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Planning to replace 12V in M3 with Lithium Ohmmu battery.

Sans-gas

Member
May 1, 2019
119
51
NW WA
I’ve had my car 2 yr. I’m planning a roadtrip and want to do this prior. I like what I’ve read about this Lithium battery.

Does anyone have any negative information? I was on doing the replacement after watching a couple instruction videos.
 
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tomas

Out of warranty...
Oct 22, 2012
4,266
3,856
Chicago/Montecito
I just had 12v replaced in my S by Tesla mobile service. The tech had to reprogram the firmware for the specific battery type. He said that if he had left the settings for the old type, it would burn right through the new one. Now knowing that the software is THAT tied into the battery, I’d never get an aftermarket 12v. Plus for the price of the LI battery you could replace with standard battery at least twice.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,755
9,717
Riverside Co. CA
I’ve had my car 2 yr. I’m planning a roadtrip and want to do this prior. I like what I’ve read about this Lithium battery.

Does anyone have any negative information? I was on doing the replacement after watching a couple instruction videos.

You dont say which one you are looking at.. Assuming its the Ohmmu, there are quite a few threads here on that battery.

here is one:

Ohmmu Battery & 2020.28.6 update


Here is another thread about changing the 12 volt...

Lithium 12v battery upgrade question
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,644
11,554
San Diego
Personally, I’d just buy the replacement Tesla 12V for $85, install it before the trip, and call it good. Should play well with the software on an ongoing basis.

Or not worry about it (depends on the destination), and I would just keep an eye on my 12V battery monitor and if any sign of problems, for sure swap it out.
 
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lUtriaNt

Member
Mar 16, 2020
624
551
Los Angeles
sadly OP, you will get a bunch of opinions from "battery experts" and "tesla experts" this forum have en masse with their own "personal" feelings, so you may end up being more confused than ever.

id just read up on the many threads on this battery and read what the ACTUAL OWNERS have to say about the battery. they are the ones with the experience and not just "personal feelings".

for me, i got model 3 in march this year and stumbled across a thread about this ohmmu battery. since the car was new and i am new to tesla , i soaked up all the info i could. after reading the OVERWHELMING POSITIVE points on ACTUAL USERS of this battery, i bought one not even a month after i got the car.

ohmmu have top shelf customer service and the owner sean will get to you right away with any questions or issues you may have about installation, etc. that to me is also worth the price -- service AFTER the sale.

if you have the funds to afford the battery, its worth the investment.
 
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animorph

Active Member
Apr 1, 2016
2,134
1,529
Scottsdale, AZ
Our 3's battery died quickly after 18 months. Given the number of replacements I've seen here it would be good to replace it before a long trip. You could also just purchase the replacement and carry it with you until needed I suppose.

We had Tesla replace the 3's 12V because of the car's weird behavior. That was performed under warranty, so no cost to us other than Service Center run around. Not an option if the car hasn't warned you yet.

We had our X's 12V battery replaced with an ohmmu after getting a warning from the car. Turns out they are local for us, so we had them install it. So far so good, but it's only been four months. As our road trip car, I felt safer with the ohmmu than a direct replacement. I haven't heard of anyone having an ohmmu long enough to reach end of life yet. ohmmu said the 3 was an easy replacement. The X has more screws to take out and a bit more complexity to the process.
 

SSedan

Active Member
Jul 24, 2017
2,948
2,313
Greenville Wisconsin
You would hope positive reviews mean a lot BUT when people convince themselves to spend twice as much on a part they often convince themselves it was a great decision regardless of the actual result.
Not saying it is bad, but think about what the claimed benefits are and if those benefits are actual are they useful.
 

Sans-gas

Member
May 1, 2019
119
51
NW WA
Personally, I’d just buy the replacement Tesla 12V for $85, install it before the trip, and call it good. Should play well with the software on an ongoing basis.

Or not worry about it (depends on the destination), and I would just keep an eye on my 12V battery monitor and if any sign of problems, for sure swap it out.
“12V monitor”?
 

KenC

Active Member
Sep 4, 2018
3,547
3,211
Maine
Has anyone tried this battery? Considerably less expensive than the Ohmmu.

12V 100A Lithium Ion Battery | GreenLiFE GL100
It's a LFP battery, Lithium-Ferrous-Phosphate. What the MIC SR+ uses. LFPs have alot going for them, but usually not as energy dense, so larger size for the same energy capacity. My only concern is that the 12V battery algorithm is meant for the OEM Lead-acid battery. Of course, that doesn't seem to be working all that well, so maybe there's less risk in changing.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,644
11,554
San Diego
Thanks for the link. I’ll check it out.

I’ve posted some plots; idle and sleep cycles are really clearly defined, and I suspect some failure modes might be clear prior to them showing up. Who knows though; I have not had a 12V failure so not clear what it would look like. Hypothesis would be that some types of failures would lead to frequent rapid discharge of the battery (so more idle cycles). But all hypothetical.

Obviously cold weather can bring out battery issues more readily, so if you will being doing a cold trip and want to be guaranteed a fresh battery that works well, could swap in the new one and lug the old one along (carefully) as a backup. Or vice versa. Just have to make sure the unused one is eventually put on a tender.

Seems lower drama to me than Ohmmu or similar, but that is just me.

Certainly, whatever you decide, taking a few steps to avoid 12V failure is prudent for a road trip if there is question about your battery.
 

grmdl3

Member
Apr 21, 2020
154
104
Oregon
It's a LFP battery, Lithium-Ferrous-Phosphate. What the MIC SR+ uses. LFPs have alot going for them, but usually not as energy dense, so larger size for the same energy capacity. My only concern is that the 12V battery algorithm is meant for the OEM Lead-acid battery. Of course, that doesn't seem to be working all that well, so maybe there's less risk in changing.

I was under the impression that the Ohmmu battery is also LiFePo? LiFePo has a higher number of life cycles than Lithium ion polymer, and is pretty commonly-used for lead-acid replacements.

When you say "not as energy dense," compared to what?
 
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grmdl3

Member
Apr 21, 2020
154
104
Oregon
So I'm going to answer my own question here: I talked to Greenlife, and they basically said they weren't confident their BMS would work with a Tesla.

Given how much an Ohmmu costs, it's tempting to try four of these plus something like this, and try to figure out the programming that satisfies the onboard sensors.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,644
11,554
San Diego
Given how much an Ohmmu costs, it's tempting to try four of these plus something like this, and try to figure out the programming that satisfies the onboard sensors.

I'm gonna go out on a limb and say that that will prove to be less reliable than a new sealed lead acid battery from the Tesla Service Center for $85. Also an SLA is probably less likely to ignite your vehicle, though I think this particular lithium chemistry is safer than most. But if you want a project, more power to you!
 
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