Any reason not to hook up a battery tender to the 12 volt battery ?

[tga]

Just plug the car into a normal household outlet 110 with the mobile charger that comes with the car and forget about it.

That doesn't help with 12V cycling.

 

[travellerva]

Thank you Kenz. I agree. That is why I'd like to know an easy way to connect the tender to the 12V battery

 

[FlatSix911]

A couple of times on this thread, members have asked a basic question: "How do hook up a battery tender to the 12V battery?" but the answers have not been detailed enough for newbies like me - not a newbie to Tesla, just to the forum. I've owned a 2014 MS 85 since new that now has only 35K miles on it. The 12V battery is the original. I'm going away for 3 months soon and after reading this thread, I want to leave the 12V battery on a tender as well as the car being plugged in to the HPWC just to cut down the recycles on the 12V battery. As I see it the only way to get at the 12V battery is by removing the front nose cone. When I do that, all I see is a +ve terminal (see pic) so I assume any -ve connection from the tender will just have to latch on to the car frame anywhere - correct? Is there some other easyView attachment 371505 way of removing the frunk lining to get a connection to the battery and just string the tender cable out of the frunk lid? I'd like to make it possible to use the tender in the future more frequently and having to pulling off the nose cone every time doesn't excite me. Thanks for help.View attachment 371506

You will be fine with the charging the 12V battery with the frunk posts behind the nose cone... here is a photo of the ground terminal.

The terminals are also a great source of auxiliary power for operating other electronics with a 750W inverter.

 

[travellerva]

You will be fine with the charging the 12V battery with the frunk posts behind the nose cone... here is a photo of the ground terminal.

The terminals are also a great source of auxiliary power for operating other electronics with a 750W inverter.


View attachment 371589 View attachment 371590 View attachment 371591

Thanks - I assumed that as you can see from my original question. However, if you look closely at the photo in my original post, it can be seen that there is no negative post on my car - only the red positive one. The second part of my question was whether these posts could be accessed from inside the frunk without removing the nose cone.

 

[FlatSix911]

Thanks - I assumed that as you can see from my original question. However, if you look closely at the photo in my original post, it can be seen that there is no negative post on my car - only the red positive one. The second part of my question was whether these posts could be accessed from inside the frunk without removing the nose cone.

You can remove the trim pieces surrounding the frunk to access the terminals from the inside without removing the nose cone.

 

[N..8]

Thanks for the reply!

When you just plug it in, what LED lights are illuminated on the NOCO G7200 charger? I had to close the Frunk latch by pushing down on the latch with a screwdriver so I can keep the Frunk open (the car thinks it is closed). This allows me to monitor the battery voltage and current draw with a DC current probe. Before I closed the latch with a screwdriver, my Model 3 would not go to sleep.

Thanks Again, Ron

Ron,

Once I plug in the NOCO is goes straight to 12v Norm mode. I tied mine directly onto the 12v battery terminals using the NOCO GC015 NOCO - X-Connect 12V Indicator - GC015 which I just routed into the Frunk.

 

[rrolsbe]

RRolsbe, I have the same set up as you do and I just plug it in and let the NOCO do it's thing. I don't change it to Cold/AGM, just plug it in. I see about 120watts being pulled a few times a day. Over a 3 day period it will use about 1.2kw. I believe the DC to DC doesn't kick on until the battery gets to 12.6 or 5. If my car is sleeping is doesn't loose any over 3 days, this is the longest my car was sleeping at one time. Once it's awake it will over power the NOGO I believe then does engage the DC to DC.

Glad the NOCO G7200 appears to be working for you. Recap of my detailed post above. The Cold/AGM mode does NOT work, even though the battery terminal voltage gets below 12.7V; likewise, the power supply mode appears to work but after some random time it switches back to the Cold/AGM mode (which was the last setting it remembered that did NOT require a manual setting, the power supply mode DOES require a manual setting). Don't know what is causing the power supply mode to be terminated nor why the charger does not top off the battery in the Cold Battery/AGM mode????? This charger appears to be worthless for my primary use needs, maybe it can at least charge a potential dead AGM battery in my Tesla Model 3 and wife's plugin hybrid Chrysler minivan!

 

[rrolsbe]

N..8

You were replying to my post from yesterday while I was posting to the forum. Thanks for the answer as to what mode you are using with your Model 3! I have not used the 12V Norm mode because the manual makes no mention of it being used for AGM batteries. From the manual, it is not clear to me if the 12V normal mode would be detrimental in any way for AGM batteries? I like the eyelet cable you supplied a link to looks like it may be a few inches longer than the one supplied with the charger and the charge level LED's is a nice touch; however, I do not what to spend any more pesos until I can get this charger to hopefully work.

Maybe someone else on this forum has tried this charger on their Model 3?

Thanks Again

 

[MichaelS]

Just plug the car into a normal household outlet 110 with the mobile charger that comes with the car and forget about it.

