12V Battery Marathon

[katekebo]

Results from your own personal testing?

The table is from engineeringtoolbox web site. Personal measurements taken with Fluke 117.

 

[basicxj]

It's an issue with all Toyota (and Lexus) hybrids.

His RAV4 is straight gasoline non-hybrid, but not shocked to find a weak battery in it.

 

[ultane]

Won't an AGM battery suffer the same fate as the flooded one? If the car’s algorithm decides to stop charging and sit at ~12.5V, it doesn't matter if the battery is a cheap flooded one or a $400 AGM—it’s not getting charged. The AGM might handle the abuse longer, but it will still be chronically undercharged.

I disconnected the battery sensor (fail-safe mode) on my stock OEM battery. This forces the system to output a constant 14.1V whenever the car is running. So far, I've had zero issues/codes, and my battery is actually staying charged.

You are right that 14.1V constant charge might eventually dry out the stock flooded battery. However, isn't that just about the perfect charging scenario for an AGM? Since AGMs are sealed and generally prefer a higher charge voltage (14.4V-14.7V), running them at a constant 14.1V should be perfectly safe and keeps them full without the risk of drying out.

Welcome to the asylum.

 

[Bad1975]

The OBD tool thing is BS, all OBD readers can clear codes on any Toyota, ABS and Airbag codes are a hard no you need a compatible factory service tool. Not all OBD tools will tell you what the Hybrid Toyota specific codes are but any code you can clear minus the safety related stuff can be cleared with any OBDII tool. There is a reason ODB II is a global standard. The safety related items like ABS and airbags is the same no matter the OEM, if your not connected with a factory specific service tool and software you can't clear those.

I've had that same message a couple times, cleared no codes and just put my NOCO into boost mode and waited a couple minutes and the messages disappeared and vehicle started right up.. Afterward I connected to GTS+ (Toyota factory service software) with factory compatible service tool and there were no codes, stored, in history or pending from those events. Followed up with a proper charge and load test, I have my own load tester think I paid 50 bucks for it and it's part of my maintenance routing on all vehicles (load test each battery once before winter and summer).

For anyone who deeply discharged their lead acid battery, or has had multiple low charge no start events even more so if you didn't fully charge up afterwards with a proper charger. I highly recommend getting the battery load tested. Even a brand new Lead Acid battery can be damaged or ruined from just one deep discharge event. Each sustained discharge leads to sulfation which kills the battery (They have battery chargers that have desulfation profiles and they work). Once the resting voltage falls to ~12.2VDC or lower, sulfation and damage is occurring to your lead acid battery and in my experience at 12.1-11.9VDC is when that message gets displayed and your in a no start situation (makes sense Toyota knows it should be properly checked out), the dealer should be charging your battery backup and load testing it if taken in with that message displayed.

As @RUN-8 said do yourself a favor and get a better battery and a NOCO jump box and be done with it.

 

[ultane]

….cold garage or worse, outdoors (poor baby) for an extended period of time?

A frigid battery will NOT accept a charge.

 

[Bad1975]

A frigid battery will NOT accept a charge.

Myth:

Cold Weather Charging Myths: What Really Happens to Your 12V Battery in Winter

 

[GaryA]

What about adding a solar panel on the hood like, Lensunsolar.com Wouldn't that help in keeping the battery charged.

 

[ultane]

Myth:

Cold Weather Charging Myths: What Really Happens to Your 12V Battery in Winter

I finally got a chance to read CTEK’s advertisement.

The wording of CTEK’s article is interesting. They seem to come close to contradicting themselves.

I’ve owned a CTEK charger for over 12 years, using it on my R1200GSA, and it would not charge the battery when temps were 32ish and below. I recently tried to charge Miss Daisy’s battery with it. I do not think it is a temperature compensating charger, but after 6 days on the charger, Miss Daisy’s battery was no where near being charged, according to the charger. I don’t remember the voltages that I was getting, but they were not improving, and the little lights on the charger showed NO progress or improvement.

