Crankshaft Position Sensor problems of the 2015 Kia Motor Optima

I have two kia, one 2013kia soul, and kia Optima 2015, first the kia soul won't start, looks like no battery at all, dealer say it was a bad battery, but the problem start again, just this time loose all power when running, they towing back to the dealer this time, they say this time was crank piston sensor, no cost at this time, this happen on 08/01/2016, now the kia Optima, same, I drive all morning, the day was hot, and I stop at the storefor water, don't take more then 5min. When I get back to my car, cars unlock the door, but have no power at all, I check the battery with a fluke multimeter, reads 12 volts when I disconnect the negative post, and 6 volts when I connected back to the battery, then my friend stop by, and jumpstart my car, same thing, I disconnect the negative post and I take chassis ground for the jumpstart, same thing, then I took of the battery from a chevy 2002 silverado, my friends truck, and I connected direct to my car, same thing, I ended to call road side assistance for Kia Motor, to take it to the kia dealer, the towing truck driver say, they pickup a lot of kia's cars for the same reason, this time happen on 04/05/2017, I did claim to Kia Motor, they say was the battery, and I just think they want sale a 300 and something battery, and a have to buy a new battery every two years, with the new kia and Hyundai recalls I think they should recall this two cars!!.