A good charger, a smart charger, will sense when the battery is fully charged regardless of its capacity, but i don't know of any chargers that will do eight, i assume AA batteries, at the same time. You might have to buy two four battery chargers or alternate the pairs as they charge.
I use a Lacrosse BC-700 for all my charging needs, i have had four different capacities in there at once, it doesnt care.
