12V Battery Marathon

[Below32]

The 12V battery is managed / charged by the hybrid inverter. As the LC doesn't have an alternator, the entire 12V system is "slaved" to the high voltage DC system comprised by the hybrid motor-generator, the hybrid battery and the inverter. The inverter takes high DC voltage from the hybrid battery (or rectifies the AC generated by the motor-generator) and steps it down to 12V to power the 12V circuit and charge the 12V battery.

There are basically five modes of operation of the hybrid system:
1) Engine on, charging hybrid battery. The engine turns the motor-generator, the inverter takes the AC generated by the motor-generator, rectifies it and charges the hybrid battery.
2) Engine on, motor-generator boosting torque. The inverter takes high voltage DC from the hybrid battery, converts it in AC and powers the motor-generator.
3) EV mode. Engine is off, inverter takes high voltage DC from the hybrid battery, converts it in AC and powers the motor-generator to move the car.
4) Regenerative braking. Engine can be on or off. Car's wheels move the motor-generator, the inverter takes the AC generated by the motor-generator, rectifies it and charges the hybrid battery.
5) Starting the engine. This one is a bit more complicated, so I will explain it further below.

In the first four modes, the 12V circuit is powered by the inverter by stepping down high voltage DC from the hybrid battery circuit. It can charge the 12V battery regardless of the engine being on or off, as long as there is enough energy stored in the hybrid battery.

However there is a caveat. When the car us turned off, the main high voltage relay completely isolates the hybrid battery from the inverter. The inverter needs the 12V battery to "wake up" and close the main high voltage relay. Hence, the car cannot "wake up" if the 12V battery is low. So, in spite of having a potentially huge energy "reserve" in the hybrid battery, the 12V battery is essential for the car to "wake up" after being powered off.

Once the inverter "wakes up", it checks the charge status of the hybrid battery. If there is enough juice in the hybrid battery, it will use the motor-generator to start the engine. If the hybrid battery is low, it will start the engine using a conventional starter and the 12V battery. In theory, this should make the LC totally fool-proof and allow to start the engine even if the hybrid battery is low. But there is a gap between theory and practice. When the 12V battery is low, the hybrid system goes into a fault mode which we are already aware of.

One last detail. Because normally the engine is started by the motor-generator, this would leave the 12V starter unused and eventually it would just "freeze up". In order to prevent it, the engine is started by the conventional starter and 12V battery every time after the fuel door is opened. This makes sure that the starter is used at least once every now and then.

All this sounds wonderful in theory. But in practice, the execution is less than perfect, and we already know that if the 12V battery gets below certain level, the inverter's brain gets confused and the car won't power up.

This isn't different from other Toyota hybrids. Complaints about hybrids being dead after being left parked for a few weeks are very common on Toyota forums. However, LC appears to be particularly bad. My wife's car is a Lexus NX hybrid. I have measured the voltages in different conditions, and at least in the Lexus the float/maintain voltage of the 12V circuit is 13.2V, so the 12V battery gets fully charged if you drive the car long enough. But in the LC, Toyota decided (for some obscure reason) to make the float/maintain voltage 12.8V, below the minimum voltage required to charge the 12V battery.

Also, it appears that the 12V charging algorithm is actually quite complicated. For example, the float/maintain voltage is 12.8V most of the time. But as soon as the car is placed in Park, the voltage jumps to 14.2V. Also, when ambient temperature is low (around 50F), the float/maintain voltage is increased to 13.2V. So it seems that Toyota did think about different conditions and requirements to keep the 12V battery healthy, but the actual implementation is faulty and needs some fine-tuning.

As all this is managed by the inverter's software, there is no easy way to change it (at least for us). It should be easy for Toyota to update the inverter software, though.

This is all really helpful. Thank you. I am somewhat familiar with BMS and float voltage from our trailer so all of this makes sense. Follow-up question, if the voltage jumps to 14.2V when the LC is put into park, then letting it run in park for a few minutes before hopping out especially when it’s cold should help?

 

[katekebo]

Curious if any LC owners on here have unplugged the mentioned sensor on their vehicles and monitored the charging voltage?

Thanks for sharing. The article is mostly right (and consistent with what I wrote above) with a few exceptions. The most significant one is that Method 2 is suitable for car battery charging, and it is actually the method used in most cars for the past 20 years or so. 13.6-13.8V float voltage WILL charge the battery, albeit slowly. So 14.2-14.4V bulk charging for a short period of time (until battery reaches ~90% charge level), followed by 13.6-13.8V float voltage is actually the best way to charge and maintain a lead-acid battery. Charging the battery continuously with 14+V will result in off-gassing and shortened life. It will require refilling the battery with distilled water every few months, just like it used to be in old cars.

