc https://amzn.eu/d/jlga9oZ

I run a dashcam from this, I occasionally fast charge my phone, but mainly use it to see the state of the 12V Battery.

Start the car in accessory mode to see the current voltage (mine has a discrepancy of -0.1V) This saves me the hassle of testing the voltage from the actual Battery.

When the car is running, you will see a voltage of 14+ volts when the 12V Battery is being charged, and a voltage of 12.5V when the 12V Battery is not being charged.

 

[Herbie]

2 hours ago, UX250h said:

I run a dashcam from this, I occasionally fast charge my phone, but mainly use it to see the state of the 12V battery.

Just be aware that you're not really seeing the state of the 12V Battery, just a voltage indication,

To get a real meaningful reading you need to put the Battery under load by using a load tester. That adapter you linked to may indicate 12.5V but once a load is applied it could drop like a stone to 5 or 6V if, for example, there's a faulty cell.

[UX250h]

When the car is running in ACC mode, load is applied by Air conditioning and lights, Audio etc.

I use the voltage display as follows:

1. Check the voltage displayed (+0.1v) is at least 12.2V, if not, I'll charge it.

2. That the Battery is being charged ok (voltage display is 14.5V)

3. Whilst driving, the Battery switches from 12.5V (not charging) to 14.5V (charging) and vice versa.

Saves me from measuring the voltage directly from the Battery !

[gdamorini]

On 6/16/2023 at 9:30 AM, UX250h said:

When the car is running in ACC mode, load is applied by Air conditioning and lights, Audio etc.

I use the voltage display as follows:

1. Check the voltage displayed (+0.1v) is at least 12.2V, if not, I'll charge it.

2. That the battery is being charged ok (voltage display is 14.5V)

3. Whilst driving, the battery switches from 12.5V (not charging) to 14.5V (charging) and vice versa.

Saves me from measuring the voltage directly from the battery !

With full hybrid cars the 12 v Battery is not loaded by AC, lights, audio, etc. The power is furnished totally by the hybrid system Battery.

The 12 v Battery has the only purpose of starting the hybrid system, and maintaining some accessory services when the car is parked (anti theft system, car locks).

To test the 12 v Battery in a full hybrid car you need a load tester.

[NemesisUK]

24 minutes ago, gdamorini said:

With full hybrid cars the 12 v battery is not loaded by AC, lights, audio, etc. The power is furnished totally by the hybrid system battery.

The 12 v battery has the only purpose of starting the hybrid system, and maintaining some accessory services when the car is parked (anti theft system, car locks).

To test the 12 v battery in a full hybrid car you need a load tester.

True but not when in ACC mode, only when in READY mode.

[gdamorini]

On 6/17/2023 at 10:15 AM, NemesisUK said:

True but not when in ACC mode, only when in READY mode.

Can you turn on air conditioning in ACC mode? I didn't think so.