mickdupleD

Thanks for the replies so far. I have in fact discovered that I still own some jumper cables. I'd not seen them for such a long time that I'd forgotten where I'd put them or if I'd even still got them. So if we can open the door and then bonnet on my friend's RC300h, in theory we can jump start it from the battery in my car, as per the owner's manual. If there's still enough juice in the Lexus' 12V battery to activate the car alarm when the door is opened (which I have my doubts over) then it shouldn't be going for long before we try to boost-start the car. But I'm expecting the 12V battery to be shot and need replacing - which possibly won't happen until the new year when my friend gets the go ahead to drive again after his heart op. If we were to fit a new battery ourselves at some point, is the RC300h one of those modern cars that needs a diagnostic tool to tell the car it has got a new battery fitted to it, before it will operate properly?

So... it finally happened. My friend has been away on a cruise, and buoyed by his Lexus dealer's affirmation that he could charge up his RC300h batteries by sticking the car in 'Drive' with the footbrake applied, and revving the engine, he has tried to do it, many many weeks after the last attempt, and sure enough, he cannot enter his car because the 12V battery is discharged. I managed to avoid using the phrase "I told you so." So, the main issue now is (and yes, I do know there isn't enough power in the 12V battery to power the door locks) if, as his dealer tells him, and the PDF user manual I've got tells me, opening the doors with the mechanical key sets off the car alarm, is there a way of cancelling the alarm? We need to open a door to pull the hood release to get to the 12V jump-start point in the engine bay. The PDF manual does not, as far as I can see, provide a method of cancelling a triggered alarm except by stating "Start the hybrid system." I'm not sure that'll happen with a depleted 12V battery. I've only got my smart charger to see if my friend's 12V battery can be recovered. I do not think I currently have any jumper cables to try to start his car from my car battery, which is what the manual tells you to do. (I used to have some jumper cables when I ran older, classic cars, but I've given that up and had a big clear-out when I did). Also, does the boot lid have a mechanical lock barrel for the metal key? Because the 12V battery is in the boot. My friend says the boot doesn't have a keyhole, but he didn't know he had a mechanical metal key in the fob until tonight. We met up this evening, but it was too dark to look at the car. I'm going back in a few days to try to help in daylight.

I wouldn't be too worried about tyres, since I used to take classic cars off the road over winter and once covered up in my garage they didn't move from about November to April. I mostly did used to use a humidity controlled bag though, and I did leave the parking brake off.

I'm not sure if a statement I made in my original post has been overlooked re. charging the hybrid battery with the engine running, but one of my big concerns, was over what my friend with the Lexus had been told to do by the dealer, and he did it while I was there. That is, press the footbrake, turn on the hybrid system, then rev up the petrol engine to charge the hybrid battery with the transmission in DRIVE. A couple of people in the thread provided me with a PDF file issued to U.S. dealers with regard to maintaining a car in storage, prior to delivery. The procedure described in the file seems to tell you to press the brake and start the hybrid system with the transmission in 'P'. "Make sure 'P' is selected" it says. While I was at my friend's house a few weeks ago when he tried this, I asked more about what he had been told to do. Apparently a female service advisor on the phone said "I'm not really supposed to tell you to do this." My friend said "Why not?" The reply was "If your foot slips off the brake, it could cause a lot of damage." In fact there was a moment where while the Lexus was being 'charged' in DRIVE, with the foot brake and accelerator pedals depressed, my own Volvo was nearly T-boned when my friend relaxed his pressure on the brake pedal, as I'd pulled onto his driveway across the front of his Lexus. The Lexus leapt towards my car. I very swiftly rolled it backwards out of the way after this, in case there was a repeat. There seems to be a contradiction over this method of charging the hybrid battery between what my friend was told to do by the UK dealer, and what it says in the U.S. PDF file.

My own battery charger, which I was going to loan to my friend (and may still do if I can persuade him it is a good idea) is branded Clarkes and was sold by Machine Mart, but it is indeed suitable for Absorbent Glass Mat and Enhanced Flooded Battery types. CB09-6/12.

