Cigarette Lighter Voltmeter

[Peter Lukasch]

They are more like within 0.1 or 0.2 volts of true.
HOWEVER… the socket is also far removed from the actual battery and passes through many devices and yards of cable before reaching the terminus. So this can drop the voltage 0.1 or 0.2 volts as well.

That is quite correct, voltage drops can hide anywhere, even where the positive button of the cigarette plug makes contact. My message was simply not to trust a $12 volt plug in a cigarette lighter socket when diagnosing battery voltage. I have personally dealt with an out of range readings with these units (and it was not millivolts), if a person were not aware of that fact it can easily lead to a costly misdiagnosis.

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[grumpyunk]

I have one for checking battery charge but also for the extra USB port . Does a good job of checking charge rate . My mav Eco doesn't have AGM battery . Battery is crappy . My auto startstop hasn't worked for months because the battery never fully charges , which is okay with me .

I was told by 'someone' that the battery in a 2.0 ecoboost is some sort of hybrid AGM battery. I wonder if sitting in Hermosillo for a month or so after completion did something to the battery. I remember from back when that battery construction had changed, and some batteries lost capacity or totally failed if allowed to discharge.
I do not know if my battery is crappy, but the AutoSS is disabled, within two days of being fully charged by a smart charger. I got the 'start the engine to have FordPASS work again' message within 5 days of a full charge. Fully charged to 13.2V 10/17, got the "Low battery, sleep mode" message 10/22 Sunday. Battery continued to discharge to 12.24V by 10/28 Saturday. Charged to 13.13V 10/31 .
Charged overnight from 12.29V Thursday 1/11 10AM to 13.25V 8AM 1/12 Friday. Drove Monday 1/15, AutoSS disabled until the leaving Harbor Freight, and then it was disabled again after driving a few miles with no accessories enabled. Got home around noon, 12.36V. Checked after sitting for several hours later that evening, 12.73V. All measured using a Fluke DVOM. I have no explanation for the voltage increase after sitting in the garage. I am flummoxed by the charging system and battery operation. Then again, the battery was manufactured in a Far East country that is not known for the quality of its products.