Hi Dave,
Thanks for your quick reply - and clarification of the slight difference between our issues.
I've had my 03-08 RX400h (which was actually registered on an 09 Plate), for 4 years, and luckily have not had ay 12v battery discharge issues, which if |I understand your post is your problem i.e. bat going flat every few week.
I just wanted to get a reliable replacement battery w/o paying over £100 for the 'yellow one Optima?)', as I know mine will have to be replaced soon.
It came with the car so:
a) Seems to work w/o issue, and
b) In my Rx400h (at least) must have lasted at least 4 years.
I did know about the issue of Rx400h 12 bats going flat (some users said in a week), if the car was not used.
So for holiday's etc I decided to get a small solar bat charger - some examples here:
Amazon.co.uk : Solar Panel Battery Charger
It just plugs into the RX's OBD(?) port. This is located in the car (drivers side corner half way down).
I wonder doing this would at least give you a temp solution to the problem?
However, I must stress that lockdown has significantly reduced my mileage / frequency of using my 400h and it never goes flat.
As such, I don't think your battery should be going flat if you don't use ur Rx it much - could there me another issue causing this?
For example I believe that some dashcams can cause this.
As an aside, what's the £57 battery like?
Dunno if I'll just get the same spec as the Bosch that's in as that seems to have lasted w/o any issues.
thanks
Jon