12V Battery Problem

[islandbayy]

From my understanding, Tesla designed a system that uses the 12V system relatively extensively compared to ICE vehicles and other BEVs. Vehicles with theft deterrent systems, thermal management, internet connectivity, or remote access can experience quite a bit more "vampire drain." It's been long chronicled that Tesla has had issues with the demands of their 12V system and relied on auxiliary batteries that could handle the load and cycling without the need for a belt driven alternator. Many manufacturers seem to have similar problems while others do not. Our old 2007 Lexus Rx400h would predictably need a new 12V battery nearly every 2 years to the day (the tell was that the power windows would slow, lights would dim, and the multimeter would register <12.2V). VW has had issues with their 12V systems on their EVs as well:

This Is How The VW ID.3 Avoids 12V Battery Issues With The 0783 Update

In a new video about the VW ID.3 12V issue, Battery Life shows how the 0783 update avoids a depleted 12V battery even if the energy drain is still there.

insideevs.com

Here are some random articles about the issues over the model years:

Tesla Moves To Solve the Problem of Dying 12-Volt Li-Ion Batteries on the LFP Model 3

Tesla Model 3 with an LFP battery can't keep its 12-volt Li-Ion charged due to a calibration issue. Tesla moved to solve this problem with a software update

www.autoevolution.com

Tesla to fix rapidly dying 12v batteries with software update, Musk teases more to come

CEO Elon Musk is teasing a fix to Tesla’s longstanding issue with its 12-volt batteries not lasting long inside its...

electrek.co

Tesla's new Model S and Model X get rid of lead-acid 12v battery, move to Li-ion

Tesla has transitioned the new Model S and Model X to a Li-ion 12-volt car battery – getting rid of...

electrek.co

However, our 2013 Fiat 500e with 82K miles on it still has its original Mopar 12V battery...granted this battery is a rather large group 47.

One of the main killers of the Tesla 12v batteries is over-charging. Not Cycling. Realistically, they aren't cycled all that much. Tesla keeps them at an abnormally high voltage, and basically "cooks them". I've disected a number of them now, including from my Model S and Model X. In each and every case, they were boiled dry. The Model S is a AGM or Gel Cell depending on what year it was installed (Flavor of the day?) where as the Model X is a sealed Flooded battery.
Now I wouldn't do this and then re-install them in the cars, but I actually was able to bring a MS and MX battery back to a highly useful life (in other applications).

With the last Model S battery I replaced (With an Ohmmu, getting tired of failing 12v's), I was able to use a syringe to inject battery acid back in over a period. As it was a AGM, that process was slow, as it had to get absorbed back in.
In the MX battery, I had to cut the sealed top off. That was a quick refill. Both nearly bone dry. After replenishing the acid, both batteries tested to about 80% original Amp Hour capacity, and had a low resistance signifying low sulfate build up. Likely would provide a good number of years of service.
So recap, Tesla's 12v management is whats killing the 12v batteries.

 

[aerodyne]

One of the main killers of the Tesla 12v batteries is over-charging. Not Cycling. Realistically, they aren't cycled all that much. Tesla keeps them at an abnormally high voltage, and basically "cooks them". I've disected a number of them now, including from my Model S and Model X. In each and every case, they were boiled dry. The Model S is a AGM or Gel Cell depending on what year it was installed (Flavor of the day?) where as the Model X is a sealed Flooded battery.
Now I wouldn't do this and then re-install them in the cars, but I actually was able to bring a MS and MX battery back to a highly useful life (in other applications).

With the last Model S battery I replaced (With an Ohmmu, getting tired of failing 12v's), I was able to use a syringe to inject battery acid back in over a period. As it was a AGM, that process was slow, as it had to get absorbed back in.
In the MX battery, I had to cut the sealed top off. That was a quick refill. Both nearly bone dry. After replenishing the acid, both batteries tested to about 80% original Amp Hour capacity, and had a low resistance signifying low sulfate build up. Likely would provide a good number of years of service.
So recap, Tesla's 12v management is whats killing the 12v batteries.

I don't believe in my old car the 12v system ever charged higher than 14.4V, which is the spec of the DCS 33 battery.

Never had a failure, as I replace proactively every two years.