I switched over to a Duracell branded charger (I do not know who makes it) that I purchased with/for the Duracell AGM’s, at Batteries Plus, for my Gravely, Kawasaki Mule, and my R1200GSA. Miss Daisy’s battery was 100% within 6 hours. Then I connected the CTEK to Miss daisy’s battery, and it too said that the battery was 100%. The CTEK just couldn’t get the battery there.

My statement, “A frigid battery will not accept a charge”, was based on info that a battery engineer posted on the ADVRider.com website well over a decade ago. Physics do not change. That probably before temperature compensating chargers were invented, but I don’t know for sure. His recommendations were to remove the battery from the bike (10 minutes max) and bring it into a warmed environment, to charge it.

Needless to say, the basic trickle chargers that are used by most, as well as many other chargers, are useless for frigid weather charging unless the battery can be warmed.

Good luck to all.

 

[Bad1975]

Concur anything below 40 degrees and most any charger is largely ineffective. The internal resistance is higher in the battery when cold, so a higher amperage charger is needed to develop the same charge voltage but at the same time charging at a higher amperage especially when cold isn't good for the battery.

 

[t3lcfe]

Oh man…Battery Drained…drained ! I had to watch it out carefully…Turned off all the lights, closed the doors, etc. while working on the LC.
Most times I got battery drained in my garage. But “never” happened “yet” in the woods or desert. Peace of mind while off-grid camping, I carry 2 battery jumpers and jumper cable which can plug-in to my 1500W Jackery
I love and love everything about my LC, but battery drain. I overcame small fuel tank by few Rotopax

Hey, still loving my LC !

 

[Below32]

Installed the block heater yesterday in a friend’s garage. Temps are in the negative double digits. LC is plugged in and cold soaking. Will see what happens when I try to start it in a few days.

 

[ultane]

Installed the block heater yesterday in a friend’s garage. Temps are in the negative double digits. LC is plugged in and cold soaking. Will see what happens when I try to start it in a few days.

How difficult was it to install?

 

[Below32]

How difficult was it to install?

Let’s just say, I am beyond grateful for good friends who are much younger and less broken than I am.

The worst part was trying to get the block heater itself into the hole. Both are precision machined and there are multiple wire bundles more or less in the way. I highly recommend a dry run before greasing the thing. I bought the one from Canada. We attached the connector first before sliding it in the hole. The force it takes to make the connection is more than I wanted to apply to the small arms coming out from it. The right front tire needs to come off. We got away with turning the wheel for the front grill connection. Really happy with it.

 

[R_che]

You are making an assumption that everyone has a garage or access to a charger. Some of us live in apartments, condos, older homes without a garage, leave our vehicles places for periods of time without access to a charger, etc.

Yes, you are correct in assuming access to a trickle charger... sorry for that. However, carrying a good jump starter will work wherever your vehicle is parked.

 

[PDundon]

Most definitely!

@BlueCruiser , If you have it installed by now, how do you like it and which model Odyssey battery did you buy?

 

[kmershly]

I had a day off today, so I was reading through the theory and operation of the charging control system in TIS as this entire battery situation is interesting to me.

According to TIS:

1. Stable use the auxiliary battery Constant voltage control is performed and the auxiliary battery is fully charged about every 20 driving hours to minimize deterioration of the electrode plates due to sulfation by repeating charge/discharge of the auxiliary battery.
2. Constant voltage control is performed when the SOC of the auxiliary battery is low or the temperature of the auxiliary battery is high/low to minimize deterioration of the auxiliary battery.

It seems that Toyota Engineering folks decided to have our LC (and maybe other models) only fully charge the auxiliary 12v batteries every 20 hours to preserve the battery.

Also, Toyota decided to charge the battery when the temp of battery is high or low to preserve the battery, so under normal operating conditions if will not fully charge the battery under 20 hours of driving.

 

[wpage]

After all this. Toyota needs to get thier engineers to upgrade software and fix whatever is causing this problem...
Evidently the current algorithm is not getting the charge done.
Shame on Toyota...

