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Lithium Iron Phosphate (LiFePO4) batteries are generally considered to be one of the safest lithium battery options available. They have several safety features that help prevent them from overheating, catching fire, or exploding: Thermal stability
LiFePO4 batteries are more thermally stable than other lithium-ion batteries. Solid electrolyte
LiFePO4 batteries have a solid electrolyte, which prevents leakage. Stable cathode material
LiFePO4 batteries use a more stable cathode material than other lithium-ion batteries, which doesn't release oxygen when heated up. Lower operating temperature
LiFePO4 batteries have a lower operating temperature range than other lithium-ion batteries. Battery Management Systems (BMS)
Some LiFePO4 batteries use BMS technology to monitor battery status and adjust charging parameters.
LiFePO4 batteries are also non-toxic, non-contaminating, and don't contain rare earth metals.
It's really not. You clearly missed the difference between your cell phone/laptop Lithium-Ion battery chemistry and LiFePO4 Lithium-Iron-Ferrite chemistry.
That battery pack is designed for occasional use not constant in car use. Plus unless you physically open the unit there is no way to know who makes the cells, there are some sketchy battery cells out there in fact most are questionable.
That battery pack is designed for occasional use not constant in car use. Plus unless you physically open the unit there is no way to know who makes the cells, there are some sketchy battery cells out there in fact most are questionable.
Your first statement is completely incorrect - if anyone simply looks at the product website, will know this.
While anyone is free to speculate online, please don't spread misinformation based on speculation.
(For example, I can speculate that any given EV sample by a certain EV manufacturer (claiming and failing to deliver full self driving for two decades) - is always a fire waiting to happen. Several people have in fact died - but I still can't make that a "claim". That has to be done with litigation as already happened/happening in the courts and then enforced by the agencies)
Your first statement is completely incorrect - if anyone simply looks at the product website, will know this.
The pack would have to be opened to see who makes the cells.
While anyone is free to speculate online, please don't spread misinformation based on speculation.
Not speculation, generic cells are not exactly made to the highest standard.
(For example, I can speculate that any given EV sample by a certain EV manufacturer (claiming and failing to deliver full self driving for two decades) - is always a fire waiting to happen. Several people have in fact died - but I still can't make that a "claim". That has to be done with litigation as already happened/happening in the courts and then enforced by the agencies)
No need to speculate EVs have much lower rates of fires vs. petrol at least 10x less. You know why? Because the cells are purpose built and there is advanced cooling, sensors and general management going on. A $100 battery pack isn't that.
Just returned from a 3 week trip to find my 2023 Lexus 350RX dead in my garage. Had to call road side assistance for a jump.
Any idea how to "store" the car if traveling for more than a few days?
These new cars have so many gadgets now-a-days that I wonder about how much battery drain may occur even when the car is off. Worst case scenario, you could detach the negative battery cable to avoid the battery draining down. But that may also reset many of your settings since the ECU won't have continuous power and will reset when it's reconnected.
Just returned from a 3 week trip to find my 2023 Lexus 350RX dead in my garage. Had to call road side assistance for a jump.
Any idea how to "store" the car if traveling for more than a few days?
You can purchase a "float" charger very inexpensively to maintain a constant voltage supply in your absence. Battery Tender and NOCO are just two of the popular ones but, there are many others. They are typically .75 amp to 1 amp units. Typically around $30 to $35 on Amazon. There are also some small solar chargers available for outdoor parking.
Last edited by StefanoS; Oct 21, 2024 at 11:39 AM.
Recently my Lexus RX450h+ 12 Volt battery has been discharging more rapidly. I use an in situ battery monitor and when state-of-charge drops to 50%, I attach a trickle charger. I used to be able to go 10 - 14 days between charges; now I need to do it every 4 -5 days. Here’s some data showing something that’s changed in the last few weeks.
The first graph (10/02/24 data) shows the battery voltage while the vehicle is ON, in “Ready” mode (driving). Before the vehicle is turned on, battery voltage indicates a 75% state of charge. When the vehicle is turned ON, the DC-to-DC converter comes on and provides 14 - 14.5 V across the battery. When the voltage across the battery is 13.8 - 14.7 V (the “Charging voltage range”) the battery is being charged. So during the entire drive (about 20 minutes), the battery is being charged. When the vehicle is turned off, the DC-to-DC converter is off and the battery measures 12.66 V, indicating 100% state of charge. Great, the drive has fully charged the battery!
