Tesla 12v battery - Proper Care & Feeding

[@Ingineerix]

If you haven't seen my previous 2 videos on t his topic: kzbin.info/www/bejne/h325d6udgNOJZrc kzbin.info/www/bejne/nHurYqVnqJ11bLs Please do not buy aftermarket junk like the Ohmmu battery. You will spend about 6 times the cost of replacing the OEM $85 unit! Even if you have to replace the OEM every few years, that's still less money over the life you'll probably keep the car! (and that's assuming the aftermarket unit would last that long!) If you liked this video, check out my other content: kzbin.infovideos You can also support the channel here: www.paypal.com/donate?hosted_button_id=DT4S6DVGSBX3W If you have any ideas for content you'd live to see, please let me know!

[@BrettButterfield]

The OEM battery is now $165 or $265 with installation. I just bought the battery today at Tesla Corte Madera, CA and completed the installation, not very hard or very fun. I'll get myself something nice with the $100 I saved! Thanks for the video, I was thinking about getting a Ohmmu battery and am happy with my choice to stick with a stock Tesla battery after your review.

[@apl175]

I had to change the 12 volt battery in my model 3 in the long term parking garage at SFO last October. While abroad, the Tesla app sent me notifications that the 12 volt battery was failing - and the SOC of the main battery dropped quickly - from 75% down to 20% in about six days. Luckily a friend was able to meet me at SFO with a replacement 12 volt battery from Tesla - and we had it changed in the garage in about 10 minutes. .(Greetings from Oakley BTW)

[@celeron55]

A failing lead acid battery can suck a huge amount of power just to keep itself at 12V. At the end it will basically boil itself dry after which it ceases to be a battery anymore.

[@celeron55]

That process will also smell really bad.

[@LawpickingLocksmith]

Better at SFO than downtown SF. I bet catalytic converter thief's will soon target quick remove lipo packs. Less to carry and easier to hide.

[@Ingineerix]

Interesting story! You could have probably waited and changed it at home though, but glad you got it solved! Yes, the car will have to keep the contactors closed to support the failed battery, so it's like leaving sentry mode on.

[@Ingineerix]

(And Yes, I'm in Oakley!)

[@fyufghdyvf]

As a new Tesla owner, and being new to EVs, I really appreciate the way you explain everything. You got a new sub, and I look forward to checking out your other videos!

[@Ingineerix]

Yeah, I have quite a few you'll enjoy! kzbin.infovideos

[@GOVAUS1]

A must watch for all Tesla owners, especially those who went with this Ohmmu disaster bomb.

[@SuspectOnTheLam]

Amazing video. Saved me from trying out those Ohmmu batteries.

[@zodiacfml]

thanks. more interesting and informative than most Munro videos! Hard to believe considering this is a one man team.❤‍🔥💪

[@Ingineerix]

Thanks! Yeah, sadly I don't have the resources Munro does.

[@desparky]

I'm an electrician/ electronics guy and the owner of an older Model S. When my 12v battery died I saw these aftermarket batteries advertised and wondered how they could possibly interface with the existing vehicle design for a lead acid battery. I know there's a lot of people that are way smarter than me and perhaps they had somehow created a BMS that would interface, but I felt too dubious about it and replaced it with another lead acid battery. I'm so glad I did now. Thank you for sharing your wealth of knowledge.

[@Galileo9.81]

I really appreciate you making this video. I totally agree. My odometer is at around 60k miles, and I just did my first lead acid 12v battery replacement. I didn't get any warnings but did it because it was just so cheap and easy, and I didn't want to be stranded in the middle of freeways. $80 from the counter it was. So cheap and so easy. No need to spend that expensive $500 for the lithium battery for which my 2021 model 3 isn't designed. Now, I am a huge believer of aftermarket parts ONLY when I know what they really are. For EVs, I know NOTHING! That means stay to the bone stock and use only genuine parts!

[@georgepelton5645]

Thanks Phil for this video. Very informative and interesting. I am glad I decided to stick with Tesla's PbA replacement batteries! They lasted about 5 years on both my Model S and Model 3. As you point out, it is easy and inexpensive to do these replacements.

[@Ingineerix]

You're welcome! I'll do a video showing how to replace it soon.

[@NoInfoFound]

Wow, thanks for that deep dive on the original lead-acid in the Model 3 and the info on the new Li ion battery.

[@NoInfoFound]

I would add, however, that some number of the lead-acid batteries died in the 2 to 3 year range - like mine. Unfortunately I fell for the hype of the Ohmmu and it did result in error messages as you pointed out. They would not refund my money. I just had to buy a Tesla lead-acid battery anyway.

[@TWEO]

@@NoInfoFound same here, regarding the battery only lasting about two years. The next one held for like 8 months but that was replaced under warranty. Glad I never considered anything but an original replacement.

[@Ingineerix]

Thanks, you're welcome! I have 2 other prior videos on this topic as well. Check the description.

