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Battery resting voltage and alternator output voltage for new 2.8D

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  • Battery resting voltage and alternator output voltage for new 2.8D

    I have started this thread to gather information on what battery resting voltage and alternator output voltage people are seeing for the new 2.8D. The reason for this is on a few posts on other threads people have reported alternator output voltages from 13.4V up to 14V, and someone had suggested it may be a build date thing.

    So it would definitely be helpful if people posted their voltages - if there is a pattern where later vehicles are getting higher voltages, then it would maybe suggest there is a software patch, and we could lobby Toyota Australia to authorize the service people to allow the voltage setting to be raised, or try to find out if we can DIY it.

    Of higher concern to me is the resting voltage I am seeing on my cranking battery - before starting I am seeing around 12.4V, and sometime as low as 12V. This seems low to me for what be a fully charged battery. For example we drove 1 1/2 hours to a campsite this weekend, car sat there for 2 days then when I went to start it the battery read 12V. So if people could post their battery resting voltage before start also, that would be helpful.

    So my info - Sept 2015 2.8D, when running outputs 13.4-13.6. Max I have seen is 13.8, but normally around 13.6. Cranking battery normally 12.4V before I start.

    (ps - Please try not to sidetrack this thread - it has split from another thread because it started heading into the VSR vs Dc/Dc trench warfare.)

  • #2
    Hi LeadWings and I have no intentions of interrupting your thread, but for the sake of collecting a common consensus of data, can I make a few suggestion.

    Most alternators fitted to vehicles these days, while they may seem to be huge, they have high current ratings to be able to supply low currents at idle.

    Basically, if a manufacture knows that their vehicle requires a minimum of say 40 amps to replenish the cranking battery and supply enough additional power to keep the vehicle’s electrics running, they may fit a 120 amp alternator.

    The reason for the high amp alternator is that at optimum RPMs, usually somewhere around 2,000+ RPM, the alternator will be able to produce it’s maximum current output.

    The problem for vehicle manufacturers is that many new vehicle spend much of the time stuck in slow moving traffic, and it is at low RPMs that the manufacturers need the 40 amps.

    So they need to pick an alternator that produces 40 amps at say 700 RPM and this may mean using a 120 amp alternator that can produce 1/3 of it's maximum current at 1/3 of it's optimum RPM.

    I am leading somewhere with all of this.

    When people take voltage readings, can they, where possible, wait till they have driven for at least 30 minute and then pull-up, leave the motor idling, and because of what I have posted above, can they turn everything else off, like Air-conditioning, entertainment system, if at night, turn off all their lights.

    The reason for turning everything off is that all alternators work the same way, and if there is a current load being applied to the alternator that is greater than the alternator can produce at low RPMs, the regulator automatically lowers the VOLTAGE to compensate.

    By turning everything off, you have a far better chance of getting the correct voltage reading that is required.

    With the motor idling and all electrics turned off, can they please take the voltage at the cranking battery terminals.

    This will then give the most accurate indication of the normal operating voltage of each vehicle, taken in a similar situation.

    The reason I suggest the voltage reading be taken at the cranking battery is that this removes any possible error/low reading that can sometimes occurs when getting a voltage ready from a cigarette type voltage monitor.

    I had a customer tell me he had one voltage reading as low as 13.2v in his new 150, but at the time, I forgot to ask him where and how he got that reading.

    Another suggestion, can each person list their normal driving habits for say at least the week before they did the voltage measurements.

    Again, the reason for this is along the lines of what you posted LeadWings, when you indicated that even though you had done an hour and a half drive, two days before, that your battery was in a low state before starting.

    If someone has been doing lots of short drives, this is the Shopping Trolley Syndrome, where continual drives shorter than 15 minutes will actually cause the cranking battery to be slowly but progressively discharged.

    Again just suggestions.

    Comment


    • #3
      Thanks Drivesafe, good points - so if people can please post the voltage when running but "resting" and no other major loads on.

      But any observations of voltage at other times that seem unusual/informative please feel free to post.

      Comment


      • #4
        Checked mine today using techstream. Engine hot 84C, on tickover at 700 rpm, ambient temp about 28C, with all accessories turned off voltage is 13.2 - 13.4v. 2008 D4D manual 155k. Voltage before starting engine yesterday was 12.4v with all accessories off.

        Comment


        • #5
          Originally posted by Dhm77 View Post
          Checked mine today using techstream.
          Across the battery terminals?

          Comment


          • #6
            No just using the techstream programme off the engine management unit.

            Comment


            • #7
              Hi guys I did as above regarding turning everything off and there was no difference. I tested this over about a 2hr drive testing every 10mins I think. I posted my results somewhere on here.

              Like the original poster I think the crank battery is low and will fail much quicker than it should.

