About to leave the car for an extended time, 1 month for sure maybe 2 and in the past every time the car sits for a month unused the 12 volt is dead. Have to either jump or charge. I just bought a 1.5 amp trickle charger and thought maybe leaving it on for the time gone would not hurt. Your thoughts? The car is a 2008 400H

 

Definitely a good idea. The reserve capacity on our 12v batteries is small and running the batteries flat multiple times will shorten the usable life of a lead acid battery.

 

I'd suggest to check if your charger is deep cycle battery compatible. As that's what you have. I have one from forgot where, $20 or so piece, that auto detects regular vs DC battery, charges it and then goes into maintenance mode, what is trickle charge. That's likely your best friend.

 

what makes you think he has a deep cycle battery?

 

It is just a wet cell battery from Auto-Zone I bought about 3 years ago.

 

Every hybrid I know, starting from 2006, has deep cycle battery. Are you sure it is OEM battery? Ones in the trunk are AGM deep cycle. For reasons obvious. I know they have battery in the engine bay on older hybrid SUVs, then it was switched to trunk location. But hybrid 12V is functionally different from conventional SUV one.

 

I suggest the smart battery charger from harbor freight about $25 It is a 4 amp max smart charger and can be configured to reg agm deep cycle battery and is a charger maintainer that you can leave on over the winter

 

Yep, 12 volt under the hood and got it at the local auto parts store 3 years ago. Looks like nothing special to me, cost about $120 bucks.

 

I don't know of any hybrids that come with a deep cycle battery from the factory. For RX400h's specifically, the 12v 'starting' battery is just a regular lead acid wet battery, non-deep cycle, and non-AGM. It is smaller than the other RX models, a 51r battery with 450-500CCA typically.

 

Hybrids do not have starting battery.
I know 200% that Camry Hybrid and Highlander Hybrid come with deep cycle AGM battery. First gen Highlander Hybrid had battery in engine bay, so it was not AGM. Then later on, it was moved into the trunk and had to be AGM for no spill considerations. All factory batteries are Panasonic, with vent tube provision and thermistor installed.
I shall be VERY surprised, if it is somehow different for Lexus, as HSD is identical on Lexus and non Lexus Toyota hybrids. Power train is also identical.
By far, I am not stating that Lexus didn't chose to do different. I am saying - Toyota is world leader in lean manufacturing. Going different battery options, for no apparent reason, as they both bear same function, pretty much, nothing but 12V storage for crucial components, what explains why it is deep cycle, would have been very un-Toyota.

 

I still don't think any of the toyota hybrids have deep cycle batteries. They are AGM when in the cabin or trunk of the vehicle. The 400h is a standard battery, with no vent tubes or thermistor.