Anybody install an Ohmmu battery in their X? Looking for feedback.

[Marcia L]

I can only find threads on S and 3 for Ohmmu battery. I have the OEM battery in my MX, it is 3 years 4 months and still going but planning an extended camping trip soon which will include have a Dometic refrigerator plugged in the 12V. OEM battery is still under warranty but Tesla won't replace for free until 'battery need replacing' message comes up. Proactive replacement would be $237. Ohmmu is 2X that. Other choice is just take our chances that we might have to have the battery serviced when out on the road somewhere, always a PITA. Apparently I will get about a week's notice from my MX before everything goes dead... Decisions, decisions.

 

[peety3]

Piggybacking on your question: I can only find Ohmmu as a distributor of a lithium-based 12V battery for the Tesla platform. Does anyone else make one? Is there any sort of standard size? Could a Victron Energy 12V LFP work?

 

[F123456]

I also just put a Dometic CXF3 45 in my 2017 Model X, and have been wondering about the 12 v battery. With sentry mode on, the fridge should stay on, per my understanding, but what does that mean for the 12V battery…and should I proactively replace with an Ohmmu? I’d seen some reviews that it is NOT an easy fit in the X; joining this thread to see if others have any experience with it.

 

[F123456]

Anyone?

 

[dmurphy]

I do not have one in my X yet, but I *did* install an Ohmmu Group 31 battery in my travel trailer. Beyond thrilled with it -- top quality, works very well, delivers exactly what it says it will (156Ah). Can run my Norcold 10DC fridge in the trailer for days on end -- almost indefinitely if I have a little sun for the rooftop solar panels.

 

[ankur1234]

sorry late to the reply party but I installed a Ohmmu on my 2017 MX. Needed to reset the car and it was not as easy as the video showed but I love it so far. My car currently has 91k miles and no issues.

 

[ngng]

Are they still having issues with Tesla firmware updates?

 

[scottf200]

Are they still having issues with Tesla firmware updates?

Seemed like a short term thing on the Model 3s and they stepped up and replaced the batteries on their dime

sorry late to the reply party but I installed a Ohmmu on my 2017 MX. Needed to reset the car and it was not as easy as the video showed but I love it so far. My car currently has 91k miles and no issues.

Would love to hear more about the reset and that it was not easy? Service manual info in below graphic.

I'm likely replacing mine with the Ohmmu but reviewing other's experience.

The below graphic is from an OTA install on Apr 13. My concern is that during the OTA we know that various subsystems are restarted including ones that control the DC-to-DC inverter and thus the 12v is "on its own". I don't think a 12v battery should be dropping below 11v and that sounds like it is going or is bad. It may be being covered up at this point with a hyperactive DC-to-DC inverter.

 

[Padelford]

I tried installing an Ohmmu battery in my 2017 MX about a year ago. Discovered that Ohmmu reversed the battery post positions from the OEM battery for some damn reason, and the vehicle’s battery wiring did not have the slack to allow swapping the terminal locations. Ohmmu said nothing about this in their website ad. Had to return the Ohmmu battery & get an OEM replacement. Did change the HEPA filter at the same time, which I highly recommend.

 

[scottf200]

I tried installing an Ohmmu battery in my 2017 MX about a year ago. Discovered that Ohmmu reversed the battery post positions from the OEM battery for some damn reason, and the vehicle’s battery wiring did not have the slack to allow swapping the terminal locations. Ohmmu said nothing about this in their website ad. Had to return the Ohmmu battery & get an OEM replacement. Did change the HEPA filter at the same time, which I highly recommend.

Thank you!! That is incredibly helpful. I will contact Ohmmu to see if they have an updated/better answer.

ASIDE: Re: HEPA filter change
I have tested my 12v a few times and the last time I used a shop vac and air compressor to clean the HEPA filter. Debating on when to change it out. I realize that there are certainly some small particles that are clogging in places I can get to or are stuck ... and thus are restricting my overall airflow by some percentage. It is such a large filter that I didn't think a 'small' percentage would matter. I do use RANGE mode when doing roadtrips and AFAIK that limits some HVAC energy usage and thus efficiencies, however, the cabin is comfortable.

