Can you use a 600 amp hour battery instead of a 400 amp hour battery in a portable phone?

The "amp-hour" number is the length of time the battery is expected to last

between charges, in normal use. It's a way of describing the battery's capacity.

The device in which it's installed won't know the difference. The real difference

is that you won't have to recharge the battery as often.

Make sure that the voltage of both batteries is the same. If they're not, then

you can't do it. If they are, then go right ahead.

And by the way, batteries with 400 Amp-hour or 600 Amp-hour capacities are

car batteries or truck batteries. They're bigger than a breadbox and weigh a

ton. The batteries for portable phones may be 400 or 600 mAh ... milliamp-hours.

1 Amp-hour is 1,000 milliamp-hours.