My iPad(4thGen) is not keeping a charge but will charge fully.

My ipad charges fully but it does not keep the charge even when not in use, it drains fast. We have taken it to change the battery twice with different repair shops both focus on apple products. In both times the ipad charged and kept the charge according to the the repair persons, but when we brought it home the charge did not hold with the new batteries each time. Both times took it back got refunded. The 1st repair shop didn't know what was wrong. The 2nd repair shop said that to logic board might not be letting the battery keep the charge. Has this happen to anyone? If it is the logic board can I replace it? Will it have any effect on the ipad? What does the logic board do to the battery? How can I be sure that it is the logic board? Could it be something else? Thank you for any response.