 

[NewbyMaybe]

One of the main killers of the Tesla 12v batteries is over-charging. Not Cycling. Realistically, they aren't cycled all that much. Tesla keeps them at an abnormally high voltage, and basically "cooks them". I've disected a number of them now, including from my Model S and Model X. In each and every case, they were boiled dry. The Model S is a AGM or Gel Cell depending on what year it was installed (Flavor of the day?) where as the Model X is a sealed Flooded battery.
Now I wouldn't do this and then re-install them in the cars, but I actually was able to bring a MS and MX battery back to a highly useful life (in other applications).

With the last Model S battery I replaced (With an Ohmmu, getting tired of failing 12v's), I was able to use a syringe to inject battery acid back in over a period. As it was a AGM, that process was slow, as it had to get absorbed back in.
In the MX battery, I had to cut the sealed top off. That was a quick refill. Both nearly bone dry. After replenishing the acid, both batteries tested to about 80% original Amp Hour capacity, and had a low resistance signifying low sulfate build up. Likely would provide a good number of years of service.
So recap, Tesla's 12v management is whats killing the 12v batteries.

Thanks for clarifying the defective system.
Did the ohmmu also cook?

 

[islandbayy]

Thanks for clarifying the defective system.
Did the ohmmu also cook?

I held off a long time with the Ohmmu, mostly due to the issue of charging Lithium in the cold/below freezing. I wanted to see others reports on the longer term viability & life before I did it. The last Lead Acid in my MS lasted less than 2 years. For twice the cost of one lead acid, I got the Lithium, especially since it was over a month wait to get a lead acid from Tesla (Self install, not even for an appointment, just to get one in stock due to all the Hazmat people quitting in Illinois).
So I've been running the Ohmmu since september. So I cant yet comment on longevity, it does have a 4 year replacement warranty though.
I will state some observations. After installing, one of the biggest changes I noticed IMMEDIATELY was the trunk liftgate. It opened surprisingly quicker than previously. I'm not the only one that noticed, wife said the same thing and I had not even told her I had noticed it. I'd attribute this to low/no voltage drop under load like the lead acid.
Another observation, which "could" just be in my head, bass on the audio system sounds "crisper". again, less voltage drop.

As for the Ohmmu handling voltages, over-charging should not be an issue. Without taking the battery apart, given what I was told by Ohmmu, cells are in a series. My brain jumps around a lot, just how I'm wired, so bare with me!
Example, Lithium jump starters for gas cars usually use 3 cells in a series. Each cell max voltage is 4.2v, so 3x4.2 = 12.6v. This is more than enough to jump start a Gas Vehicle and keeps costs down.
Due to the higher voltage requirement of Tesla's, they are using a series of 4 cells (actually, more than that but keeping it simple, multiple cells in parallel to increase capacity than in series for higher voltage).
4 Cells X 4.2 maximum volts per cell= 16.8v fully 100% Charged. I need to guesstimate for what they would consider dead or discharged, so rough practice would be 2.8v per cell, so 4 cells X 2.8v = 11.2v fully discharged. What this means is the Ohmmu lithium replacement, has a HUGE voltage operating range compared to lead acid.

I have not seen the Lead Acid based Tesla's supply that high of voltage to the 12v battery as of yet, either on lead acid or lithium. As Aerodyne mentioned, the rough average voltage is kept around 14.4v. So if you take 14.4v and divide by 4 cells, you get ~3.6v per cell, right in the middle.
So what does this mean? Since Ohmmu uses LiFePO4 instead of Lithium Ion, they are mostly full (96-98ish %) at 3.6v per cell, but have voltage leeway to 4.2v.

So again, I know I go all over the place with this. Basically, the Ohmmu is kept pretty much smack in the middle voltage wise. As long as the car doesn't exceed 4.2v per cell, life of the Ohmmu should be fairly decent.
I still don't think I'd recommend the Ohmmu where the temps would drop below 0*F regularly, but a few spurts here and there seem to be fine. Did not see any issues in last weeks rare, prolonged negative temps here in Wisconsin.


So, could I recommend Ohmmu now? After seeing the longer term life in other peoples vehicles, yes, I'd feel comfortable recommending the Ohmmu for the MODEL S and MODEL X in climates where temps stay above 0*F. AT THIS TIME, there appear to be Issues with the Ohmmu batteries in the MODEL 3 and MODEL Y, caused by Tesla's changing in the charging profile of the 12v battery. This was stated by Ohmmu, I have no direct experience with this, however, they are trying to petition Tesla to support the Ohmmu battery.


