Easy taming :

1) Use med brew to heal yourself while you extract blood packs with a blood extraction syringe. About 100 is fine.

2) Agro bats and run away. Wait until a lower level one gets left alone.

3) Get your best armour and clear the area. Put blood packs in your last slot and let the bat pick you. Don't struggle, just stay still.

4) After taming, use it to gather blood packs. Then tame a Higher level bat.