^This.
Here is what I think happens after doing some extensive voltage logging exercises.
First, the 12V battery does not "discharge" when the car is sitting.
The DC-DC converter raises the charge voltage to the float level and turns off. Around 12.5 volts, the DC-DC converter charges the battery back to the float voltage.
The nominal voltage of a 12V battery resting is about 12.1 volts. So all the car is doing is floating the battery. My 24 Kwh backup battery in my solar system works in exactly the same way. Keeping the battery at float is the best way to get the most life out of the battery. It has to do with the chemistry that I won't go into.
I tried the external charger bit, and gave up after a short time. It was a hassle and you still use electricity, whether it's from the auxiliary charger or the car charger.
By the way, the easiest way to access the 12V battery connection is to pull the 12V socket relay in the frunk and put in a jumper across the output terminals. This makes it live all the time. Very handy for charging a cell phone when the car is off.

 

[NeverFollow]

^This.
Here is what I think happens after doing some extensive voltage logging exercises.
First, the 12V battery does not "discharge" when the car is sitting.
The DC-DC converter raises the charge voltage to the float level and turns off.
Around 12.5 volts, the DC-DC converter charges the battery back to the float voltage.
The nominal voltage of a 12V battery resting is about 12.1 volts.
So all the car is doing is floating the battery.

My 24 Kwh backup battery in my solar system works in exactly the same way.
Keeping the battery at float is the best way to get the most life out of the battery.
It has to do with the chemistry that I won't go into.

I tried the external charger bit, and gave up after a short time.
It was a hassle and you still use electricity, whether it's from the auxiliary charger or the car charger.

By the way, the easiest way to access the 12V battery connection is to pull the 12V socket relay in the frunk
and put in a jumper across the output terminals.
This makes it live all the time. Very handy for charging a cell phone when the car is off.

I was worrisome about the 12 V battery on my Model 3, so I put a local voltmeter on the auxiliary 12 V plug.
I noticed that the voltage constantly stays around 14.8 V

Since the auxiliary 12 V plug get disconnect when the car goes to sleep,
I also connected a voltmeter directly into the frunk, and when the car locked itself, the voltage was still the same .

 

[N..8]

^This.
Here is what I think happens after doing some extensive voltage logging exercises.
First, the 12V battery does not "discharge" when the car is sitting.
The DC-DC converter raises the charge voltage to the float level and turns off. Around 12.5 volts, the DC-DC converter charges the battery back to the float voltage.
The nominal voltage of a 12V battery resting is about 12.1 volts. So all the car is doing is floating the battery. My 24 Kwh backup battery in my solar system works in exactly the same way. Keeping the battery at float is the best way to get the most life out of the battery. It has to do with the chemistry that I won't go into.
I tried the external charger bit, and gave up after a short time. It was a hassle and you still use electricity, whether it's from the auxiliary charger or the car charger.
By the way, the easiest way to access the 12V battery connection is to pull the 12V socket relay in the frunk and put in a jumper across the output terminals. This makes it live all the time. Very handy for charging a cell phone when the car is off.

Mike, nominal voltage of 12v is 12.6v at 12.1 that's about 52% SOC. I've attempted to monitor the CAN Bus and it looks like the DC-DC comes on about about 12.45 volts (80%) to top it back up. I don't have a data logger so it might be a little higher or lower, I'm sure someone on the forums knows the exact answer.

 

[Rocky_H]

Just plug the car into a normal household outlet 110 with the mobile charger that comes with the car and forget about it.

Plenty of people do that, but you're being really unhelpful for the purpose of accomplishing what this thread is about.

 

[MichaelS]

Mike, nominal voltage of 12v is 12.6v at 12.1 that's about 52% SOC. I've attempted to monitor the CAN Bus and it looks like the DC-DC comes on about about 12.45 volts (80%) to top it back up. I don't have a data logger so it might be a little higher or lower, I'm sure someone on the forums knows the exact answer.

Mike, nominal voltage of 12v is 12.6v at 12.1 that's about 52% SOC. I've attempted to monitor the CAN Bus and it looks like the DC-DC comes on about about 12.45 volts (80%) to top it back up. I don't have a data logger so it might be a little higher or lower, I'm sure someone on the forums knows the exact answer.

You are right. As a data point my second battery lasted four years before it had to be replaced
Michael

 

[iCharge]

