Power consumption using PPOB only vs truck on

[K6CCC]

There have been various discussions - particularly with the addition of PPOB with the truck off being added to older truck - related to the battery consumption of running just PPOB vs leaving the truck on. I did a test so there are some real numbers as opposed to opinions. The reasonably obvious part is that leaving the truck on will take more power because more stuff is running - but how much more.

I need to explain my somewhat odd situation that makes this test possible. I have a completely stand alone Aux 12 volt battery system that powers some radio equipment and my dashcam. I did not want to run the radios off the normal (tiny) 12V battery. My aux battery consists of two Group 24 deep cycle batteries in parallel which comes out to about 100 AH. They are charged from an IOTA battery charger that is in turn powered from the rear seat 120V outlet. Normally that is on whenever the truck is on. When the aux battery system is fully charged, the IOTA charger is drawing 30 watts or 64 Volt Amps (no one said the power factor was great at low load) according to a Kill A Watt power meter. The Ford app reports that as "less than 90 watts". Note that with that draw, the PPOB will stay on without any other load.

Test methodology. On Saturday evening, I turned on the truck and disabled the power down timer, turned off the AC completely, and turned off the radio. I also put the 15 inch center screen to "Calm". I measured the HV battery Energy and SOC using CarScanner at the beginning and end of the test. I also screen captured the Ford app front page. Lastly I took a photo of the IPC. After capturing the start data, I disconnected CarScanner, but left the OBD-II reader connected. Closed up and locked the truck. A few times overnight I looked at the Ford app just to make sure the truck was still on and PPOB was still supplying power. Other than that, the truck was not touched. Exactly 12 hours later, I took the same screen captures and photos. I also captured a temperature chart from my home weather station. That really should not matter much, other than nothing that it was quite warm during the test...

Sunday evening I repeated the test with everything the same EXCEPT that the truck was not on, only PPOB.

The results - more results in images.
Battery energy with truck on started at 77.74 KWH / 57.81% and ended at 73.75 KWH / 55.56% for a difference of 3.99 KWH / 2.25%
Battery energy with PPOB only started at 67.53 KWH 50.64% and ended at 64.59 KWH / 48.97% for a difference of 2.94 KWH / 1.67%

Here's all the images. The filenames should make stuff obvious...

Sponsored

 

[The Weatherman]

So, if I’m I read your writeup correctly, we can save ~1 KWH per 12 hrs with truck off as opposed to having to leave it in on.

Thats not nothing!

 

[RickLightning]

When the truck was left on, were the headlights also turned off?

While this is interesting, it's missing the following:

- Battery temperature of HVB impacts the energy. Sure, these aren't far off, but how much does it take for a fraction of a kWh to be gained or lost, in the energy reading?

- When the truck is running, some energy MAY be used to charge the 12v, if it believes it needs it.

What this proves is that the truck uses almost no energy running with things turned down.

 

[bmwhitetx]

Nice testing! The only thing that I would change is to use an incandescent light bulb as your constant/dummy load instead of your IOTA battery charger. Unless you're absolutely sure it pulled the exact same constant load across both test sessions.

There would not be any doubt with an incandescent bulb plus you could calculate true losses in the whole system - which is what you are really after (battery kWh used - bulb kWh = loss). I would even put the Kill-A-Watt meter on the bulb to get it's true kWh used.

 

[K6CCC]

So, if I’m I read your writeup correctly, we can save ~1 KWH per 12 hrs with truck off as opposed to having to leave it in on.

In my test, that is correct.

When the truck was left on, were the headlights also turned off?

Yes. All lights off.

Nice testing! The only thing that I would change is to use an incandescent light bulb as your constant load instead of your IOTA battery charger. Unless you're absolutely sure it pulled the exact same constant load across both test sessions.

Once the Aux battery is charged, the draw from the IOTA changes very little - as verified with the Kill A Watt MANY times in the past year.

 

[chl]

Interesting.
The effect on the HVB SOC is minimal confirming that the truck uses little HVB energy even when on and idle.

But I wonder about the effect on the 12v battery, and about what the effect would be if the full PPOB was being use, i.e., the bed outlets were active as well.

