Tesla 12V / 16V Battery Warning: What Owners Replaced and What It Cost

A 2021 Model Y owner at about 95,000 miles found the 12V reading only 5–6 V, with the car waking itself overnight ^[1]. Replies warned of two side effects: the car can sit in a low-voltage survival mode until the battery is replaced, and opening or closing the frameless doors on a weak battery can damage the window glass, a repair that costs far more than the battery ^[1].

Another 2021 Model Y with the lead-acid battery got a “needs replacing soon” alert at 52,000 miles ^[6]. Do not wait weeks once that alert appears.

Owners following Tesla’s own Model 3/Y DIY procedure did the swap in about ten minutes, a little longer when the HEPA filter has to come out ^[1]. The consensus was to buy the battery from Tesla: about $85 over the counter in 2025, with others reporting $48–85, because it matches what the car’s battery management expects ^[1].

If you would rather not do it, mobile service is cheap by Tesla standards. A California owner paid $122.64 all-in, and a 2021 Model Y owner paid $155 including tax, less than the $205 a parts store wanted for the battery alone ^[1][6].

A 2018 Model S owner replacing the battery before it failed collected part numbers from other owners: 1083774-00 for a 2014 Model S P85D and 1046200-10-C for a 2020 Model X ^[2]. Prices quoted were $226 for the battery alone at one service center, $212.55 installed on a 2016 Model S, and about $165 plus about $76 labor for S/X elsewhere ^[2].

One owner tried a $99 Duracell battery from a battery store and found the terminals were on the wrong side. Another tip from the thread: after a swap, check the low-voltage battery type setting in Service Mode, because a mismatch can trigger warnings ^[2].

Ohmmu lithium batteries drew owners with lower weight, a built-in BMS and a four-year warranty. One owner paid $439 and installs took about ten minutes with Ohmmu’s video ^[4]. Most early reports were trouble-free, but a Performance Model 3 owner said a software update started rejecting the battery and ended up buying a Tesla unit anyway ^[4].

Another owner got a “replace low voltage battery” warning the day after a software update, months after fitting an Ohmmu. A hard reset (window down, disconnect the 12V negative and the first-responder loop, wait a couple of minutes, reconnect) cleared it. Others saw the warning come back, and one received a free revised unit from Ohmmu ^[5].

For lead-acid Model Y cars, owners also looked at retrofitting Tesla’s own lithium part 1598486-00-C, listed at $165 over the counter in 2021, against over $400 for an Ohmmu. No finished retrofit was reported on the first page of that thread, so treat it as pricing information only ^[3].

A 2023 Model Y Long Range owner asked whether to replace the lithium low-voltage battery pre-emptively. Replies, including a moderator, said it is considered long-life and should not be replaced early: check its health on the low-voltage page in Service Mode and carry a portable jump pack instead ^[6]. Ohmmu also notes that its Model S battery does not fit cars built from June 2021 with the revised system.