[@olyalphy]

Wow! I had the Ommhu on my list of things to upgrade on my May 2021 Model 3. I was of course waiting for the existing Lead Acid battery to die before replacing it. But not anymore. This opened my eyes to how bad (and how overpriced) the Ommhu product is. Such a shame. Do you think there is any way to get a well engineered aftermarket LFP battery that mimics the existing Lead Acid battery?

[@BraveRock]

Sounds like your 2021 car might already have a better lithium 12 volt battery, since that is the year they switched.

[@dennisschlieckau8723]

Very Informative, Thank you. I had thought about doing the Ohmmu battery swap. Not anymore. I had no idea the OEM lead acid was the cheap. $85 from Tesla is nothing compared to typical automotive batteries these days. What is the AH rating of the 12V lead battery. Is the OEM battery AGM or flooded cell?

[@Ingineerix]

I don't recommend LFP for the reasons I talked about in the video. If the BMS opens because the car thinks it's charging a lead-acid, you get alerts, and then stress out the PCS. For $85 every 5 years, it's not worth it either.

[@Ingineerix]

Early cars had flooded, later were AGM in most cases (but it varied). It's 45Ah as I show in the video.

[@tesladura3085]

Probably one of the most concise and valuable information videos I've seen about Tesla 12v batteries and the aftermarket Lithium replacements to AVOID AT ALL COSTS. Since they're priced so high, it's easy to do. Thank you very much for the education and warnings.

[@Laserblade]

Excellent content Phil, you just saved me from an expensive mistake. So glad you are back sharing your valuable expertise with us! Thank you!

[@jimmyfreeman9968]

Thank You So much. My Tesla Model 3 flashed a warning that the 3 year old battery needed to be replaced. And I was going to buy this new battery to replace the lead battery in my car. Luckily I found your video before making this mistake.

[@andrewdekoning]

Great video - this explains some issues/behavior I've seen and corrects some misconceptions I had about the new battery! One note: there is a very specific edge case problem with the 'new' Tesla/CATL 12V battery C rev that will cause it to pop the e-fuse and in newer firmware reset after 20 seconds. The D rev supposedly fixes this issue by upping the current limits in hardware (and software.) We had this issue pop up during an autocross, due to lots of current in/out of the rack per the Tesla engineer who helped us look at the issue and gave us the above info. Just a FYI for those that might watch this and have the same issue!

[@Ingineerix]

Interesting, Thanks for posting that! This is exactly why you need a stiff 12v bus. Autocross is severe duty.

[@DanielHyles]

Thank you. I was looking at the Ohmmu and now I will stay with old tech :)

[@stal5861]

Good thing I saw this video. Before I'd for sure hook that battery up to the bench power supply and try to charge it - not anymore. Just connect jump leads to the car and activate battery in service mode!

[@Ingineerix]

Luckily the internal BMS prevents external charging, the explosion was caused by someone recharging it by cracking it open and bypassing the internal BMS. People don't understand dendritic damage.

[@colinh.3252]

Thank you so much for this video. I am the owner of an Ohmuu 12v battery for my 2019 Model 3 and it lasted about 4 years. It did a fine job for those 4 years. But now the car won't start (12v is dead) so I am looking at my options. You really made the case for why these Ohmuu batteries are not a good idea. I will get a standard lead acid replacement. Cheap, simple and safer. You really have an impressive knowledge of batteries!

[@rkgsd]

So glad I found this video. I was just about to get one of those Ohmmu batteries. Will stick with the led acid. Honestly it's not that big of a deal to have the old tech battery. When Tesla switches to 48v, that will be the game changer.

[@Ingineerix]

Agreed, I can't wait to have a look at the 48v system!

[@voidthewarranty1429]

Thanks for the info: It will save Tesla owners many dollars.

[@dougdority5589]

My 2014 p85d with 130k on it still has the original battery. I have gotten the batter replacement warning twice. Both times, I removed the clamps from the posts, cleaned the posts with stainless steel wool, and replaced the clamps. The key issue is the clamp design, it is stainless steel folded sheet metal and has the nut and bolt both made of the same grade of stainless. The nut and bolt will Gaul and bind if not treated with anti seize, and the stainless clamp on the lead post appears to loosen over time. I really don’t think the primary issue is the failure of the lead acid battery, instead it is increased resistance through the posts and inability to deliver or take sufficient current. Btw, I am an engineer with 35 years experience, not just some rando

[@Ingineerix]

I would replace this as a preventative measure. It's not worth "chancing" it. You will probably have a failed software update soon that leaves your car undriveable. The car depends on the reserve capacity while updating software in the HV battery.

[@treborg777]

I tried the Ohmmu battery three years ago. It came with the battery terminals reversed from the OEM battery, and I returned it. Your internal battery discussion makes me very glad I did return it.

[@mitchellbarnow1709]

Phil, I’m so glad to finally have this explained to me and I hope that lots of other Tesla owners find it as informative.

[@Ingineerix]

Your're welcome!