 

[dato6966]

At this point I'm now getting annoyed with the 12v battery failure issue I've experienced. As I delve into it I'm beginning to think that this has the potential to be a serious safety issue. My LC was dead after parking it overnight and the battery had previously been replaced after lasting only 16 months. I've been doing research on the issue and am working on a draft complaint to Transport Canada and possibly a draft for the LC 250 to be included in an existing class action that a law firm in British Columbia has filed.

At this point, the below document is only a DRAFT - as I'm still gathering facts which I hope members of this forum will elaborate on their experience. If you've had the 12 volt battery fail I'd appreciate your outlining in this blog the circumstances - how old was your LC, mileage, what happened, how did your dealer respond?

I'll rework the below based on your feedback and I'll also tighten up the wording - if I go ahead and submit it - This is only a DRAFT

DRAFT -

TRANSPORT CANADA — MOTOR VEHICLE DEFECT COMPLAINT

Complaint Type: Vehicle Safety Defect — Electrical System / 12-Volt Battery / Hybrid System Shutdown / Steering

---

OWNER INFORMATION

Name:
Address: [ street address]
Phone: [phone number]
Email:

---

VEHICLE INFORMATION

Manufacturer: Toyota Motor Corporation
Make: Toyota
Model: Land Cruiser (LC250 Hybrid)
Model Year: [model year]
VIN: [ 17-digit VIN]
Purchase Date: [Date of purchase]
Current Mileage: [Current odometer reading in km]
Dealership: [Name of dealership where serviced]

---

DEFECT DESCRIPTION

The vehicle's 12-volt auxiliary battery has failed on two separate occasions. The first time requiring replacement as it was diagnosed by the dealer with a dead cell. The second time the dealership charged the battery, tested it, and determined the battery was good. On the first failure, the battery's depletion caused the power-steering system to lose calibration, requiring a steering recalibration by the dealership.

The 12-volt battery in this hybrid vehicle is critical to booting the electronic control modules, initiating the start sequence, and maintaining stored calibration data for safety systems including the steering. When the battery discharges, the vehicle can become completely inoperable, which was the first instance — no start, no accessories, no electronic door releases, no smart-entry function. the e-brake is locked on — and there is no owner-accessible override to recover the vehicle without towing it to a dealer.

This is not an isolated incident. Numerous owners of 2024–2027 Toyota Land Cruiser LC250 hybrids have reported failures across multiple forums and platforms, including:

• Dead battery after sitting overnight or for only a few days
• Multiple warning lights and "Drive/Start Malfunction" messages
• Repeated jump-starts required
• Complete no-start conditions
• Cascading electronic system failures when battery voltage drops
• Sudden loss of power or limp mode while driving (documented on Land Cruiser Forum)

---

TIMELINE OF FAILURES

First failure — December 2025

• The 12-volt battery discharged completely after [the vehicle sat for 1 day / normal overnight parking].
• The vehicle would not start. Warning lights and various fault codes flashing, no crank, clicking, error messages on dashboard, the e-brake was set and could not be released causing the vehicle to be physically immobilized
• The vehicle entered a protective lockout mode — the system shut down to protect the computer systems from low voltage, and there was no way to override this lockout without towing the vehicle to a dealer.
• Toyota assist dispatched a tow truck who tried to jump start the vehicle with no success. The e-brake would not release so it could not be towed as it could not be rolled up onto the deck of the tow truck. A second tow truck was dispatched and could not put the LC on the dolly as the LC was too heavy for it as it was designed for lighter cars - This tow truck also attempted to jump start the LC as it had been sitting about an hour with the battery disconnected, in the hope that the lockout had cleared - it had not. A third tow truck was dispatched with a dolly appropriate for the LC size. Of particular importance, ordinary towing was impossible → specialized four-wheel dolly equipment was required. The vehicle had to be transported to the Toyota dealer in this immobilized condition.
• Upon battery replacement, the dealership found that the power-steering system had lost its calibration as a result of the battery depletion. The steering required recalibration by the dealership.
• The dealership tested the battery and replaced it under warranty.
• No root cause diagnosis was provided. The dealership did not identify any parasitic drain or charging system defect.

