What V is the 12v battery suppose to be

[pedrofromredro]

Sorry if this has been covered before but I have done a search and couldn’t find it.but We bought our is300h in may but never noticed that when you switch the car on in the morning you can’t put the heated seats on or the fans/windscreen demister straight away.so not sure if the 12v Battery is on its way out or if this is normal 🤷🏻‍♂️.I have checked the 12v Battery and the voltage varies as to how long it is left.generally the car is used daily 

[Mincey]

There's a very useful chart floating around (from Herbie I think - apologies if not) which shows the condition of a Battery against the voltage it is putting out. I can't find it though, but here's some info from Lexus:

"The Lexus manual page 584 9-1 Specifications Electrical system states:

12.5 V or higher: Fully charged

11.0 – 12.4 V : Half charged

10.9 – or lower; Discharged

(Check the voltage 20minutes after the hybrid system and all lights are turned off)"

I am no expert in this field, but there are several extremely clued-up members on here who will be able to give you the definitive answer.

[pedrofromredro]

8 minutes ago, Mincey said:

There's a very useful chart floating around (from Herbie I think - apologies if not) which shows the condition of a battery against the voltage it is putting out. I can't find it though, but here's some info from Lexus:

"The Lexus manual page 584 9-1 Specifications Electrical system states:

12.5 V or higher: Fully charged

11.0 – 12.4 V : Half charged

10.9 – or lower; Discharged

(Check the voltage 20minutes after the hybrid system and all lights are turned off)"

I am no expert in this field, but there are several extremely clued-up members on here who will be able to give you the definitive answer.

Haven’t seen the chart you mention but have checked the voltage.when the car has been left for a day the voltage has been 10.4 v.I have taken the Battery of and charged it but the voltage still drops slowly but it drops.when it is in the car and ignition is on or in ‘ready’ mode it is 14 v.but unsure if the heated seats should still come on when the car is switched on 

[Mincey]

Do you know how old the Battery is? 

[pedrofromredro]

I am assuming it is the original Battery and the car is a 14 plate so that be 7 years old 🤷🏻‍♂️

[Mincey]

1 minute ago, pedrofromredro said:

I am assuming it is the original battery and the car is a 14 plate so that be 7 years old 🤷🏻‍♂️

If it's that old, then I'd seriously consider replacing it. I'm sure that others here will agree.

[pedrofromredro]

Will do will give Lexus a call now and get one ordered thanks mincey

[Mincey]

7 minutes ago, pedrofromredro said:

Will do will give Lexus a call now and get one ordered thanks mincey

With Winter coming, that's a great idea. Also, depending on the version of the audio system you have, there can be issues when the Battery is changed, so if you get Lexus do to it, any issues are their problem. 

[route66]

Extract from this thread: link

... which in turn came from the is300h battery problems thread:

(My Battery level is indicated above)

If you say "when the car has been left for a day the voltage has been 10.4 v", then according to the chart, you, eh, definitely need a new Battery asap.

[Thackeray]

2 hours ago, pedrofromredro said:

when the car has been left for a day the voltage has been 10.4 v.I have taken the battery of and charged it but the voltage still drops slowly but it drops.when it is in the car and ignition is on or in ‘ready’ mode it is 14 v.but unsure if the heated seats should still come on when the car is switched on 

The heated seats and the fans should come on as soon as the car is in Ready mode. It may be that if the 12v circuits still have low voltage the computers don't allow them to start until the voltage is high enough. I've never experienced this. When the voltage is showing around 14 or 14.5v, this is because the high voltage Battery has begun feeding the 12v circuit to recharge the 12v Battery. It doesn't mean the 12v Battery is healthy (or unhealthy for that matter - it just means the recharging has started.)

Just out of interest, would the car start at 10.4 volts? I've seen it start at 11.4v but I don't know whether it can still start at lower voltages. Mincey has made the interesting discovery (above) that the manual seems to imply that the car should start down to 11v. I didn't know that was in the manual. It would be interesting to know how true it is.

 

[pedrofromredro]

8 minutes ago, Thackeray said:

The heated seats and the fans should come on as soon as the car is in Ready mode. It may be that if the 12v circuits still have low voltage the computers don't allow them to start until the voltage is high enough. I've never experienced this. When the voltage is showing around 14 or 14.5v, this is because the high voltage battery has begun feeding the 12v circuit to recharge the 12v battery. It doesn't mean the 12v battery is healthy (or unhealthy for that matter - it just means the recharging has started.)

Just out of interest, would the car start at 10.4 volts? I've seen it start at 11.4v but I don't know whether it can still start at lower voltages. Mincey has made the interesting discovery (above) that the manual seems to imply that the car should start down to 11v. I didn't know that was in the manual. It would be interesting to know how true it is.

 

Yes it has always started even when the Battery was that low I haven’t yet had to jump start the car.when I first tested the Battery that was the voltage it was 10.4 v.it was only the fact that I wondered why we had to wait perhaps 2mins or so for the fans to come on to demist the windscreen now the cold weather has started 

[Thackeray]

Interesting (and reassuring) that the car will start on such a low voltage!

As for the fans, bear in mind that if you have the climate control on Auto they will scarcely operate in cold weather until the engine is warm enough to provide some heat. This can be several minutes depending on the outside temperature. There's a long discussion on this issue on the NX forum here.

[pedrofromredro]

No the fans won’t even come on at all they won’t switch on or the heated seats for a good 2 mins 

[Thackeray]

3 hours ago, pedrofromredro said:

will give Lexus a call now and get one ordered

It'll be interesting to see if a new 12v Battery solves the problem. People often point out that with conventional cars you can tell that the 12v Battery is failing because you can hear the starter motor getting slower and slower whereas on these hybrids there's no warning that the 12v Battery is about to fail. But perhaps a lack of heated seats is a signal that you need a new Battery. Maybe you can report back when you find out the answer!

[pedrofromredro]

So got to Lexus and bought a Battery.managed to fit it and no major difference with the heated seats and fans.but at least the Battery is new and isn’t going to fail at any time soon when I least expect it 😂🤣

[Mincey]

1 hour ago, pedrofromredro said:

So got to Lexus and bought a battery.managed to fit it and no major difference with the heated seats and fans.but at least the battery is new and isn’t going to fail at any time soon when I least expect it 😂🤣

I'm sorry it didn't fix your problem but a new Battery will give you peace of mind over the winter. Don't forget to follow the Lexus advice and run the car for an hour in Ready mode (transmission in Park, the car not in an enclosed space and not somewhere it will get stolen!) to keep the 12V Battery charged up if you are not going to be using it for some time.

[Duggie B]

19 minutes ago, Mincey said:

to keep the 12V battery charged up if you are not going to be using it for some time.

Or if possible put the car on a Battery charger/maintainer if you have off road parking next to house...

[pedrofromredro]

6 hours ago, Mincey said:

I'm sorry it didn't fix your problem but a new battery will give you peace of mind over the winter. Don't forget to follow the Lexus advice and run the car for an hour in Ready mode (transmission in Park, the car not in an enclosed space and not somewhere it will get stolen!) to keep the 12V battery charged up if you are not going to be using it for some time.

It’s peace of mind with a new Battery.but have also noticed that they must be linked the seats and the blowers as they both come on at the same time.but thanks everyone for your help 👍🏻

[pedrofromredro]

I have discovered as it was brought to my attention about a fault with the fans by a member on here.it’s fault code B1455 which I have checked and is on my car it’s to do with the servos on the Ac/fan unit,that’s why they don’t come on straight away might start another thread regarding this see if anybody has tackled this 🤞🏻