iCharge

What mode did you set your NOCO G7200 when you connected it to the battery. I connected my G7200 to my Model 3 battery and set it to the 12 Cold/AGM mode and the charger never topped off the battery. In this mode, the charger is supposed to top off the charge when the battery terminal voltage reaches 12.8V +/- 0.2V. I have a Kill-O-Watt meter and the G7200 AC line is being monitored by it. It only drew 20 watts over a 12 hour period so I know it did not top off the battery. The car however did top off the battery when the voltage across the terminals got below 12.7 volts probably closer to 12.6V. The power supply mode outputs 13.6V and appears to be supplying the Phantom current the car requires. After the Model 3's DC-to-DC converter completes the top off cycle the voltage at the battery terminals is 13..6V. Using the power supply mode, I am not sure the charger will back off if the cars DC-to-DC converter kicks in (ie.. the drivers door is opened or the phone app accesses the car); likewise, the G7200 charger does not remember the power supply mode setting and must be manually enable after losing AC outlet power. I think power supply mode would not overcharge the battery but simply maintain 13.6V and should also deliver the power required for the Phantom drain. Even if the G7200 topped off the battery at around 12.8V, it would still be cycling the 12V battery thus reducing it useful live. If the charger could just keep the battery topped off, supply needed Phantom current and not require the traction battery/DC-to-DC converter to top off the 12V battery, that would be ideal. I calculated the approx power usage using the power supply mode and it appears to be less than 9KW/month as apposed to over 30KW allowing the car to maintain the 12V battery. The traction battery should theoretically not loose any range even if parked for several weeks.

Hey
just seeing this today, sorry I have an exam coming up and not much active here recently.
Happy to talk to you over the phone and explain my (very simple) set up. sent you a PM with my number, call anytime after 10 AM tomorrow or sunday

 

[iCharge]

A couple of times on this thread, members have asked a basic question: "How do hook up a battery tender to the 12V battery?" but the answers have not been detailed enough for newbies like me - not a newbie to Tesla, just to the forum.

I've owned a 2014 MS 85 since new that now has only 35K miles on it. The 12V battery is the original. I'm going away for 3 months soon and after reading this thread, I want to leave the 12V battery on a tender as well as the car being plugged in to the HPWC just to cut down the recycles on the 12V battery. As I see it the only way to get at the 12V battery is by removing the front nose cone. When I do that, all I see is a +ve terminal (see pic) so I assume any -ve connection from the tender will just have to latch on to the car frame anywhere - correct? Is there some other easyView attachment 371505 way of removing the frunk lining to get a connection to the battery and just string the tender cable out of the frunk lid? I'd like to make it possible to use the tender in the future more frequently and having to pulling off the nose cone every time doesn't excite me.

Thanks for help.
View attachment 371506

I cant say about a 2014 MS and an not sure if its similar to 2017MS
If it is, Ifeel free to read what I did
I am of the simple and stupid principle, I just opened hood, removed the 3 plastic covers [left right center] and exposed the battery housing.
my MSs battery is exactly in the center, its covered by a fuse box that was easily moved to the side [ may be there was a screw or snap/tab, I dont remember]
with the fuse box out of the way, It was easy to hook the D rings to the terminals, I took care not to let the native wires lose touch, i was afraid the car may lose its settings, reboot, call mothership, blow up etc etc.
then I snaked the NOCO wire towards the driver side, there are 2 caps here for fluids, forgot what fluids, but here is where I brought up out by the side of one of those caps. I have taped the cord and the Noco charger sits in the frunk for now.
I am in the process of putting a standard SAE Quick Disconnect Wire Harness in between the Noco Cord
2pc 10 Gauge 2 Pin Quick Disconnect Wire Harness - SAE connectors | eBay and run a wire stealthily out either from the nose cone or near driver side tire well.
This will enable me to keep the NOCO out of frunk and charge it with the NOCO or using standard SAE [ Battery Tender /Minder / other similar] while traveling, esp if the 12V dies for some reason.
thoughts / comments welcome

 

[iCharge]

Thanks for the reply!

When you just plug it in, what LED lights are illuminated on the NOCO G7200 charger? I had to close the Frunk latch by pushing down on the latch with a screwdriver so I can keep the Frunk open (the car thinks it is closed). This allows me to monitor the battery voltage and current draw with a DC current probe. Before I closed the latch with a screwdriver, my Model 3 would not go to sleep.

Thanks Again, Ron

for me, depending on the times when I check, it is either flashing red [charging] or steady green [ fully charged]
you u using TeslaFi to see if your car is asleep ? or some other way ?

 

[vickh]

does Tesla have CANbus enabled to Charge the 12V battery directly from the 12-volt port?

see:

NOCO - .75A Battery Charger and Maintainer - G750

 

[dhanson865]

does Tesla have CANbus enabled to Charge the 12V battery directly from the 12-volt port?

see:

NOCO - .75A Battery Charger and Maintainer - G750

.75A won't even cover the "vampire drain". Any reason not to hook up a battery tender to the 12 volt battery ? says 4amps is your minimum target.

 

[scottm]

I attached my Ctek charger at the fuse box, near the cowl under that frunk surround trim piece. Charger lays in the frunk and I pop the hood when I plug the car in, rather than having the 120V cord dangling out the front of the car which would look too much like a block heater.

I used the Ctek's optional binder posts attachment instead of the alligator clips attachment option.

I attached at the cigarette lighter circuit, and also did another modification while I was in there... removed that's circuit's relay with a solid jumper, so the lighter socket is now powered at all times.

 

[vickh]

.75A won't even cover the "vampire drain". Any reason not to hook up a battery tender to the 12 volt battery ? says 4amps is your minimum target.

but will it work thru Canbus with 4 or more amps directly from the 12-volt port?