Hi all, I don't know anything about cars, and I've scoured the forums and web and no luck. What I want to do is to draw power directly from the 12V battery into the cabin. I want to run things like a thermoelectric cooler, HAM radio, laptop etc, all of which will exceed the 120 W cabin power available through the cigarette lighter outlets. I talked to the Lexus maintenance (sales rep) and they don't recommend it. I'm wondering why not, but I don't know anything about how it is designed. I know that this can be done with other vehicles, but perhaps there is a unique issue. Has anybody ever done this and if so, how did it work out? Thanks

 

So u want to run electronic item that exceed the maximum draw from the battery and u want to know how that "will work out". Really?? Why don't u just do it and let the forum know.

 

I'd look up threads on priuschat re: running a DC->AC inverter (for mains-powered equipment) off of a prius. Similar idea. It's mostly a matter of how much load can the DC->DC converter in the HV inverter assembly take. If you do anything wrong (connect, overpower, etc), you risk damaging said converter, which pretty much means a new HV inverter assembly. I'd read up on what's been done before.

 

The 12v battery of a conventional car is large enough to provide around 400 Amps for the starter.
The conventional alternator puts our 100 or more amps to charge the system while running.

The smaller 12v battery of the Lexus/Toyota Hybrid system stabilizes the voltage for the radio, lights
and wipers but doesn't start the IC engine directly. The large 288v Traction Battery behind the back
seat does that initially and repeatedly while stop and go driving. The Motor Generator that is
connected to the IC engine then produces the high voltage to recharge the Hybrid battery,
There is a High voltage to low voltage converter to keep the12v battery charged.

All this to say that you will have a more limited source of 12v amperage from the smaller battery
and its charging source. Jump starting another car is Specifically Discouraged by Lexus.

 

Brilliant post!

Got me thinking about years ago when I was trying to be a good samaritan and gave someone a jump start in a Pontiac Grand Am.
Little did I know his shorted out alternator would kill mine and send me limping to the auto part store to replace my almost new alternator.

I can't imagine the carnage it could do to a Hybrid! lol

 

Thanks for your detailed explanation. I had no idea about the 12V battery and it all makes sense now. I'm wondering now if that 12V battery can be replaced with something that can deliver more current? Then hopefully it would be a simple matter of replacing the fuse with a higher capacity. I can't download the schematics for the electrical system so I have no idea what is going on.