DEL92

Kent2174,

I've had a similar experience in a parking lot structure with cars on both sides. In my experience the road service truck came with long enough cables to reach the terminal under the hood. Be sure they understand the negative cable goes in a different spot. While you are waiting for the service vehicle to arrive, pull out the Owner's manual so you can show the driver the picture where to land the negative jumper cables
As I understand, the jump pads purpose is to power up the 12 volt dc path. The engine will be started using the traction battery, but you first have to get the 12 volt path powered up - this will power up the dash so the start button functions. I expect the ECM (Engine Control Module and all other electronics are powered from the 12 volt dc path.

Also, I have read in many previous post on this topic where owners have installed a harness to the battery and routed it out of the tire/battery allowing them to connect an external battery maintainer to charge a low battery or to power up the 12 volt dc path in the case of a bead battery.

TO all others, if I have understated or overstated anything above, please provide more details for Kent2174.

Regards, DEL

wrinkle

Yes, this is a potential challenge, especially given that AAA in US that Lexus roadside subcontracts, reportedly also has a policy of not extracting/towing any car from inside a garage, reported by deaded above. This situation got me thinking, and I ordered an adapter that can connect my 12 V jump starter battery directly to my permanently attached 6 feet cable running from the car's 12V battery to my rear passenger door/seat. I use that cable normally for the external battery charger through the rear window occasionally, but with this adapter cable and the jump starter, I can directly provide 12 V supply to the car's dead 12 V battery terminals with just opening my rear passenger door of my dead car (without having to connect far apart points under the hood to the jump starter). Since the startup current is relatively low for the Hybrids (no cranking amps), a high amperage cable shouldn't be necessary for powering on the car by this method, by my thinking.

WellsB

The vehicle pulls 20-30 Amps in ACC mode with nothing on such as seat heaters, headlights, etc. I don't know if it's more when "starting," but I imagine there would be a greater momentary current as all the systems are powered up.

Keep in mind that a dead battery will accept quite a few amps, initially. I've seen the vehicle charging system send as much as 56 amps to the battery immediately after starting. I imagine a dead battery would accept considerably more for a short time.

While those amp draws are low compared to a traditional starter, I would be concerned if one tried to pass them through a charging pigtail.

wrinkle

I must never forget to thank Lexus to making us even having to think about these things to cope, as we have the privilege of owning their exquisite 12 V battery subsystem "design", based on their "sterling reputation for reliability"

That noted, my 6 foot cable has a 10 Amp fuse built-in, which will blow if the start-up current is too high, and prevent any mishap. If that happens, it will not solve the "drag out a dead $76K car out of tight garage-space in the dead of winter" challenge, but it will at least not create a bigger challenge like my car+house burning down. It also turns out that there are 10AWG cables with 30 Amp fuses available, to likely cover the jump-starting need from rear seat. Hm.

In the Northern Hemisphere, things are quiet now with regards to this problem - as the deficient-charged battery voltages are relatively higher in summer weather conditions. Once winter arrives in the Northern hemisphere, all bets will be off as far as this problem is concerned.

One other point: Even if the rear-door charging cable is not used to immediately start the car, it can be used to gradually charge the dead 12 V battery - so that the battery can be charged with the voltage displayed on the charger, after having charged the dead 12 V battery for a few hours. This assumes we don't have a completely dead and unchargeable 12 V battery.

kent2174

Please allow me to restate the most important/simple part of the question for my understanding:
Assuming I can open the tail gate, is it safe to jump start from actual battery terminals in the tail gate area?

WellsB

Yes, it's safe. There is a way to open the hatch from inside. It's detailed in your owner's manual.

warlock

Please humor me with the answers to the following question.
I start the car in EV, leave it in park and exit the car leaving the key in the car which is in a locked garage. The driver's window is open. The heads-up screen asks if I want to turn off after 1 hour. I press "yes".
I assume the car is charging the 12V battery.
Is that correct?
Situation 2, same as above but I take the key. There is no offer to turn off the car. I leave it running in park. The green READY is off.
Is the car charging the 12V? Are there any other changes I should note?
What a mess. Had surgery without permission from Lexus followed by 2 failures to launch in 4 days.

StefanoS

As long as your vehicle is in READY mode, in Park, the vehicle will be charging the 12v battery from the LiIon battery pack. I do this every few days for 30 to 60 minutes in both of my PHEV's and it works well. The key here is that the READY light must be on for this to occur. You can take the fob with you.

wrinkle

I think this scenario should work towards charging the 12 V battery (especially if the "READY" green symbol is ON), based on reports/data by others in the thread - others, who have directly tested this with hard data on the charging voltage of the 12 V battery. You can also do the same thing by using the phone app to "remote start", which would charge the 12 V battery for 15 minutes, if 1 hour of charging is not necessary.

This is more questionable, because the green READY is OFF, which happens when the car is ACC mode, and that actually discharges the 12 V battery rather than charge it. Again, I havent done the necessary chore of actually collecting data and confirming, so looking for others with hard data to confirm this is a likely problem.

warlock

Thanks to StefanoS and wrinkle for their prompt answers. This is something practical to work with.