Near annual replacement of 12V battery is typical according to Tesla Service Tech

[JPP]

Sometime mid/late 2013 I believe... I got my car in May and that was one of the first visible running changes that came out not too long after I got mine...

Yup--my May 2013 does not have the perforated grille/aspirator in the center console. I just set the climate control to some 'random' setting and use my comfort level as a guide (have not actually measured the inside ambient temperature and compared to the climate control setting). And, FWIW, prior Lexus vehicles were not very accurate either.

 

[NOLA_Mike]

Edit: Both my home and workplace have underground garages that likely wouldn't be large enough for a tow truck. Can they jump the battery temporarily, or am I in big trouble if this thing dies?

Nope. They can send a Ranger and he can carry the puny little battery they use and change it wherever the car is parked...

 

[jerry33]

Nope. They can send a Ranger and he can carry the puny little battery they use and change it wherever the car is parked...

And you can jump the battery using the terminals under the nosecone with one of those jumpstart kits. The Ranger replaced my battery in an underground parking lot--no problem. However, mine didn't die, just got the warning so it was regularly scheduled service.

 

[Gizmotoy]

Nope. They can send a Ranger and he can carry the puny little battery they use and change it wherever the car is parked...

And you can jump the battery using the terminals under the nosecone with one of those jumpstart kits. The Ranger replaced my battery in an underground parking lot--no problem. However, mine didn't die, just got the warning so it was regularly scheduled service.

Thanks, guys. I feel a little better knowing it's not going to be trapped down there with some weird method required for extraction. It got me to and from work yesterday just fine. Hopefully it can do that a few more times before it gives up!

 

[santana338]

So the first attempt at logging was a bust. I thought I would be able to monitor the 12V from the cigarette lighter, but I don't get any voltage there, not even when I am in the car and driving. Has anyone used their cigarette lighter? I'm wondering if my lighter outlet is bad.

So it turned out to be a blown fuse. It must have been from the last time I used my 12V inflator to put air in the tires. Note to self to check that later.

After the fuse distraction and a little snow storm up here I was able to start taking data this weekend. I have put an xlsx file on Google docs with a sharable link. I'm hoping the file can be read as an xlsx without being munged by the google formatter. if you are not able to see a good chart and you are interested, PM me with your email address and I will send you the data file directly.

12V battery charging

So it looks like the float charger had the same effect as leaving the car plugged in. I am still trying to wrap my head around what this means.

 

[Cottonwood]

15 Volts seems a little high for a charge Voltage, but that would be correct at 32 F, 0 C, if the chargers are temperature compensated. About what was the temperature of the car when you collected these data?

What do you mean by "Float Charger?" Is that an external charger that you have put on the car? Remember that the MS seems to draw about 4 Amps at 12 Volts when in typical "off" mode. I would use at least an 8 Amp, external, float charger to see any effect. Maybe the decreased discharge rate was because your "float" charger was providing some of the current for the MS, but could not keep up with the 4 Amp load.

 

[wycolo]

Outside of the few cases where dc-dc Converter might get out of synch with the load and the 12v battery ends up being dead, TM seems to be doing all the right things wrt 12v battery maintenance. Such as charging at the correct voltages and with periodic pulsed charging to prevent sulfation etc. The problem is that these high quality batteries are really being used almost constantly handling heavy loads, unlike their brethren in an ICE which enjoy a much lighter average duty cycle. There just is no better animal on the horizon to handle this necessary chore. An alarm system that constantly monitors the 12v to alert you to voltages below 12.0 so you would have time to get your spare 12v battery ready for defibrillator duty - is a bit beyond the capabilities of most owners. Today the safest policy seems to be to replace the 12v battery each year during annual service.
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[kennybobby]

Clamp-on current probe?

Does anybody have a DC current probe to clamp around the cable going to the negative terminal to measure/monitor the 12V battery current to go along with these voltage graphs?

MichaelS recorded nearly the same thing 2 years ago when tracking down an over-voltage charging condition:

 

[santana338]

15 Volts seems a little high for a charge Voltage, but that would be correct at 32 F, 0 C, if the chargers are temperature compensated. About what was the temperature of the car when you collected these data?

