Ohmmu 12V Battery Feedback

[Flybyglass]

One of the problems appears to be that long before you get an error code, the operating system stops charging the ohmmu battery completely. Not sure what that's about, but the day I got my last error code and I swapped out my V2 for the new V4 plus with Bluetooth, I checked the battery and it was nearly completely dead. So it had not been getting charged for many days or even weeks prior to the VC front error code appearing. This means everybody with Ohmmu's battery should be trickle charging until they get the V4 replacement.

I found it very helpful to install a battery monitor on my V4 to get the picture what the charging system was doing. Something like this:

Amazon.com

It ism also possible right now the charging routine is different for the FSDBeta people and the non FSD. I have 2022.20.x and the charge voltage is about 14.25. Some on here with 2022.28.x have shown a charge about 14.6 and that small difference may make the difference with errors messages. Your observation on content changing charging profiles is correct. My fully charged V4 when installed was about then same voltage and the charing system was putting out. After each battery install, I notice it is normal for the car to charge for 4-6 hours then start resting that is when I received multiple VCFront errors until the system locked out charging the battery. I can only guess that since the battery was at 14.25 volts, and the charging system was off and that moment it was looking for 13.x or less and concluded worthing else was charging the battery and isolated it. Just a guess based on observed behavior. Raising the charging voltage .2-.3 on the non FSDBeta branch of software raises this differential and may prevent error generation. My battery again is a V4 not the V4+ (not sure if the + has a different capacity). I did find it interesting when talking to Electrified Garage folks that heir first comment is "Tesla has been messing with the charging of these cars for years" implying going back to the early S.

 

[Darmie]

One of the problems appears to be that long before you get an error code, the operating system stops charging the ohmmu battery completely. Not sure what that's about, but the day I got my last error code and I swapped out my V2 for the new V4 plus with Bluetooth, I checked the battery and it was nearly completely dead. So it had not been getting charged for many days or even weeks prior to the VC front error code appearing. This means everybody with Ohmmu's battery should be trickle charging until they get the V4 replacement.

I take it, once you connected up the new V4, the DC/DC charger started charging the battery?

 

[dfwatt]

I take it, once you connected up the new V4, the DC/DC charger started charging the battery?

As far as I can tell yes but with the Bluetooth monitoring I will know quickly whether or not the system is charging because the battery voltage obviously will drop seriously in a matter of days if the system refuses to charge. I will post for sure if it turns out for some strange reason the operating system is not instructing the dc/dc bridge to charge.

I do not understand why the prior generation was not charging as I posted earlier it's pretty clear that long before the code was thrown the system was not putting any energy into the battery. There's no way that the car sitting there for a day or so and being driven minimally would have drained the battery down to virtually nothing. So there's more to this problem than meets the eye. In other words we have long assumed that the dysfunction in the system is indexed by the first appearance of the VC front codes on the Cars computer screen. I am increasingly convinced that that is not the case and that the dysfunction is emerging somewhere well before the code is ever thrown.

 

[dfwatt]

I confirmed that our version 2 battery is intact - after charging up it's holding a normal float voltage. So this only deepens the mystery around what in the world is going on with the charging process. I have to guess and again this is just a guess that the vcfront code emerges long after some kind of failure of the handshaking between the battery and the charging system. Like days after when the battery voltage dips below some nominal value due to many days of not charging and draining. This also might explain why folks get stranded so quickly after that code emerges. They are operating essentially on fumes from the 12 volt system. One of the implications of all this is that you need to trickle charge your battery the second you get that code unless you want to get stranded - whether that's OEM lead acid or whether it's aftermarket lithium ferric phosphate. If this is true it just becomes more evidence that Tesla has no idea what they're doing with this system. People should have an alert the second the handshaking fails not when the battery voltage falls to the floor from days of non-renewal from the dc/dc circuit.

 

[Flybyglass]

I notice today the LithiumMoto.com Model 3/Y battery is unavailable until the battery builder finds a solution for "the problem Tesla created".

Sounds like similar issues as followed on this thread.

 

[dfwatt]

I notice today the LithiumMoto.com Model 3/Y battery is unavailable until the battery builder finds a solution for "the problem Tesla created".

Sounds like similar issues as followed on this thread.

I am pretty sure that the problem may be charging voltage but I would like to get confirmation of that from folks who are running a external Bluetooth monitor with recording capability on their batteries. I'm not comfortable monitoring a bluetooth app while I'm driving (my battery has a Bluetooth monitor on it built in) but perhaps somebody who has recording capability on their Bluetooth system can clarify whether or not we are seeing charging voltage hit 15 volts. That's a bit of a red line for the lithium ferric phosphate chemistry at least in a four cell system. Most battery Management Systems disconnect at 14.8 or 14.9 volts. Even the Earth X battery line which allows a 15 Volt Drive may be challenged and disconnect if Tesla is monkeying with the upper reaches of charging voltage territory. Also my battery will disconnect at least from charging but not from discharging once its float voltage gets to 14 volts. In other words it does not like sitting with that much charge and it likes a lower float voltage.

