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Ummmm....that would work, though 'ol school is a simple volt meter and replacing the battery every 5 yrs or so. :)

We have a '15 ED w/15k, and I was curious how to replace the stock original battery when needed. It is necessary to disconnect a breaker under the steering wheel first before "junkyard" removing the battery so as not to trip the BMS? And, what is done if the 12v battery ever discharges? Dealer service only?

TY.
 

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Checking the battery at the battery with a volt meter is a PIA. I just did it today and that reminded me to ask this question. As for replacing the 12v battery, I did it a year ago on one of mine. That was after five years and that was probably a little too soon, but I do sleep better at night knowing the battery is good. I did a post on some tips and procedures. It's just above in the stickys. I also use the battery test tool my son builds to keep tabs on how both the HV battery and the 12v battery are doing.

Len
2014 EV Coupe 21,500 miles
2014 EV Cabriolet 22,500 miles
2015 EV Coupe 20,000 miles
 

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Ummmm....that would work, though 'ol school is a simple volt meter and replacing the battery every 5 yrs or so. :)

We have a '15 ED w/15k, and I was curious how to replace the stock original battery when needed. It is necessary to disconnect a breaker under the steering wheel first before "junkyard" removing the battery so as not to trip the BMS? And, what is done if the 12v battery ever discharges? Dealer service only?

TY.
Cheaper......


With USB charging....

 

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Used to sell a 1.5A Schumacher unit at Walmart. I have a bunch. Now Walmart has these 3A units for about the same price:


Comes with ring terminals just like the old Schumacher units, connect them to the battery lugs, run wire towards the passenger door, where disconnect is somewhat convenient to access. Connect and forget. (To be honest once in a blue moon I'd come back to a dead battery, so best to check on them once in a while just in case).

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MY08 cabrio MY09 cabrio Brabus MY15 ED
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After diving into the passenger footwell at some of the most inopportune DARK times I have installed pigtails (ring terminals to SAE) from the battery posts to an easy connect (that sleeps under the carpet) to my Viking (Harbor Freight) 4 amp charger/maintainer.

You can also add a 3’ extension and run it through the firewall under the dash. Motorcycle enthusiasts have done this for YEARS! Don’t ask why it took me 10+ years to figure it out???
 

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Do any of you use something like this to keep an eye on the 12v battery?
Yes, but my Nulaxy Bluetooth FM transmitter has other features to include MP3.

Here’s pix of my older version, note battery info at the bottom. Readings are from our Brabus ICE with AGM battery...

66086
806184B3-F6FB-4E7A-99AC-C93A6E650423.jpeg
 

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Is there a key position / mode on the EVs where the 12V accessory plug (cigarette lighter) has power but the DC-DC convertor is not enabled?

(IOW, you can read the 12.8V reading above on a gas car with the engine not running [and alternator therefore not turning/charging]. Can you do the same on an EV?)
 

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According to the owner's manual, the aux power outlet is activated when the key is turned to position 1. Wonder if the actual 12v battery reading will quickly pop up until the HV battery is activated and supplies juice to the 12v battery? Also on your battery test unit, leaving the key out/off and clicking the door lock/unlock buttons the test unit reads the 12v battery number, because the HV battery is not engaged. Wonder if the same thing will happen with the accessory plug? If no to both, then I just wasted my money buying the unit. :)

Len
2014 EV Coupe 21,500 miles
2014 EV Cabriolet 22,500 miles
2015 EV Coupe 20,000 miles
 

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MY08 cabrio MY09 cabrio Brabus MY15 ED
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According to the owner's manual, the aux power outlet is activated when the key is turned to position 1. Wonder if the actual 12v battery reading will quickly pop up until the HV battery is activated and supplies juice to the 12v battery?

Wonder if the same thing will happen with the accessory plug? If no to both, then I just wasted my money buying the unit. :)
Quickly pop up but don’t blink,

No money wasted, Jeff will allow you to return it...
 

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Okay, my battery monitor arrived today. Good new - bad news. Bad news is that the 12v "cigarette lighter" is not activated to get a 12v reading when the door lock/unlock buttons are pressed. The battery test unit that many of us have does give a 12v reading by doing that. Once the HV battery kicks in, then it sends juice to the 12v battery and you won't get a real reading. Good news is that when the key is turned to position 1, you do get a momentary reading of the 12v battery before the HV battery kicks in. I'm not sure if I can attach a video, but I'll give it a try. If this doesn't work, then I'll try to take some screen shots of the video. No go on the movie clip, so I've attached stills as the unit powers up.

