When my TV remote control stops working and I test the both batteries, I always find that one is still fully charged whilst the other is completely flat.
They are connected in series.
Why is this?
Simply because no two batteries are identical, although they may be brand new and rated the same the ratings are just an average and a small discrepancy either side of the rating (current and internal impedance) is allowed and the battery with the lowest rating will always discharge first.
(contrary to popular myth it's nothing to do with which is the first or second battery in the series)
When one goes bad they should all be changed out because the others will have developed greater internal resistance and will drain the newer batteries faster.
Thank you for your replies, HowardKennitby, Rdman41,ChuckFickens and mibn2cweus for your prompt answers. The batteries are both the same and it has happened twice since Virgin supplied me with a new remote control.
Same (type of batteries), different characteristics. I've noticed this for years. When it comes to using re-chargeable batteries, there'll be one or more that flatten quicker than the rest, despite being the same measured voltage after being re-charged on an 'intelligent' charger