my charging is maxing at 3.5amps when i select 5amps for my 4200 nimh 6 cell.
doing it with both my nimh packs(both are 18 months old) and getting really hot when "peaked"

is this a battery problem?

What charger are you using?

v6ac, same as the b6 with acdc part

chargeing at high amps will make the pack get pretty hot try chargeing at 4-4.2 amps when the batteries peak should be pretty warm and ready to go.

but do you think its time for new ones after 18 months?

It's not always about the age of the battery, it's more about its performance. Batteries can last a very long time if really well maintained. If your packs still have good power, good run times and don't leak, you should keep them.

Also, you should charge you packs at 3 amps. That is better for the batterie's life.

They should get to 120-125F when they peak, if they're too hot to hold, then they're getting too hot. You can try reducing your peak sensitivity, but I'm guessing you'd have to be running NiMh mode in manual.

well if it's still holding a charge then it should be ok and when charging at a higher amp rate you trying to push the pack for more punch. but most likely lose longeivity of the battery. and most if not all macthed pack say to charge at 5-6 amps

If you've been overheating them, you'll see shorter run times and less punch. If they are just getting old, the runtime should still be pretty good.

Personally I think you'd get a better charge in manual mode.