Good luck! Let us know how it comes out, hope it all works out ok.
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2017 M3 left for 2 years! what steps should I Take?
- Thread starter Ray Brown
- Start date
Good luck! Let us know how it comes out, hope it all works out ok.
OK I followed the advice and everytrhing went very smoothly so far THANKYOUVERYMUCH. Display booted up clean with only one box appeared stating the 10/22 update has not been installed. I have now plugged in the charging cable using the 110V. Screen states it is charging at 4 MPH (green bolt) along with the green flashing charging port light.All loos good but It has been charging about 30 minutes but still at ZERO miles. Will it eventually register a charge?
Would leave it overnight charging.
Hope it works out for the best! Is an interesting / cool story for us in the forum without the personal attachment aspect as to why one lets a car sit for 2 full years.
Hope it works out for the best! Is an interesting / cool story for us in the forum without the personal attachment aspect as to why one lets a car sit for 2 full years.
OK all IT IS CHARGING!! Just logged 3 miles using 110V.
It will take a fe day at this speed but most likely better for the battery.
MUCHOS GRACIAS!!!
It will take a fe day at this speed but most likely better for the battery.
MUCHOS GRACIAS!!!
All L2 charging is slow at about 1/10 C. There's no difference between slow and really, really slow.
It would be interresting to hear about this car, about the battery and range etc.
Could you report back when you know?
now up to 4 miles per hour charge, currently 78 miles
johnny_cakes
Member
I'm not sure about your plan, but I believe the best course of action would be to charge to 100%... it may take hours though at the top end to go from 98% to 100%. The reason is that a full charge will allow the BMS to appropriately calibrate... and going 0% to 100% is probably the best way to do this
This all is rather fascinating. Everybody knows about the background discharge of a Tesla due the computer running Sentry, keeping the door locks accessible, and so forth. And there’s been stories of people running the car dry with the heat or A/C on, or doing some YouTube exploit to see how the car reacts when the battery goes all the way down on a drive.
But that’s not this case. As a guess, sitting in a garage, no random pings, wi-fi off, and everything genteely discharging.
I think I’ve heard that a Tesla HV battery has a contactor in there that disconnects under the right circumstances. Which might be low charge, when disconnecting wouldn’t be a bigger disaster (as in running from a tidal wave, or not freezing to death). IF that’s true, there’d be two things going on:
- Self-discharge, where the (non-linear) internal resistance of the battery provides a path for current flow backwards through the internal cells, discharging the batteries down to squat.
- Residual charge. Even with a fully discharged battery, there’s a bit of voltage across the battery terminals, caused, more or less, by the differences in electron speed in the anode and cathode materials. (One sees stuff like this with P-N diodes and thermocouples. And is vaguely related to how solar panels work.)
But here, I wonder. Contactor, if it exists, is open. The battery management computers.. may not draw much, if any current? Does the whole thing.. I dunno, balance itself out evenly? With bare microamps doing the balancing?
Wouldn’t surprise me if a bunch of cells are dead. But if any were, well, shorted, like the way a 12V battery dies, would it take a charge at all?
Fascinating. I really want to know if this battery comes back from the dead. And if there’s a real battery guy out there, any thoughts?
The fact that this car is charging at all means that there is no cell group that is completely dead. The BMS would prevent charging if that was the case. The only real questions at this point are:
1. How much has the battery capacity been permanently reduced by sitting at low charge for so long?
2. Was any cell group damaged more than others that will lead to the battery going irreparably out of balance?
1. How much has the battery capacity been permanently reduced by sitting at low charge for so long?
2. Was any cell group damaged more than others that will lead to the battery going irreparably out of balance?
I'm sorry, but this is just full of lack of knowledge of the Tesla architecture.
The center computer, sentry, etc, all run off the 12V battery. Nothing to do with HV.
The HV battery absolutely has a contactor that disconnects it from the whole car. This is critical to safety. This is the "clunk" you hear as you unlock the car sometimes. The HV disconnects about 15 minutes after you get out of the car, and requires 12V to turn it back on. This is why a dead 12V can prevent a Tesla from "starting" and why you can and have to "jump start" a Tesla with a dead 12V even if the HV battery is fully charged.
Now, if the 12V gets low, the HV turns on and the DC-DC recharges the 12V. This happens every 1-2 days or so if the car just sits idle. Yes, this will eventually discharge the HV battery. But this is a purposeful action by the system, and it has logic to not do this at very low charge states for the HV battery, preventing over-discharge of the traction battery.
This is all why I said the 12V needed to be "jumped" first and then the car could be charged. You have to have 12V to get the contactor closed so the charger can access the battery. And once you do have that contactor closed, the DC-DC can maintain the 12V to keep the contactor closed, but you want to get that charger on ASAP to provide the car a source of power that isn't coming from the HV battery.
This is pretty much gibberish.