Some final information for MS and MX:
Model S, can usually go quite a while once the 12v warning notification pops up. The systems in the Model S are much much less power Hungary than the Model X. I personally went a month with the warning. I could tell things were declining and kept a modified jump box (home built that uses Milwaukee Tool batteries) in case I had to "jump start" (Wake the car long enough for the high voltage contactor to close allowing the vehicle to run off the dc to dc converter) so I could get home if necessary. Finally gave up waiting for Tesla Service to get the battery in stock and ordered the Ohmmu. Shoutout to the local service center, they really really tried getting me that battery. It actually came in stock the day after the Ohmmu arrived, so I told them to give it to my friend who was also in need of the battery before his wife went out of town with the car.

Now the Model X, the MX is an absolute power beast when sucking power! When that 12v warning comes on, DO NOT WAIT. Get that 12v replaced ASAP! One of the biggest power sucking devices on the MX are the stupid as heck Falcon Wing Doors. God I hate those doors. Quite high amperage draw for those, heaven forbit you open both falcon at the same time and the trunk. Just don't wait, try and get a replacement, lead acid or a Ohmmu, sooner rather than later. Don't take a road trip, don't wait a month.

 

[islandbayy]

I don't believe in my old car the 12v system ever charged higher than 14.4V, which is the spec of the DCS 33 battery.

Never had a failure, as I replace proactively every two years.

That is a good way to prevent failure, replace before it fails. I'd be interested in seeing how much acid is left though when you replace after 2 years. My MX battery was 4 years old at replacement time, the last MS battery was less than 2 years. Both nice and dry. If only they were serviceable batteries, where the electrolyte could be topped off, these 12v batteries would not be dying so soon.
Heck, my home built battery lawnmower is at 19 years with the same battery. It is a flooded lead acid starting battery. I use it to trim the back yard train tracks. Doesn't last very long anymore, it's a starting battery that is being used like a deep cycle. I top the acid off usually every spring and check it in fall. Tested it's CCA, which is still around 500 CCA, about 600 if I remember correctly was it's sticker rating. Not too shabby. I also have the battery from my first car, the original factory installed battery. a 1991 Alfa Romeo 164. It was a Sealed flooded battery. Replaced it in the late 90's out of preventative maintenance, even though it worked just fine. That battery is now 31 years old, and resides in my manual push electric lift fork lift in my garage. It's finally reaching the end, very impressive actually. A couple cells finally sulfated. I can get about 10 up's and downs of the fork lift before it's dead. For my usage, thats plenty. If I want, I can leave the charger plugged in while using, which slows the drain, but I don't do that much lifting now that I don't have my motorcycle shop. I use it like an elevator to get in my garage attic, among other things like lifting narrow gauge locomotives.

The old MS and MX lead acid batteries I revived in my previous post, currently reside in our 15" gauge electric shunting locomotive at the historical railway we volunteer with. Built a electric shunting locomotive out of 95+% Scrap at our 2020 shutdown project. Nearly everything came from the scrap bin, body is all pallet wood, motor is from a 1950's cushman golfster golf cart that was sunken 2 ft in the mud behind the railway bunk house as the electrical had finally fried on the cart. Those two revived batteries give about 10 miles of operating range for the shunter. Likely more, but thats the furthest we've done on a charge. The line is ~1.5 out, and then turn table to turn the engines and ~1.5miles back.
Sorry, my brain goes all over the place. Not sure what the medical term for that is.... Conclusion, properly "watered" lead acid batteries will last a LONG time.
Killers are over charging, leaving left dead, and not keeping them watered.

 

[stacelina]

they do.

Ok so I guess demand is just outstripping the supply or whoever is managing their inventory has no idea how to do their job? Entire companies live and die on accurately assessing demand so inventory levels stay at the correct amount.

If I ordered a 12v Ohmmu battery now (I understand there's a wait, would be an issue keeping it around until I had a battery problem?) It's my understanding my 12v battery has only been replaced once since 2015 so I'd wager a bet, it's due for another better sooner rather than later.

 

[Mike Robinson]

they do.

Apparently not

 

[aerodyne]

I have had numerous problems in procurement of parts with 4 different service centers in SoCal. In some cases, refusing to sell me Over the Counter parts.

A little better luck getting rivets and clips from Mobile, if they had them.

On several occasions, SvC forgot to give mobile the parts needed, or the wrong parts.

Third party body shops, three to be exact, all said they have a hard time getting parts.

So, I'm sure there is a Tesla somewhere where parts and service is not a problem, but it is no where near me.

