replaced nicd batteries in cordless razor with nimh, but capacity doesn't increase

i have a ~8 year-old norelco cordless razor whose batteries recently failed (won't hold a charge). the original batteries were 600mah nicd--i replaced them with 2000mah nimh. this is actually my second replacement--the first time, i replace them with nicd batteries.

i have two questions:

first, is it okay to replace the the nicd with the nimh? i bought the battery from http://www.batteryspace.com, and on this page "how to choose a battery" (under "how to choose the correct razor battery"), they state that it's okay as long as the voltage is the same.

but then when i opened up the razor and unsoldered the nicd battery, there was a sticker saying "only use nicd batteries".

and then when i did some searching on the web, i found the following page from a competing battery seller, stating that they can't be substituted for one another unless the device supports it: http://www.batteryweb.com/faqbw.cfm#q44

who's right?

my second question is about capacity. with the nicd batteries, the razor would show about 16 shaves when fully charged. since the nimh batteries were over 3 times the capacity, i thought i would have 40+ shaves on a single charge. to my surprise, the razor only showed 16 shaves available after a full charge, same as before.

is this related to the warning to use only nicd batteries? or is there perhaps some circuitry limiting it to a 600mah charge, since it's only expecting a 600mah capacity battery?

Re: replaced nicd batteries in cordless razor with nimh, but capacity doesn't increase

It will show 16 shaves, but you'll have more than that, in other words the shave meter will drop slower. The charging circuit probably is a trickle charge and not smart cut off, which nimh needs to live a long time. I'd charge them the standard charge time, take it out, and test the voltage. If it's full, then that's ok. But it may take longer since they are higher capacity. Do not leave it on the charger all night, as I doubt it's smart and will shut off when they are full, it's probably a trickle charge and once full, nimh can be damaged by more charging.