The 12 Volt battery in the Model 3, not AGM?

Long Ranger

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I frequently see statements that the 12V lead acid battery in the Model 3 is an AGM battery, but I don't believe this is true. I can't find anything authoritative that states it's an AGM battery. I often see this website quoted as a source:
https://teslatap.com/articles/12-volt-battery-compendium/ but they don't really provide any evidence for their claim that the AtlasBX 85B24LS uses AGM technology.

However, if I go to the battery manufacturer's website, it's pretty clear to me that this is not an AGM battery. Hankook doesn't quote very complete specs, but here is the evidence that I can see:
1. Per https://cdn.hankook-atlasbx.com/PRD...3451a848e7e5/HANKOOK_AtlasBX_small(final).pdf the part number is MF85B24LS. All of their AGM batteries start with an AGM prefix. All of their Sealed Maintenance Free batteries start with this MF prefix.
2. The MF85B24LS https://www.teslarati.com/tesla-model-3-dashcam-power-12v/ looks exactly like the AtlasBX SMF JIS family of batteries (except for the handle color) https://www.hankook-atlasbx.com/en/product/automotive/passenger-car-smf.do but it doesn't look anything like their AGM batteries https://www.hankook-atlasbx.com/en/product/automotive/passenger-car.do which have a different style of handles.
3. The top of the battery has the "Advanced Seal Double Lid" per the AtlasBX SMF Technology https://www.hankook-atlasbx.com/en/technology/automotive/mf-technology.do not the "6 Valve Design" with pressure relief valves that is characteristic of AGM design https://www.hankook-atlasbx.com/en/technology/automotive/agm-technology.do
4. You can get the battery for only $80 or $85 from a Tesla SC. That seems pretty cheap to me for an AGM battery.
5. I found this photo of a packing box that says it is SMF type.
 

bitmanEV

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I had / have 3 EVs (Zoe, Leaf & M3) and they all had ICE 12v Lead Acid batteries what's a shame because Lead Acid batteries can indeed deliver enormous amps to crank an starter motor but don't hold charge for a long period and with an EV there's no need for crank amps as there's no ICE to start
It's just cost cutting and i really do not understand why Tesla uses Lead Acid batteries for their 12v system and not uses Lithium batteries
 

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I had / have 3 EVs (Zoe, Leaf & M3) and they all had ICE 12v Lead Acid batteries what's a shame because Lead Acid batteries can indeed deliver enormous amps to crank an starter motor but don't hold charge for a long period and with an EV there's no need for crank amps as there's no ICE to start
It's just cost cutting and i really do not understand why Tesla uses Lead Acid batteries for their 12v system and not uses Lithium batteries
Lithium batteries have relatively poor cold-weather performance. Lead acid batteries are less expensive and perform well in the intended application.
 

android04

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I've looked in the Hankook batteries website before and couldn't find specific info on the Model 3 battery on their lists, but didn't think downloading their catalog PDF would help. It obviously did help in finding more info, thanks for sharing. Here's a screenshot of the relevant page. The three batteries with (*1) next to them are in Teslas. The first one goes in the Model S and has a AGM in the name, the second goes in the Model X and only has MF (maintenance-free) in the name, and the third goes in Model 3/Y and also has MF in the name. So you seem to be right that our Model 3 batteries are not AGM. The question now is does it matter for longevity in our application?
Screenshot_20200904-084755__01.jpg
 

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I don't recall anyone ever claiming this is an AGM battery. That would perform better likely since there is not starter, but I don't think this claim is wide spread. Maybe I've just read right over AGM, but all of the talk I recall is why they didn't use something other than the maintenance free battery.
 

JasonF

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I don't recall anyone ever claiming this is an AGM battery. That would perform better likely since there is no starter, but I don't think this claim is wide spread. Maybe I've just read right over AGM, but all of the talk I recall is why they didn't use something other than the maintenance free battery.

I assumed AGM by reference, because the type recommended for the Model 3 is a "deep cycle" battery. And all of the deep cycle batteries I've found are AGM. It's very difficult to find one that isn't AGM.
 
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bitmanEV

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Lithium batteries have relatively poor cold-weather performance. Lead acid batteries are less expensive and perform well in the intended application.