 

[scottf200]

I tried installing an Ohmmu battery in my 2017 MX about a year ago. Discovered that Ohmmu reversed the battery post positions from the OEM battery for some damn reason, and the vehicle’s battery wiring did not have the slack to allow swapping the terminal locations. Ohmmu said nothing about this in their website ad. Had to return the Ohmmu battery & get an OEM replacement. Did change the HEPA filter at the same time, which I highly recommend.

The above (reversed OEM post) does not appear to be true anymore. See their response:

Ohmmu (Ohmmu Support) - Sean
April 18, 2022 12:22 PM (UTC-07:00)
No, this isn't accurate at this time.
There have been times in the past where we utilized a reverse configuration but
we are currently shipping in the OEM configuration, this isn't an issue for you Scott

 

[scottf200]

My 12v Ohmmu battery is supposed to arrive tomorrow. I will likely install it tomorrow or the next day and take readings with the same devices I did with the old one.

TMX install page: Tesla Model X 12V Battery - Installation Video
FYI, Saw this on the page today: "(Note: Battery terminals are no longer reversed)"

Direct YT video:

 

[scottf200]

I installed the Ohmmu 12v in my 2017 X yesterday. It was not the most fun I've ever had
Here are some tips and annotated pictures in case it helps someone else.
Also have included pictures from the 12v monitoring tool I've used for a couple of years.
A couple things to note about the graphs. I didn't see a noticeable drop in the voltage
during an OTA install that happened yesterday as I did with the previous one recently.

• Mostly because I didn't have the flexible ratcheting wrenches as they used in the video above.
  I did have various sizes of socket wrenches and I found a medium one that worked pretty well
  but it was slow to untighten and retighten because of limited space around all the wires.
  My Amazon wishlist now has this in it: https://smile.amazon.com/dp/B07SYCY2SW?th=1
• The install video hints at the wire harness attachment and it made it much easier after doing that.
  (highlighted this location in my picture below (see the white box and blue lettering).
• The bracket is a pain in the butt to get both in and out. Install video does hint about this.
• I had to bend the bracket a little because of the lips on the top of the battery because
  it didn't want to drop down that extra ~1/2" that was necessary to put the L-shaped lock down bracket back.
• After taking out the old battery and bracket, I didn't see where the 12v battery terminal size adapters were.
  I panicked slightly thinking they forgot to include them. They were underneath a sticker in the
  styrofoam packaging.

SUMMARY reference for order of wire disconnect/reconnect. (service manual suggestion).
Take out
1) Disconnect 12v ground (-)
2) Disconnect the first responder loop
3) Disconnect 12 positive (+)

Put in
4) Connect 12 positive (+)
5) Connect the first responder loop
6) Connect 12v ground (-)

[ Jump in the vehicle and verify all boots up OK.
A msg will show up to calibrate FWD; hold the button for several seconds and
follow instructions. They only move a few inches and do not fully open. ]

PURPLE arrows point to the lip on the battery which was the reason to bend the bracket a little.

New battery is still charging higher than I'd expect above 14v. You can see after the installation the charging voltage crept up from ~13.4.

 

[ngng]

I haven't searched because I'm lazy...but do you still need to wait for Ohmu to vet firmware releases before installing them?

 

[scottf200]

I haven't searched because I'm lazy...but do you still need to wait for Ohmu to vet firmware releases before installing them?

Never heard of that. So many myths out there and propagated by post on various forums / reddit "because [people being] lazy". <grin>

I got a software update within 6 hrs of me installing my new Ohmmu battery yesterday.

They've had issues one that I know of with 2021.36. See: Tesla | Model 3 / Y | "Schedule service to replace low voltage battery" Error - Ohmmu Support
>>>>>>>>>>>>>>>>>>

Support Notice Information​

A potential issue has been identified for customers with Tesla Model 3 and Model Y vehicles, running software updates 2021.36.x and later.