Len
2014 EV Coupe 21,500 miles
2014 EV Cabriolet 22,500 miles
2015 EV Coupe 20,000 miles
 

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Yes, you only have a second or so to read the 12v battery voltage at the cigar-lighter socket before the DC-DC kicks in and it jumps up to 14.6'ville. Sometimes just opening a door can activate DC-DC so you have to be sneaky.
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Okay, my battery monitor arrived today. Good new - bad news. Bad news is that the 12v "cigarette lighter" is not activated to get a 12v reading when the door lock/unlock buttons are pressed. The battery test unit that many of us have does give a 12v reading by doing that. Once the HV battery kicks in, then it sends juice to the 12v battery and you won't get a real reading. Good news is that when the key is turned to position 1, you do get a momentary reading of the 12v battery before the HV battery kicks in. I'm not sure if I can attach a video, but I'll give it a try. If this doesn't work, then I'll try to take some screen shots of the video. No go on the movie clip, so I've attached stills as the unit powers up.
Len
I long ago simply ran wires from the battery terminals to a convenient location under the service flap ("hood"). There is a rubber wiring harness gland near the steering column for getting the wires through the "firewall". The wire ends are faston connectors which are covered by dropper bulb sheaths to prevent shorting. So I can check, and charge, the battery even if I am locked out with a dead battery.

Maybe it is too low tech for some poeple...
 

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Okay, my battery monitor arrived today. Good new - bad news. Bad news is that the 12v "cigarette lighter" is not activated to get a 12v reading when the door lock/unlock buttons are pressed. The battery test unit that many of us have does give a 12v reading by doing that. Once the HV battery kicks in, then it sends juice to the 12v battery and you won't get a real reading. Good news is that when the key is turned to position 1, you do get a momentary reading of the 12v battery before the HV battery kicks in. I'm not sure if I can attach a video, but I'll give it a try. If this doesn't work, then I'll try to take some screen shots of the video. No go on the movie clip, so I've attached stills as the unit powers up.

Len
2014 EV Coupe 21,500 miles
2014 EV Cabriolet 22,500 miles
2015 EV Coupe 20,000 miles
I actually completely forgot about this. Can still get one of these with the charger:


I haven't verified it's the correct plug end

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Discussion Starter · #15 ·
Okay jzchen please clarify. How would this thing work? Where does it connect? Help the electronically challenged. :)

Len
 

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Please bear with me as I'm also learning something new here. I didn't know the unique shaped quick connect had a name "SAE".

Option 1:. You want to use your new cigarette lighter V-meter. You buy a ring terminal to lighter socket. Connect the ring terminals to the bolts that clamp the terminals on the battery, run the wires as you please and plug your new V-meter in. Amazon search:. "ring terminal to lighter socket"

Option 2:. You'd like the option to charge the battery directly as well as use your new V-meter at other times. Can get the unit I previously posted or any of your choice with the SAE connector to ring terminals, then buy SAE to lighter outlet. Amazon search:. EDIT! OOPS! "SAE to lighter socket"

Option 3:. There are actually WiFi enabled battery chargers now. It seems reviews claim a challenge to connect to your home WiFi without a call to tech support, but you can monitor your battery charging from your cell phone or other device. Amazon search:. "Schumacher SC1344".

Sorry I didn't provide direct links I always seem to get "tokenized" links which are so long and annoying. (A moderator on another forum pointed it out and helped me remove them but I still don't know how).



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This is what I use:

12v dc voltmeter - cigar_outlet.png


This thing lives in the cigar lighter convenience outlet. As soon as you get into the car you push it all the way IN. Once you turn the key to first position you should get a 12.2 to 12.6 volt reading which is what you want. This is the battery voltage before the dc-dc kicks in and you see 14.7 volts. On an unlucky day all you get to see is this 14.7v; if you really really want to read the battery volts you can turn off the key and try the process again. And if you have been away for weeks you should have disconnected the 12v battery and put it on a float charger anyway, so there!!

Float charger:

Float charger - 12v.png


The beauty of these tiny float chargers is that they use very little current and have tiny wires that will not allow harmful electrical currents to cause any issues. When you are away for weeks, disconnect the negative terminal on the 12v battery and then hook up the float charger. When you return from your vacation you will find a fully charged 12v battery and a high voltage battery that has not lost much capacity at all. I usually set the hv battery at about 80% before I leave home.
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