I worked through the problem (at least temporarily) with my Ohmuu Model Y battery. I re-charged it with the Dakota Lithium Charger I mentioned in my previous post. The battery seemed to gain some voltage just resting in the garage because when I removed it after attempting the hard reset several times, it was down to 10.88 volts. According to this CHART that was about a 4% state of charge. This morning, my multi-tester read about 11.6 v just sitting in the garage, which is +/- 6%. After charging it with the DLC for a while, the multi-tester read 13.6 volts, which according to the chart is 100% resting. The DLC didn't show a green light, or anything, but I think the Ohmuus' BCM just stops it around 13.6 to avoid over-charging. I'm not sure exactly how long it took the DLC to raise the voltage from 11.6 to 13.6. I left it running for more then 2 hours. Neither the battery or the charger became hot. It might have only taken it a few minutes, until the BCM cut off additional current. I threw the Ohmuu back into my Y Perf and it's working fine, now. No more errors. We'll see how long it holds up. Not sure if the dip in voltage was from an OTA update, or the fact my kid sits in the car and plays and watches HULU for hours, or that I've been recently using the battery pre-conditioning feature 5 days a week, or a combination of all 3. There was another update just a couple days ago. Hopefully Tesla fixed the 12V issue on their end from that update?
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Ohmmu 12V Battery Feedback
- Thread starter LasVegas2019
- Start date
First, I would forward your experience to Ohmmu. Field information helps them in solutions. Including voltage readings and as much information as possible. I did that along with all my error messages to assist them on at least temporary solutions. In this particular case. I'm going to speculate. I suspect that once the error warnings were generated, until a reset was performed, no 12 volt charging was occurring. Add hours of HULU with no charging lead to the depletion of the 12 volt battery. (Had the errors not occurred the DC-DC charger on board would have kept the 12v battery charged.) Step one in the reset procedure is to drive at least 10 minute if able. I believe (again Ohmmu could add clarity) is to add charge to the 12 volt battery prior to attempting the reset. The following is an excerpt of a note from Ohmmu discussing what is going on (they have run data collection modules to help with the understandings):
"Our commitment to you is to provide a solution, alerts are unacceptable, we know this, we will provide the solution for free to all existing owners as soon as available.
In the meantime your battery is actually healthy and fine, we believe what is happening is that the vehicle has a new "over-charge" mode that it is employing because of a new Tesla 12V team employee with an old-school flooded lead-acid mentality. In old flooded lead batteries you could over-charge them and boil off excess water but when doing so you were supposed to replace the lost water with distilled water, these were the 12V batteries that required maintenance. However, Tesla, and most other automakers, don't use this type of battery, they use AGM which are susceptible to damage when over-charged. LFP is also susceptible to damage during overcharge and to this end we have an overcharge protection circuit in our batteries. What we are seeing in the latest updates is that the vehicle now trips that safety sometimes; it was added as a fail-safe for a malfunctioning vehicle to prevent overcharge. Anyways, when the Tesla trips the battery safety it results in a brief battery disconnect internally which the vehicle sees as a disconnected battery and throws an alert code.
To this end we are developing a solution. There is a way to reset your vehicle for this alert and that will get rid of it but it sometimes comes back quickly, it all depends on when the vehicle decides to do an over-charge session. The reset instructions as well as future updates to this issue are in this thread here:"
Tesla | All Models | "Replace 12V Battery Soon" Alert
There is a note if a multimeter reads 0.0 discussing the BMC protections how it disconnects cools then resets in an overcharge situation. It sounds like the BMC was just doing its cell balancing (not overcharge protection from the portable charger) near top charge just like the Tesla does during sleep after charging. I also had to remove my kid who wanted to play with video watching. The next generation of Tesla buyers.
lUtriaNt
Member
just a friendly PSA to some of you cats new to tesla and/or this battery.
i made a thread a while ago about this little BT thingy you attach to the battery. it connects to your smartphone when in BT range and tells you the charging state of the battery. it also gives you a historical graph on charging behavior.
its mostly designed for conventional combustion engine vehicles as some of the features wont apply to the electric car, but the main feature is the battery status which is what you want.
teslamotorsclub.com
i made a thread a while ago about this little BT thingy you attach to the battery. it connects to your smartphone when in BT range and tells you the charging state of the battery. it also gives you a historical graph on charging behavior.
its mostly designed for conventional combustion engine vehicles as some of the features wont apply to the electric car, but the main feature is the battery status which is what you want.
