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Do you just clamp the negative cable of the charger to negative, spare jumper cable? Alligator clip to alligator clip?
And, for you and others that keep their jump box and cables under the cargo floor… what do you do when the battery is dead and you’re locked out?
You should keep the jump starter/cables where you can get to it from the passenger compartment. Getting the hatch open is much more involved than getting the front driver's door open and requires the driver's door open anyway. From there, you can easily get the other passenger doors open from inside.
FYI - I am a little leery about permanently connecting a lithium battery to my 12 volt like the Ionic Emergency Starter.
Keep in mind that the Ionic Emergency Start uses a Lithium iron phosphate (LiFePo4) battery which is much safer than traditional LiPo batteries. LiFePo4 batteries are actually becoming a popular performance crowd replacement for lead-acid since it is lighter for the same energy storage. Some even have a reserve feature for a built-in jump-start.
Keep in mind that the Ionic Emergency Start uses a Lithium iron phosphate (LiFePo4) battery which is much safer than traditional LiPo batteries. LiFePo4 batteries are actually becoming a popular performance crowd replacement for lead-acid since it is lighter for the same energy storage. Some even have a reserve feature for a built-in jump-start.
Thanks
I was aware of the LiFePo4 make up of the Ionic but I wasn't aware of the battery replacement with built-in jump-start. Very cool
My car is RX350h therefore might be different but I had a similar experience a while back. It ended up with multiple system malfunctions after jumpstart. Car was with the dealer for 3 days because they could not figure out how to get rid of the alarms. Apparently they had to call Lexus support directly for assistance and ended up resetting the computer (I assumed they mean the ECU).
It happened again to my 350h. Was out driving for a few hours with various stops here and there. Got home for a quick 15 minute pit stop, did not leave head lights on or use ACC mode, on the way back out was able to unlock the doors but not get into READY mode. I checked my battery monitor and noticed the sharp voltage drop below 12V. I quickly boosted it back online but this is unacceptable. After starting it I had a 1.5 hour highway drive and noticed it never went into charge mode for the entire drive. I will take it in again for another battery check and at least add another incident to their records in hope that Lexus fixes what I think is a simple software issue. (monitor 12V battery levels and charge it automatically with traction battery as required). I'm tempted to buy the IONIC emergency starter, does anyone know if I can run it along side my existing BT battery monitor or is it redundant ?
Last edited by YYZRX350; May 15, 2025 at 07:10 AM.
I have the Ionic Emergency Start and a Bluetooth battery monitor working together. The Emergency Start app only monitors the Emergency Start so is not redundant to a battery monitor.
On one cold day back in December I was gearing up for my morning dive. Because it was pitch black outside I thought it would be a good idea to leave the lights on (come/leave home stays on until the car is locked). The lights were on for about 40 minutes. I then locked the car (RX500h). Hazards flashed, buzzer beeped. I came back an hour later and popped the hatch open. The car beeped again and hazards flashed. And this is where the problems began. I tried opening the side door but to no avail (gotta thank Lexus for those idiotic electronic release handles). Pressing the unlock button on the fob only resulted in flashing lights but no buzzing. Doors were still locked. I had to climb over the back seats to reach the rear door manual release handle. Once the doors were open I tried starting up the car. It beeped again but the dash didn't even light up. Dead battery symptoms... Luckily another diver was parked nearby and had jumper cables. We jumped the battery and the car started right up.
Two weeks went by with zero issues.
Having feared being left alone with a dead battery in the middle of nowhere, I decided that my wife's husband deserves another Christmas gift in a form of a booster.
Sure enough, couple of days ago I had the same issue. No lights were running before locking the car but same symptoms came up again. The hatch opened no problem but then the car died on me again. The booster was put to its intended use and voila the car was brought back to life.
I blame the battery but wondering if this happened to anyone else. The car is less than a year old and Lexus keeps scoring top three across all known reliability charts. My next servicing is coming up soon so I will definitely have them look into it but my guess is that they will offer a battery replacement at my own expense.
