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Smart Fortwo ED3 451
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Discussion Starter · #1 ·
Hello.

Would it be possible to test the 12V battery using a LED Car Auto Thermometer Electric Cigarette Lighter Voltage Meter Tester 12V as the one on this eBay link: LED Car Auto Thermometer Electric Cigarette Lighter Voltage Meter Tester 12V UK | eBay and on the pic here?

I am using one on my ED3, but it always (or at lease I see it that way) shows 14.5V ...
I was wondering if there could be a position of the ignition key in which the real voltage of the 12V battery will be shown on the LCD display.

Regards.
 

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On my 451's I have a similar device. As soon as the key is turned on, it goes to the charging voltage of around 14v. Mine unit flashes through several numbers on its way up to 14 and I try to convince myself that the first number I see as 12 point something is the actual charge of the 12v battery. Correct? Not sure. To be sure I pull back the carpet on the passenger side and take a multimeter to the 12v battery every few months.

Len
2014 EV Coupe 23,000 miles
2014 EV Cabriolet 24,000 miles
2015 EV Coupe 22,000 miles
 

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2017 453 Passion ED/EQ
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If the 12volt power outlet only comes on when the key is turned, then no. If the power outlet is on all the time, even with no key in ignition, then yes.

I had the same problem, went with a Victron "energy smart battery sense" monitor with a bluetooth connect to cellphone. see "
Easy way to monitor 12V battery voltage" discussion for more.
 

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As I've posted before, when using one of those digital cigar-lighter-plug voltreaders you get an immediate reading of the 12v lead-acid battery voltage, say 12.2v, then followed closely by the 14.5v reading as the dcdc charger turns itself ON. But sometimes the reader is not pushed all the way into the cigar socket, or twisted into full contact, etc. So if it doesn't work on first try, turn OFF the key and wait 15 seconds for the car to turn itself OFF, and then try again. Usually it works ok and you get the momentary 12.2v reading which gives you a sense of just how pathetic a condition your lead-acid powerhouse is in as you skirt the edge of EV-insanity.
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I was serious.

Something like noticing a momentary 12.2 volt battery BEFORE a bricked battery is a big deal in my book. It might seem trivial, but a nugget of wisdom like this might save someone from a lot of anguish.
 

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Much easier than any on this - just run some leads with insulated faston or other connectors on the ends (ring connector on the battery end) from the 12V battery to a convienient location for making voltage measurement and also for charging the 12V battery. Mine run through a wiring harness gland through the firewall near the steering column to under the service flap where they can be accessed even if the car is locked.
 

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I usually get readings in the 12.2 > 12.4vdc range when the ED3 or the Chevy SparkEV has been idle for a few days. Go figure. Maybe there are other instantaneous current draws happening just before the dcdc kicks in. The Sparks originally came with genuine AGM batteries so maybe that is an inherent characteristic of AGMs. Certainly you don't want to see a batt dip below 12.2v - then it would need immediate recharging.

My 2016 ED3 built 5/2015 still has an OEM batt so I assume it is the actual factory installed battery. Yes, I'm tempting fate, but I'm using the car every few days and when I leave here the batt gets disconnected and put on a float charger (see separate thread on this).
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OK my five cents on this topic.
If you really want see what is going on i propose to install a 12V bluetooth battery monitor device direct at the 12V battery.

Reason: The cigarette plug is only powered if you switch on ignition. By this also the DC/DC Charger of the system will start and you will only see the 14,5V from the charger and only for short time the state of the 12V battery.

Additional it is totally different of behaviour to a classical combustion car. There the 12V get charged only during engine is turning.
On the Smart 451 ED3 the only source for recharging is always the HV battery via DC/DC charger after the main switched (contactors) of the HV battery.
Means independent of the state of the 12V battery the charge and energy will always be provided by the HV battery.
Only the necessary amount of charge depend on the state of health of the 12V battery. Also the internal resistor of the 12V battery will need additional charge.
Worst case is a broken shortend 12V battery which will empty the HV battery or short repeated charging cycles which will trigger the protection function to stop the recharge and cause to trigger the kill of 12V battery which trigger a damage path inside the HV battery killing the HV battery in parallel.

