text: The only way to know for sure is if they do not hold a charge for any length of time.  Rechargeable batteries can only be recharged a number of times before they will not hold a charge.  When you purchase a new battery, it should state how many times the battery may be recharged before it will no longer hold a charge.  Might be a good idea to keep track of how many times you recharge each battery to know for sure.