Do Not Sell My Personal Information Jump to content


Help! Battery Voltage Drops In My Car While Driving


Recommended Posts

HI Guy's

Vehicle: IS220d Multimedia

Year: 2007

I hope someone can shed some light on my bizarre problem, only noticed it couple a weeks ago when my s3 car charger refused to charge my phone even though the charging indication was showing red on the s3. The charger works fine on my other vehicle. I have ruled that out.

I decided to hook up my obd2 ELM Bluetooth dongle with Torque Pro software to monitor what the voltage was. Here is my finding:

Car switched off = 12.6V

Car switched On (idle) = 14V

Car switched On (Rev 1500) = 14.5V

When driving, foot on acceleration my voltage drops to 12.3V as soon as i lift the foot off the accelerator the voltage shoots up to 14.1V, even if i'm in gear or while driving putting in neutral same problem when accelerating.

** For the above test Climate control, Radio/CD, windows etc,, were not in use, No load apart from engine running**

I have even done a parasitic drain test using my voltmeter and that shows reading of 0.15 micro amps which i assume is normal aslong as its below 0.50 micro amps.

The only thing i haven't checked is the ground straps. Can some please tell me how many ground straps there are for this vehicle and where are they located on the vehicle. I just hope its something simple like a loose or broken strap.

P.S I also have at my disposal the latest TIS techstream software on my laptop..i can look at other readings in depth but not sure where to look with this problem.

Look forward to your reply

Thanks in advance

Link to comment
Share on other sites

I appreciate some form of fluctuation will take place and controlled by ECU but in my case the voltage never goes over 12.4v when vehicle is being driven and foot on the accelerator pedal. I did a test drive today for 20 miles and was monitoring the voltage, it was constant at 12.4v as soon as i take foot off the accelerator pedal the voltage goes up to 14.1v. Its seems odd this should happen, its like something is pulling the voltage down when i press down on the pedal.

Link to comment
Share on other sites

I suspect the 220d uses a ECU controlled variable voltage alternator to improve fuel economy, performance and meet emission targets. It is likely that the output is reduced when accelerating to improve performance, the system is designed to provide most of the charging when decelerating.

Link to comment
Share on other sites

Interesting you both mentioned ECU, now this got me thinking. About a fortnight ago my vehicle had a new egr valve replaced under warranty at lexus, while doing that replacement they mentioned to me they updated my ECU with the latest release firmware map by lexus. Just out of curiosity would be great to hear from other is220d drivers about their Battery voltage levels on their cars.

What i don't understand is why my mobile phone will not charge under these conditions, with the current situation i can not use the cigarette lighter port or Aux port under the armrest to charge my phone. Yet i have ruled out the car charger as it works fine in my other vehicle.

Link to comment
Share on other sites

Thank you ChumpusRex and ColinBarber.

After reading your post's last night i decided to go for another test drive today but this time i turned on my climate control to full blast when voltage was showing 12.4v and guess what!! voltage shot up to 14.4v even though my foot was on the accelerator pedal when i turned it down to medium the voltage dropped back to 12.4v whilst accelerating so it seems as you guy's mentioned controlled by the ECU if and when demand is required.

I did test the ground straps/points on the chassis, the readings were all fine as they should be. No difference in voltage.

Not sure where i'm left with the car charger issue. Only solution might be just buy a spare Battery.

My car charger is genuine samsung which i purchase directly from samsung online shop -- >

http://www.samsung.com/uk/consumer/mobile-devices/smartphones/smartphone-accessories/ECA-U21CBEGSTD

Link to comment
Share on other sites


  • 2 years later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



×
×
  • Create New...