Transfer light bar & siren to 2023 Lexus RH350h. Where to get 12-volts DC in engine compartment

During a routine bloodelivery, the 2021 RX350 emergencyehicle stopped behind traffic stopped on an interstate highway.
Young woman hit the back of the RX350. (My insurance agent is exceedingly pleased that I stopped far enough behind vehicle ahead to not be forced into it!)

Collision shop estimates 2 weeks in their facility.

Need to transfer light bar and siren to the 2023 RX350h - already authorized emergencyehicle.
Where to connect power to the light bar/siren unit? (Normally I connect directly to the battery in thengine compartment with in-line circuit breakers.)
The 2023 RX350h battery is in the very back.

Thank you.

There should be a “jump point” somewhere in the engine compartment. Basically a bolt with battery cables attached that can be used to jump start the car from underhood. Look in your owner’s manual, the location should be there.


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Yep, my olds had the battery under the seat but a post was provided in the engine compartment. Red=positive, black=negative o4 anything metal.

There are usually several types of power connections available

  • 12 volts all the time
  • 12 volts when key is in “on”
  • 12 volts when key is in “acc”
  • 12 volts when engine is running

Suggest the first step is to give some thought as to which of those works best for your light bar application. Next step is to determine the maximum current needs for the light bar. Next step is to find a feed point. Usually it would spade-connector compatible & near or in a fuse box. Final step is to make sure that feed point’s circuit is capable of supplying the current needs.

Suggest to avoid hacking it in. At the very least make sure the wiring is properly sized & fused. The fuse should be located very close to the power’s feed point.

Thank you, ALL.

Plan totally changed now that wife has the SUV home.
Below the cargo floor, the siren power wires run forward just a few feet from the right rear battery
to the siren control unit justo the right of the spare tire.

The light bar cable squeezes through the rear right door top rubber seal to the siren unit.
The passenger-side firewall has a large rubber grommet through which the wires for the siren speakers behind the grill and front LED lights will pass.

Thank you.

Everything I do is soundly hacked!
Wires sized well over current draw.

The circuit breakers are attached directly to the battery post bolts.

The switch box, located athe dash, is energized from the cigarette lighter wire, so when thengine is off, nothing can operate. It uses very little power, sending signals to the siren control unit.

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If ever needing a jump, I have cables to attach directly to the rear battery.
But I have jumped others’ vehicles.

I was just showing you where you could get 12 volts from under the hood.


I would not jump cars from a hybrid. The 12v battery is small, and lots of electronics involved.

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This battery is unexpectedly normal size - to starthengine?
I could charge another vehicle’s battery directly from it and then disconnecthe other vehicle so nothing comes back.

The 12v battery doesn’t start the engine, the hybrid battery does.

Thank you. Was wondering abouthat.
I’d use the high voltage battery to the motor/generator.