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Maybe one of these? Years ago I worked for Johnson Controls and we would get steep discounts on yellow or Red top. Not sure if the quality is still the same with the new company putting these out?
After reading Wrinkle's post regarding this issue, I disconnected the voltage sensor at the plug on the negative battery post and drove around the area to pick up some items. My plug-in voltage meter in the center console showed a constant 13.8v output the entire time, (normally reads 12.6v when driving) when I was in drive. Normally, when in park, the voltage would rise to 14.2 to 14.4v but, with the sensor disconnected it remains at a steady 13.8v. I did not drive more than about a total of 17 miles and when I returned home, the battery had charged from 12.44v, when I left home, to 12.63v at return. Normally, after a trip like this, the battery SOC would have decreased in voltage by the time I arrived home.
How did you disconnect voltage sensor? can you please share a pic?
After reading Wrinkle's post regarding this issue, I disconnected the voltage sensor at the plug on the negative battery post and drove around the area to pick up some items. My plug-in voltage meter in the center console showed a constant 13.8v output the entire time, (normally reads 12.6v when driving) when I was in drive. Normally, when in park, the voltage would rise to 14.2 to 14.4v but, with the sensor disconnected it remains at a steady 13.8v. I did not drive more than about a total of 17 miles and when I returned home, the battery had charged from 12.44v, when I left home, to 12.63v at return. Normally, after a trip like this, the battery SOC would have decreased in voltage by the time I arrived home.
After the above experiment, I did reconnect the sensor when I returned home. Yesterday, I did a little more experimentation with this "sensor". After returning from a short trip to Costco, I disconnected the sensor once again and then plugged the car into the 240v charge point while it was in my garage. This time, the 12v auxiliary battery began charging along with the Lithium battery pack. This tells me that this is not just a sensor but, also a switch which regulates the flow of current from the lithium pack to the auxiliary battery. So, the mystery continues.......
After the above experiment, I did reconnect the sensor when I returned home. Yesterday, I did a little more experimentation with this "sensor". After returning from a short trip to Costco, I disconnected the sensor once again and then plugged the car into the 240v charge point while it was in my garage. This time, the 12v auxiliary battery began charging along with the Lithium battery pack. This tells me that this is not just a sensor but, also a switch which regulates the flow of current from the lithium pack to the auxiliary battery. So, the mystery continues.......
I like your experiments
Yes, it does seem more complex than a dumb voltage sensor, and likely integrated well into the 12 V charging subsystem in a more complex manner, together with the firmware code of the car that implements the 12 V charging logic.
By the way, the 12 V battery charging when the external plug-in charger (for the Li traction battery) is charging - might have helped a lot in preventing car deaths, if it had been implemented as the default logic. Perhaps Lexus did not do that, again to reduce the load on the DC-DC converter. Interestingly, in the very early phase of the Rav4 Prime life-cycle (2021, if I recall correctly) - there had been a DC-DC converter recall by Toyota for field failures, if my memory serves me right.
After the above experiment, I did reconnect the sensor when I returned home. Yesterday, I did a little more experimentation with this "sensor". After returning from a short trip to Costco, I disconnected the sensor once again and then plugged the car into the 240v charge point while it was in my garage. This time, the 12v auxiliary battery began charging along with the Lithium battery pack. This tells me that this is not just a sensor but, also a switch which regulates the flow of current from the lithium pack to the auxiliary battery. So, the mystery continues.......
Have you observed any drop in milege after disconnecting the voltage sensor due to the increased DC/DC converter workload? I wonder if this may be more notieable in a 350h vs your 450h? Thanks for your research.
Have you observed any drop in mileage after disconnecting the voltage sensor due to the increased DC/DC converter workload? I wonder if this may be more noticeable in a 350h vs your 450h? Thanks for your research.
No but, I only did this briefly and not long term, as I just wanted to gather more information about the charging routine. I was not expecting to see the 12v battery charging with the sensor/switch unplugged. Since the standard hybrid's smaller battery pack is different (Nickel Metal Hydride) than the PHEV models (Liion) there might be a more significant difference but, I am not certain as to what that might be.
After the above experiment, I did reconnect the sensor when I returned home. Yesterday, I did a little more experimentation with this "sensor". After returning from a short trip to Costco, I disconnected the sensor once again and then plugged the car into the 240v charge point while it was in my garage. This time, the 12v auxiliary battery began charging along with the Lithium battery pack. This tells me that this is not just a sensor but, also a switch which regulates the flow of current from the lithium pack to the auxiliary battery. So, the mystery continues.......
Thanks for sharing your experiment. Its very valuable. I don't believe issue is in charging system as many of us using trickle charger to keep aux battery charged. I park my car in garage and a fully charged battery drains under 4 hours. This means a massive draw is happening. A fully charged 60Ah battery must take at least a week to fully discharge, hence 4 hours means something using battery badly. one reason can be week cellular signal inside garage. As I believe the car must contact Lexus remote server and weak signal means retry, retry, ... this can drain the battery very fast. Like our cellphone battery drains very fast when dealing with weak signal. when I park the car outside (where cell signal is strong), the charged battery hold itself much longer (more than 3 days that I tried so far). Two experiment can help proving this theory: a. disable remote services from app, b. install cellular signal booster inside garage. I'm going to try and share the results.
Ours sat for 25 days in a metal siding garage (basically the building is a Faraday cage) for 25 days and had no battery issues. I really need to fire up my instruments to see if/when/how long the car is attempting to connect.
My 2024 RX450h+ was draining the 12 V battery whenever it sat for a few days. I bought a battery monitor on Amazon that tracks battery voltage and downloads data to the phone. I noticed a cyclical draining of the battery when the vehicle was off. I measured fuse voltages (vehicle off, doors latched) and found the drain was thru fuse ECU-DCC No. 3. I put a fuse extender in and monitored the current thru this fuse. (Fig. Below). Something was evidently turning on and off continuously (vehicle off) and drawing a lot of current. One of the items on this circuit is the Bluetooth Digital Key receiver assembly. (The Digital Key system uses an App on the cell phone to lock/unlock doors and even drive the vehicle without the key fob.) By chance I noticed that the cyclical discharging of the battery was triggered by the garage door opener! (See Fig. Below). It seems the Bluetooth Digital Key receiver was responding to the garage door opener, cycling on and off and discharging the battery. When I disabled the Digital Key system in the car (Settings -> Info & Security -> Enable Digital Keys -> OFF), the problem went away! I’m still able to use the Lexus App to unlock/lock the car, and see info about the vehicle (linking to it through cell phone or WiFI, I guess). But beware the Digital Key—it seems to be a source of serious parasitic battery drain.
Do you use the garage door opener button on the homelink rearview mirror? Did you find that this drains the battery?
Thanks for sharing your experiment. Its very valuable. I don't believe issue is in charging system as many of us using trickle charger to keep aux battery charged. I park my car in garage and a fully charged battery drains under 4 hours. This means a massive draw is happening. A fully charged 60Ah battery must take at least a week to fully discharge, hence 4 hours means something using battery badly. one reason can be week cellular signal inside garage. As I believe the car must contact Lexus remote server and weak signal means retry, retry, ... this can drain the battery very fast. Like our cellphone battery drains very fast when dealing with weak signal. when I park the car outside (where cell signal is strong), the charged battery hold itself much longer (more than 3 days that I tried so far). Two experiment can help proving this theory: a. disable remote services from app, b. install cellular signal booster inside garage. I'm going to try and share the results.
Does that make sense to you guys?
I haven't read this thread, do you lock your car in the garage?