The second graph shows data from 10/11/24. Before starting the vehicle the battery voltage indicates a 74% state of charge (close to previous test). When the vehicle is turned ON, the DC-to-DC converter comes on and briefly brings the voltage into the “Charging voltage range.” But within 2 minutes the voltage drops down to about 12.8 V and remains there for the rest of the trip. The 12.8 V seems like a “maintenance” level that doesn’t discharge the battery but doesn’t charge it either. The net result of this trip is the battery is about 66% charged at the end. So I started at 74% charged, drove for about 27 minutes, and ended up at 66% charged! This isn’t sustainable! No wonder I now have to put the battery on a trickle charger every few days. I’m wondering if this is a hardware or software problem. Maybe there was a software update that caused the charging duration to be way too short. Any thoughts are appreciated! Lexus needs to fix this problem.
While researching alternative batteries for the Lexus Hybrids and non-Hybrids plagued by the 12 V Battery death issues, I ran into a solution that I thus far consider to be my firm and permanent solution at a reasonable cost. This thread is therefore about this solution space discussion, rather than the problem-space discussion that is the merged thread with 739 posts and over 66000 views, speaking only of the 5th Gen RX (and many times over posts and views with considering the 2nd Gen NX and RZ forums).
The solution I have adopted is this BMS-integrated "Emergency Start" that essentially is a permanently mounted Lithium-Iron-Phophate 5 A-h Battery with Integrated Iphone/Android App. It thus provides a solution for dealing with any unexpected 12 V battery deaths, without having to even open doors, hood or hatch of the RX, NX, RZ that need battery power to operate these basic items of the car - by using its integrated App. The item also completely charges directly from the car's 12 V charging subsystem (when the terminal voltage is above 13.8 V) and since its only 5 A-h, it shouldn't load that charging subsystem. It is also designed to auto-shutoff and not discharge itself, when the car battery terminal voltage drops below 13.6 - 13.8 V. This latter fact takes care of any problem that this parallel circuit of the separate 12V battery will NOT discharge itself when the car is being driven around (that is when car not being charged with Ready and Parked states or without battery tender) - it essentially a backup parallel battery system that eliminates all the problems of our cars in every way I can so far tell. Finally, being of Lithium Iron Phosphate chemistry (and not Lithium Ion) with lower energy density, AND being designed for under the hood with high temperatures/conditions by a reputed LiFePo battery maker, I consider it safe for placing it in trunk area near the stock battery (which has much lower temperatures than under the hood) - safer than or at least as safe as carrying around a Li-Ion jump starter in the passenger compartment. The app provides many details about the unit, and in fact doubles as bluetooth voltage monitor providing data about the stock battery's voltage, aside from its own diagnostics. Finally, its a reasonably priced item between $ 100 - 150 depending on where you buy it from online. The Walmart price is the higher end I found, but it provides Walmart's store return benefit till end of Jan 25 - I, however, took the risk of buying it from Performance Fishing, since the product has been around since 2020 and I think I could take the risk given the product is well warrantee'd by the manufacturer and well reviewed for the past ~4 years.
"The Emergency Start will stay active until a discharge voltage of 13.6V is
reached. When reactivating the unit again by repressing the circular
button the Emergency Start will stay ON until the Emergency Start
battery is fully discharged at ~10V. An engine start attempt can be made
during any time when the unit is active.
Any time a charging system is charging, such as from vehicle alternator
the Emergency Start will turn ON to receive a charge.
The Emergency Starter disconnects itself automatically from the vehicle
battery system when the battery voltage drops below 13.6V, keeping the
Emergency Starter at full charge and to prevent the Emergency Start
from discharging. If Emergency Starter not used for 3 months,
BlueTooth activations is not possible and would need to be reactivated
by manually long press on the unit or with a charging sytem.
Output Voltage: 9V to 15V
Peak capacity 4.5Ah or 18,000mAh equiv.
