I have a 2013 Toyota Venza and I unhooked the battery to clean the cables full of corrosion and re connected the battery. When I started it up it shut off immediately. After about 10-15 seconds I started it again and was back to “normal” in assuming it was the ecu resetting? Does this sound normal? Now a week later (today) my battery died to like completely no power to anything. It has been dead for about 4 hours now because I haven’t had time to go get a battery and such. How should I go about this? With it being completely dead for 4-5 hours?
No, that’s not normal. You need to determine why you have intermittency in your electrical circuits. Possibilities include a broken/intermittent battery post (internally; seen this), a fusible link blown, a relay gone flakey, and maybe even a key cylinder gone bad. If it’s a keyless ignition, you might even have a bad START button.
As always with power loss, check all your fuses before making any assumptions.
Unfortunately, with the exception of an internal battery problem or a bad fusible link, I know of no way to find the cause of this type of intermittent problem. A battery problem can often be found by simply wiggling the cables while the engine is operating (WEAR LEATHER GOLVES and eye protection!!!) or, since you currently have no power, wiggling the cables with the headlight switch ON and seeing if the lights blink. A fusible link may be evidenced by a bubbling of its insulation… if it’s the old fashioned type.
I wish I had a better suggestion, but until you find out why you have no power you’re stuck, and these are the first things that come to my mind.
How many miles on the car? If the throttle body is pretty dirty, the ECU compensates for that and stores it in the memory. When you disconnect the battery, the ECU resets to factory. The solution is to give it a bit of gas and drive around until the ECU adjust, OR clean the throttle body 
Now, I am not sure why your battery is dead though, the corrosion seems out of proportion to a 2013 model. Someone has to check the charging system and the battery connections.
Start and stall after connecting the battery is normal. The powertrain control module performs an electronic throttle body calibration the first time the ignition is turned on, this causes the engine to stall. To avoid this after connecting the battery switch the ignition on for a few seconds (push the start button twice without pushing the brake), to allow the PCM to calibrate the throttle body.
If your positive battery post was corroded the post is probably leaking due to a crack in the case, only a matter of time before it completely failed.
I agree with Nevada
Totally normal . . . for a Toyota with electronic throttle body
But now that the car is idling normally again, this will likely be the last we hear of it
Charge the battery w/a battery charger overnight at the 2 amp rate. 12 hours at that rate should give you 24 amp-hours charge, even if you start with a completely discharged battery, that should be enough of a re-charge to crank the engine.
I prefer to remove the battery from the vehicle when I do a re-charge like that. Do the recharge on the garage floor. Less chance of damaging the electronics in the car by hooking a connection to the wrong spot or the charger tipping over inside the engine compartment.
After that you’ll have to address why the battery discharged. Suggest to start with the above. With any luck the problem of why the battery went dead won’t come back.
The old battery is probably still under warranty, so check that out. My guess (a blind shot in the dark) is that the cables are not cleanly connected to the battery yet. Try again.
From the title I think he intends to buy and install a new battery. Recharging a leaking failed battery is a waste of time. I replaced 5 batteries last week, they fail.