Longer term Ohmmu experiences?

[Dysan911]

Looking back at some dates. So I got my V3 on May 10th. On May 23rd I was emailing Sean about getting the "Please schedule Service and Replace 12v battery" error. So approx 2 weeks is all it took for V3 to trigger that type of alert which requires a hard reset. I doubt I'll put V3 back in now. I obviously did a hard reset when I installed it and doubtful any recent Tesla Software updates would have changed anything that I would expect things to start working fine again. . Hopefully, Testing is going well with Sean and soon we'll get an update that V4 is ready.

 

[dfwatt]

Looking back at some dates. So I got my V3 on May 10th. On May 23rd I was emailing Sean about getting the "Please schedule Service and Replace 12v battery" error. So approx 2 weeks is all it took for V3 to trigger that type of alert which requires a hard reset. I doubt I'll put V3 back in now. I obviously did a hard reset when I installed it and doubtful any recent Tesla Software updates would have changed anything that I would expect things to start working fine again. . Hopefully, Testing is going well with Sean and soon we'll get an update that V4 is ready.

Without having the ability to actually track voltages there's no way to know if any of the recent updates pushed the voltage above 14.5-14.6. There is reliable evidence that the original difficulties were triggered by firmware updates in late 2021 that went above those numbers. It does seem as though Tesla can't make up their mind on this point. Why one would be pushing the envelope on a lead-acid chemistry (where a Max charging voltage is 2.45 volts per cell or roughly 14.7 volts in a 6 cell battery) is difficult to understand. There is no margin at all in getting close to that max value and lots of reasons to avoid it. So it just suggests that somebody doesn't really know what they're doing. As I said in previous post there's lots of reason to believe that the overcharging brought a lot of OEM batteries into failure prematurely. It wasn't just a hassle for those of us with lithium ferric phosphate batteries. That said, folks with aftermarket lithium ferric phosphate batteries that have a 15 volt charging limit built into their BMS appear to be skating by without issues. Not sure why ohmmu can't do that?

 

[Dysan911]

Without having the ability to actually track voltages there's no way to know if any of the recent updates pushed the voltage above 14.5-14.6. There is reliable evidence that the original difficulties were triggered by firmware updates in late 2021 that went above those numbers. It does seem as though Tesla can't make up their mind on this point. Why one would be pushing the envelope on a lead-acid chemistry (where a Max charging voltage is 2.45 volts per cell or roughly 14.7 volts in a 6 cell battery) is difficult to understand. There is no margin at all in getting close to that max value and lots of reasons to avoid it. So it just suggests that somebody doesn't really know what they're doing. As I said in previous post there's lots of reason to believe that the overcharging brought a lot of OEM batteries into failure prematurely. It wasn't just a hassle for those of us with lithium ferric phosphate batteries. That said, folks with aftermarket lithium ferric phosphate batteries that have a 15 volt charging limit built into their BMS appear to be skating by without issues. Not sure why ohmmu can't do that?

So do you think it's possible Tesla has since corrected whatever they changed that suddenly made our Ohmmu's trigger false failures? I'm wondering if the timing of whatever they changed was right around the time when they introduced their own LiON 12v battery. Maybe they were trying to figure out a one size fits all and realized this isn't going to work with the Lead Acid Battery equipped cars.

 

[dfwatt]

So do you think it's possible Tesla has since corrected whatever they changed that suddenly made our Ohmmu's trigger false failures? I'm wondering if the timing of whatever they changed was right around the time when they introduced their own LiON 12v battery. Maybe they were trying to figure out a one size fits all and realized this isn't going to work with the Lead Acid Battery equipped cars.

Well my question is whether they corrected meaning going from 14.8/14.9 back to 14.5 but whether somehow someone bumped the voltage up back to 14.7 or above. It's unclear what Ohmmu's Max voltage is for version 3 (in other words what voltage they can tolerate before the BMS disconnects) even with their add-on module which I assume is some kind of gated power resistor that allows a slight voltage drop so that the battery never sees more than 14.5. In any case we're just guessing and speculating. It would be nice if ohmmu would transparently update us about what the heck they're seeing out there and why version 3 isn't cutting the Mustard anymore

 

[Flybyglass]

I have found nothing in the manual but the charge and float voltages and behavior (how often a charge cycle is initiated) must be published somewhere so maintenance can compare actuals to spec. Who can locate that information and post it or show were to find it?

Thanks

 

[gearchruncher]

That said, folks with aftermarket lithium ferric phosphate batteries that have a 15 volt charging limit built into their BMS appear to be skating by without issues.

I keep saying it- I've hooked a 30Ah LiFEPo4 pack to my car with NO BMS. It always gets detected within two weeks. It's more complex than just having a BMS cutoff. And other batteries do have issues:

Quite a number of error messages...

www.teslaownersonline.com

Why one would be pushing the envelope on a lead-acid chemistry (where a Max charging voltage is 2.45 volts per cell or roughly 14.7 volts in a 6 cell battery) is difficult to understand.

Max LA voltage is a function of cell temperature. It could be that variance we are seeing is due to a temperature curve that Tesla has implemented. But it also appears Tesla only applies this high voltage intermittently, not in every charge cycle. Maybe it's part of a desulfation activity? Part of a capacity check?

I have found nothing in the manual but the charge and float voltages and behavior (how often a charge cycle is initiated) must be published somewhere so maintenance can compare actuals to spec.

There's no reason to believe it's published anywhere. This is internal, proprietary information to Tesla that is likely only documented in the code that actually does it. Tesla can use a variety of methods in service to check if a specific car is broken or not that does not involve someone measuring voltages and timing charge cycles. They don't use spectrum analyzers to test if the radar is working or dynos to test if your drive unit is healthy.

