Battery keeps going dead. Especially if car not driven for day or two. KIA ran checks of electrical system but found nothing. Am on sixth battery. Newest one only 3 weeks old and went dead over weekend.

Remove negative cable from battery, connect a test light to negative terminal, opposite end off light to negative battery post. ( let sit for 3 to 5 minutes). Then start pulling fuses, when the light goes out that's your bad circuit. God-Bless! Its worth a try.

The charging system is not working. Common suspects include:
Loose wires or connections
Blown fusible links
Bad alternator

Also, if the charging system is working, and the battery lives as long as you drive it regularly, you may have a phantom power draw that is draining your battery while it is parked. You may have some accessory plugged in, such as a gps or a cell phone charger or alarm that is causing the current draw. If not, some part of your car may be drawing current when it shouldn't.

A proper electrical diagnosis is needed to reveal the source of your symptom. In the meantime, you can rig a cheap trickle charger to the car while it is not being driven while you find someone who can diagnose electrical systems. This may or may not end up being a costly repair, depending on what the tech finds during the diagnosis.

sound like alternator has bad diode allowing battery discharge

sounds like a bad ground to your solinoid its not the starter try tapping the solinoid

Sounds like a battery to me. The cold doesnt drain the battery it just makes it more difficult to produce enough energy to crank the car. If the battery is weak already, the cold just makes it worse. Replace it and move on!

alternator diodes is most common cause

circuits will drain batteries not fuses you will need to have someone check the draw on each circuit in the vehicle. start with any recent electrical installations. keep keys out of the vehicle then remove negative battery terminal and then use 12 volt light bulbin between the battery and cable. bright light means power draw. remove fuses one at a time till the light goes out. the circuit that makes the light go out is bad.

buy cheap tester check alt for output 14-16 volts, check for blown fuses

Have the altenator checked.

Does the fuel pump stay running at all like when you shut off the engine?