Cigarette Lighter Voltmeter

[WayneGL]

Just put one in after dead battery, taking to dealer who 'recharged it". It shows a 14.8 V charging level voltage whenever in Run or Accessories mode. When turned off, as usual it stays in some kind of accessory mode until door is opened, but in this interim period, it show 11.8 or so volts

Is DC to DC charging working full time when the key is on? This should quickly ruin the battery.

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[The Real Maverick]

It is on full time the key is turned.

Evidenced by the voltage being above 12.x on your display.

Why do you think it will ruin your battery? The alternator makes power anytime the engine is spinning in a traditional vehicle.

The voltage declines after a while to the “safe” standby/trickle charge rate. Amps are usually about 1 or 2 going to the 12v battery.

 

[WayneGL]

Thanks. I guess I don't drive long enough to see the battery fully charged at about 12.5 V and have the voltmeter show that. The 14.8V or so charging voltage can't stay at that level can it? I can see the actual battery volts (may start above 12 but quickly drops below that) for a few moments when the ignition is off and the door is opened before everything is shut down. When driving or "idling" in electric, only the charging 14+ voltage.

Read that over-charging a lead-acid battery will destroy it.

 

[SLJ]

Read that over-charging a lead-acid battery will destroy it.

Mine on my ecoboost is an AGM, not lead acid. Not sure what it is on the hybrid but I doubt lead acid. The ecoboost has a battery management system that will not let the battery overcharge. Betting the hybrid has a similar one since there's a lot more battery stuff going on.

 

[The Real Maverick]

Mine on my ecoboost is an AGM, not lead acid. Not sure what it is on the hybrid but I doubt lead acid. The ecoboost has a battery management system that will not let the battery overcharge. Betting the hybrid has a similar one since there's a lot more battery stuff going on.

The EB came with AGM for the most part.

Hybrids come with Flooded Lead Acid.

EB need more power for starting. And frequent restarting with the idle stop feature. (Auto stop)

Hybrids have less demands on the 12v since the HV battery does all the heavy duty work.

 

[The Real Maverick]

Thanks. I guess I don't drive long enough to see the battery fully charged at about 12.5 V and have the voltmeter show that. The 14.8V or so charging voltage can't stay at that level can it? I can see the actual battery volts (may start above 12 but quickly drops below that) for a few moments when the ignition is off and the door is opened before everything is shut down. When driving or "idling" in electric, only the charging 14+ voltage.

Read that over-charging a lead-acid battery will destroy it.

My Hybrid 12v battery is showing age and may be going bad at 18 months old.

The charge voltage at startup is 15.2 to 15.3 volts. Tapers after an hour to 14.9 or 15.0 volts.

Tapers to 14.3 volts after 6 to 8 hours of driving, which I rarely do. Alas, my 12v battery is rarely fully charged.

 

[Bob The Builder]

I have measured as much as 15.5 volts from the alternator while charging my battery.

While I love my truck a lot, I am not optimistic the battery is going to last very long.

 

[grumpyunk]

Thanks. I guess I don't drive long enough to see the battery fully charged at about 12.5 V and have the voltmeter show that. The 14.8V or so charging voltage can't stay at that level can it? I can see the actual battery volts (may start above 12 but quickly drops below that) for a few moments when the ignition is off and the door is opened before everything is shut down. When driving or "idling" in electric, only the charging 14+ voltage.

Read that over-charging a lead-acid battery will destroy it.

AFAIK, most charging systems run in the 13.5-14.5V range. A battery at 11.8, from the first post, is significantly low on charge. The smart charging system sets a goal of State Of Charge - SOC - and attempts to get to that point. Ford has set the goal battery SOC to be less than fully charged which would be 6 X 2.1V(each cell), or 12.6V. You can find a battery voltage vs charge state on the web. Below 12 is 50% or lower per the chart(PDF) downloaded in 2015.
SOC V
100 12.73
90 12.62
80 12.5
70 12.37
60 12.24
50 12.10
40 11.96
30 11.81
20 11.66
10 11.51
Ford sets its smart system goal to improve fuel economy as the charging system is not put to hard work to quickly charge the battery. It more or less lazes about charging at less than capacity and takes its time getting to the goal.
I drove 500 freeway miles and the SOC was such I had one AutoSS function when I got off the freeway. A few days later it no longer worked. Return trip was the same, and it no longer worked.
Sunday I charged to 13.72V using a smart charger set to AGM. AutoSS did not work until a restart, then it worked once. Drove further, and it again no longer worked. The engineers seem to have set the SOC too low for AutoSS to work. FWIW.
tom
Added...
The cigarette voltmeter should show the battery SOC voltage. A hybrid will not be charging the 12V battery while parked. An ecoboost will not be running the alternator at all with the engine stopped. The cigar lighter or accessory sockets should show battery voltage, or charging voltage which must be higher in order to charge the battery, and is also used to run any accessories, so will show 'operating voltage' with the engine running(charge voltage) and battery with the engine stopped, until the timer shuts it down.

 

[Peter Lukasch]

Be wary of the small cheap digital volt meters like the one in the picture below, designed to plug into your cigarette lighter, although quite useful for keeping tabs on different charging conditions, the readings can ultimately be quite inaccurate. I would use a quality Digital voltmeter to verify the display before I would trust readings. And yes, I do do know this from personal experience, and I also own one of those accessory plug in voltmeters.

 

[WayneGL]

Not good, Maybe I'll install a permanent VM under or behind the back seat

 

[Waterick]

The problem with any volt meter when the truck is static is by the time you can see it, you have already opened the doors and activated the lights or turned on the hybrid battery. It does give a good reference over time to see if voltage is getting worse. Can also be useful to see volts at shut down. Unless you leave the hood open and check at the jump post, I don't know a way to check voltage after sitting awhile. Once you turn the key or push the button needed to activate 12v socket your volts are coming from the HVB, even if you turn off accessory power after it is not a true static reading (but can be used as a reference as stated earlier).

 

[inline_five]

It is on full time the key is turned.

Evidenced by the voltage being above 12.x on your display.

Why do you think it will ruin your battery? The alternator makes power anytime the engine is spinning in a traditional vehicle.

The voltage declines after a while to the “safe” standby/trickle charge rate. Amps are usually about 1 or 2 going to the 12v battery.

Lead acid & AGM batteries kept below 12.5V or so will start to sulfacate, and this greatly reduces their long term life.

What is a Sulfated Battery and How To Prevent It - Power Sonic (power-sonic.com)

 

[Peter Lukasch]

Not good, Maybe I'll install a permanent VM under or behind the back seat

Just check and verify that the readings from a quality Multi meter and the reading on the cigarette socket lighter display are close to the same, if so, then you can trust the reading. From my experience those small plug voltage displays can be out by 1-2 volts, the quality of a $12 display is just too inconsistent. They are however useful, I just wouldn't trust them, especially if it would require spending money on a possible unecessary repair.

 

[The Real Maverick]

Just check and verify that the readings from a quality Multi meter and the reading on the cigarette socket lighter display are close to the same, if so, then you can trust the reading. From my experience those small plug voltage displays can be out by 1-2 volts, the quality of a $12 display is just too inconsistent. They are however useful, I just wouldn't trust them, especially if it would require spending money on a possible unecessary repair.

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.

 

[Jah.]

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 .

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