 

[islandbayy]

Ok so I guess demand is just outstripping the supply or whoever is managing their inventory has no idea how to do their job? Entire companies live and die on accurately assessing demand so inventory levels stay at the correct amount.

If I ordered a 12v Ohmmu battery now (I understand there's a wait, would be an issue keeping it around until I had a battery problem?) It's my understanding my 12v battery has only been replaced once since 2015 so I'd wager a bet, it's due for another better sooner rather than later.

Not sure what current demand for Ohmmu is, I had my battery the next day. They are in Phoenix, AZ I believe, I'm in Greendale, Wi.

 

[cobra]

Not sure what current demand for Ohmmu is, I had my battery the next day. They are in Phoenix, AZ I believe, I'm in Greendale, Wi.

Interesting thread, I just replaced our MX battery. Devon, PA had it in stock when I walked in without pre-ordering it. On install I noticed its date code is 1 1/2 years old (mid-21). So either they don’t rotate stock or no one here replaces their MX batteries…. (I wasn’t super happy about the age, but if I replace in about 2 yrs I’ll still be under a 4 yr battery life or so.)

 

[aerodyne]

Interesting thread, I just replaced our MX battery. Devon, PA had it in stock when I walked in without pre-ordering it. On install I noticed its date code is 1 1/2 years old (mid-21). So either they don’t rotate stock or no one here replaces their MX batteries…. (I wasn’t super happy about the age, but if I replace in about 2 yrs I’ll still be under a 4 yr battery life or so.)

That's terrible. Any lead acid will be permanently damaged if not charged for that length of time.

 

[islandbayy]

Interesting thread, I just replaced our MX battery. Devon, PA had it in stock when I walked in without pre-ordering it. On install I noticed its date code is 1 1/2 years old (mid-21). So either they don’t rotate stock or no one here replaces their MX batteries…. (I wasn’t super happy about the age, but if I replace in about 2 yrs I’ll still be under a 4 yr battery life or so.)

Thats not good. I get that at the local auto parts store as well when I buy deep cycle batteries. I usually can get a nice discount though talking to the manager, half off or so. And they usually fail fairly soon, so I just get to warranty out with brand new ones before the 1 year deep cycle warranty expires.
I'd personally, for a tesla that relies heavily on it, not accept that, or have them swap with a fresh one once back in stock.

When I had my cycle shop, I'd be ordering a pallet of motorcycle batteries at a crack (These people never put the batteries on maintainers over the winter. Just like clockwork.... I even had winter battery maintainers for only $5-10!). I had the option of getting them pre-filled or filling them myself. I just ordered them dry, and they'd give me 5 gallon pouches of sulfuric acid to fill them as necessary. That way, even if it was sitting on the shelf for 5 years, no ageing until the acid was added.

 

[Dukeybootie]

Just chiming in to add a data point for the Ohmmu. Had mine installed (2015 85D) @ 100k miles as a preventive measure. It has been just over 3 years and 65,000 miles since and I have had no 12V related problems at all. Very happy with the purchase.

 

[islandbayy]

Just chiming in to add a data point for the Ohmmu. Had mine installed (2015 85D) @ 100k miles as a preventive measure. It has been just over 3 years and 65,000 miles since and I have had no 12V related problems at all. Very happy with the purchase.

Thanks for adding that in. So far the only thing that makes me nervous is sub-zero charging of the Ohmmu. It held up at negative temps a week and a half ago, and I've been monitoring it and so far so good. It appears the new Ohmmu's also have Bluetooth capability as well as their own app from what I can see??? Lets you see the Ohmmu Batteries own internal BMS. That is awesome and would love to have had that access! I guess I will get it when I replace the Model X 12v on the next round.

 

[cbdream99]

The bad thing about Tesla battery replacement is it only warranty for a year, so it looks like there may be a reason for that. I tried the ohmmu replacement in August last year but after a week it gave a warning for battery replacement, it seems to be the same problem that plagued the M3/Y because of Tesla firmware changes, I emailed question from them but never got a response from them, eventually, I got a private response from TMC but it ended up getting nowhere, since then they have multiple fixes to the BMS and battery for 3/Y, and I happened to have other battery charging diagnostics to be done, so I put back the original battery (still works fine after 5 years) and asked Tesla to replace the 12V at the same time during service. I still have the ohmmu lying around in the house as a backup just in case and charge it occasionally, will see how well the Tesla replaced battery works in months ahead.