The general understanding on lead acid chemistry is 14.7 volts is a maximum charge rate but the chemistry allows higher voltage drive as long as that tapers down once the battery gets close to its float voltage which is about 13.6. Lithium iron phosphate with a battery management system on the other hand will disconnect if you try to apply higher voltages, and that's probably what's leading to the error codes. Why Tesla would want to push the limit on this is beyond me and there is evidence from at least what happened with my wife's car that when they push the charging voltage they also induce failure in borderline lead acid batteries.

I believe that it is both instructive and relevant that our powerwalls in Florida just showed a failure of the 12-volt battery which allows the powerwall to still operate once it has been drained. So it looks as though Tesla doesn't know how to manage 12 volt systems either in powerwalls or in cars. The power walls were only 2 years old. Of course once the 12 volt lead acid battery fails if the power wall is bottomed out, it is essentially bricked and has to be rebooted by Tesla service. In other words fully analogous to getting stranded in the car we are stranded without power in Florida even though we've got functioning solar panels and lots of sunshine because of the same issue. So for all the folks trolling on this website about aftermarket batteries, please focus your attention and ire on the real problem. Tesla does not know what they are doing with 12 volt batteries. That's been shown over and over and over. Indeed the entire aftermarket of the lithium iron phosphate replacement camp is energized by people trying to find a way around the frequent 12 volt failures

 

[gearchruncher]

Again, Dfwatt won't see this response from an EE, but for everyone else, who can help set him straight:

Lithium iron phosphate with a battery management system on the other hand will disconnect if you try to apply higher voltages, and that's probably what's leading to the error codes.

LFP has a max cell voltage of 4.2 before damage. That's 16.8V for a 4 cell, "12V" pack. Now there is bascically no energy stored between 14.6V and 16.8V, but there is also no damage. There is zero reason for a BMS to shut off below 15V, and in fact in a lead acid replacement application, that would be pretty silly.

How to charge Lithium Iron Phosphate lithium ion battery packs including packs with high current and High Capacity.

High capacity LiFePO4, Lithium Iron Phosphate batteries.

www.powerstream.com

I can also verify, as I have said multiple times, that Tesla will throw errors without ANY BMS on the LFP pack. Zero electronics. Nothing to shut off the pack from the car. It is not the BMS turning off due to overvoltage causing these error codes (or at least it's not the only reason).

Why Tesla would want to push the limit on this is beyond me and there is evidence from at least what happened with my wife's car that when they push the charging voltage they also induce failure in borderline lead acid batteries.

Because it's good for lead acid batteries. Look up desulphation. It's not "pushing" the voltage. This is Tesla doing good things for the battery as they get more sophisticated and smart about LA batteries:

https://chargetek.com/assets/equal.pdf

Tesla does not know what they are doing with 12 volt batteries. That's been shown over and over and over.

Yeah, because it's the VOLTAGE of the battery Tesla doesn't know how to deal with. 400V that comes from 100 4V cells? All good. 14V from 4 of them? Tesla are idiots.

 

[Flybyglass]

I am pretty sure that the problem may be charging voltage but I would like to get confirmation of that from folks who are running a external Bluetooth monitor with recording capability on their batteries. I'm not comfortable monitoring a bluetooth app while I'm driving (my battery has a Bluetooth monitor on it built in) but perhaps somebody who has recording capability on their Bluetooth system can clarify whether or not we are seeing charging voltage hit 15 volts. That's a bit of a red line for the lithium ferric phosphate chemistry at least in a four cell system. Most battery Management Systems disconnect at 14.8 or 14.9 volts. Even the Earth X battery line which allows a 15 Volt Drive may be challenged and disconnect if Tesla is monkeying with the upper reaches of charging voltage territory. Also my battery will disconnect at least from charging but not from discharging once its float voltage gets to 14 volts. In other words it does not like sitting with that much charge and it likes a lower float voltage.

The general understanding on lead acid chemistry is 14.7 volts is a maximum charge rate but the chemistry allows higher voltage drive as long as that tapers down once the battery gets close to its float voltage which is about 13.6. Lithium iron phosphate with a battery management system on the other hand will disconnect if you try to apply higher voltages, and that's probably what's leading to the error codes. Why Tesla would want to push the limit on this is beyond me and there is evidence from at least what happened with my wife's car that when they push the charging voltage they also induce failure in borderline lead acid batteries.

For whatever it's worth, our powerwalls in Florida just showed a failure of the 12-volt battery which allows the powerwall to still operate once it has been drained. So it looks as though Tesla doesn't know how to manage 12 volt systems either in powerwalls or in cars. The power walls were only 2 years old. Of course once the 12 volt lead acid battery fails if the power wall is bottomed out, it is essentially bricked and has to be rebooted by Tesla service. In other words fully analogous to getting stranded in the car we are stranded without power in Florida because of the same issue. So for all the folks trolling on this website about aftermarket batteries, please focus your attention and ire on the real problem. Tesla does not know what they are doing with 12 volt batteries. That's been shown over and over and over.