Second failure — September 2026

• The replacement 12-volt battery discharged completely under [similar circumstances — parked overnight / after short period of inactivity].
• Similar symptoms: [no start, warning lights, Drive/Start Malfunction message, e-brake frozen etc.]. The battery was not completely dead so it was placed on a charged for a few hours and started with the charger still connected in case the battery voltage was too low which could cause the lockout to occur. It was driven immediately to the dealer and they were shown the multiple error warnings that were flashing.
• The dealership charged the battery overnight and tested it. They also checked for a parasitic draw a second time.
• Again, no root cause was identified. The dealership stated the vehicle tested normally but it showed a low voltage condition had caused the various fault codes..

---

SUSPECTED ROOT CAUSE

Based on extensive owner community documentation and independent technical analysis, the repeated 12-volt battery failures appear to stem from two related defects in the hybrid charging system:

1. Chronic undercharging: The charging system software operates at low charging voltage during normal driving, leaving the 12-volt battery insufficiently charged. One owner measured only 12.18V (approximately 50% state of charge) after a six-hour highway drive. Toyota's charging logic reportedly only recharges the 12-volt battery from the traction battery after 14 days of inactivity — far too long for a vehicle that is not driven daily.
2. Parasitic drain / modules not entering sleep mode: At least one dealership has confirmed that an electronic control module may be continuously activating the vehicle, preventing it from entering sleep mode and draining the 12-volt battery completely. This is consistent with Toyota Technical Service Bulletin T-SB-0016-21, which addressed a similar Hybrid Vehicle ECU not-sleeping condition on the 2021 Sienna Hybrid — but no equivalent TSB or software fix has been issued for the Land Cruiser LC250.

The 12-volt battery is not the root cause; it is the symptom. Replacing the battery does not resolve the underlying charging system or parasitic drain defect.

---

SAFETY IMPLICATIONS — CRITICAL

This defect presents a real, substantial, and documented safety risk across multiple failure modes:

1. Loss of motive power while driving (documented)

A 2024 Land Cruiser LC250 owner documented a sudden loss of power while accelerating from a neighbourhood onto a main road at 900 miles. The vehicle went completely limp — the engine RPM increased but the vehicle barely moved. Three error messages appeared simultaneously: "Drive-Start Control Malfunction Visit Your Dealer," "Hybrid System Malfunction Visit Your Dealer," and "System Malfunction Visit Your Dealer." The vehicle was towed to the dealership, which found no codes and could not replicate the issue. A second LC250 owner (2024 First Edition, 452 miles) experienced the identical failure.

When the 12-volt battery voltage drops below approximately 12.2V, the Hybrid Vehicle Electronic Control Module (HV ECM) shuts down hybrid functions as a protective measure to prevent undervoltage damage to the computer systems. A consistently draining 12-volt battery can cause "a no-start condition, a blank dashboard, or even a complete system shutdown while driving. When the 12-volt system goes completely dead, the vehicle loses power steering, brake assist, and critical control modules" (AutodataPlug technical analysis, 2026). This is explicitly described as "a real safety risk, not just an inconvenience."

This failure mode is not theoretical. Toyota has issued multiple NHTSA recalls for the identical hazard — hybrid system shutdown causing loss of motive power while driving — on other Toyota hybrid models:

• NHTSA Recall 18V684 (2018): 807,329 Prius and Prius V (2010–2014). Toyota's recall document states: "A hybrid system that shuts down instead of entering a failsafe mode could result in the vehicle losing motive power while driving at higher speeds. Loss of motive power at higher speeds increases the risk of a crash."
• NHTSA Recall 21V734 (2021): 2022 Prius and Prius Prime. Toyota stated: "If the vehicle loses motive power while being driven at a higher speed, there could be an increased risk of a crash."
• NHTSA Recall 20V369 (2020): Additional Toyota hybrid models, same loss-of-motive-power hazard.