What do you mean by "Float Charger?" Is that an external charger that you have put on the car? Remember that the MS seems to draw about 4 Amps at 12 Volts when in typical "off" mode. I would use at least an 8 Amp, external, float charger to see any effect. Maybe the decreased discharge rate was because your "float" charger was providing some of the current for the MS, but could not keep up with the 4 Amp load.

I didn't measure internal car temp, but it usually around 29F to 34F in the mornings. So I would suspect it would have been around there. The ambient temp in the garage was around 20F for most of the time.

The charger I used was this Yuasa charger. It is only rated to 900 mA so if 8A @ 12V is required, this is obviously not going to do it. It looks like you would need something like this for that level of charging.

 

[SteveS0353]

So it turned out to be a blown fuse. It must have been from the last time I used my 12V inflator to put air in the tires. Note to self to check that later.

After the fuse distraction and a little snow storm up here I was able to start taking data this weekend. I have put an xlsx file on Google docs with a sharable link. I'm hoping the file can be read as an xlsx without being munged by the google formatter. if you are not able to see a good chart and you are interested, PM me with your email address and I will send you the data file directly.

12V battery charging

So it looks like the float charger had the same effect as leaving the car plugged in. I am still trying to wrap my head around what this means.

View attachment 71072

Very interesting. The slowly declining terminal voltage between the charge cycles is indicative of the vampire load. With the car sitting unplugged the charge / discharge cycle looks to be roughly 50% (~2.5hrs charging, ~2.5hrs discharging). A voltage a little above 12V triggers charging. The application of a ~1A float charger slows down the cycle -- roughly the same time charging, but the discharge time has extended, probably supported by the ~1A supplied by the float charger not the 12V battery, but that's not sufficient to supply the vampire independently of the 12 battery.

It would be very helpful to have a synchronous plot of current flowing into / out of the battery along with the voltage. But I think this shows clearly that a trickle charger (a larger current that the ~1A one you used), would lessen the stress on the battery caused by the charge / discharge cycles to feed the vampire.

 

[Cottonwood]

I didn't measure internal car temp, but it usually around 29F to 34F in the mornings. So I would suspect it would have been around there. The ambient temp in the garage was around 20F for most of the time.

The charger I used was this Yuasa charger. It is only rated to 900 mA so if 8A @ 12V is required, this is obviously not going to do it. It looks like you would need something like this for that level of charging.

Yup, the 4A average draw of the MS is huge! You need a bigger charger. To put in perspective, each MS needs about one of those solar panels that you see on the solar canopies just to make enough power to offset the vampire loss

That was exactly the charger that I was going to recommend. I use several of them. They work great! Read the manual, at least for setup. It's a little confusing because you have to set the charger to AGM and 8A after you connect the to the 12V DC and before you connect the 120V AC.

Are you saying that the cigarette lighter plug stays on while the car is off and you charge with that? If so, I may make up a CLA for a BatteryMinder very soon.

 

[Moonwick]

If the cigarette lighter stays active when the car's off, that's certainly an easier avenue for enabling trickle-charging than having to connect to the nosecone terminals. Interesting...

Also, does anyone think we'd face warranty issues by taking actions like this to preserve the 12v battery?

 

[santana338]

That was exactly the charger that I was going to recommend. I use several of them. They work great! Read the manual, at least for setup. It's a little confusing because you have to set the charger to AGM and 8A after you connect the to the 12V DC and before you connect the 120V AC.

Are you saying that the cigarette lighter plug stays on while the car is off and you charge with that? If so, I may make up a CLA for a BatteryMinder very soon.

I found a similar charger that is for AGM batteries only that doesn't require the setup, but it seems that it is only 2A so it is still probably undersized. I'd be interested in results you would see from a 4A/8A setting on your charger.

The 12V adapter in the cabin does NOT stay on once you leave the car and the interior lights turn off. This is what I discovered after I replaced my blown 15A fuse.

