The car is killing batteries.

Orion · November 26, 2023

I have a 2008 RX400h, backin March of this year I bought a new Battery (The standard one). The on already in was about 5 years old.

The batter would fail (totally) very so often, so I had one of the new jump start batteries you can get.

From time to time, it would fail. Eventually this got so bad that I replaced it this month. Still under warranty of course, o problems.

The new one failed within a week. Totally dead. This time I got the AA to come and check it over. Batter shows him as needing replacement. Voltage in is about 14v so that is ok. Switch everything off to check for a drain. Nothing more than 1 amp.

So, another new Battery, this time a Bosch. All ok for a few days, then totally dead again. Use my jump start Battery, starts no problem. Drive it around, restarts no trouble.

Overnight, dead.

I've looked for something being ON when it shouldn't be. Nothing so far as I can tell.

So, either I am being VERY unlucky with batteries, or something is wrong. Can anyone steer me in the right direction?

The main Battery shows no troubles at all.

ColinBarber · November 26, 2023

5 minutes ago, Orion said:

Nothing more than 1 amp.

Drain once the vehicle has gone to sleep should be 0.05 A.

This should help, although you need to push in the door switches rather than the latches in the video and you would need to disable the interior sensor on the alarm otherwise it will go off with the doors open:

Russell Wheeler · November 26, 2023

I have the same problem, as the car is only used a few times a month. In the summer I have a solar panel that keeps it topped up. In winter I have a Battery disconnect, so pop the bonnet and lock the car - then disconnect the Battery. It's a pain but has been like that since I inherited the car. My Dad used it a few times weekly so the problem didn't occur for him.

ColinBarber · November 26, 2023

22 minutes ago, Russell Wheeler said:

I have the same problem, as the car is only used a few times a month. In the summer I have a solar panel that keeps it topped up. In winter I have a battery disconnect, so pop the bonnet and lock the car - then disconnect the battery. It's a pain but has been like that since I inherited the car. My Dad used it a few times weekly so the problem didn't occur for him.

If you aren't using the vehicle at least a couple of times a week then yes, you will run into issues. But I think the OPs specific problem is worse than that if it is losing charge overnight.

Greisingel · November 27, 2023

I use a .5A trickler overnight nearly daily after experiencing drain. It seems to keep everything stable. Parasitic drain somewhere. Did scrub up my ground points. And wire brushed my Battery points and clasps.

Went through all my fuses to check condition. AOK

Made sure nothing was plugged into lighter sockets over night (I don't really know why)

Romasato · December 1, 2023

Does OP have iPod connected to the car via integrated cable?

I used to have the discharge problem, disconnected the iPod Nano and also changed to Varta Battery as the old one was ruined due to discharging. I suspect iPod Nano is draining it.

Now the car can stand for weeks without any problems of starting.

Jimbrodie1 · December 12, 2023

It happens on newer vehicles too.

My 2022 450 RX went flat after about 10 months ownership from new.

I had left it 5 days when we went for a long weekend away and came back to it being flat and a car which wouldn’t start.

Same thing AA came out and jump started it. I ran it for a couple of hours and it seemed OK. Next morning, flat again. Called the AA out again and again they jump started it. He also tested it and told me it required replacement. I then called my dealer and booked it in for testing. They charged it and left it over night tested it the following morning and assured me it was good to go.

A couple of days later it was flat again this time after only 2 days of not being driven. AA out again to jump it. Back to the dealership and Battery replaced under warranty.

I have also now bought a trickle charger and if I’m not going to drive it for a few days it goes on charge. Not what you expect to have to do with a £60k car !