Like you observe, it looks to me like Tesla is experimenting. One group with FSDBeta charging and one without. Here is a graph of charging taken today with 2022.20.18 (10.69.2.3). This profile has been fairly consistent with earlier profiles (looking at July) all with a peak around 14.3V.

I have a V4 on the shelf (not a V4+) that I charged to 100%. I took a reading and voltage was 14.3v. (Ohmmu has indicated the V4 and V4+ is essentially the same except for the Bluetooth). I would like to see graphical data from V4 users who are NOT using FSDBeta. The 2022.28 branch may have higher charging voltage (slightly like 14.6-.7). If so, that may be why so far the V4 is working with no errors. This graph is with a DiehardEV battery that only comes as AGM and is designed for the Model 3/Y. No errors since installation (active or passive) a month ago. BTW, opening the Bluetooth app on the Ohmmu while the car is awake should show charging voltage. Diving not needed.

 

[citywide4100]

The Ohmmu worked ok for the first year. There were always errors that popped up, but they cleared with a hard reset. I can't clear the latest round of battery errors from a recent OTA update. The original Hankook 12V is back in. I shaved off a few pounds, briefly with the Ohmmu replacement, but if you swap out the 21" Uberturbines for some T Sportlines, you could save significantly more weight through performance wheels.

 

[Stanwood Steve]

Really sorry to hear that so many have had issues with the Ohmmu battery. I've had mine installed for about three years now and never had an issue. The install was straightforward, and it's worked flawlessly since it was installed. I've never received an error code or anything (now that I've said this I'll probably see one next time I have it on the road). I keep the car updated with the latest software as soon as they're pushed to the car (currently on 2022.20.18), and the car is a 2018 Performance model 3 with over 83,000 miles. I believe the battery is the 2nd generation but I could be wrong about that. In any case, I have no complaints with my Ohmmu battery at. all. Maybe I'm the exception:?

 

[Pied]

Sad you see this still hasn't been resolved.

After 9 months of no error, I finally got the error again. I think the combination of being cold and not driving the car for ~1 week set it off. I think I'm just going to get the 12v from Tesla and recycle the Ohmmu. I thought coming back to this thread there might be fix by now. oh well

 

[xmodem240]

Sad you see this still hasn't been resolved.

After 9 months of no error, I finally got the error again. I think the combination of being cold and not driving the car for ~1 week set it off. I think I'm just going to get the 12v from Tesla and recycle the Ohmmu. I thought coming back to this thread there might be fix by now. oh well

Im not sure yet if anyone has received a v4+ yet which has the bluetooth bms. This was the one that should hopefully fix the problem.

 

[dmurphy]

Sad you see this still hasn't been resolved.

After 9 months of no error, I finally got the error again. I think the combination of being cold and not driving the car for ~1 week set it off. I think I'm just going to get the 12v from Tesla and recycle the Ohmmu. I thought coming back to this thread there might be fix by now. oh well

I agree with going back to the lead acid, but no need to recycle the Ohmmu. It’s still a viable 12V battery, just not for use in a Tesla. Can still be used to power a variety of things around the home - battery backup for your internet router, for example?

If you enjoy tinkering, it can be a useful tool to have.

 

[Wennfred]

I take mine as a spare on my long cross country trips.

 

[daniloreyes]

So is Ohmmu not replacing the batteries? I keep reseting after each update but last time it was painful ( 3 times)

 

[Perscitus]

If you havent seen the thread in the Battery/Charging subsection, read on... plenty of v4+ info (and Teslas flawed LVB diagnostic logic still causing havoc):

Longer term Ohmmu experiences?

I got MOS lock in when charging and discharging are disabled via app. If it’s happening outside of that it may be an under/over voltage detected. Have a feeling we need the BMS firmware update.

teslamotorsclub.com

Admins - perhaps the two should be merged in the Battery/Charging section?

 

[daniloreyes]

Question still stands. The other subsection talks mainly about the solution for the V4+ batteries.

Is Ohmmu not replacing/refunding? not even the previous models?

 

[citywide4100]

The Ohmmu worked ok for the first year. There were always errors that popped up, but they cleared with a hard reset. I can't clear the latest round of battery errors from a recent OTA update. The original Hankook 12V is back in. I shaved off a few pounds, briefly with the Ohmmu replacement, but if you swap out the 21" Uberturbines for some T Sportlines, you could save significantly more weight through performance wheels.

Question still stands. The other subsection talks mainly about the solution for the V4+ batteries.

Is Ohmmu not replacing/refunding? not even the previous models?

No. I can't even get them to reply to my e-mails. So, buyers are faced with the question: "Do I shell out $450 bucks AGAIN for a battery that may or may not work?"

 

[Flybyglass]

No. I can't even get them to reply to my e-mails. So, buyers are faced with the question: "Do I shell out $450 bucks AGAIN for a battery that may or may not work?"

They are not selling it right now.

 

[daniloreyes]

No. I can't even get them to reply to my e-mails. So, buyers are faced with the question: "Do I shell out $450 bucks AGAIN for a battery that may or may not work?"

I got the vendor to help. I think I'm getting the bluetooth as a replacement