Flat Battery, Then Nothing

Tump · March 15, 2015

Just flown in from a 10 day USA holiday to be told by my meet and greet parking company that they couldn't start my 2006 RX 400H. They said they had tried jump starting from another car, but still no joy.I got them to give me a lift to the car and, sure enough the Battery was completely flat despite having a solar panel on the dashboard.

Put the jump leads on, but still nothing - no dash lights, no door locks, nothing at all. I know there is a good 12V across the Battery as I have a red LED on the solar panel that glows bright when I put the jump leads on.

I've located the 3 fuse boxes under the bonnet and visually checked all the fuses, but nothing seems blown. I'll be going back to the car in the next day or so with a multimeter, but can anyone advise me if there is a main Battery fuse that I've missed?

Any idea where I can find a wiring diagram for the car?

I know there are horror stories about ECU being fried, but I want to check out all the basics before calling the experts.

RXJasonRX · March 15, 2015

hello i was just wondering if you are supposed to jump start hybrid? I'm not sure maybe other people can tell us.

LexusCT200H · March 15, 2015

Matey I think that company you used has fryed your car electrics as they jump started it... Hybrids should NEVER be jump started, sorry to say but I don't think you will be getting anywhere soon.

Tump · March 15, 2015

Strange comments, as the owners manual has a detailed procedure for jump starting the 400H :

1. Check that the auxiliary Battery terminals are tight and
clean.
2. If the auxiliary Battery terminals are O.K., the auxiliary
Battery is discharged. You may try jump starting. See “(b) Jump
starting” for further instructions.

Jump starting
If the auxiliary Battery is discharged, the hybrid system
can be started by jump starting. Depending on the vehicle
condition, however the engine may not start.
Before jump starting, remove the engine compartment
cover. (See “Removing the engine compartment covers”
on page 538.)
To avoid serious injury and damage to your vehicle which
might result from an explosion of the auxiliary Battery,
acid burns, electrical burns, or damaged electronic
components, follow instructions carefully.
If you are unsure about how to follow this procedure, we
strongly recommend that you seek help from your Lexus
dealer, Roadside Assistance or Customer Service Assistance.
(See “Foreword”.)

It then goes on to describe the normal method of attaching the jump leads etc.

Barry7 · March 15, 2015

I agree with Tump, no probs with jump starting a Hybrid as long as you follow the above procedure.

When my aux Battery failed I jump started it to get it to the dealer, and asked them to check that all was OK after the event. I did use a Battery pack to do the jump start though as I know using a running vehicle can cause voltage spikes that can damage any electronic system!

I was having a look at the handbook (page 515) and found a set of fuses on the positive Aux Battery terminal, one of these is the main 180 amp fuse for all electrical components, just wondering if the car park people may have either blown this or disturbed it while trying to get the car going...........

Good luck, and let us all know how you get on please!

Sorry just realised you have got a 2006 RX400 so the handbook will be different, but the fuses should still be there.....

ColinBarber · March 16, 2015

Yes, sounds like that have blown one of the major fuses. You can get the wiring diagram from http://www.lexus-tech.eu

Tump · March 17, 2015

All sorted, but remains a bit of mystery. A quick check with a meter showed no voltage on the main input terminal of the large fuse box. Tracing the cable between the Battery and this terminal caused the Battery clamp to come away in my hand, showing the cable had parted about 1 inch from the clamp. The Battery end shows signs of melting, but when I stripped back the cable, the strands showed a clean break. :eerrrmm:

Anyway, patched out the break and the car is fine. I can't think of a reason for this - if it did melt, then there must have been excessive current into the fuse box, but no fuses are blown...

I can only conclude that in removing the red plastic cover from the Battery terminal, the car park guy must have broken an already weakened cable. Still, all's well that ends well, and a fairly simple fix.