12V battery issues (error messages/car charging problems)

[MichaelS]

Hi,
I hooked up a Measurement Computing USB-503 voltage recorder to the charging terminals behind the nose cone and left it there for a day. Here is the graph of the 12V

From the graph, it takes about 2 hours for the 12V battery to discharge to point where the DC-DC converter starts up. Then it charges for another two hours and then starts the cycle all over again.

The scary part is where the voltage goes to over 16V at the cursor. That is way too high to charge a 12V battery. This happened after the car finished fully charging to 190 miles.

I'd be happy send anyone the csv data file.

Michael

Edit: Here is the link to the csv file in my public Dropbox folder.

https://dl.dropbox.com/u/16819482/Tesla%2012V.csv

 

[dtich]

oh, excellent, good to have. why would they ever let it get close to 16? 15 is bad enough really. and a 4 hour discharge and charge cycle seems awfully short. no way to prolong battery life. i think they used small cheap 12v's, when they probably should've used bigger, better ones.

what size traction batt do you have and what fw are you on, just for thoroughness?

thanks for posting.

 

[MichaelS]

Hi,
I have the 60 kWh pack and latest 4.3 (1.25.45) firmware.

 

[wycolo]

Explains why I've finally seen under 14v now that I have ver 4.2 in my 85 kwh. Thanx!!

Appears your car holds it to a 16v max during a trip. That is a bit harsh! ICE practice is to hit the batt with a good 15+ volts until it is recharged. The ICE style battery is a 'quick discharge' (to start the engine) and 'quick recharge' (5 min +/- max). Then the regulator drops this to maybe 14v max until loading increases. These batts have lightweight plates designed to do this one function, and do it well. Seems to be the situation here also. Maybe we should just hook up a solid state regulator to the ModelS 12v battery to remove the stress!

If properly used there is nothing inherently 'short lived' about small 12v lead acid batteries. The one on my micro pickup (Kei truck) has got to be at least 8 years old; still starts instantly at any temp and recharges quickly.
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[MichaelS]

I believe that Tesla has not yet fully fixed the problems they were seeing in January where the cars were cooking the batteries, to the point where they bulged.

I am going to send this chart to Tesla.

The high voltage is occurring both when parked and driving. Right at the end of the graph just before I pulled the logger out, it was at 15.5 volts sitting in the garage.

 

[wycolo]

The logical next step is to monitor the current from DC-DC converter going into 12v system(battery and load). Place calibrated resistor in series with the load and monitor its v, aka system current. If your vm can chart 2 different voltages concurrently that would be excellent. Assuming all accessories require only 12.6v nominally, management should not be rocket science. Priorities probably are necessary, like when you need to turn on air pump to go to HIGH suspension, something else may have to temporarily be disabled by relays. Basic stuff. No boom boxen here drawing 1000 watts audio. :smile:
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[MichaelS]

I've been trying to figure out a way to measure the current and voltage at the same time. I need to get in series with the ground lead of the battery to do that. I have no idea how to get at the battery. My understanding is that it's buried up in a fender somewhere.

The data logger i have been using is only single channel.

 

[wycolo]

I'd caution against putting any resistance into the batt>GND. Might mess up some onboard sensing. Putting a cal res in series with the load is inconsequential. Measure *that* current with your gizmo and post the chart for us. :love:

The Roadster has an ammeter for its accessories. We need this for the S.

To get at the batt just search on 'remove nose cone'.
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[dtich]

omit... (i bored myself with my question....)

 

[jomo25]

I continue to be concerned about 12V battery issues. That people (including me) are feeling compelled to buy a voltage meter and keep it handy speaks to the perceived frequency and consequences of the issue IMO.

I know some people have been told by Tesla that there were just a bad batch of batteries. And some of the readers here seem to agree with that. But the 12V issues seems to have ranged quite far across the delivery dates. There doesn't seem to be a concentration of people having the issues around a certain date range.

And the voltage charts above from MichaelS would seem to indicate it may not be a simple issue with the battery, but more of an issue with how it is being charged and discharged.

I read there was a service bulletin re: the DC-DC connection. Is that officially posted somewhere on Tesla's site or otherwise? Has anyone who had that fix done had issues since? Can someone who has had it monitor their voltage to see if it matches the graphs above?

As a side note, Im slightly more concerned about this because if my car did need to be towed because it was completely immovable, it could be an issue. I live in a high-rise condo with an underground garage. The garage has limited height clearance. So a normal flatbed wouldn't be able to load and take my car out. It would need to be a trailer hitched car carrier. I suppose I'd have to let them know in the event I ever did need a tow. I hope that never happens, but seeing all these 12V issues, makes me worry it may be just a matter of time.