Tesla has pushed several new features with their recent updates, which appear to alter the method and extent that the vehicle utilizes its 12V battery. Due to these changes, it is possible that you may receive error alerts for your 12V battery on your Model 3 or Model Y vehicle when it updates to these software versions.

IMPORTANT NOTES:

1. We have identified the issues causing these errors.
2. Ohmmu is currently developing a hardware revision to resolve this issue for existing customers, which should be available in January/February 2022.
3. Ohmmu began developing a revised battery design in December 2021, which will also resolve and prevent these issues from occurring in the future. The revised batteries will be available in March/April 2022 for new customers and potentially existing customers on a case by case basis.

<<<<<<<<<<<<<<<<<<<<<<<

 

[ngng]

Never heard of that. So many myths out there and propagated by post on various forums / reddit "because [people being] lazy". <grin>

I got a software update within 6 hrs of me installing my new Ohmmu battery yesterday.

They've had issues one that I know of with 2021.36. See: Tesla | Model 3 / Y | "Schedule service to replace low voltage battery" Error - Ohmmu Support
>>>>>>>>>>>>>>>>>>

Yeah, that's what I was referring to. Tesla changing their 12v charging/monitoring which threw errors.

I didn't mean that Tesla firmware was blocked, but rather you have no idea if the next update is going to brick your car.

Here's the thread that I previously read that I was referring to (which is related to the link you posted):

The 12v Ohmmu issue with 2021.44.30 update

www.teslaownersonline.com

 

[scottf200]

Yeah, that's what I was referring to. Tesla changing their 12v charging/monitoring which threw errors.

I didn't mean that Tesla firmware was blocked, but rather you have no idea if the next update is going to brick your car.

Here's the thread that I previously read that I was referring to (which is related to the link you posted):

The 12v Ohmmu issue with 2021.44.30 update

www.teslaownersonline.com

Re: to vet firmware releases before installing them
You indicated to vet fw before installing them.

Did you see this part? They replaced them (jan/feb 22). They revised the design to avoid the issue in the future. ie. these batteries have been used for several years and this happened once and they proactively dealt with it. Seemed legit to me.

Quote:

1. Ohmmu is currently developing a hardware revision to resolve this issue for existing customers, which should be available in January/February 2022.
2. Ohmmu began developing a revised battery design in December 2021, which will also resolve and prevent these issues from occurring in the future. The revised batteries will be available in March/April 2022

 

[ngng]

Re: to vet firmware releases before installing them
You indicated to vet fw before installing them.

Did you see this part? They replaced them (jan/feb 22). They revised the design to avoid the issue in the future. ie. these batteries have been used for several years and this happened once and they proactively dealt with it. Seemed legit to me.

Quote:

1. Ohmmu is currently developing a hardware revision to resolve this issue for existing customers, which should be available in January/February 2022.
2. Ohmmu began developing a revised battery design in December 2021, which will also resolve and prevent these issues from occurring in the future. The revised batteries will be available in March/April 2022

Yeah I saw that but did not see any updates on whether it has been resolved. The most recent post from somebody earlier this month who is having issues:

Kctime: Apr 1, 2022

I got the error eight days after installing the beta battery. Informed Ohmmu five days ago. No response as of yet.

 

[scottf200]

Here is my voltage chart from yesterday. I'm pretty happy with how the built-in Ohmmu BMS is handling it and it is much closer to how my AGM battery was showing up when it was new. As well I liked the lack of voltage sag when the OTA install stopped the DC-to-DC convertor process (link of graph above) -- my old battery was not looking good there as shown in this graph.

 

[ngng]

Here is my voltage chart from yesterday. I'm pretty happy with how the built-in Ohmmu BMS is handling it and it is much closer to how my AGM battery was showing up when it was new. As well I liked the lack of voltage sag when the OTA install stopped the DC-to-DC convertor process (link of graph above) -- my old battery was not looking good there as shown in this graph.

Please post long term thoughts after you've had the battery for a bit. I'm torn because I've always been skeptical of a company that has "improved LED and audio" as a selling point, but I also have used LiFePO4 batteries on my motorcycles in the past with great success. At some point, I suspect I'll be replacing my 12v in the X.