[@ColeBlack2]

Wow. Really good info as always. My Model Y is only about 18 months old so I'm not too worries anytime soon about 12v bat failure but I probably would have gotten the Ohmu battery thinking it'll last forever being a LFP. But it totally makes sense why the Ohmu battery throws a bunch of errors. Essentially the lead acid battery is acting like a capacitor on the 12v bus. Could be easily fixed if you could tell the PCS to limit it's voltage so the BMS on the Ohmu doesn't have to cut out due to cell over voltage.

[@Esteb858]

If your Model Y is only 18mth old then it would have the newer Li-Ion battery anyway. This change occurred in 2021 and was mentioned in the video.

[@alexadams1627]

Thanks for this video. Sticking to an OEM battery when it goes bad.

[@kalpanchal6614]

Wow, I have been looking to replace with ohmmu, thx for making this video. I will not replace it with anything other than lead acid at this point. Even every 3 years for $85 battery replacement is nothing.

[@curlytoezz]

Wow,thank you for this informative video.. I was so close to buying an Ohmmu battery but this certainly has changed my mind! You saved me $400! New sub

[@Ingineerix]

You're welcome!

[@thesteaktc]

Very interesting video, thank you. My model 3 12V battery failed after about 3 years and I replaced it under warranty. I was not tempted to get that lithium iron replacement due to the cost. Now I know it’s a total no-no anyway. I am surprised by the low cost of the Tesla lead acid battery, much lower than the equivalent from an auto parts store. I remember researching it at the time and a compatible non-Tesla one has to be group 51R, AGM.

[@Ingineerix]

You're welcome! Glad you kept the OEM!

[@Theeslickness]

Thank for you this video. I would have bought an OHMMU if I didn't see this. Coming up to 4 years of ownership and no issues.

[@Ingineerix]

Yeah, probably a good time to go ahead and replace it. (Before you have issues)

[@jondecker1372]

I was one of the suckers that bought an Ohmmu battery. It has never worked for the very reason you point out. They have made a few revisions along with promises for a fix to no avail. Im stuck with a $500 paperweight, as I put the original battery back in. They refuse to refund, stating its Teslas fault and not their own

[@Ingineerix]

Exactly! For the price they are charging for that crap, you'd think they'd be better servicing their customers.

[@TWEO]

Thanks for the fantastic information! Always a pleasure to watch your videos.

[@Ingineerix]

Thanks, much appreciated!

[@magnusbae]

Had a software update last year that made the contactors close all the time. No warnings about battery though, but I disconnected the 12V and let it sit over night and it still read as 100% SoC on my 3 year old model 3. Put a load on it and no significant dip in voltage. Fingers crossed for a 6+ year battery.

[@Ingineerix]

If the contactors are closed all the time, then it's never using the 12v battery. Keep in mind this is NOT normal unless you have sentry mode on, and will result in a lot of miles of range lost each day you aren't driving the car.

[@TeslaRebuilders]

Good advise on that Li-ion LVB as I know many people have tried that very thing. I hate that I even suggested thinking it was a true LFP cells and was safe to do.

[@shelberkmandmd2075]

Great presentation on the battery system. At 4 years on my 2020 Tesla Y ownership I am doing a preemptive battery replacement. It's worth the peace of mind knowing we should be safe while traveling for only $85.

[@michaelswindler]

Great video (as are all of yours). Just passed the 4yr mark on my 3 and was tempted to go non-OEM when the time comes; thanks to you, now I know better 👍

[@jayreynolds4386]

I changed my battery to this OHMMU and had 0 issues. I have a 2021 Model Y as well.

[@Ingineerix]

Just because you have not YET had an issue, doesn't mean you wont. If you do have a PCS failure, it will cost thousands. Is it worth it?

[@Rick9482]

Pretty damn good video! Every Tesla owner should see this video.

[@nvptx]

My YLR build June 1,2021. Did not get the 12 volt lithium and the bio weapon filter on my car build . This must be starting sometimes in July. Though I was able to retrofit the bio weapon , cost 450 installed mobile service . It was worth it to have clean filter HEPA air coming in to the cabin.

[@Miketime969]

How do you get tesla EPC to give you pricing?

[@Ingineerix]

You have to apply for an account, it's not easy!

[@Jack-kc9ic]

Just a heads up. There is a procedure for not just changing but resetting the warning on the 12v tesla systems. The omu will work. You can actuality put your car into service mode. Unlock the gateway and set it up for lithium. Also if you put a brand new lead acid in your tesla and it still says service 12v battery. You just need to turn the climate control off. Remove the neg 12v cable. Lift the back seat. On passenger side there's a grey lv contactor plug. Disconnect it. Wait 30 seconds. Reinstall neg cable. Connect contactor plug and you're set. Most of the time if your 12v battery goes low it will tell you to replace it even if it's charged back up and good. The procedure will clear the warning without replacing the battery. If it happens again then you will need to replace it.

[@taoh780]

Glad to find a reinforcement to why I shouldn't buy the Ohmmu.

