I've found the cells were around 2.4V each, so still ok, if a little low. ANyway, I've recharged them to 4.2v each using an external charger, but the Macbook still doesn't see the battery, so the protection circuit must be stopping the battery from functioning. Is there a way this can be reset? I've tested the cells using a dummy load and they are fine, so I just need the protection circuit to play ball and I should have a working battery again. Has anyone done this and if so, how?