In each recall, Toyota acknowledged that hybrid system shutdown causing loss of motive power at speed is a safety defect warranting a recall. The LC250's 12-volt battery problem can cause the same outcome through a different mechanism — low voltage triggering the protective shutdown — yet no recall has been issued for the Land Cruiser.

2. Steering system malfunction and loss of calibration (personally experienced)

When the first battery failed on my vehicle, the power-steering system lost its calibration, requiring a steering recalibration by the dealership. This is not an isolated consequence. Toyota has formally admitted to NHTSA that battery depletion causes steering system malfunction.

In the U.S. class action McClure v. Toyota Motor Corp. (2020 RAV4 Hybrid), the complaint alleges that battery depletion causes the power-steering mechanism to lose calibration, causing vehicles to "drift off-center" and "veer dangerously between driving lanes." Paragraph 77 of the complaint states: "In a document filed by Defendants with the National Highway Transportation Safety Administration (NHTSA), Defendants admit that battery depletion causes the steering system to lose calibration, which causes the steering wheel to pull or drift to one side while driving." The plaintiff in that case alleged that steering inputs were so strong that the steering wheel "jerked out [his] hands" while entering a traffic circle, and that the vehicle drifted off-center at all speeds, worsening at higher speeds.

The steering recalibration required after the first battery failure confirms that the LC250's steering system is vulnerable to the same battery-depletion-induced calibration loss that Toyota has admitted to NHTSA in the RAV4 context.

3. Protective lockout — no owner override

When the 12-volt battery voltage is too low for the computers to boot, the vehicle enters a protective shutdown mode from which there is no owner-accessible recovery. The system is designed to protect the computer systems from undervoltage damage, but this creates a stranded-vehicle situation with no override. This lockout occurred during my first battery failure. Toyota's emergency-response documentation also specifically contemplates situations in which the 12V system prevents normal vehicle movement and says that wheel dollies or similar equipment may be required in certain electrically locked conditions.

The low-voltage condition caused the vehicle's electronic parking-brake system to become unavailable for release, resulting in complete vehicle immobilization.

This created a safety and recovery concern because the vehicle could not be moved under its own power or conventionally towed and required specialized four-wheel dolly equipment.

4. No warning of 12-volt battery condition

Unlike the key-fob low-battery warning system, there is no warning indicator that alerts the driver to a degrading 12-volt battery before it fails. The 2010 Prius NHTSA complaint database documents that "12-volt battery fails suddenly causing loss of all electrical power including steering and propulsion at highway speed. Vehicle coasts to stop with no warning indicator of battery failure." The LC250 exhibits the same lack of pre-failure warning.

5. Additional safety consequences

• Loss of mobility: The vehicle can become completely inoperable without warning, including in remote locations, extreme weather, or emergencies.
• Inability to access the vehicle: A dead 12-volt battery disables smart entry, keyless start, and in some cases electronic door releases. Owners may be locked out of their own vehicle.
• Repeated roadside strandings: Each failure requires a jump-start or tow, creating repeated roadside exposure.
• Towing limitations: Toyota's roadside assistance covers towing for only 36 months, after which owners bear the cost of repeated tows for a defect Toyota has not acknowledged or remedied.
• Safety system degradation: Low 12-volt voltage can disable ABS, Vehicle Stability Control, and other safety systems that depend on stable voltage. One technical source notes: "Low voltage sets warning lights and can disable intervention when you need it."
• Complete battery failure occurred at approximately −30°C, an extreme temperature at which 12V battery capacity is materially reduced. The resulting low-voltage lockout rendered the vehicle completely immobile and prevented release of the electronic parking brake. Had the same failure occurred while the vehicle and occupants were travelling in a remote location under −30°C conditions, the inability to release the electronic parking brake or move the vehicle could have created a potentially life-threatening exposure to extreme cold, particularly if recovery equipment capable of moving a vehicle with locked wheels was not immediately available.