Kinda ironic that a hybrid car is immobilized because of a dead battery.
Does anyone have any pictures of the low voltage warning on the instrument cluster? Vehicle is at the dealership and service and service tech is asking for pictures. I was running late to work and didn't capture the warning.
I recently had the 12 volt battery replaced in my 2024 RX350h. The service rep told me that it is my fault because I don't drive enough. When I pointed out that this is not proper customer care, she told me that what the service department tells her. I then pointed out that I have had multiple RXs over the years including an RX400H, all driven with same mileage per year with no battery problems.
I have yet to take the car on an overnight road trip but I am wondering if this is not the right vehicle to take on trips if I have to worry about the battery going dead and whoever jumps it doesn't know what they are doing?
So is this a design defect in the battery/charging system or did Lexus just have a bad batch of batteries? And does this mean if I do start taking it on road trips, I should really carry a jump pack.
Joe
The service rep told me that it is my fault because I don't drive enough.
Ask the dealer guy why the engine isn't programmed to run longer if that is required to charge the 12V battery.
In the current cool (50F.) ambient temps, our engine shuts OFF and the car runs in EV mode after the initial 3/4 of a mile!
Keep the Energy Usage display on on the center screen. Ours shows that the traction battery is 1/4 to 3/4 fully charged.
60% of our trips are 4 miles, each way.
I have a 2023 RX350h and finally had my battery replaced under warranty by the dealership. The service advisor told me it's very common, and very indirectly told me it's my fault the battery was having these problems. Apparently the culprit was infrequent driving and mostly very short trips (a mile or two). They kept the car for a few days to monitor the battery and then got approval from Lexus to replace it under warranty.
This is the replacement battery --
The new battery is holding a charge much better than the original (which had gone totally dead five times). I'm now using a bluetooth battery monitor to watch the voltage. After a 180 mile trip that charged the battery 12.05V to about 12.85V, the battery slowly fell to 11.96V 42 days later. A 14 mile trip then charged it to about 12.5V, and after 9 days has dropped to about 12.05V. Once I charged the battery in Ready mode for about 20 minutes which took the voltage from 12.15V to 12.65V, and it was back to 12.13V just four days later. The original battery was going dead after 5-10 days even after a full charge.
My experience with the original battery prompted me to buy a Schumacher SL1611 jump starter. I also know from my experience with the original battery that I shouldn't open the rear hatch when the battery is low as the hatch will open but the battery will be drained enough from that to prevent the car from starting. I've also uninstalled the app so the car doesn't periodically try to phone home with status updates (as suggested by the service advisor).
Last edited by jeffgo; May 31, 2025 at 12:00 PM.
Reason: Clarity
Ask the dealer guy why the engine isn't programmed to run longer if that is required to charge the 12V battery.
The engine doesn't need to be running to charge the 12V battery. The 12V battery is charged by the high voltage traction battery system. Assuming the traction battery has enough of a charge, you can charge the 12V battery by starting the car as though you were going to drive it, but just leave it in Park (referred to elsewhere as "Ready mode"). In my experience the ICE only runs if the traction battery charge gets too low when doing this. Doing this for 20-30 minutes periodically is a documented way to keep the 12V battery charged. Of course, you need a 12V battery that hasn't been deeply discharged many, many times and doesn't go dead after less than a week after being fully charged.
X2 on getting a battery that hasn't been repeatedly discharged. That is a killer of batteries.
Our dealer cautioned us to keep the car in READY mode (NOT ACCessory) when 'learning' the car's functions.
+++++++++++
...And just as a point of reference, our 3/4 mile trip only entails 5 minutes of running...60 seconds of which is slow-backing out of our narrow garage, to prevent the BRAKE! system indicator from coming on.
We often don't start the RX for 4 days in summer, when the weather is nice enough to drive our three sports cars.