I also had trouble getting access to the positive terminal of the battery. I was poking it with my multimeter but could not get a voltage reading. There is something on the battery post and at first I assumed it was just something to make all the connections to. But it may be something else like a relay. Anyway, it was easier to measure the voltage at the terminals at the nosecone. I took off the interior plastic covers rather than remove the nosecone to get at the terminals.

 

[Cottonwood]

I found a similar charger that is for AGM batteries only that doesn't require the setup, but it seems that it is only 2A so it is still probably undersized. I'd be interested in results you would see from a 4A/8A setting on your charger.

The 12V adapter in the cabin does NOT stay on once you leave the car and the interior lights turn off. This is what I discovered after I replaced my blown 15A fuse.

I also had trouble getting access to the positive terminal of the battery. I was poking it with my multimeter but could not get a voltage reading. There is something on the battery post and at first I assumed it was just something to make all the connections to. But it may be something else like a relay. Anyway, it was easier to measure the voltage at the terminals at the nosecone. I took off the interior plastic covers rather than remove the nosecone to get at the terminals.

Do you think that it would be easy to attach the ring terminal adapter to those terminals under the nosecone? That would make connecting the BatteryMinder as easy as plugging in the car to an HPWC. On some ICE's that sometimes sit for months, I have attached the ring terminals to the 12V battery and it is pretty simple to connect the BatteryMinder whenever needed.

 

[wycolo]

Schumacher makes a 10 amp charger that is microprocessor controlled and weighs very little. I could open my frunk and connect this quickly enough (I've brought out terminals from the battery) while the car is parked at home, which is 95% of the time. Then see if this helps get more life out of the 12v battery.

Think I'll pass on doing this as long as TM can be convinced to just give me a new battery at each annual service. And they don't have to be convinced, they just do it, I think, for all owners who are outliers. But some owner local to the Service Center should really try this. Might get the 5 to 6 years of nominal usage out of their 12v battery by removing most of the instantaneous heavy loading.
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[santana338]

Do you think that it would be easy to attach the ring terminal adapter to those terminals under the nosecone? That would make connecting the BatteryMinder as easy as plugging in the car to an HPWC. On some ICE's that sometimes sit for months, I have attached the ring terminals to the 12V battery and it is pretty simple to connect the BatteryMinder whenever needed.

View attachment 71175

Yes. It should be easy to connect to the terminals. It would be a little more difficult to put a hole in the frunk liner to pull the wires through so the battery minder can live in the frunk. The hole will have to be water tight. Then the problem will be that to plug this in you will have to have the frunk open (could lead to mice in the frunk -- see another thread on that topic)

I don't plan on doing this until Tesla stops replacing the batteries. But it is good to know that when they do there is a solution to the problem.

 

[scottm]

So, in the end we're all going to have a cord hanging out the frunk... like ICE have block heater cords?

I'm all for it so long as it proves my 12V will get added years.

Care and feeding instructions:
1. plug this one in all the time you are parked.
2. plug this huge cable in the rear when you want to fill 'er up.

 

[santana338]

So, in the end we're all going to have a cord hanging out the frunk... like ICE have block heater cords?

I'm all for it so long as it proves my 12V will get added years.

Care and feeding instructions:
1. plug this one in all the time you are parked.
2. plug this huge cable in the rear when you want to fill 'er up.

Unless Tesla comes out with a retrofit to put a charger like this in the car, I'm afraid this is what it is going to come down to. Replace the battery every year or plug in all the time.

Of course, if the vampire drain can be reduced by an order of magnitude, maybe the battery will last much longer.

 

[wycolo]

I think eventually Service will let you take the 12 month old battery home rather than sending it back to TM. Still lots of life left in it esp for small ICE applications. And if the SCs recycle locally it is really premature to do that.
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[EarlyAdopter]

To everyone discussing getting a float charger - doesn't santana's data show the 12v recharge cycle being extended the same when plugged in as when on the float charger? This suggests that leaving the car plugged in effectively acts like having a float charger. It's only when he unplugged the car that you see the rapid discharge and frequent top offs on the 12v. I don't see any reason to get a float charger from his data.

"A plugged in Tesla is a happy Tesla." Perhaps this is one more reason why.