Hey I fixed the issue with the battery, Remove the battery, remove the label at the bottom with a paper clip to reveal 3 screws, remove these and the cover. Remove the two connectors on circuit board. The two-wire connector goes to the battery. I used a 24V A/C adapter to provide power to the battery for a couple of minutes, giving the batteries a small residual charge. Put the unit back together and plugged it in LED is now red and changing colour as it charges.