A similar thing happened with my friend's stairlift down to street level, it always went down the stairs fine, but the problems were when it carried back her up, it got steadily slower over the months, especially towards the top. Eventually it dropped down to a slow crawl for most of the climb.
The main problem was the Maintenance Contract lulling her into a false sense of security. They are careful in the way they 'test' the lift so as not to detect worn out parts - because then they would have to replace them at their cost.
They would arrive and 'inspect' it periodically, she would sign the paperwork and they'd leave and they would carry on getting the annual fee. Meanwhile she'd stopped going down to street level altogether because she didn't trust the lift, even though it was 'officially in perfect working order'.
Some weeks later on I witnessed this lift stopping a few steps short from the top. By that time she'd already lost her confidence in it and she'd specially chose a time when she had someone with her (me).
Here's the technical details: When the Engineer did the last 'service', he'd measured the battery voltage (while under charge) which was the correct voltage. He operated the lift a down for a few steps and then back up again. From these 'tests' he deemed the battery as OK. Wrong.
The only real way to test the battery is to watch its terminal voltage while loaded with a person and climbing up the stairs.
Instantly the problem was revealed, and what that the maintenance contract had failed to pick up on each time. On one of the batteries, the terminal voltage was rapidly collapsing under load, and towards the top the other battery was suffering the same problem. Replacing both batteries (bought off ebay very cheap) restored the lift to perfect working order. The maintenance contract has been cancelled and the money saved spent on more useful things.
This failed battery would not of been picked up by the maintenance contract.
MArcus, February 2013