Dimensions: 6.5in x 3.5in x 1.8in (165mm x 89mm x 44mm)
Weight: 1.7lbs
Start Current: 800A
Peak Current: 1,600A
Cycle life: 2,000 at 80% Depth of Discharge (DOD)
Application Temperature: -4F to +140F (-20C to 60C). Cell performance
may degrade at low temperature."
If anyone else wants to get it, and/or discuss it, I created this thread for solution-space discussion - requesting the mods to keep this thread separate from the problem-space discussion.
That is really a great idea and product. I have just one concern about it. Many cases where people experience dead batteries on a relatively new car or new battery are caused by simply not driving the car enough to keep the battery charged, i.e. infrequent short trips. I and many other older retired Lexus owners fall into this category. This backup battery relies on the car’s charging system to keep it charged, same as the primary 12V battery. So, if the primary 12V battery is not being charged sufficiently, would not the backup battery also be susceptible to not being charged sufficiently to start the engine? The reality it would seem is that if one doesn’t drive enough to keep the 12V battery, and the backup battery, charged, one would still need to use a battery charger/maintainer to keep both batteries charged. The backup battery only stores energy; it does not create energy.
I’m wondering if this is a hardware or software problem.
Software. The charging system is complex and software controlled not like for example an alternator on an old vehicle that uses a "dumb" voltage regulator. I don't understand why the charging algo doesn't simply keep the battery at 14 volts when you drive.
Recently my Lexus RX450h+ 12 Volt battery has been discharging more rapidly.
I experienced rapid discharge early on, that I think was due to the key fobs being to close, and also once when a Bluetooth and WiFi EVSE seemed to be waking the vehicle up repeatedly. That time, the battery died in a couple of days. We've had our RX450h+ just over one year and have put just over 15k miles on it. . Since getting rid of the buggy EVSE and keeping the fobs over 20' away, this has been my experience;
The battery and 12 volt systems in the vehicle are charged/powered by a DC/DC converter that draws from the traction battery. It doesn't matter what driving mode the vehicle is in, EV, HV, Auto EV/HV, or Charge mode. It always charges the same.
As best I can tell from watching the battery monitor app, it charges the battery any time the vehicle is park and in Ready mode. By "charging," I mean the voltage goes over 14v.
After putting it in drive, it may charge for a few minutes, but then drops voltage to the point where it is powering the vehicle, but not charging the battery. Occasionally, I'm guessing once a month, the charging system will actually charge the battery while driving. It seems to be all time based and not voltage based.
The only other time the system charges the battery is about 5 minutes after remote start and for the next 15 minutes, until the remote start times out.
I put the vehicle in park any time I am stopped for more than a minute or so, and use Remote Start religiously when on road trips. This has resulted in the battery keeping a higher state of charge, though still not fully charging. At home, I use an external charger as needed to keep the battery above 12.4 volts resting. That's usually about every 14 days, but sometimes it's more often.
You can purchase a "float" charger very inexpensively to maintain a constant voltage supply in your absence. Battery Tender and NOCO are just two of the popular ones but, there are many others. They are typically .75 amp to 1 amp units. Typically around $30 to $35 on Amazon. There are also some small solar chargers available for outdoor parking.
So you are saying that I have to put my car on a battery charger if I leave for more than a couple of weeks?
So you are saying that I have to put my car on a battery charger if I leave for more than a couple of weeks?
Is your RX350 a hybrid or a standard model? If it's a hybrid, there is no alternator charging the 12v battery. The 12v battery in hybrids is charged via the lithium battery pack. If it is a hybrid, then I would recommend using a float charger to maintain the battery during your absence. If you do not have a hybrid, you may want to have your battery load-tested in order to see whether your battery is sulfated and on it's way out.
So you are saying that I have to put my car on a battery charger if I leave for more than a couple of weeks?
Yes and No.
No, if you drive the car regularly and long enough so that the battery is charged before you leave for two weeks. In this case, the battery can sit for two weeks without a problem.
Yes, if you do NOT drive the car regularly and long enough so that the battery is in a weak state of charge before you leave for two weeks. In this case, there is a high probability that the battery will be dead when you return after two weeks.
It's really just simple physics and common sense.