[@android04]

I replaced my Model 3 lead acid battery at 5 years (110,000 miles) even though it was still working fine. I connected a Bluetooth battery monitor to the battery to see how often my car was waking up to charge it. Was waking up every 4 hours. Decided to replace it with an enhanced flooded lead acid from AutoZone and it now wakes up every 8 hours. This will reduce cycles on my high voltage contactors, which are way more work and money to replace than the lead acid. I opened up my original lead acid and saw that the water level was low in it and I could see the plates clearly. This contributed to the reduced capacity.

[@Ingineerix]

Yeah, replacing it every 4 years is a good idea. Keep in mind the car expects AGM chemistry, so you might run into issues with the aftermarket.

[@TV_Covers]

I'm always impressed by the master knowledge that you display in your videos. Thank you very much for putting in all the work it takes to get to the bottom of all the details.

[@Ingineerix]

Thanks!!!

[@MarkStatkus]

Agreed on mystery packs not listing their string/parallel setups. Need nutrition facts stickers on the sides of these things!

[@lazerusmfh]

Lithium battery fires are no joke I had a 4s 10A pack do this exact thing in my basement it wasn’t cool, but luckily also didn’t burn my house down, I got the battery outside after it had puffed and hissed but seconds before it burst into a fireball

[@Ingineerix]

Exactly, you have to treat them with respect.

[@rossishima]

I and a lot of other Tesla owners never received the 12v battery about to fail error. Instead received a bunch of error codes. The car would not charge. Car operations still worked and drivable. Wall charger was pumping out power but the car would not accept it. Look like PCS issue as not doing an AC to DC conversion. Also getting 0miles charging. Car was towed to Tesla. Turned out to be the 12v battery. The $130 battery install turned out to be $330 as Tesla tacked on 1 hr diag fee which incl testing out charging circuit/battery pack, testing out my charging cable, checking AC charging was ok, supercharging to 80%--car was down to 10%, clearing out codes. If I received the 12v failing error, would have simply had Tesla replace the battery. Wish Tesla did a better job with the 12v proactive warning.

[@axon62]

My 2018 M3, which I love driving and owning, suddenly died after parked in the garage for about an hour. It still had 78% SOC. Doors, trunk, frunk and charge port won't open. The screen was totally dark. The 12v battery was about 2yrs 10mos old. I was able to open the frunk via the terminals inside the front bumper using a 12V a23 battery. I charged the 12v battery to 100% from 75% charge. It still didn't work. The computer was still dead. Mobile service came and replaced my 12v battery...it still didn't work ($150). Eventually I had it towed to Tesla Service center ($180, since I cannot put it in "Tow Mode", and AAA does not have wheels dolly towing). At first they didn't know what happened. But then they were asking me if I had plugged any device in the 12v socket. "I hadn't used that socket for more than a year." They were claiming that the "efuse" tripped. So they replaced the efuse...$280! My question to you (and I also asked Tesla)...since I didn't use any overloading device in the 12v socket, I can assume that they didn't really know what happened...do you? Is it possible that this can happen again anytime? Do you know where this "efuse" is? I am pissed that this efuse has cost me over $600. Any suggestion or advice is appreciated. Thanks!

[@Ingineerix]

The whole point of the eFuse is that it's electronic! It does not need to be replaced! You can reset it in software, or by a power down. The 3/Y ICE (Car computer) is very sensitive to power, and if you bounce the battery voltage or arc it, such as when connecting or disconnecting, it can trip out. The fix is simple; remove power, wait 2 minutes, then reconnect, and when you reconnect do it swiftly and do no allow it to bounce. I think you got screwed, but good luck proving it. If they replaced a part, then you are entitled to the old part back. If you send have it and send it, I can test it. Remember this: If you have any "black screen" problems, try the 2 minute reset before you get a car towed! The eFuse that feeds the ICE is part of VCFRONT, the eFuse that feeds the 12v oulet is not, IIRC it's VCLEFT (Might be VCRIGHT), but it's not VCFRONT.

[@axon62]

@@Ingineerix Thank you sir! I just hope it doesn't happen again especially since they didn't know what caused it. When you said "remove power...", do you mean disconnecting the 12v terminal cables? At the time, the doors won't open. Therefore the computer was not accessible. Thanks again. (I just subscribed too).

[@Ingineerix]

@@axon62 No, remove power to the 12v system by disconnecting the negative lead on the 12v battery. You can gain access to the frunk even if the car is dead with a jump pack or other 12v supply.

[@jeremyloveslinux]

It would be cool to know how Tesla is able to detect the 12v lead acid getting weak/needing replacement. Maybe the voltage drop upon the HV contactors closing in?

[@AlexBesogonov]

Lead-acid battery degradation can be easily seen by the voltage drop when the battery is under the load. So they just need a voltage and a current sensor for the 12V circuit.

[@jamesengland7461]

A $10 battery tester can tell you. ALL modern computerized cars should be able to inform you on the state of the battery.

[@Ingineerix]

They "coulomb count" all current into/out of the battery, that's why it's super-important not to hook anything else up to the battery. Once the car sees the total amp-hour capacity go below a set threshold, it will set the "replace battery" alert.