Low cost way to monitor your 12V Battery
So I had this little gadget on my combustion engine vehicle and , well, with all the talk about the 12V battery error message popping up, I thought to revisit this little doo-dad. its this cat...
teslamotorsclub.com
medphys3
Member
just a friendly PSA to some of you cats new to tesla and/or this battery.
i made a thread a while ago about this little BT thingy you attach to the battery. it connects to your smartphone when in BT range and tells you the charging state of the battery. it also gives you a historical graph on charging behavior.
its mostly designed for conventional combustion engine vehicles as some of the features wont apply to the electric car, but the main feature is the battery status which is what you want.
Low cost way to monitor your 12V Battery
So I had this little gadget on my combustion engine vehicle and , well, with all the talk about the 12V battery error message popping up, I thought to revisit this little doo-dad. its this cat...
Not to change the direction of this thread too much, but I got this little doo-dad to set as a low voltage alarm so I would know if my battery level got low.
Amazon.com
Interestingly, it shows that the voltage drops fairly low upon start-up (opening the door) and then the car ramps the charging up to 14.9 volts. Not sure if it always charged this high or if this was a change with V11. Could the high charging voltage be what's messing with the Ohmmu battery? (I have the OEM battery FWIW)
Here's a video of the voltage being read directly from the battery after opening the door.
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android04
Active Member
The reason the battery voltage drops when you open the door is because that's when it engages the high voltage contactors to wake up the car and also starts charging the battery. This situation is the closest we get to having a high draw from the battery, but not quite as high as cranking an engine.
Once the car is awake, the DC to DC converter acts like the alternator and pretty much powers everything 12V, as well as charges the battery. Tesla can and does change the charging characteristics with software updates, but the most likely reason for the higher charging voltage is that it is cold where you live. The charging characteristics of lead acid batteries need to be adjusted based on the ambient temperature.
I don't really think the low voltage alarm will be useful to you unless you normally park for long periods of time where you can hear the alarm from wherever you are.
Woke up to a drained Earth-X ETX900 tapped off DC-DC converter (for 5kW PPI amp voltage support with 15 Farad cap) with Ohmmu installed. Re-installed lead acid battery and no issues. Something about the Ohmmu BMS that doesn't play nice with some Tesla updates. Will wait for the fix before trying the Ohmmu again. I think the Earth-X doesn't cause any issues (yet?)
Jeremy3292
Active Member
I was considering getting an Ohmmu 12V LFP battery before I did some more research and found out about the couple times they have had to "update" their battery in order to work properly. There are a lot of threads on this that I read through, including this one. It happened in mid/late 2020 and just happened again a few months ago is my understanding. They shipped everyone a new "V2" battery in late 2020 and now they are working on a new "V3" battery that will be released soon per their website. The BMS and Tesla software is only calibrated for a certain 12V battery and I imagine the software is different for the new 2022 models with the Tesla lithium 12V.
I like the idea of having a 12V lithium or LFP battery. However, every time Tesla updates the software that has to do with the 12V battery it messes things up, making the situation untenable for aftermarket parts. So I essentially would be trading one problem for another. Since I live 100 minutes from the closest Tesla dealership, my new plan is to proactively replace my 12V battery via mobile service every 2 years. $100 every 2 years is nothing. I also leave Sentry mode on at work every day during the week for 9-10 hours, which is cycling my 12V battery constantly. I imagine I will need one every 2 years for sure.
Someone can let me know if I missed something or am misconstruing facts unintentionally.
