Replace 12 volt battery

[Ravire]

After reading some more on another forum, including replies from the Ohmmu founder himself, I plan to buy one of their batteries sometime after my car hits 50k miles. That should be in about 12-13 months, after which my OEM battery will no longer be warrantied. If it can really last 4 years, that's worth the extra price IMHO. It should also reduce phantom drain, which is a nice bonus.

It’s only worth it for the extra life imo the difference is phantom drain in minuscule

 

[RKBA]

It’s only worth it for the extra life imo the difference is phantom drain in minuscule

Thanks for the first-hand info! I'm gonna claim I got it right when I said it was just a bonus.

 

[smatthew]

Thanks for the first-hand info! I'm gonna claim I got it right when I said it was just a bonus.

How much phantom drain do you think the 12V battery causes?

Let's do the math. Self-discharge on lead acid batteries is about 5% per month.
The Model 3 battery is 45Ah. 45Ah x 13 volts = 585 watts capacity
585 watts x 5% = 29.25 watts a month.
Or less than a watt a day.

Charing your cell phone at home will have more of a difference.

 

[RKBA]

What I read (in either this thread or one elsewhere) was that the phantom drain savings wasn't due to self-discharge but because of the vampire loads while the car is parked. Those loads take more from the SLA battery and therefore it needs to be recharged more frequently. The claim was that the 12V SLA battery gets recharged 2-4 times per day whereas the ohmmu was only being charged once per day at most. To be clear, I have no idea how reliable that information is.

 

[miimura]

What I read (in either this thread or one elsewhere) was that the phantom drain savings wasn't due to self-discharge but because of the vampire loads while the car is parked. Those loads take more from the SLA battery and therefore it needs to be recharged more frequently. The claim was that the 12V SLA battery gets recharged 2-4 times per day whereas the ohmmu was only being charged once per day at most. To be clear, I have no idea how reliable that information is.

The discharge curve for most LiFePO4 batteries is flatter than an AGM Lead-Acid battery. The Tesla vehicle is going to use it's own voltages to decide when to recharge the 12V battery. Just to pull some numbers out of thin air to illustrate the point, let's say the Tesla normally does 50% DoD (depth of discharge) and those same start and end voltages result in 80% DoD on the LiFePO4 battery. The factory battery is 45Ah and the Ohmmu battery is ">40Ah". 50% of 45 is 22.5Ah and 80% of 40 is 32. So, for these imaginary figures, if the factory battery recharged 3 times per day, the lithium battery would recharge 2 times per day. The self-discharge of each battery is inconsequential, the vampire drain is caused by 12V loads in the car that persist when the car is parked.

 

[GSP]

How much phantom drain do you think the 12V battery causes?

Let's do the math. Self-discharge on lead acid batteries is about 5% per month.
The Model 3 battery is 45Ah. 45Ah x 13 volts = 585 watts capacity
585 watts x 5% = 29.25 watts a month.
Or less than a watt a day.

Charing your cell phone at home will have more of a difference.

You forgot to include the higher round trip (charge + discharge) efficiency of Li-ion vs. PbA batteries. All of the vampire drain has to cycle through the 12 V, resulting in more energy loss from the HV battery for the less efficient PbA 12 V. This is how Li-ion reduces vampire drain.

You are correct about the 1 Watt-hour per day self discharge of the PbA battery being negligible.

GSP

 

[dcm3]

Is something like this useful?

Innova Battery Tester (Free Shipping)

 

[sh0719]

I decided to change the 12 volt battery before it left me stranded as the car is coming up on 2 years old this summer. After much measuring I figured that an Odyssey PC1100 would fit. I perfer Odyssey
batteries as I have received 10 plus years of service in several motorcycle applications. Also with standard battery prices going out site these are now reasonable. Battery cost was 226.79
Top post lug kit was 15.25 and shipping was free. The new battery fit in with no modifications. Specs are 45ah and 500 cca.View attachment 535663

Hi, I just purchased the same battery (Odyssey PC1100) and try to find the well-fit terminal stud post on the battery. Can you let me know which one did you successfully fit on? (I already failed to fit with 2 terminals and I am about to buying my 3rd trial one...) help me please.