[@alexeydatsyuk5180]

Old Model 3 use not AGM, but usual lead-acid battery. You can find this info in Hankook data sheet

[@android04]

I agree. The OEM lead acid are not AGM but maintenance-free flooded lead acid batteries. I opened up the top cover of mine after 5 years (110,000 miles) and saw the lead plates inside. The water level was really low. My battery still worked fine and I had no errors, but it had a reduced capacity and my car was waking up more often than usual to charge it.

[@Ingineerix]

Yeah, I think you are correct.

[@kencox737]

Excellent video! Very informative. I talked to Tesla yesterday, 12v batteries are now $120.

[@kencox737]

An update for everyone. I purchased a battery from Tesla today. It was $182 not $120. The warranty on it is 12 months 12,000 miles. Tesla told me they make the batteries. It says made in Korea on it. Next time I will use a battery from the auto parts store….3 year or better warranty. This model x is junk. Extended warranty is worthless. I will probably cancel my order for the truck. Very disappointed in Tesla.

[@gregorycooper7340]

Very well said. Thank you for educating me a little on the 12v battery.

[@Ingineerix]

Thanks!

[@brddukaty7460]

Thanks for the Super Great public safety announcement 👏👏👏

[@Ingineerix]

You're welcome. Once I saw the explosion video, I knew I had to make a video. (among the other reasons)

[@dschlessman]

If you want to look at the MPP earthX lithium ion battery, let me know. I have an extra.

[@Ingineerix]

I'd love to! You can find my email in the "about" tab of my channel (use a full browser, not a phone): www.youtube.com/@Ingineerix/about

[@johnreese3762]

Didn't know! We just bought a 2023 Model 3 which has the new LI battery. Thanks for the great info and video!!!

[@steinmar2]

Nice to see you back again (:

[@1forrest1]

The Tesla LV system is such an interesting topic, glad you keep posting on it! Why Tesla chose the lead acid was a favorite interview question for my old manager. Im really curious why they ended up going with the lithium LV battery. If the bom cost is really 2.5 times the lead acid I cant really see the benefit. Overall the system is definitely more complex and we had engineered out most of the warranty replacements of the lead acid even back in 2017. I feel like the time to do the switch would be when they go to 48V systems as the Lead acid versions at that range are not nearly as price competitive.

[@Ingineerix]

Thanks! My estimation on the BoM cost of this is well under $50. Tesla (Elon) promised to never attempt to profit on service, but clearly this is not the case. I would have went with a larger capacity LFP with a proper BMS if I was going to do it. Going with NMC and raising the bus voltage to 15.5-16v was a bad idea, it's creating all kinds of problems for the aftermarket too.

[@jamesbruce1183]

Thanks for the video. I hope you can do more. I look forward to them.

[@Ingineerix]

I definitely intend on it! Please also check out my back catalog: kzbin.infovideos

[@basembarakat]

Thanks so much for this valuable information. I had an early model S and its led acid battery lasted ~ 8 years. Tesla mobile tech changed it for $200! However, I noticed that technician installed/updated a new battery firmware and always since then wondered why?

[@georgepelton5645]

The original Model S 12 V batteries were no longer available in 2020 when I had mine replaced. The Tesla tech installed new firmware so that the DC-DC would use the correct parameters to charge the new 12 V battery.

[@Ingineerix]

Yes, @George is correct here. The newer C&D model has a slightly different charging profile, so to make it last longer, they have a setting in the Gateway for this specific model (C&D Nano). It's not firmware, just a setting the gateway uses to modify the charge algorithm.

[@robertyu7341]

Invaluable information of owning a Tesla.

[@harmanx.]

Thanks for all the great information. With other cars I've owned, I've had good luck rejuvenating a dying lead acid battery by adding distilled water to the cells. The batteries might be good for another few years after that simple bit of maintenance -- and it can often be done more than once. Tesla's lead acid batteries aren't user-serviceable to allow this. I managed to pry the top panel off mine (was quite the ordeal) and add water (it took a lot of water -- was fairly depleted) -- but only got another month or two of life out of it. My guess at the time was that I polluted the cells by using a silicone adhesive to re-attach the top panel (since it had been glued on originally and wasn't designed to just snap back on) -- but perhaps you could give better insight. The distilled water thing is usually so effective -- I wish Tesla's lead acid batteries allowed for it. $85 isn't a huge amount -- true -- but 25 cents worth of distilled water is far better, and there's no time spent driving to a service center.

[@Ingineerix]

I'd recommend against this. Your time is worth more than the $85. I've seen someone do this, and it leaked acid all over the frunk.