Sure may be not Lithium batteries but some sealed low maintenance or deep cycle batteries would do a better job IMHO

Lots of problems with EVs are due to flat 12v batteries happened to me also
 

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There are lots of lead-acid deep cycle batteries and they are very common in the marine industry. The only EV I have ever had that was not flooded lead-acid was my 2016 Volt PHEV which was AGM lead-acid...
 
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JasonF

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There are lots of lead-acid deep cycle batteries and they are very common in the marine industry. The only EV I have ever had that was not lead-acid was my 2016 Volt PHEV which was AGM...

AGM batteries are lead-acid. Maybe that's what's leading to the confusion. The difference is AGM's have fiberglass mats in them to absorb the electrolyte, making it more efficient, using less lead, and packing more into a smaller space.

Doing some research, it looks like AGM batteries' achilles heels are extreme heat and over-charging - pretty much the same things that kill Lithium batteries. Maybe if the Model 3 software would be updated to charge the battery less often, or even undercharge it a little, they will last longer. After all, ICE car batteries are almost never idled with a full charge (because after you turn off the car, accessories run for a while afterward, and there is no charging with the engine off).
 

Long Ranger

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So you seem to be right that our Model 3 batteries are not AGM. The question now is does it matter for longevity in our application?
Yeah, good question. It may not be that significant. There's a lot more to lead acid battery design than just AGM vs. flooded. I think AGM is generally more reliable, particularly when it comes to vibration, but just being AGM doesn't guarantee more charge cycles.
 

JWardell

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Seriously, seems like folks are acting like AGM means it is some advanced technology. It's just a slight update to hundreds-year-old lead acid technology which seals the battery off so it is disposable instead of renewable (frankly, a downgrade)
 

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The 12 V battery problem is not unique to Tesla. 12 V battery failures were common in early plug-in Ford CMax and fusions, Chevy volts and even hybrids. Toyota, Lexus and Ford hybrids had 12 V failures fairly commonly in the first few years. I know this was a problem with model S and model X, especially the early years. I was not aware that it was a significant issue in model 3.
 

JasonF

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The 12 V battery problem is not unique to Tesla. 12 V battery failures were common in early plug-in Ford CMax and fusions, Chevy volts and even hybrids. Toyota, Lexus and Ford hybrids had 12 V failures fairly commonly in the first few years. I know this was a problem with model S and model X, especially the early years. I was not aware that it was a significant issue in model 3.

I did notice that a lot of the 12 volt batteries that are only lasting 2 years are Korean brands. This whole issue might be caused by a bad electrolyte formulation - like the bad capacitors from the 90’s that make any electronics from that era suspect, or the exploding LiOn batteries from Samsung. We might be looking for reasoning and workarounds for an industrial defect that might not reoccur.

But it’s also possible that it is intentional, and certain manufacturers have taken a “we’re not selling enough 12 volt batteries so let’s build them cheaper and shorten the warranty” approach. It worked for home appliances!
 

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AGMs also require slightly different charging characteristics and voltage than flooded cells...

Doing some research, it looks like AGM batteries' achilles heels are extreme heat and over-charging - pretty much the same things that kill Lithium batteries.
 

JoeP

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in my Toyota Rav4EV (which has a Tesla drivetrain but is otherwise a Toyota) i replaced the battery with an AGM a couple years ago becuase of the self-discharge issue with non-AGM batteries. Many people who own that car (which isnt all that many, there were only 2400 made!) have done this swap.
 
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garsh

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The Nissan Leaf was legend for this! They had problems in their charging algorithms...
Really? I hadn't heard of that one, and I hung out on mynissanleaf.com for many years.
My Leaf's original 12v battery managed to last the entire 6+ years of ownership.
 

TomT

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I didn't have an issue either but many did and there were a number of threads about it on MNL... Biggest issue was cars that were left for many days or more. The inverter would not properly keep the battery charged over an extended period.

Really? I hadn't heard of that one, and I hung out on mynissanleaf.com for many years.
My Leaf's original 12v battery managed to last the entire 6+ years of ownership.
 
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TheMagician

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Really? I hadn't heard of that one, and I hung out on mynissanleaf.com for many years.
My Leaf's original 12v battery managed to last the entire 6+ years of ownership.

My experience was the same. 3 Leafs (‘11, ‘13, ‘15). ‘11 was sold in ‘18 with original battery, ‘13 made it to 6 years and ‘15 made it to 5. Think that’s outstanding especially since the ‘13 & ‘15 lived in Vegas most of their lives.