There is an important unanswered engineering question:

Why does Toyota's low-voltage protection strategy leave a 2.5-ton-plus vehicle physically immobilized in a manner that can make ordinary recovery impossible?

• TOYOTA'S RESPONSE
• Toyota has not issued a recall, Technical Service Bulletin, or software update specifically addressing the Land Cruiser LC250's 12-volt battery charging defect or its safety consequences.
• Toyota updated its battery inspection procedures in May 2026 to provide free replacement when a vehicle is found to need a new 12-volt battery. This addresses the symptom (dead battery), not the root cause (charging system software and/or parasitic drain), and does not address the safety risks of steering loss, shutdown while driving, or protective lockout. This replacement is only while the vehicle is under the initial 36 month warranty.
• The May 2026 recall (NHTSA 26V341 / Transport Canada Recall 2026421) for 2024–2025 Land Cruiser Hybrid vehicles addresses an unrelated instrument cluster software issue, not the 12-volt battery problem.
• Toyota has recalled other hybrid models (Prius 2010–2014, Prius 2022, and others) for the identical safety hazard — hybrid system shutdown causing loss of motive power while driving — but has not extended this action to the Land Cruiser LC250 despite documented instances of the same failure mode.
• Toyota admitted to NHTSA that battery depletion causes steering system malfunction, yet has not issued any warning, TSB, or recall addressing this consequence on the Land Cruiser LC250.
• Toyota has not acknowledged the charging defect, extended warranty coverage for the 12-volt battery or electrical system, or committed to a software fix.
• A Canadian class action lawsuit (Gudari Holdings Ltd. v. Toyota Motor Corp., et al., BC Supreme Court, filed March 13, 2026) alleges a similar 12-volt battery charging defect in Toyota bZ4X, Lexus RZ, and Subaru Solterra vehicles, but does not yet include the Land Cruiser LC250.
• A U.S. class action lawsuit, John Wade v. Toyota Motor North America Inc., et al. (U.S. District Court, Eastern District of California, Sacramento Division, filed April 2025; Case No. 2:25-cv-00948), alleges the identical 12-volt battery charging defect in 2023–2025 Toyota bZ4X and Subaru Solterra vehicles. Plaintiffs: John Wade, Franklin Huffman, Danielle Buls, Claudia Diez, and Matthew Kull. Plaintiff attorneys: Keller Rohrback L.L.P.; Shub Johns & Holbrook LLP; Wittels McInturff Palikovic. Toyota and Subaru filed motions to dismiss in late 2025; as of January 2026, no ruling has been reported and the case appears pending. Toyota's defense strategy is notable: Toyota argues that the plaintiffs describe only the effects (dead batteries) without identifying the specific defective components. This is a critical gap that the Land Cruiser LC250 evidence helps fill — the LC250 owner community has identified the DC-DC converter, the charging system software, and the HV ECU not-sleeping condition as the specific defective components, supported by Toyota's own T-SB-0016-21 precedent on the 2021 Sienna Hybrid. Sources: Toyota Says 12-Volt Battery Class Action Lawsuit is Drained ; Lawsuit: Toyota bZ4X and Subaru Solterra 12v Battery Problems
• A YouTube video published June 15, 2025 ("Toyota's Battery Problem Affects up to a Million Vehicles," ) documents the scope of the problem across Toyota hybrids, reporting that the issue potentially affects up to one million vehicles including Prius, Corolla, and RAV4 hybrids (2019–2023) in addition to the bZ4X and Solterra (2023–2025). The video reports that an expert report referenced in the U.S. legal filings alleges the 12-volt batteries are 15–20% undersized relative to the vehicles' electrical system requirements, and that a software-logic flaw causes parasitic drain. The video explicitly states that replacing the battery alone does not fix the problem because the software also needs to be fixed. One owner reportedly had her 12-volt battery replaced three times in 18 months. Toyota reportedly charges up to $450 per replacement battery plus labor.
• The scale of the problem — potentially affecting up to one million Toyota hybrid and electric vehicles across multiple model lines — underscores that this is not a Land Cruiser-specific issue but a systemic defect in Toyota's hybrid charging system architecture that affects numerous models sharing the same DC-DC converter and Battery Management System design.

