batteries won't charge?1 of 2 chargers works sometimes,takes hrs!

I have 2 chargers & 2 batteries for my TZ5; purchased in 8-08.

neither charger works most of the time; occasionally I can get one or the other (1 Panasonic, 1 CTA brand) to charge 1 or the other battery: also same 2 brands.

It makes no sense.

Can the chargers go bad? I have read that the batteries may eventually stop being chargeable.

I have kept chargers & batteries in clean conditions, & in cool conditions most of the time.

I also make sure they are mostly or completely discharged before recharging.

Thanks for any help!