So come back to the 12V battery monitor supervisor device. This even allow you to see the state in the off state as it is transmitted via bluetooth to your mobile, where you could see any changes of the state of charge and some times also the state of health. Better devices even allow to send you a trigger for check your car and battery. Means if the 12V battery is falling below 11,7V you should react fast not to run in killed HV battery case.

There are also some other nice solutions you could install on the maintenance OBD2 connector but this could cause trouble with the service center in case of malfunctions.
 

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Smart Fortwo ED3 451
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Discussion Starter · #11 ·
I usually get readings in the 12.2 > 12.4vdc range when the ED3 or the Chevy SparkEV has been idle for a few days. Go figure. Maybe there are other instantaneous current draws happening just before the dcdc kicks in. The Sparks originally came with genuine AGM batteries so maybe that is an inherent characteristic of AGMs. Certainly you don't want to see a batt dip below 12.2v - then it would need immediate recharging.

My 2016 ED3 built 5/2015 still has an OEM batt so I assume it is the actual factory installed battery. Yes, I'm tempting fate, but I'm using the car every few days and when I leave here the batt gets disconnected and put on a float charger (see separate thread on this).
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Not me.

I get over 14V on the display right away ...
 

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Smart Fortwo ED3 451
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Discussion Starter · #12 ·
OK my five cents on this topic.
If you really want see what is going on i propose to install a 12V bluetooth battery monitor device direct at the 12V battery.

Reason: The cigarette plug is only powered if you switch on ignition. By this also the DC/DC Charger of the system will start and you will only see the 14,5V from the charger and only for short time the state of the 12V battery.

Additional it is totally different of behaviour to a classical combustion car. There the 12V get charged only during engine is turning.
On the Smart 451 ED3 the only source for recharging is always the HV battery via DC/DC charger after the main switched (contactors) of the HV battery.
Means independent of the state of the 12V battery the charge and energy will always be provided by the HV battery.
Only the necessary amount of charge depend on the state of health of the 12V battery. Also the internal resistor of the 12V battery will need additional charge.
Worst case is a broken shortend 12V battery which will empty the HV battery or short repeated charging cycles which will trigger the protection function to stop the recharge and cause to trigger the kill of 12V battery which trigger a damage path inside the HV battery killing the HV battery in parallel.

So come back to the 12V battery monitor supervisor device. This even allow you to see the state in the off state as it is transmitted via bluetooth to your mobile, where you could see any changes of the state of charge and some times also the state of health. Better devices even allow to send you a trigger for check your car and battery. Means if the 12V battery is falling below 11,7V you should react fast not to run in killed HV battery case.

There are also some other nice solutions you could install on the maintenance OBD2 connector but this could cause trouble with the service center in case of malfunctions.
Thank you for the useful information.
Another option is to install a: "DC 5V-48V LED Panel Digital Voltage Meter Car Motorcycle Battery Capacity Display Voltmeter with Touch ON/OFF Switch" like the one on the pic here.
Gauge Measuring instrument Gas Circle Auto part
 

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> I get over 14V on the display right away ... [Marginal]
Then I would ask what year is your ED3. My 2016 may have a slight delay in the DCDC turning on, which proves useful. If it had no delay I would go to the small trouble of hooking up an external voltmeter wired directly to the 12v battery. The idea is to read the 12v voltage accurately just before you turn the key ON.
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Smart Fortwo ED3 451
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Discussion Starter · #14 ·
Then I would ask what year is your ED3. My 2016 may have a slight delay in the DCDC turning on, which proves useful. If it had no delay I would go to the small trouble of hooking up an external voltmeter wired directly to the 12v battery. The idea is to read the 12v voltage accurately just before you turn the key ON.
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The year is 2014.
The voltage meter I put a picture of in my previous post will do the job.
Thanks :).
 
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