[@moestrei]

At a friends 2015 Model S the system popped up a warning to replace the 12V battery soon. On my 2014 Model S there was no warning but i noticed an increased overnight phantom drain paired with more frequent clack noise from the HV contactors when the car was parked. Then one night during a software udate the 12V battery died and the car was bricked, i could not open any doors. Luckily on older S you can access two posts behind the nose cone and i could hook up a power supply. The car was still undrivable (due to the incomplete software update) but i installed a battery from my ride-on mower and Tesla shot through another software update. It worked but the car complained about the wrong battery. To my surprise the new Tesla battery was only AU$160, which is a fair price. I live 500km away from the next SC and i was very happy that it was possible to fix a bricked car OTA. Any other manufacturer it would have been a super expensive tow truck job.

[@Ingineerix]

Good story! Yeah the update process depends on the 12v battery because they have to shut down the HV to update it's components. That's usually when you find out it's weak. (or the car does)

[@user-ry9ls2xn2i]

My twelve volt Atlas AGM battery over the counter at Tesla service center was $176.14 out the door!! January 2024 $85.00, I WISH!

[@samclonce]

Thanks to you just ordered my battery from Tesla. 👍🙏

[@paulhortonatcoxnet]

Thank you for this information! I have purchased one used and very happy I didn’t try to use it. (21 model S)

[@adammatye]

My 2019 Tesla Model X has required two changes of the 12 volt battery with the last one lasting only 18 months.

[@marctronixx]

never had an issue with my ohmmu battery in the 2 years i had it in the car. lots of other people also had good results with it.

[@Ingineerix]

Just because you haven't had to replace an expensive PCS, doesn't mean it's not going to happen. It's risky, there is plenty of evidence out there to support my assertion.

[@thomas1254]

Very informative channel. Thank you very much

[@markclark4154]

Just wondering: are you involved with the Maxwell EV van conversions? Great content BTW.

[@Ingineerix]

Yes, That's my "day" job. I am CTO, and developed all the tech we use in the vans.

[@JasonEsquivel]

Thanks for the tips. 👌

[@Ingineerix]

You're welcome!

[@mondotv4216]

FYI - on my old Mitsubishi Outlander PHEV - 8 years on the lead acid battery and never needed replacing!

[@101rotarypower]

Hard to understand why the new LV battery is not a LFP ? Wouldn’t a 4S LFP Pack better align with standard voltages required for existing devices if Tesla is not going to step down the sockets or supply 12v nominal voltage at the trailer for a brake controller?

[@Ingineerix]

Agreed, I think they wanted the low cell resistance of this particular battery so they could keep it under 100Wh.

[@jimadams2113]

4-6 years? Mine lasted 26 months. I do appreciate your information. Thanks.

[@Ingineerix]

That's a pretty rare short life. Where do you live? Even so, it's only $85 so not a big deal. Think of what you would have spent on an ICE car by now!

[@RK-kn1ud]

It baffles me that Tesla, in 2021, did not opt for a LiFePo4 12V battery. Edit: It also baffles me that they'd use such a small capacity battery.

[@carholic-sz3qv]

As always they are cutting more corners!!

[@Ingineerix]

Yeah, cost was a consideration and also they had to keep the battery under 100Wh to make shipping easier. With a battery this size, they need special low-resistance cells to ensure the same bus stability. I'm not aware of any LFP that can do the same in that size.

[@Ingineerix]

I don't think this is "cutting corners" as it will prove to be more reliable in most cases (unless abused).

[@BecauseTesla]

Thank you for the deep dive. Very insightful! To be fair to Ohmmu, they did recently redesign their BMS within the past few months, and it's supposed to get rid of a lot of the Tesla alerts on the screen. It also includes a Bluetooth module to give more details on its health. I haven't had a chance to test it out yet, but this is what they've told me.

[@vinny9152]

It's good that they made improvements, but I'd still stay away from Ohmmu. It's hard to trust them after their disregard for safety with their initial battery design.

[@Ingineerix]

It's just not worth it. You are spending almost 6 times more money for a less-reliable solution! Not to mention a new $2000 PCS if the Ohmmu causes it to fail. $85 every 5 years is NOTHING. Just keep it OEM and enjoy your Tesla!

[@Ingineerix]

Not just that, but they clearly "took the money and ran" for most all of their customers so far.

[@BecauseTesla]

@@Ingineerix I appreciate your insight. Thanks!

[@pri0ritize]

I appreciate this video and how informative it is, but you really should change the title. I didn't see anything about maintaining the 12v lead acid battery. I would have liked to know if I can use a battery tender or something similar on the battery to keep it lasting longer.

[@TreyCamp]

Great topic, I've always been curious about how these work. Also really interesting on the other aftermarket lithium battery, haven't seen very much information on those besides where they're sold. Thanks for sharing

[@jrobillos]

Thank you for this informative video; cutting corners is pricy and leads to double work.

[@jacobheinz8236]

Thanks man! You’re a Legend!

[@warrenmcelroy6998]

2019 M3. I needed this video 2 years ago when I installed the $400 OHMMU battery, thought I was upgrading. Couple of weeks ago started getting the low voltage warnings, "It's a Tesla software problem". No solution other than just replace it with the much cheaper 12v OEM battery. After watching video now afraid to re-purpose the OHMMU battery.

