I soak my beans overnight with apple cider vinegar. I am not very strict with the amount ( I eyeball it) but its approximately 1 tsp for 1lb of beans I find this addition of acidic medium helps a lot with digestion.
Next day I rinse out the beans. I dont use the soaking liquid.
Load the instant pot with the drained beans and cover it with water. You want to add about an inch more water than the beans. Since its already soaked beans, it won't need a lot of water like dry beans. Its optional but you can use any kind of flavoring. Since I make a big batch (to freeze for various uses through the month) , I just tend to add some bay leaves/ Epazote (for digestion) and some salt.
Important Note: I am using a 6QT Instant Pot and 2lbs ( 4 cups of dried beans). Since the beans are already soaked, they don't need much water while cooking as opposed to cooking unsoaked beans. If you want to use dried beans right away (without soaking) I would suggest going with only 1lb of dried beans and using 8 cups of water.
Close the lid and make sure the pressure valve is set to "Sealing".
Set the timer to 25 minutes. This time makes perfectly cooked beans, soft yet retaining shape. If you are looking for a mushier consistency (soups/mashed beans), then go for 35 minutes.Also, the cooking time will vary depending on the age of the beans and brands. Go with this time and adjust accordingly if needed.
Important Note: For unsoaked beans (1lb), it takes about 45 minutes of cooking time. Add another 10 minutes for a mushier consistency.
I let the pressure settle on its own and go for natural pressure release (around 15 minutes). I find this helps to cook the beans with better texture - no shriveling or broken pieces. At this mark, switch off and turn your vent to release pressure if any to open the lid. By this point you will find the pressure release will be less without much steam or noise (as opposed to quick release).
Press to check if completely cooked. This time gives me cooked beans with its shape retained. But if you want it really soft - bordering mushy, you can cook it for 30 minutes. Depending on the age of your beans and type/brand, the timing can vary a little bit +/- 10 minutes. Adjust accordingly.
Note:Consuming undercooked kidney beans is said to be toxic. You should be able to easily press on the beans. If not add another 10 minutes although I havent faced this issue in all the 6-7 times I have cooked them.
Shorter Cooking Time for Light Kidney Beans
These lighter shade of Kidney Beans though ( organic Food to Live brand) that I have used was cooked to perfection for 10 minutes at High Pressure with a natural release at around 10 minutes. You can adjust the cooking time anywhere from 8-10 minutes. Test your batch to adjust timings.