Hi, that's me. What happened here is that the 12V discharged long ago. The contactor on the HV was open, and the HV battery was at a fairly low SOC. But Teslas reserve about 5% of the pack at the bottom for this very case. So now there is no load on the Lithium battery except the internal BMS, which maybe draws 1W. Which might seem high, but you have ~4kWh of battery left before you do any damage to the cells. So you have thousands of hours to run the BMS. Plus, the BMS, if well designed, goes to very low power when the SoC gets low, possibly even completely off. So there really is no load on the battery, only self discharge. Self discharge is very low when you're at low SoCs.
It really doesn't surprise me that all the batteries (including 12V) in this car would be just fine. This is not like leaving a light on in an ICE car. They were not over-discharged. The various smart systems prevented that. They discharged to near zero, turned off, and sat for 2 years. That's really not very rough on a battery. It's likely better than sitting at 100% for two years.
The contactors disconnect every time the car sleeps. And connects when it wakes up.
Its easy to hear the clonks when the car wakes up or falls asleep.
The same connectors will open when the BMS sees that the battery reaches the lower voltage limit. This is done to protect the battery from getting too drained.
When you discharge a battery to to lower end (”0% SOC”) and stop the discharge the cells will recover voltage after the load has been taken away (as happens when the connectors open).
Self discharge is almost nil at 0%, so after the voltage recovered it will take very long time before the cells reach dangerous voltage levels.
The BMS never let the cells ”fully discharge” (people might interpret that term different).
Min voltage is 2.5V/cell and that is the 0% SOC level (that is true SOC, displayed 0% is 4.5% true SOC so 0% true SOC is -4.5% Displayed SOC)
We can be pretty sure that Teslas BMS shut down the battery when the lowest cell reach the lower voltage limit.
It normal to have around 20-40mV imbalance at 0% displayed SOC and it increases the closer true 0% we get.
But in this case, the battery is shut down when the lowest cell reaches the 2.5V limit (all other option would be bad).
I would not be surprised if the battery is as fresh as it was before these two years.
Low SOC is very good for reducing the calendar aging so unless any cells went way below 2.5V they should be very fresh.
Overdischarge do not cause much damage (or non at all) as long as the voltage is not reduced far below the 2.5V limit (there is good research on this).
Um. FWIW, while not being a true-blue battery guy, I have been involved in Telecom faults where, without city power, the CO battery backup, stacks and stacks of 48V lead-acid batteries, went all the way down. Most of the battery plant had to be replaced. As a result of all this, a squeaky-new AT&T PUB standard got issued: All Telecom Gear Shall Have, Built-In, A Low Voltage Cutoff.
At the time this caused much sturm and drang since, natch, a lot of that gear, some of which I was responsible for, didn't have such a thing. That was 20+ years ago; most gear has got that now. Or the CO battery plants have really impressive contactors, or the equivalent thereof.
At the time this caused much sturm and drang since, natch, a lot of that gear, some of which I was responsible for, didn't have such a thing. That was 20+ years ago; most gear has got that now. Or the CO battery plants have really impressive contactors, or the equivalent thereof.
MLXXXp
Member
Lead-acid batteries are different from lithium batteries. Lead-acid likes to be maintained with a trickle charge at full voltage. Any discharge, especially to low capacity, is hard on them. This applies even to so-called "deep discharge" lead-acid. On the other hand, as has been stated, lithium batteries are comfortable being at a low state of charge for long periods.
As long as the cells did not go way to low in voltage, the battery would have the least degradation in this state.
0% true SOC (a.k.a - 4.5% displayed SOC) causes the least calendar aging.
There is very much research on this and 99.9% of all research agrees to this:
The lowest calendar aging happens at 0% true SOC. (Contrary to the battery myths, 0% is good).
We do not know that but as we know that the BMS most probably disconnects when the lowest cell group reaches the low limit and battery cells that are in rest regains voltage and also have very low self discharge ( in practical terms self charges a little), we can expect that the time from shut down until the cells get damaged from overdischarge is very long.
To get damaged from overdischarge the cell voltage need to go below around half the minimum voltage. So 2.5V min, and 1.5V would not kill the cell.
The picture shows cells normally discharge to 0% (2.7V for this type) to the left, 1.5V next which is quite much overdischarged.
No problems, but a slight loss after 150 such overdischarge cycles.
The two to the right shows that overdischarged to 0.0V (completely dead) is very bad.
I think it is a good chance that the battery lost almost nothing during this time and that it actually has better capacity than other comparable cars that was used during these two years.
Lead acid batteries is very sensitive.
They start to degrade when discharged to 50%, just like the LV 12V lead acid batteries used earlier in teslas.
They sulfate from low SOC, and should not be discharged below 50%, and preferably they are held at 100% all the time.
Its a completely other battery with very few common things to lithium ion
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