You cannot directly access the battery of the DS1270. Unlike the RTC devices that may have a ‘low battery indicator bit’, with the NVSRAM products there is no such indicator. So the only way to really test if the battery is still good is to remove VCC and then re-apply and see if the data is still there. This is not ideal, but there is no other option since there are no direct connections to the battery. Be sure to copy over the memory contents before performing the VCC removal test.