2001 hyundai sonata , battery drain after changing coil pack

I wouldn't think so , but you never know ! Do you know what a parastic drain on a automotive electric system is ? How To Perform Parasitic Draw Test EricTheCarGuy Suggest you test and not guess !

A mechanic would test the battery for a dead cell, then each circuit on the car for a voltage drain.

check the injectors with a noid light you may find a bad one. if not check the compression.

Use a high pressure AIR jet so that the water is blown off and also use a hot air dryer on the coil.
It is possible that the wet coil has reduced the firing intensity and made the engine rough with a change of timing.

2001 Hyundai Sonata 2.5 liter SOHC V-6

There are some possibilities which you will have to check in this case:--
1) First of all check the power and voltage to the battery.with meter it will show exact 12 volt if the battery is charged.if the voltage is less get the battery charged at local auto repair shop.if the battery is internally drained and not getting charged then its time to replace the battery.
2) When you crank the car do you see spark coming at the spark plug? if no then its time to check the spark plugs and coil pack.if the spark plugs are not worn out and looks new then its time to check coil pack.the spark plugs gets power to spark from coil pack.
3) The other thing to check in this case is the starter solenoid of the car.if the battery is charged and you start the car then it gives power to the starter to start the car.but if starter is faulty or not connected properly then car will not start.
4) The other thing to check in this case is fuel in the car.if there is fuel in the car then check the blockages in the fuel pump if the fuel pump looks proper then check the fuel filter above the fuel pump.
5) If all the above possibilities mentioned above checked out OK/perfect then its a electrical issue and the wiring's in the car needs to be checked.the car gets power from the battery to get started.so the wires from battery needs to be checked one by one.
Thanks. keep updated for any more query.you can rate this solution and show your appreciation.

They are directly below the coil packs (10mm bolts).

The other 2 are under the intake plenum

I had the same problem and it turned out to be the Ignition coil. I brought a new ignition coil and replaced it which is very simple to do as they lie just under the engine cover. Obviously you should disconnect the negative terminal on the battery first! Disconnect the coil leads either side and replace.. it's that simple! Now if the probelm continues ( there are two coils) replace the one you didn't change with the one you did. When I reconnected the battery negative terminal all of the error lights were out!! Result.

I think that the coil packs has installed wrong because you said that the problem started when you replaced them... so i think you should re-install.