Tesla Won't Install Ohmmu [aftermarket 12v battery]

[ApexProxy]

You know that LFP batteries are a type of li-ion battery, right?

They're not. The voltage curves are different:

And even if you could match the curves exactly, the problem is that lead acid needs to be stored at close to 100% SoC for maximum life, whereas LFP likes to be stored at something far less than close to 100% SoC. So you need to tell the charging system to not top off the battery all the time. If this chemistry were so great and it could just be used as a direct drop-in replacement and have OEM reliability, Tesla would have just used it as the OEM battery and wouldn't have redesigned anything else.

That curve is totally wrong. LiFePO4 cells hit peak SOC at 3.65V. 4.2V would be complete destruction.

Also, LiFePO4 prefers 100% SOC (read up on official Tesla LFP battery procedure) but does not require constant float like lead acid due to significantly lower self discharge and a good BMS will prevent constant float charge degredation.

 

[STS-134]

That curve is totally wrong. LiFePO4 cells hit peak SOC at 3.65V. 4.2V would be complete destruction.

Also, LiFePO4 prefers 100% SOC (read up on official Tesla LFP battery procedure)

No, we discussed this on the other thread: Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

LFP actually prefers to sit below 70% SoC. The only reason Tesla tells you to charge to 100% frequently is that the voltage curves don't vary too much in the middle, so the BMS could lose track of exactly what the SoC is and leave you stranded. But you don't want to store a LFP at or close to 100% any more than you'd want to store a NCA battery at or close to 100%.

 

[ApexProxy]

Another

No, we discussed this on the other thread: Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

LFP actually prefers to sit below 70% SoC. The only reason Tesla tells you to charge to 100% frequently is that the voltage curves don't vary too much in the middle, so the BMS could lose track of exactly what the SoC is and leave you stranded. But you don't want to store a LFP at or close to 100% any more than you'd want to store a NCA battery at or close to 100%.

I didn't say storage. I should have been more specific but I figured since we were talking about charging it wasn't necessary.

I also maybe shouldn't have said "prefers" (so I'll give you that) but LFP handles 100% SOC extremely well, so well in fact at 100% SOC they constantly out-cycle LA.

 

[STS-134]

Pure FUD and the latest illustration that a little knowledge is a dangerous thing. Reminds me of all the self-styled exports on the Forum who predicted that the aftermarket lithium ferric phosphate 12 batteries were all going to catch fire.

Speaking of catching fire, what do you think is going to happen if those solder joints come loose when you go over a bump? This thing looks like it was put together by an amateur, lol: Longer term Ohmmu experiences?

 

[israndy]

Wow! I just got the Bluetooth app email from Ohmmu, I thought they were icing me out. At least I made the owner list even if they won't honor the warranty for me as a second hand owner

 

[ApexProxy]

Speaking of catching fire, what do you think is going to happen if those solder joints come loose when you go over a bump? This thing looks like it was put together by an amateur, lol: Longer term Ohmmu experiences?

That looks like a terrible design but odds are nothing would happen if one of those leads came desoldered aside from a loss of power. The potential for a short is there but even if you shorted those cells its unlikely they would do anything but get hot or blow one of the cell bridges. It's pretty common for a cell pack to have a fuse link within the pack itself. I probably would have gone with Antigravity anyway since they have a pretty solid rep.

 

[dfwatt]

Speaking of catching fire, what do you think is going to happen if those solder joints come loose when you go over a bump? This thing looks like it was put together by an amateur, lol: Longer term Ohmmu experiences?

Keep that FUD coming. At least on a night with relatively little entertainment from Sunday Night Football it keeps things amusing.

 

[STS-134]

Possibly that specific battery since it's not a very good build. This does not hold for well built and properly constructed LiFePO4 replacement batteries. They do have real benefits. Lead acid batteries are ancient technology that has been ready for retirement for years.

Doesn't change the fact that, ancient as it is, the charging system was built for lead acid and should be charging a lead acid battery. If you want a LFP battery as your LV battery, change the charging system to accommodate it. It's even dumber to change battery chemistries because there had been a software bug that wasn't alerting people to a dying LV battery, and somehow expecting that the charging system that wasn't even designed for LFP is somehow going to alert you before the LFP battery goes kaput. Then people have started putting Bluetooth monitors on their LFP replacement batteries to figure out what's going on with Tesla's firmware and why it's throwing errors on a battery chemistry it was never designed for. Have these people not realized that you can put a Bluetooth monitor on the OEM lead acid battery too in order to figure out if it's dying? Or you can buy a load tester for about 1/4 to 1/8 of the cost of these LFP replacements. Or both.

 

[Darmie]

(OEM 12V = $85, 4 of those = $340, Ohmmu battery = $439)

From a value point of view, this is great prospective.

The OEM battery is only 85 dollars? I was going to get a Ohmmu battery when my OEM battery died but for 85 dollars I would just replace it with another OEM battery. I assumed they were 150ish

For the Model 3 and Y that is what they go for. I just proactively replaced our Model Y battery. They gave me a price to include them changing it out that I couldn't refuse when I went to purchase just the battery. For the Model X, they are much higher. I think the battery and labor was $250.00.

At least the service manual is available free and the battery replacement procedure is not difficult but longer than an ICE car. Tesla Service

On the 3/Y it's so easy to just pull the black cover and yank out the battery. I've seen and worked on my share of ICE vehicles that were much more of a challenge. The newer they are, the more stuff covers up the battery. Some ICE vehicles even have the battery under the back seat or worse crammed in the trunk.
Now the Model X is a different story. The front tub needs to be removed to gain access to the battery.

 

[Flybyglass]

On the 3/Y it's so easy to just pull the black cover and yank out the battery.

Not quite. Error messages will be generated. The procedure also requires turning power off, disconnecting main battery under rear seat and also removal of USB devices. Just removing terminals and swapping will work but procedure.

 

[bmanchanning]

I just got an estimate from Tesla for a Model X LV battery replacement through mobile service of $460. If it were $250, I'd go with OEM, but now the Ohmmu looks like a great value. Has anyone else received such a high quote?

 

[RayK]

@bmanchanning Well, you've posted in a Model 3 forum so I don't know what the costs involved for a Model X 12V battery replacement would be.

 

[brkaus]

I just got an estimate from Tesla for a Model X LV battery replacement through mobile service of $460. If it were $250, I'd go with OEM, but now the Ohmmu looks like a great value. Has anyone else received such a high quote?

Model S/X are $400+ installed. Model 3/Y are much less. The S/X are harder to access and they are AGM batteries. The 3/Y are standard FLA (flooded lead acid). Of course newer cars have moved to some flavor of lithium..

 

[ucmndd]

Model S/X are $400+ installed.

This must be recent, I paid $204 installed ($165 part, $39 labor) for a 12v in a Model S less than a year ago. $400 is insane.