[@Ingineerix]

Might be safe to repurpose as a battery for a lawn tractor, or you can use it for portable power. Just get it out of your Tesla before you have problems.

[@FrankGraffagnino]

great video... although it is disappointing to see tesla move a part that has a common interface in the industry to something proprietary. Hate to see people become less and less able to do maintenance on their cars with interchangeable parts. But this info is great!

[@Ingineerix]

I think their goal was to eliminate the 4-6 year replacement of the lead-acid battery and save costs, but looks like their dependence on a supplier (CATL) didn't go as anticipated.

[@boredKiwi]

So, regarding the 16V lithium-ion battery and it's integration into the car's systems, I asked John Kelly about the charging protocol, as given the low capacity I was concerned about contactor cycling. This is what he said: "Beginning in late 2019 - When the contactors are open, an unswitched portion of the HV battery supplies power to a unique standby power supply DC-DC converter, which supplies power (500 mA maximum current) to the front vehicle controller to maintain the charge of the 12V or 16V battery." I'm not sure if you had mentioned anything like this in your videos and I'm wondered what your thoughts were on his comment?

[@Ingineerix]

The Model S/X had a small DC-DC converter added some time around 2015 that could provide some standby power the the BCM and CID, but these are not made anymore. The only DC-DC in the 3/Y and 2021+ S/X that is connected 24/7 is located in the BMS, but I'm not aware of it outputting any power to any external systems. This is the DC-DC that's used by the HV protection system that can fire the Pyrofuse in the event of a fault. If there was another DC-DC, it would have to be located in the pack, because no HV leaves the pack when the car is asleep. You can see from the wiring diagram there are no external power lines coming from the pack. John is a great guy, but he doesn't know a lot of the details. I have emailed him several times for corrections. The way Tesla eliminated the contactor cycling was to get the standby loads in sleep down to a very low level. This is why it's important to be careful with aftermarket connections.

[@boredKiwi]

@@Ingineerix thanks for the detailed reply!

[@afpv2225]

I think 6s LTO battery without bms should work in older model 3:s and S/X. No cutoffs and charging at -40 celcius ok. Super safe also. It will outlast 2 cars or more. :D

[@Ingineerix]

Yes, but the charging algorithm is not designed for this, and it will likely result in a lot of nuisance alerts and inability to update software.

[@ronolsberg1468]

Just watched this great video again! You mentioned the LV battery helps minimize voltage spikes on the LV buss and gives the PCS buck converter some help with said spikes. I read somewhere the VC-Front controller limited the inbound and outbound current to/from the LV battery. If true, the outbound surge current from the LV battery might be somewhat limited. The new 16V 6.9ah battery probably can't deliver the same current when voltage spikes occur on the LV buss as the lead-acid could? In my opinion the PCS should be able to supply power to the low voltage bus, without potential damage, even if the car was driven with the LV battery disconnected for an extended amount of time (this assumes the HV contactors are closed and remain so). If the LV battery or anything on the LV buss developed a short, I assume the car is designed to handle such an event without damaging a $2K plus PCS board? Is that one of the functions of the big fuses located on the Model 3/Y PCS board?

[@Ingineerix]

First off, the PCS LV is a DC-DC converter, not technically a buck because it's isolated. (and it is bi-directional) Yes, the eFuses in VCFront limit current, but the spikes and load-dumps I'm talking about are extremely short events, but very destructive if not clamped. Because of the short duration, the eFuses pass these ok. Also, I have not tested the performance of the 16V Lithium pack, but I suspect, even though it's very small comparatively, it will have superior spike/dump handling capability than the much large PBA unit. Without bus stability, EVERYTHING on the LV bus is exposed to a lot of stress, not just the PCS. Yes, in a pinch (fault condition) the PCS can carry the loads, but it's not designed to do this continuously, just in an emergency where it's not important for it not accept damaging conditions. Having a noisy bus can stress and/or damage anything on it, and cause a lot of SEUs (Single-Event Upsets) that could result in unexpected/undesired consequences. Yes, the PCS could be designed to handle this mode, but that is non-trivial to engineer, and it would definitely drive up costs, so Tesla is not going to do it.

[@techdadnyc]

Thank you for this video

[@lbartlett403]

Thanks so much for this video!

[@Ingineerix]

Wow, awesome, much appreciated!!! Feel free to email me if you ever have questions.

[@leeoldershaw956]

Nice video, as usual. How often do the HV contactors close to charge the Li low voltage battery when the car is sleeping. If it's a lot more often will that not put more wear on them?

[@Ingineerix]

They have gotten the sleep loads down enough that it's very infrequent. (as long as no aftermarket equipment) The contactors should last the life of the car in this case.

[@sorliej]

Thorough and objective. Thank you!

[@Ingineerix]

You're welcome!

[@paulgracey4697]

Have you tested an Optima 12V lead acid as a replacement for the Tesla OEM? I have used those in my old Prius, and the size it somewhat similar. I am glad to learn that that clunk I hear each time I approach my Tesla is the traction battery taking over the function of all the 12 accessories leaving only standby functions like Sentry Mode as a load, which in my case is only invoked when I am away from my home. Good to know.