I like the idea of having a 12V lithium or LFP battery. However, every time Tesla updates the software that has to do with the 12V battery it messes things up, making the situation untenable for aftermarket parts. So I essentially would be trading one problem for another. Since I live 100 minutes from the closest Tesla dealership, my new plan is to proactively replace my 12V battery via mobile service every 2 years. $100 every 2 years is nothing. I also leave Sentry mode on at work every day during the week for 9-10 hours, which is cycling my 12V battery constantly. I imagine I will need one every 2 years for sure.
Someone can let me know if I missed something or am misconstruing facts unintentionally.
android04
Active Member
I agree with most of what you said, except for the part where Sentry Mode will cycle your 12v battery constantly. It doesn't cycle your battery -- it actually fully charges it and keeps it at a the float voltage of about 13.45v the whole time (varies a bit by temperature). I think that's actually a little better for the 12v battery health, so you might not actually need it replaced every 2 years unless you live in a very hot climate.
You raise valid concerns. I would ask Ohmmu directly. I have noticed in cold climates that the car is VERY SLOW to wake up with the standard 12 volt vs. the Ohmmu. Ohmmu is responding with a fix (there will be a module you attach to an exiting Ohmmu) and the Version 3 will have that included. I temporarily put my original 12 volt battery back in (I removed it days after ownership and kept as spare) and I am eagerly waiting for the fix to come.
Jeremy3292
Active Member
I had only used it a couple of days when I installed my Ohmmu. I put a charger on it after sitting on the shelf a year and it still had 95% charge. I kept since it only had a few cycles as a spare.
Jeremy3292
Active Member
Jeremy3292
Active Member
What is the biggest factor in 12V battery degradation and useful life? What causes the most cycles then?
android04
Active Member
I don't know the exact answer, and there are likely multiple factors at play. But Tesla can and has changed exactly how the battery charges with software updates. If they had/have a bug that overcharges or undercharges the battery, that will reduce its lifetime. Some of it could be defects or quality control of the battery from the manufacturer. And some of it is exposure to heat, because it reduces the lifetime of lead acid batteries.
As for what causes the most cycling, I'd say letting the car sit without using it or driving it will cause the most cycles. In that case the 12v battery will be drained a certain amount before the car wakes up to recharge it. I believe it cycles about 3 times a day. I don't know how much depth of discharge Tesla allowed before recharging, but I'm pretty sure it's more shallow than in the past based on my recent measurements.
Stanwood Steve
2018 Performance Model 3
Maybe I'm the exception, but I've had no issues with my Ohmmu battery at all. I installed one right after the initial version 2 replacement, so it was the updated configuration, and I'm running software release 2021.44.30.10 currently. I've never received any warning messages and the car is running fine. By the way, the car was a 2018 August delivery.
Let's hope. I was running for a couple weeks when the 3 warnings noted earlier appeared. I swapped out temporarily the Ohmmu for the Factory battery. Perhaps .10 corrected but based on my discussions with Ohmmu it will occur when the software decides to do a 12 volt battery overcharge check. Then the Ohmmu's built in BMC gets wonky and the car interprets faults. The Ohmmu correction module should be out shortly.
lUtriaNt
Member
you are not the only one. many people have no issues with these batteries but they don't decide to come to an enthusiasts forum to talk about it. they just get in the car and enjoy. ohmmu told me they only saw 60 or so out of hundreds of their batteries in the wild that are having this issue.
Jeremy3292
Active Member
With how you went through this thread and disliked every single post that was remotely critical of Ohmmu it makes me think you work for Ohmmu or something.
If it was only 60 batteries and an isolated incident they wouldn’t be on version 3 of their battery after having issues in late 2020 as well. Many threads on those issues as well.
Trading one set of issues for another isn’t something I’m interested in and many others feel the same way here as well.
There is a current issue with the Li 12v battery for me now since Tesla updated their equalize charger to 14.8v in the car. It has bricked the safety switch in the Ohmmu battery which has taken out heated seats, heated air, and sentry mode for the car. It also cannot receive updates due to the softwares change and Ohmmu has been dragging their heels on getting a fix for the past 2+ weeks. If they can’t support their batteries and gives the car all the functions it needs, no one should buy from them. This especially sucks during winter. I am currently very pissed at them for being so slow to respond with a fix to this.
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