If I use a 6V charger to charge my 5V battery bank, will it affect the battery life?
So the battery manufacturer answer is always use the correct charger for your battery pack. The home garage answer is it depends. Assuming that both batteries are the same chemistry and the battery charger is made for that chemistry you are likely ok. When you say 6V battery there is a range there just like charging a car battery. It is called 12V but likely 14.6v.
What makes me worry about your question is that 6V is often a lead acid and a 5V is more commonly a Lithium battery. The charge circuits for these batteries are very different and over-charging a lithium battery can be catastrophic(to the battery anyways).
Thank you for your answer.
But I am using 6V charger (adapter which converts 220V AC input to 6V DC output) and not the 6V lead acid battery to charge the 5V Lithium battery bank.
Since this is a Lithium Battery Pack I would strongly advise against using anything other that the recommended charger.
That being said some lithium battery packs do have charge circuits built into them to monitor and protect from over charging. If this is the case you may be able to find the information on that circuit and 6V may be within the acceptable charge tolerance.