10/2/2013 5:10 PM
on wiki info,
Short answer, no.
Not so short answer, it depends on the battery's chemistry. In all cases, you're not going to charge it completely no matter the chemistry, but you might charge it anywhere from nothing to ~75% depending on the chemistry and the 6 volt charger's top voltage(It's not 6 volts! If it's a lead charger, you might expect a top voltage of ~6.8 volts). Also, you want to make sure the charger's amperage doesn't exceed the battery's charging current's ability or you might overheat the battery and destroy it.
In a longer answer, it is possible to convert a 6 - 7 volt supply to 8-9 volts with a "boost up" converter but that's either going to require buying the device or making it yourself. Even if you we're to do that, you need to make sure the battery's chemistry's safe limits aren't exceeded. NiMH, for example, has a quick downtown in its voltage near the end of its charging, and if the charging isn't cut-off there, the battery will keep absorbing charge until it overheats and explodes.
another comment: yes if it fits into the device normally though it would take a little longer to charge
Keith