That said, the article is right in terms of pointing out the issues with Toyota's charging algorithms in hybrids.

 

[katekebo]

This is all really helpful. Thank you. I am somewhat familiar with BMS and float voltage from our trailer so all of this makes sense. Follow-up question, if the voltage jumps to 14.2 when the LC is put into park, then letting it run in park for a few minutes before hopping out especially when it’s cold should help?

Maybe. I don't know how long the car will keep the voltage at 14.2V in Park. I only checked it for a few minutes.

 

[Below32]

Yes it has a ‘back up’ starter.

My LC wouldn’t start in cold weather a couple of days ago and you could hear it (unsuccessfully) trying to turn the engine over.

As soon as I jump started it, the dash lit up like a Christmas tree and I had to bring it to the dealer to reset the codes. I’m in the process of getting a proper Odyssey AGM battery to be done with this nonsense

I look forward to hearing how it goes with the Odyssey. I am of the mindset that Toyota needs to supply a battery that works in our weather especially since it doesn’t state, warm weather vehicle only, in the instruction book. I will keep this thread updated as the winter progresses.

My wife has a Toyota hybrid that is 6-7 years old, it still has the same battery as when we bought it and it also lives outside in our driveway. I know it isn’t the LC but it is precedent.

 

[katekebo]

A few additional observations ...
We live in Tucson, AZ so we never experience sub-freezing temperatures.
For the past several days we have been in Colorado, so much colder.
I have noticed that the charging algorithm seems to vary with temperature. Compared to Tucson, the initial bulk charging voltage of 14.2V stays for much longer than in Tucson. While in Tucson voltage drops to 12.7-12.8V a couple of minutes after starting the car, here it stays high for entire 30-40 min drive. Also, it appears that in addition to the low 12.7V float, there is an intermediate voltage setting of about 13.2V, which stays on for as long as the battery is cold (which can take a long time).
So apparently the car does adjust the charging program in cold weather to compensate for the low temperature and charge the battery to a higher level.
I think part the problem of the battery dying in cold weather may be due to sudden temperature drop overnight. The car "thinks" that the weather will stay warm and does not "prepare" the battery for cold weather. The car has no way to know the weather forecast and assumes that tomorrow's weather will be just like today. If the temperature drops suddenly overnight (something like 30 degrees or more drop, going from 50s to 20s), the battery is caught off-guard and insufficiently charged for a cold morning start.

 

[b407driver]

My battery has died twice while camping (for no reason, other than sitting for two days). First time it happened, the dealer tested the battery good. Second time a couple months later, dealer tested it bad, and replaced it recently. Don't know yet if it will matter.

 

[Area 51]

How cold does it get?
It has nothing to do with the vehicle.
Its is a relatively small battery.
If it is new it has not been peak charged, so lower than it should be to start with.
Colder/ colder, batteries suffer. Simple as that.
If people use block heaters where you live that should be a clue.
Mine sits in excess of a week or so often, indoors, no issues to date 10k mi 1 year old almost.
Just at freezing so probably not as cold or as long, no issues here, factory batterie.
Peak charge whatever you end up using.

 

[Below32]

How cold does it get?
It has nothing to do with the vehicle.
Its is a relatively small battery.
If it is new it has not been peak charged, so lower than it should be to start with.
Colder/ colder, batteries suffer. Simple as that.
If people use block heaters where you live that should be a clue.
Mine sits in excess of a week or so often, indoors, no issues to date 10k mi 1 year old almost.
Just at freezing so probably not as cold or as long, no issues here, factory batterie.
Peak charge whatever you end up using.

Single digits for much of the winter are fairly common. All of our vehicles have block heaters. The Land Cruiser gets its block heater this weekend.

My wife’s hybrid doesn’t have the fancy climate control on the app at start up. Turned that off for the LC. Will preset the interior temps, fan etc prior to shutting down. This should help limit the battery draw on start up as well.

 

[Area 51]

Single digits for much of the winter are fairly common. All of our vehicles have block heaters. The Land Cruiser gets its block heater this weekend.

My wife’s hybrid doesn’t have the fancy climate control on the app at start up. Turned that off for the LC. Will preset the interior temps, fan etc prior to shutting down. This should help limit the battery draw on start up as well.

That's cold for any vehicle once its gets into cold soak.
You may want to consider a trickle charge for the 12vdc system.
I believe there is a convenient place under the hood to pick up the 12vdc.
I would peak charge the existing battery and find something that works before spending 300-400$ on a battery that you are not sure you wont have the same problems.