---

REQUEST

I respectfully request that Transport Canada:

1. Open an investigation into the 12-volt battery charging and parasitic drain defect affecting 2024–2027 Toyota Land Cruiser LC250 hybrid vehicles, with specific attention to the safety consequences of hybrid system shutdown while driving, steering system calibration loss, and protective lockout.
2. Investigate and evaluate whether this defect constitutes a safety-related defect warranting a recall order under the Motor Vehicle Safety Act, given that Toyota has recalled other hybrid models for the identical hazard (loss of motive power while driving) under NHTSA Recalls 18V684, 20V369, and 21V734.
3. Investigate whether Toyota has evaluated the consequences of a low-voltage shutdown/lockout of the LC250 under extreme winter conditions, including the inability to release the electronic parking brake, inability to move the vehicle without specialized equipment, and the potential consequences to occupants if such immobilization occurs in a remote location or while travelling in severe cold.
4. Request that Toyota Motor Corporation and Toyota Canada Inc. provide data on 12-volt battery failure rates, warranty claims, steering recalibrations performed after battery failures, and customer complaints for the Land Cruiser LC250.
5. Request that Toyota explain why the Land Cruiser LC250 has not been included in any recall or service action addressing the hybrid system shutdown / loss-of-motive-power hazard, despite documented instances of the same failure mode in the LC250.
6. Evaluate the steering system vulnerability: Toyota has admitted to NHTSA that battery depletion causes steering calibration loss. Investigate whether the LC250's steering system is equally vulnerable and whether this constitutes a separate safety defect.
7. Mandate that Toyota implement a 12-volt battery diagnostic and early-warning system as a remedial action. The Land Cruiser LC250 is equipped with numerous electronic control modules and a sophisticated infotainment display. Toyota already monitors 12-volt battery voltage through the Battery Management System and Hybrid Vehicle ECU. This data should be surfaced to the driver through the infotainment system as a real-time battery health display — showing battery voltage, state of charge, and charging status — with an early-warning alert when the battery voltage drops below a safe threshold or when the charging system is not maintaining adequate charge. This would address the critical gap identified in the safety implications section: there is currently no warning of 12-volt battery degradation before catastrophic failure. The vehicle's computers already have the necessary data; Toyota need only display it. Such a diagnostic could be delivered via a software update and would give owners the opportunity to address a degrading battery before it causes vehicle shutdown, steering malfunction, or a protective lockout that strands the driver.
8. Consider whether a software update or Technical Service Bulletin should be mandated to address the chronic undercharging and/or parasitic drain condition, as well as the protective lockout that strands owners without any override.
9. Extend the scope of investigation to include other Toyota and Lexus hybrid vehicles that may share the same charging system architecture and exhibit the same defect.

 

[t3lcfe]

I would like to share with gang this information:

From BS200 system, I can monitor whenever the 12v battery charged.
I everyday observed that during my driving daily 8 mi from home to work, the battery is almost not charged. When I pull in parking at work or home, stop moving but engine is till on, the battery is started charging. Many times, I just left my LC engine running on my driveway so that it can charge the 12v battery (if I am not using the Norco one)

For most other vehicles, the battery must be charged during driving by alternator…The hybrid system is different because of no alternator…and… ?! Never had hybrid one before in my 58 yrs life.

 

[R_che]

Yes, you are correct in assuming access to a trickle charger... sorry for that. However, carrying a good jump starter will work wherever your vehicle is parked.

Better late post than never. My 2025 LC original battery had a dead cell in May of 26, with under 7k miles, which Toyota caught during their standard vehicle inspection. The battery was replaced with an original equipment battery under warranty. There was no option for a different battery. I asked about a recall on the battery type or the LC programming, which has been mentioned often on this site, and I was told there was nothing on the Toyota maintenance site indicating anything other than a replacement.
I wonder if this one will last through the mild winter in N. TX? The battery still reads fine 4 months later...