[@SuspectOnTheLam]

Those are made in Mexico now. Honestly I don’t think the Optimas are that much better than Tesla’s AGM battery. They should be pretty similar. I used to have a Prius too and used the Optima battery but it wasn’t different than the OEM battery at all when it came to longevity.

[@Ingineerix]

For $85 every 5 years, I'd stay OEM. The fitment and cost of the Optima will be an issue. FYI: When Sentry mode is enabled, the car keeps the contactors close so as not to put stress on the 12v battery.

[@FirstClass-]

Really Thanks for this video… saved me BIG TIME !

[@davidhite1868]

So that's what the CLUNK CLUNK sound is! Thank you!

[@Ingineerix]

I also have other videos that get more in-depth.

[@user-ki3vh4uz4i]

Thank you for always providing good information. I have a question. When a vehicle using a lead-acid battery is in sleep mode (HV contactor is open) The vehicle's electrical system uses a 12V battery. At this time, does VC_FRONT check the status of the 12V battery? I wonder how it wakes up from sleep mode to charge the 12V battery. and I contacted AtlasBX, the 12V lead acid battery manufacturer that supplies Tesla, and they said that the 85B24LS lead acid battery is MF, not AGM. :)

[@Ingineerix]

The ones on the S/X are AGM, 3/Y is lead-calcium. Yes, VCFront wakes up periodically to check things, including voltage. But the main way it tracks when it needs to charge is by coulomb-counting (watching total current in/out over time). It is possible to add an external load to the battery and have it die before VCFront wakes up again, but a unmodified car is unlikely. Once VCFront detects the loss of amp-hour capacity in the battery it will set an alert until you replace it.

[@user-ki3vh4uz4i]

@@Ingineerix Thanks for your reply. In rare cases, we now know why the 12V batteries in some vehicles discharge without warning!

[@drdremd]

I don’t recommend them, but I’m 7 years into an Ohmmu on my signature model S. Only issue I’m aware of having is Tesla service CLAIMING that it caused my MDU to fill with coolant.

[@drdremd]

I’ll add that the only reason I installed it was to save a 500 mile drive to the nearest Tesla parts counter.

[@Ingineerix]

The biggest problem you have now is that the Ohmmu is putting extra stress on your DC-DC converter, and on your Gen1 Model S, these things are getting harder to come by and are not cheap nor easy to replace.

[@sorliej]

Thanks!

[@Ingineerix]

Thanks James, Much appreciated!

[@CampTeslaFun]

Very useful info. Thanks!

[@yonathantafesework6970]

Thanks for the great video! Question, is there any recommended / safe locations to connect aftermarket accessories to constant battery, ignition and ground. I’m struggling to find constant battery as you mentioned in your video due to the low amp hours of the 16v battery it shuts off all non critical loads. What loads stay on? where can I find them? and are they safe to connect a 100mA active 25mA sleep draw?

[@PaulHoke]

Wow, Thanks! I almost bought one of these. 😮

[@jtr82369]

Great info here, I stumbled on this video while researching how the power outputs work in Teslas (wondering if they turn off automatically or if they can be set to stay on (lets say I want to run a 12v mini fridge).

[@Ingineerix]

Really I advise against this. Safest move is to use a portable power station. Tesla also voids your battery warranty if you do this. ("Stationary power" is specifically called out in the warranty)

[@lettcco]

Thank you for the informative video. I have a 2023 MY so I found that the small capacity 15V lithium battery is limiting my camping option. I ended up getting one of those portable battery "generator", so I have 2 questions for you sir: 1) What's the tell tale sign that the DC converter is charging the LV pack? (coming from AGM, I would see a 1.5V different) 2) How much current does the DC converter provide when on/charging the LV pack? (so I can estimate how much I can draw from the 12V without depleting the LV batt). Thanks in advance!

[@Ingineerix]

Just run a line from the Audio Amp power in the trunk and use that to drive a relay to the PCS connection on the Penthouse. (USE A FUSE!) You can drain 100A without any issues. The biggest issue is finding an inverter the allows up to 16.5V DC.

[@TonyPham-Creations]

Good stuff here! What’s the best way to connect 12v accessories? Air compressors for air bags, LED underglows, etc.

[@Ingineerix]

Complex subject that depends on which Tesla you have, when it was made, and what your loads are.

[@TonyPham-Creations]

@@Ingineerix Looking at Model 3 / Y’s with SLA and, the newer ones with the small 16v lithium battery. Dual compressors draw about 40 amps @ 12vdc when running, underglows draw around max of 15 amps at 12vdc

[@Ingineerix]

@@TonyPham-Creations Put a relay/contactor on the large PCS feed (under back seat) and have it's coil hooked to the accessory power circuit. You cannot just connect loads there without a relay. Underglows can been hooked directly to the power amp feed in the trunk. (~40A rating)

[@ImaginetMedia]

Excellent info. Thanks for sharing.