 

[katekebo]

Here is the summary of my conclusions re. the battery issues:
1) For some reason, Toyota chose a charging algorithm that charges / maintains the 12V battery at ~60-65% charge level instead of charging it to a more typical 90-100%.
2) This leaves the battery with little charge reserve for activities such as camping or working on the car, or sudden drop to sub-freezing temperatures.
3) Flooded lead-acid batteries work best and last the longest if cycled between 100 and 60% charge level. Cycling the battery to or below 40% causes sulfation, which quickly results in loss of storage capacity. This loss of capacity exacerbates the issue in point (2).

This problem can be (partially) remedied by replacing the OEM flooded lead-acid battery with one that can tolerate deep discharge cycles better, like an AGM one. Deep cycle batteries are commonly used in application such as boating or RVs.

Ultimately, the solution would be implementing a charging algorithm that keeps the battery fully charged. Disconnecting the battery monitoring sensor to force the system to default to a higher float voltage (14+V) will result in off-gassing and require periodic addition of distilled water (like it used to be in the 1960s or 70s). It may also damage the battery in hot climate.

 

[swampdog]

It's small comfort to hear that many LC owners have similar issues to ours. Our LC already would not start last winter when it was only several months old. This year it went from bad to worse and ended up with a tow truck ride to the dealer. The starting battery failed its test, resulting in battery replacement on warranty. I see that the new battery has a large "TOYOTA" label, unlike the original battery; not sure if that will make a difference.

The dealer suggested installing a trickle charger directly at the starting battery; probably better than hooking it to the boost points in the engine compartment. Running the trickle charger cord to the outside presented a problem as the LC will not shut off its systems and headlights if a rear window is open even a small crack. But thanks to another poster on this forum and their suggestions and pictures, it didn't take long to run the cord at the back of the LC. Now, when parked outside in the winter, one has to plug in two cords, one for the block heater at the front and another for the trickle charger at the rear. We also put the LC in the heated garage and only plug in the trickle charger there.

I expect that the combination of the block heater and trickle charger would start the LC in cold temperatures. If not, one could add a battery blanket. One owner from the Yukon had his battery fail in the middle of a long drive, probably because the battery became too cold to function. A long tow followed. The battery compartment next to the cold rear fender likely becomes very cold. My suggestion for that type of situation is to drive with the cover off of the battery compartment, to allow warmer air from the car interior to keep the battery thawed. Of course, also keep the largest NOCO booster fully charged and warm. If heading out into an isolated area, in winter or summer, it also would be a good idea to take survival gear, such as a 5 Star Woods sleeping bag, candles, water, food, a portable Starlink or InReach, etc. You don't want to become an item on "Outdoor Disasters."

Had we known of these issues, there is no way we would have bought the LC. But to get rid of it with 12,000 km could result in a huge loss, so we will stick with it for now. Toyota, why are you even selling these in Canada or in other areas with a cold climate? Maybe it's time for recall to fix these issues.

 

[BB3]

Yes it has a ‘back up’ starter.

My LC wouldn’t start in cold weather a couple of days ago and you could hear it (unsuccessfully) trying to turn the engine over.

As soon as I jump started it, the dash lit up like a Christmas tree and I had to bring it to the dealer to reset the codes. I’m in the process of getting a proper Odyssey AGM battery to be done with this nonsense

Yes, I have also been considering a battery upgrade given all the reported issues, not much cold weather exposure but do leave mine parked for extended periods. I do have a jumper but the reports of error codes and returns to the dealer to clear them is not at all appealing. My question is given all interesting info above on charging profiles etc, will the AGM "fix" the issue?

 

[Area 51]

Here is the summary of my conclusions re. the battery issues:
1) For some reason, Toyota chose a charging algorithm that charges / maintains the 12V battery at ~60-65% charge level instead of charging it to a more typical 90-100%.
2) This leaves the battery with little charge reserve for activities such as camping or working on the car, or sudden drop to sub-freezing temperatures.
3) Flooded lead-acid batteries work best and last the longest if cycled between 100 and 60% charge level. Cycling the battery to or below 40% causes sulfation, which quickly results in loss of storage capacity. This loss of capacity exacerbates the issue in point (2).

This problem can be (partially) remedied by replacing the OEM flooded lead-acid battery with one that can tolerate deep discharge cycles better, like an AGM one. Deep cycle batteries are commonly used in application such as boating or RVs.

Ultimately, the solution would be implementing a charging algorithm that keeps the battery fully charged. Disconnecting the battery monitoring sensor to force the system to default to a higher float voltage (14+V) will result in off-gassing and require periodic addition of distilled water (like it used to be in the 1960s or 70s). It may also damage the battery in hot climate.

Regular peak charging cycles reverse sulfation to a high degree, i do not nwo how high in consumer products.
AGM absorbed glass matt batteries are a catch all, consumer grade vs industrial grade a big difference as well as even in industrial grade, 5, 10, 15, 20 year life cycle designs.
algorithms and added complexity is not the answer, simplicity and a solid application specific use recommendation is.
These things are consumer grade products, built and designed to a price point, not a space station.

