Pros and Cons of Li+ 12V battery replacement: Options, costs, downsides?

Dfwatt

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#1
Thinking about replacing the heavy 12V front battery. Heard many negative reports about how the normal fairly deep cycling of front 12V battery not a good match for Li+ technology. I know MPP has a product out, along with some others, but would love to hear from folks either highly knowledgeable about this aspect of the Model 3 operating system or with actual experience and decent miles on a Li+ product. Just for example, do you throw a code and disable your vehicle just by any temporary disconnection of the front battery to replace?

Weight differences between stock and various replacements? BMS in various options? This forum has great resources, so expecting to learn great things!:cool::cool::cool:
 

Perscitus

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#3
Yeah a few threads re this already.

Plus lots of answers scattered across the interwebz for both ICE, Hybrid and EV applications.
From full on racecar to DD, various climates. etc.

In terms of product, so long as a BMS is in place, capacity/reserve capacity specs look good - consider:
Ohmmu, ArcAngel, FuelZero, MPP, Braille, and even the eBay generics
https://www.ebay.com/itm/112865946707?ul_noapp=true
 

Dfwatt

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#4
I can imagine you've been through this thread

Lots of discussion on weight and concerns.
But not a lot of feedback from folks that had installed and owned for at least several months, in a cold climate. Most of the owner-centric responses were from the original poster about Braille batteries. Nothing on the MPP, Omm
 

Perscitus

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#5
I've shared my feedback re Ohmmu (and generic/no-brand LiFePO4) in a few places.
Zero issues thus far with ambient temps down to 25F and up to 80F.
Extended unplugged and plugged-in deep sleep sessions, HPWC re-charging from 30% or 50% SoC,
out-of-chassis LiFePO4 conditioning using a dedicated LiFePO4 charger shows no issues either.

Immediate Pros:
- stock PUP audio quality improvement (especially bass response, and any sustained load)
- clear decrease in Parasitic/Vampire drain at any SoC vs stock AGM (with car in/out of deep sleep)
- decreased or eliminated headlight flicker (might be placebo and actually caused by 2019.8.x 2019.12.x series firmware updates)

Need more time with Ohmmu @ summer temps and winter temps to see how it behaves in such conditions.
 
Last edited:

Jay79

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#6
I feel like the 12v is the weak point of the car, I've read about multiple owners being stranded because the battery failed. It not common but still is a concern, I'm very interested if the Ohmmu battery is more reliable or not
 
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#7
Just for example, do you throw a code and disable your vehicle just by any temporary disconnection of the front battery to replace?
I disconnected the 12V battery a couple times (once to switch to the Braille battery, and once to connect the bluetooth-connected battery voltage monitor) and didn't get any error codes. I actually couldn't tell any difference in the state of the car with/without the 12V battery connected; since the high voltage battery was connected (the driver side door and frunk were open), it must have been using the high voltage battery to generate the 12V supply needed by the car while the battery change was going on. I guess one of the key functions of the 12V battery is to engage the connector for the high voltage battery. Once that happens, the 12V battery isn't really in use until the car goes to sleep again.
 

Perscitus

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#8
Yes, that sounds about right. To err on the side of caution, its best to force a Power off via the Service Menu,
and only then attempt any work on the 12V battery.