Jump starting RX400h

[david-now]

I have recently replaced my 12v Battery ( see other thread )

While googling my problem I read somewhere that the RX400h shoudn't be used as a donor for jump start.

Is this correct and what is the general advce regarding use of jump start both as donor and receiver of jump start.

I don't nee to do either immediately but it would be good to know for future reference.

[Spock66]

Jump starting from a Hybrid is a definite no-no as the electrical system is not designed to provide the required current output (typically a short duration of several hundred amps to crank an engine), the 12V Battery just boots the electronics with the power to crank the engine coming from the Hybrid Battery.

Jump starting from another vehicle should be ok, probably don't even need the engine running as you just need sufficient power to boot up the electronics.

The third scenario would be a flat Hybrid Battery (eg vehicle left standing for a long duration), I assume there is a dealer procedure for this.

[ColinBarber]

4 hours ago, david-now said:

While googling my problem I read somewhere that the RX400h shoudn't be used as a donor for jump start.

Is this correct and what is the general advce regarding use of jump start both as donor and receiver of jump start.

Yes it is correct, you shouldn't use your vehicle to jump start another - certainly not unless you disconnect the 12 v Battery from the car first and just jumped from your 12 v Battery. You run the risk of pulling current from the DC/DC converter and blowing the 120 A fuse if you jump from the vehicle. The only exception would be jumping another Toyota/Lexus hybrid, but even then I'd avoid doing it.

Receiving a jump start is fine - you will only draw around 10 A from the donor vehicle (assuming your lights are turned off) so even the smallest of vehicles could be a donor.

You cannot bump start a hybrid.

[david-now]

Thanks for the helpful replies

[Greisingel]

Maybe keep a Battery jump starter in the car. This might control exactly the input amperage. From the

Jump Starting - Lexus RX400h Towing And Road Service Manual

JUMP-STARTING:

The Lexus RX400h has one Battery which is located under the hood. It is positioned on

the right (passenger's) side of the engine compartment behind the right front headlamp

assembly

The RX400h uses the high voltage system to start the gasoline engine. If the 12 volt

Battery is discharged, the high voltage system does not function so there may be the need

to jump-start these vehicles.

The following jump-starting procedures should be followed when rendering assistance to

a Lexus RX400h:

• Never use jump-starting equipment that can exceed normal 12-volt charging

system voltage.

• Ensure that all electrical accessories and the ignition switch are turned OFF

before connecting jumper cables or a jumper box to the discharged vehicle.

• If using jumper cables, make connections in the following order:

1. Connect the positive (+) jumper cable to the positive Battery terminal of the

discharged vehicle and to the positive (+) Battery terminal of the donor vehicle

or jumper box.

2. Connect the negative (-) jumper cable to the negative Battery terminal of the

donor vehicle. (Skip this step if using a jumper box.)

3. Connect the negative (-) cable to a good ground on the engine of the

discharged vehicle. NOTE: You may have to remove the decorative engine

cover to access a good connection location.

Allow the discharged Battery to charge for a few minutes before attempting start the

vehicle. Since the high voltage system actually starts the gasoline engine, there may not

be any "cranking" that takes place. The computers on this vehicle decide whether or not

the gasoline engine needs to run to charge the high voltage Battery which in turn charges

the 12 volt Battery through a connection in the system's inverter/converter assembly. The

RX400h usually moves at low speeds and in reverse under electrical power only.