 

[Vermont]

Here is the summary of my conclusions re. the battery issues:
1) For some reason, Toyota chose a charging algorithm that charges / maintains the 12V battery at ~60-65% charge level instead of charging it to a more typical 90-100%.
2) This leaves the battery with little charge reserve for activities such as camping or working on the car, or sudden drop to sub-freezing temperatures.
3) Flooded lead-acid batteries work best and last the longest if cycled between 100 and 60% charge level. Cycling the battery to or below 40% causes sulfation, which quickly results in loss of storage capacity. This loss of capacity exacerbates the issue in point (2).

This problem can be (partially) remedied by replacing the OEM flooded lead-acid battery with one that can tolerate deep discharge cycles better, like an AGM one. Deep cycle batteries are commonly used in application such as boating or RVs.

Ultimately, the solution would be implementing a charging algorithm that keeps the battery fully charged. Disconnecting the battery monitoring sensor to force the system to default to a higher float voltage (14+V) will result in off-gassing and require periodic addition of distilled water (like it used to be in the 1960s or 70s). It may also damage the battery in hot climate.

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.

 

[Mikie]

Yes, I have also been considering a battery upgrade given all the reported issues, not much cold weather exposure but do leave mine parked for extended periods. I do have a jumper but the reports of error codes and returns to the dealer to clear them is not at all appealing. My question is given all interesting info above on charging profiles etc, will the AGM "fix" the issue?

Short answer is, probably not, our charging profile will not be able to charge an AGM any better than it can a flooded cell (in fact, the AGM requires an even slightly higher voltage for optimal charging).

I upgraded my OEM battery to an AGM shortly after I bought the car (the original was fine, and tested to be healthy, but I wanted to see if a proper AGM would help with my battery drain problem). While it's likely that my AGM Is more resilient and able to accept more of a discharge than the OEM, I still have a huge problem with the battery draining VERY quickly. This in spite of the fact that I've done everything I can to limit the electrical "overhead" in my LC.

While AGM batteries offer a number of big advantages over a flooded cell, the fact is that an AGM did not fix the battery drain issue for me, at least that's been my experience.

 

[basicxj]

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.

Interesting- staying tuned.

 

[D-mac]

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.

There appears to be some that believe AGM batteries need higher charging voltages for "best'' performance, and a few have managed to sell gear to try to satisfy the urge for higher levels of 12v battery charge from OEM charging systems. I have not yet seen any AGM battery manufacturer that has documented the need for this "solution".

 

[Mikie]

There appears to be some that believe AGM batteries need higher charging voltages for "best'' performance, and a few have managed to sell gear to try to satisfy the urge for higher levels of 12v battery charge from OEM charging systems. I have not yet seen any AGM battery manufacturer that has documented the need for this "solution".

Interstate Batteries makes batteries for LOTS of other brands. This particular reference from them addresses the requirements for charging an AGM battery (vs. a flooded cell)...

How to Charge an AGM Battery and Why It’s Different

Edit: I've heard that some folks have had a problem with the link -- so I've attached the page as a JPeg if you need it...

 

[bluescruiser]

Yes, I have also been considering a battery upgrade given all the reported issues, not much cold weather exposure but do leave mine parked for extended periods. I do have a jumper but the reports of error codes and returns to the dealer to clear them is not at all appealing. My question is given all interesting info above on charging profiles etc, will the AGM "fix" the issue?

In the winter we experience temperature swings from 0°C to - 40°C. My vehicle is never plugged in and sits for 2 weeks out of most months.

I had a NorthStar AGM in my last vehicle (‘02 Sequoia) and I never had an issue getting it started; although it protested a little when it dipped below -30

 

[Vermont]

There appears to be some that believe AGM batteries need higher charging voltages for "best'' performance, and a few have managed to sell gear to try to satisfy the urge for higher levels of 12v battery charge from OEM charging systems. I have not yet seen any AGM battery manufacturer that has documented the need for this "solution".

I think there is some confusion here.

My point is about the default charging profile of the car itself. When driving, the Toyota hybrid system often drops its output to around 12.5V to save fuel. 12.5V is physically not enough pressure to charge any lead-acid battery (AGM or Flooded). Because of this, the stock battery is often sitting at only 50–60% capacity even after a long drive. This low baseline capacity is why people's batteries die so quickly from minor things (like leaving the trunk open or the stereo on for 20 minutes). The battery isn't being charged up. By disconnecting the sensor (the fail-safe), we force the car to output 14.1V, which actually charges the battery. The downside of disconnecting the sensor is that the battery is constantly being charged with 14.1V while driving.