Unfortunately my friend would be unable to leave his Lexus on trickle charge indefinitely simply because he is storing it outside, and would have to connect a charger to either a house or garage socket through an open door or window. I've never seen inside his integral garage but I'd imagine it is full of household items like most people's garages! Thanks for the confirmation info on the 'brake and throttle' technique of charging the hybrid battery. I didn't know the RC300h specifically had a CVT - very recently I've had experience with an 11 year old Peugeot automatic that uses an automated 'manual' box - it is obvious that a clutch engages and drive is taken up as soon as the footbrake is released. Apart from if you are on a gradient when the car will roll backwards until you either press the throttle pedal or hold it against rolling back on the handbrake... also I've got a lot of experience with automatic lorries that use similar gearboxes, and not torque converters. Obviously a torque converter-type transmission would not have tolerated 10-15 minutes of being held on the brake with the engine being revved, like my friend's Lexus did! The only reason I was wary of using an earthing point for a charger rather than the negative terminal of a battery is because I have read somewhere (possibly Car Mechanics magazine, possibly somewhere else) that cars with Stop-Start, like my own diesel Volvo, may experience a malfunction of that system if a battery charger is connected up to the positive and negative terminals of the battery. I do not remember the reason why being gone into in detail - I just assume electronic software, which modern cars are crammed with, can be very finicky and easily upset, so when I wanted to maintain the battery on my own car while it wasn't being used much, I chose to use a metal bolt under the bonnet as an earth, and I never had a problem. Last time I was at my friend's house, he reckoned the RC300h didn't have a stop-start function - though I imagine the petrol engine will start and stop as the software so wishes, in order to transition between electric and ICE power.

I have an elderly friend with a Lexus RC300h and he is unable to drive it for six months due to having had a heart operation. He has covered the car up on his driveway. I was concerned that the 12v battery may discharge over time, due to alarms and immobilizers. I have a 'smart' battery charger and wanted to loan it to my friend, to periodically top up the 12v battery. He allowed me to look at his car, but I knew nothing about the RC300h at the time. My own car is a Volvo with a front mounted battery, and to trickle charge that, I connect the +ve charger clamp to the +ve battery terminal, and the -ve clamp to an earth point, and it charges fine. This is what I expected to do on the Lexus, but initially I could not find the 12v battery, and my friend's Lexus handbook was very little help! I have since discovered from online sources the 12v battery is in the left side of the boot under a cover. However I want to mention what my friend did to the car, on the advice of his dealer. My friend talked to his dealer about my concerns on the telephone. His dealer advised the following - start the car, put it in 'D', press the footbrake pedal, and at the same time press the accelerator pedal, rev the engine, and this will charge the 'battery'! My friend did this while I was present because I failed to find the 12v battery! I was horrified at first because any automatic car I've known before would destroy the transmission by such a procedure! However, a screen display inside the car indicated that the engine was indeed charging a battery, and my friend kept this practice going until all the bars on the battery display on the screen had turned green. He then thanked me for my efforts and told me he would repeat this process every few weeks for the duration of his driving suspension! It later occurred to me both my friend and the dealer had mistaken my concerns about the 12v battery for the hybrid battery, and that my friend's practice of revving the engine in 'Drive' with the brakes on had recharged the hybrid battery and had not done anything for the 12v battery. I can only assume that the transmission was not destroyed because it is a robotized manual, and that keeping the brakes on must had disengaged the clutch. I have to say though, that I disliked the whole process. Returning to the 12v battery, I assume that will still be in danger of discharging, especially if the car goes nowhere for six months and keeps getting crank started to recharge the hybrid battery, which I see as not important at this stage. I've found an online PDF manual and from that, found instructions for starting a car with a discharged 12v battery by using another 12v battery and jumper cables, connecting to a dedicated positive 'jumper terminal' under the fuse box lid under the bonnet, and using an earthing point for the negative jumper cable, which appears to be a metal shield at the side of the engine in the illustrations. I am wondering if these are safe connection points for a 'smart' trickle charger like I have, and should I contact my friend again, and try to convince him that he needs to keep his 12 v battery healthy, and not run the car in 'Drive' with the brakes on!