We have a RX 330, 2003 model, We do not use the car very often, after it set's for a week I have to charge the battery to get it started.
What normal battery load does this model have to drain a battery when the unit is not in use ?

 

When battery is strong and no accessory is left running and every bulb is turned off, the battery should last 3-4 weeks.

Now if your charging system is weak, or you dont drive enough [where the start and use (discharge) is more than the aggregate charge] then it can go bad in a day or two.

Have the battery tested and the charging system tested [alternator bench test is very conclusive].
Then invest in battery tender [about $5 from harbor freight with coupon]. Plug this once a week (or more frequently).

You may like to search on Parasitic draw if you are after some real numbers.

Salim