              Comment


              • #8
                I’ve just had my car in for its 6 months service, and noted the battery charging voltage was low (ie once the car is off, the battery is only at around 12.4 – 12.6 V) and asked if there was any way to get the voltage turned up.

                The service guy was really good, and when I picked the car up we had a long chat. He had got in touch with their electronics expert (I assume from Toyota) to discuss.

                Summary of the discussion is that the system has been designed to only charge to the voltages I am seeing, mainly to increase battery life – ie charging the battery to a higher voltage has been shown to decrease battery life, and as it is cranking/starting battery in normal operation (ie read around town service) it doesn’t need to have lots of stored charge (unless you are having trouble starting and have to crank continuously). This also improves fuel consumption as the alternator is not generating power that would just be burnt off by heat/electrolysis in the battery.

                It is also a highly complex system (there is a brain just for the alternator/charging system) and they are not aware of a way to alter the set points/voltages etc.

                Obviously there are a whole lot of issues around this if you want an offroad 4WD with second battery etc, I just thought I would feedback what I was told.

                Comment


                • #9
                  I have replied in your other post but here is a chart to help you understand what the different voltage levels mean.

                  Comment


                  • #10
                    Originally posted by LeadWings View Post
                    Summary of the discussion is that the system has been designed to only charge to the voltages I am seeing, mainly to increase battery life – ie charging the battery to a higher voltage has been shown to decrease battery life, and as it is cranking/starting battery in normal operation (ie read around town service) it doesn’t need to have lots of stored charge (unless you are having trouble starting and have to crank continuously). This also improves fuel consumption as the alternator is not generating power that would just be burnt off by heat/electrolysis in the battery.
                    I see what they are saying , I dont neccessarily agree with it but i dont think the concept works well in the real world. We were camping at Rainbow Beach recently , on a hot day , and left the radio on with doors open , with the Engel running , while setting up camp. After no more than 2 hours went to restart the engine , and guess what - flat battery. RACQ tech suspected insufficent charge voltage as he had seen it many many times.
                    since that incident ive added a second battery , voltmeters on each , 40A DCDC unit with jump start , LED cabin lights and no longer leave the radio on. Watching the voltmeters - main battery volts rise to 14.1 when car starts then settles down rapidly to 13.4 after about a minute. Aux battery volts rise to 14.1 when unit kicks in and drops to 13.6 after a few minutes. I'm not real happy with the charge voltages but will put up with it and see what happens to each battery long term.

                    Comment


                    • #11
                      Some insight into the battery voltage during a 30-minute trip and data logged at 1sec intervals.
                      I had replaced the Alternator regulator some months ago as the voltage was somewhat lower (13.5V) and erratic. After replacing and cleaning the brushes the regulator seem to correct the erratic and low voltage issues to some extent. As can be seen, the voltage still has low voltage spikes when the alternator is clearly not charging for very short periods while slowing down through the gears (6-speed manual). The ambient temperature was about 18C.
                      I'm still not happy about the low voltage as it takes the smart battery charger some hours to fully charge the battery to 14.6V then drop back down to 13.8V float. I would recommend regular overnight charging of the battery to keep the battery fully charged.
                      It does seem Toyota has a poor strategy for looking after the start battery, no heat shield to protect the battery, no boost charge which is going to fully charge the battery and only some notion of 13.8V float.


                      Attached Files

                      Comment


                      • #12
                        Ecogeek, if your smart battery charger is a DCDC charger then the alternator out voltage is irrelevant to how long it takes to charge as the DCDC charger should be stepping the voltage up to the required level, more likely the issue is the output amperage of the charger you have is too low to properly charge your batteries in the time the engine is running.
                        '18 VX, Billies with Dobinson springs, Summit bar with Narva Enhanced Optics to help my old eyes

                        Comment


                        • #13
                          Not trying to be a smart @$$, but it's common knowledge that all lead acid batteries can't get to full charge unless hours & hours of driving & it's not the job of the alternator to do this! The last 10-5% takes forever (more so when battery ages) and the only real tried & true way to deal with this is to charge & top up outside of driving. Not even a dc-dc will help in most cases. Simply put it's pointless to complain about the alternator chronically undercharging the starter.
                          As for resting V of battery, after car has stopped, turn on headlights for 10-15secs to bleed off surface charge & wait half a day, A healthy wet cell will hold 12.6V. 12.5V is cause for concern but may be bad multimeter. 12.3-12.4 is pretty much getting into replace. AGM is slightly higher voltages like 12.8-12.9V full 100% healthy. Actual numbers vary brand to brand of battery.

                          Get a small solar panel & keep the starter topped up & never worry about this again. And replace the battery at the right times.

                          Comment


                          • #14
                            Sort of related. What size of small solar panel is needed to keep a 100 ah deep cycle battery alive in a camper trailer without using a regulator? It could also be used on the car as per above.

                            Comment

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