 

[Doug_G]

It is probably easier to charge the 12V with a booster pack than tow the vehicle, no matter where it is parked. As long as the battery is not completely toast you should be able to charge it and drive it to service.

 

[jomo25]

It is probably easier to charge the 12V with a booster pack than tow the vehicle, no matter where it is parked. As long as the battery is not completely toast you should be able to charge it and drive it to service.

Thanks, either that or replace the battery, then drive it, I suppose. Hope that would do it, though I can imagine where it still might depending on the issue. And again, hopefully never need to find out. And more importantly, hope they find and address the issue for good!

 

[Babylonfive]

Unfortunately, from the pictures I've seen of the frunk cover removed, the battery removal would be complicated by a large number of converging connectors (presumably from various 12V devices, the recharger DC-DC, the cone connector, etc.) right on top, instead of neatly bundled into a single battery cable. I can't imagine why the 'crazy bus bar' method is better, even from a safety POV, but... what do I know.

It does appear that they didn't consider upsizing or user replacement of the 12V battery, and I am disappointed about that.

 

[wycolo]

> battery removal would be complicated [Babylonfive]

Why worry about battery replacement? That's Tesla job. Hooking up a 2nd battery in the frunk just requires connecting to existing 12v terminals/busses and attaching a battery box to the rear wall of frunk, or whatever arrangement you decide upon. Caution against connecting 2nd battery until it is really needed *and* being sure to DISconnect one terminal of original battery! Then providing foolproof access to frunk.
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[jomo25]

> battery removal would be complicated [Babylonfive]

Why worry about battery replacement? That's Tesla job. Hooking up a 2nd battery in the frunk just requires connecting to existing 12v terminals/busses and attaching a battery box to the rear wall of frunk, or whatever arrangement you decide upon. Caution against connecting 2nd battery until it is really needed *and* being sure to DISconnect one terminal of original battery! Then providing foolproof access to frunk.
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I am just thinking of what could be done if my car was incapacitated and couldn't get a low riding hitch tow. Yes, charge the battery and drive it out of the garage would be first option. but if that didn't work, could have Tesla come out and replace the battery then drive it out, as a next option. Only if those fail, then need to wait for the trailer.

 

[bellwilliam]

fyi: Tesla replaced my 12v battery after voltage dropped under 6v in 7 days.
it took Tesla technician ~2 hour to replace the battery.

 

[wycolo]

The Tesla 12v battery has a module *within it* that communicates data to System. I learned this from good sources yesterday. Otherwise it is just an everyday 35 ah lead acid battery. Knowing this, it will be necessary to retain original battery connected in stock fashion at all times. If you discover that its voltage is down to 6v [@bellwilliam] one fine morning, then connect a charger to bring it up to a 'working system minimum' at which point the dc-dc converter will resume functioning. Connecting a 2nd battery in parallel at this point might help ensure you arrive at the TM Shop. The 2nd battery should not affect operation of the car, (my assumption).

Important to:

1. Be able to open Frunk in a dead car. This could be a tuffy!!
2. Have cables from 12v battery available in Frunk. Easy.
3. Have voltmeter in Frunk to read battery voltage since if car is OFF the power outlet will be OFF. Easy.

If 12v battery simply will not accept a charge then I would remove battery and drive another car to TM Shop to get a replacement. But that's me, being over 200 miles away.
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[qwk]

In case your 12V battery goes completely dead rendering the door handles/keyfob unoperable, one can connect a 12V battery with jumper cables to the 12V posts behind the nose cone, and get the car unlocked and keyfob working to open frunk/trunk. A jump from an ICE vehicle also works PROVIDED THE ICE CAR IS NOT RUNNING!

 

[jomo25]

In case your 12V battery goes completely dead rendering the door handles/keyfob unoperable, one can connect a 12V battery with jumper cables to the 12V posts behind the nose cone, and get the car unlocked and keyfob working to open frunk/trunk. A jump from an ICE vehicle also works PROVIDED THE ICE CAR IS NOT RUNNING!

Cool, good to know. Would that jump be enough to release the emergency brake pawl? Or does that require the car to actually turn on?

 

[FlasherZ]

Releasing the electric parking brake caliper requires the car to be put in neutral, which requires the car to be "on". I don't call it a pawl because, well, it's not.

That said, I recall from a past discussion (perhaps even in this thread -- yes, I'm lazy to go back and dig) that all that's necessary is a momentary "touch" of 12v to the lugs behind the nosecone, and then to power up the car, where the DC-DC converter will become active and supply necessary power to all 12v needs. I don't think that's been completely proven out, but that's what I recall reading at least.