 

[scottf200]

Without having the ability to actually track voltages there's no way to know if any of the recent updates pushed the voltage above 14.5-14.6.

Why not just connect this device up to your 12v so you can monitor it.
https://smile.amazon.com/gp/product/B01MT4583U/ref=ppx_yo_dt_b_search_asin_title

 

[Dysan911]

Is anyone still running their ohmmu battery and still getting the regular alerts or maybe everyone gone back to the lead acid batt.

 

[dfwatt]

Why not just connect this device up to your 12v so you can monitor it.
https://smile.amazon.com/gp/product/B01MT4583U/ref=ppx_yo_dt_b_search_asin_title

Best way to track 12v subsystem is with one of the proprietary third-party apps. I just don't go that far

 

[Skione65]

May 10th.

I received my supposed V3 on April 14th. In my correspondence Sean specifically stated the new battery was Version 3. And that I was to send the V2 back as well. I specifically asked Sean this “Is the new BMS in the Rev3 the same as the new BMS module add on you were Beta testing or an improved different module?” I never received a response. It was my understanding that the module on the V3 was internal, however I never got a verbal confirmation on that.

Ski

 

[dfwatt]

So I just heard from Sean. What I have is actually version 2 with an add-on module. He has offered to swap this out for version 4. But I still don't understand why these modifications that all ostensibly are aimed at accommodating higher charging voltages are all failing to clear firmware updates.

 

[Dysan911]

So I just heard from Sean. What I have is actually version 2 with an add-on module. He has offered to swap this out for version 4. But I still don't understand why these modifications that all ostensibly are aimed at accommodating higher charging voltages are all failing to clear firmware updates.

Oh interesting he offered V4. I assume that must mean they're getting closer to a successful version. Are you going to take him up on that offer? I wonder if he'll explain what they ended up having to do with V4 to make it work with the latest firmware.

 

[scottf200]

Best way to track 12v subsystem is with one of the proprietary third-party apps. I just don't go that far

Not sure what "I don't go that far means". This is a monitor directly on the 12v drawing a tiny tiny amount. No 3rd party data going anywhere but your phone. It is only $27 and gives you the data you are asking for.

 

[gearchruncher]

He has offered to swap this out for version 4. But I still don't understand why these modifications that all ostensibly are aimed at accommodating higher charging voltages are all failing to clear firmware updates.

Too bad @dfwatt has me blocked or he'd hear me say that the BMS max voltage is not the issue and it's trivial for Tesla to detect a LiFePo4 battery without triggering the high voltage protection in a BMS. Just look at the resting voltage. Any kind of sophisticated lead acid charger has a reasonable chance of flagging a LiFePo4 battery as an unhealthy Lead Acid.

 

[dfwatt]

Oh interesting he offered V4. I assume that must mean they're getting closer to a successful version. Are you going to take him up on that offer? I wonder if he'll explain what they ended up having to do with V4 to make it work with the latest firmware.

It does seem like there is a real one-way Street on technical information right now about what is driving the codes. They seem happy to receive yours but they don't seem to be giving out much. From the email I got the impression that they were very close to shipping version 4 and it would be a straight swap for me. Still pretty nice that they are doing all this work to update and upgrade folks who bought the battery years ago. Fortunately it's such an easy process to drop in a new battery I don't mind being a little bit of a test mule. What I don't understand is why all of their attempts at getting their BMS to tolerate voltage Drive in the high 14s are not working. My understanding is that EarthX has a BMS that will tolerate up to 15 V and none of their users are reporting any difficulties. Have to believe the chemistry is the same so I just don't get it

 

[Flybyglass]

The latest I have from Ohmmu is the Gen 4 battery is in a dozen test vehicles with another dozen this week. They are being cautious this time before releasing Gen 4 for wide use.

 

[Skione65]

Is anyone still running their ohmmu battery and still getting the regular alerts or maybe everyone gone back to the lead acid batt.

So I just heard from Sean. What I have is actually version 2 with an add-on module. He has offered to swap this out for version 4. But I still don't understand why these modifications that all ostensibly are aimed at accommodating higher charging voltages are all failing to clear firmware updates.

@dfwatt,

So you actually had a V2 and was sent an “add on module“ to run on top, not an actual V3 updated battery like myself?

Ski

 

[dfwatt]

@dfwatt,

So you actually had a V2 and was sent an “add on module“ to run on top, not an actual V3 updated battery like myself?

Ski

Yes based on what Sean said that would be correct. I thought it was version three but it was actually version two with an add-on module

 

[James Cole]

Hello guys, is there a problem to continue running the V2 or could it actually get me stranded?

 

[dfwatt]

Hello guys, is there a problem to continue running the V2 or could it actually get me stranded?

I'm assuming your not getting the 12 volt error code right now yes? If you do have that code popping up, as long as it will accept a reset you are never stranded. People get stranded only when the car has been showing the error for a while, meaning that the 12 volt subsystem is not getting charged and eventually the 12 volt drains down to zero. This happens of course with either the OEM lead acid or aftermarket lithium ferric phosphate. We had a trickle charger during the period we were getting this error on my wife's car which had the stock battery and that kept us from draining the battery down to zero. As soon as you get the warning do the reset and you have a period (poorly defined of course in terms of length) of no issues. Whether that's a week a month or four months is unclear. I got four months with Version 2 without any issues until having to do the first reset. Having a 12v trickle charger or even a regular battery charger is a good idea given all these uncertainties.