Father-in-law had a stair lift, he switched it off, the batteries (7 Ah VRLA) went flat half way up stairs, it would not power up or down and no instructions on how to release the brake. So fitted two new batteries with the idea of charging the other two latter, however they went missing, only to be found three months latter on his death. So tried to charge with a Lidi battery charger, the only charger designed to charge small batteries which I have, however on switch on it hits 15 volt and switches off again. So cheated, put one battery at a time in parallel with at 75 Ah battery, and one battery of the pair seemed to recover after some 3 days. Tested both batteries by trying to power a cool box, one seems to work, other dropped to 6 volt in seconds. So now both VRLA batteries in parallel and the charger was alternating between 0.1 amp and 0.8 amp at 14.4 volt it drops to 0.1 amp and at 12.4 volt it returns to 0.8 amp you can see the bump around 1 pm where batteries were tested on the cool box, by 20:20 the charge rate started to rise, by 23:20 full 0.8 amp which continued for 3 hours then started to tail off again. Now 12:30 sitting at 13 volt. I have not seen this sudden change before, one hour will not take any charge next hour taking full charge, however in the past I have not powered the battery charger through an energy meter to be able to see it. It has take 5 days to get the battery to recover, not tried to measure Ah capacity I would guess it is reduced, but seems 4 days nothing happened then all happened in 4 hours. Interested to hear comments.