A couple things about the test:

1) Most battery 'maintainers' have a duty cycle, that is they are not on 100% of the time, they come on and off as needed to keep the battery at 100% but avoid overcharging. So I wonder about that in the tests. I would not expect a 'smart' battery maintainer to have a steady 90W the whole time.

2) I also wonder about the 12v battery data captured by the OBD scanner. The scanner charts seem a bit inconsistent to me:

At the start of the ON test, the first one says 14.5v and 97% SOC.
At the end of the ON test, 13.3v and 100% SOC.
Those SOC numbers are not consistent with 'reality.'

For the OFF test, starts at 13.85v 100% SOC and ends at the same numbers 13.85v 100% SOC, as if no 12v battery energy was used up.

To run the PPOB the 12v battery has to hold the HVB contactors open, run the communications and monitoring, etc. so some energy must be used for those functions.

If the DC-DC converter is on while the truck is off and PPOB is on, then I could see that the DC-DC converter is keeping the 12v battery fully charged and covering the minimal PPOB, etc. 12v system use.

A few months ago, before the PPOB with truck OFF OTA was sent out, I did some testing for a Ford team working on some problems with draining the 12v battery when the truck was ON or OFF and running the PPOB bed outlets after a few hours. That was causing in the PPOB shutting off before the reserve was met.

The DC-DC converter was NOT providing enough energy to keep the 12v battery from getting too low leading to a shut down while using the PPOB.
( see https://www.f150lightningforum.com/forum/threads/pro-power-reserve-limit-fails.35984/ for the details)

Keeping the 12v battery on a maintainer solved that issue as a temporary workaround.

Perhaps Ford fixed that problem with the OTA change and it is no longer a big issue?

After 12 hours, if the scanner test data is correct, with the truck ON the 12v battery voltage did drop from 14.5v to 13.3v.

However, generally, around 13v 'resting voltage' is 100% for an AGM battery. The 14.5v would be a typical charging voltage applied by a charging system to bring the 12v battery up to 100% before it settles down to a resting voltage.

Anyway, I think this test shows that an OBD scanner cannot distinguish between the charging voltage being applied to the 12v battery and the resting voltage, and the SOC numbers of the 12v cannot be relied on.

I presume the 12v battery data is derived from the 12v battery BMS which uses coulomb counting and has to periodically correct itself due to 'drift.'

It appears the test only had the 90W load and only used the 2.4kW outlet.
It was not using the rear bed inverter(s) which provide 240v at 30A (running wattage 7.2W).
So I wonder what the drain on the 12v battery would be if the bed outlets also being run?

It seems to get accurate information about the effects on the 12v battery from running PPOB with the truck ON vs OFF cannot be done with an OBD car scanner.

If I had the time and inclination to find that out I would:

1) disconnect and fully charge the 12v battery
2) test the fully charged 12v battery for terminal voltage and SOC after at least a few hours 'rest'
3) reconnect and run the PPOB for some time
4) after turning off the PPOB, disconnect the 12v battery and let it 'rest' a few hours
5) do another test of the battery terminal voltage and SOC and
6) compare the two test results.

BTW, just for fun, try running the PPOB and then pressing the climate button in the app.
It was causing the PPOB to shut off when I was running the tests.
Same when a scheduled departure time with climate was reached.

 

[K6CCC]

I was not paying any real attention to the 12V side of it for these tests. On the truck on test, it had been on for most of 90 minutes prior to starting the test. On the truck off test, PPOB had been on for at least an hour prior to starting the test.

BTW, just for fun, try running the PPOB and then pressing the climate button in the app.
It was causing the PPOB to shut off when I was running the tests.

Yes, turning on climate turns off PPOB when the truck is off.
Opening the frunk turns off climate when the truck is off...

 

[chl]

I was not paying any real attention to the 12V side of it for these tests. On the truck on test, it had been on for most of 90 minutes prior to starting the test. On the truck off test, PPOB had been on for at least an hour prior to starting the test.



Yes, turning on climate turns off PPOB when the truck is off.
Opening the frunk turns off climate when the truck is off...

Well the 12v battery screwed up reaching the reserve, so just watch out for that if it is still an issue.

Sponsored