One of the most confusing items from Motorola is the T7100 radio. This is because there are two models with the same name. Both of them will work with AA bateries, but if you need recharable batteries, you have to be very careful. There are two batteries, KEBT-047 (left) and KEBT-046 (right). Both are 4.8 V Nickel-metal Hydride. Both batteries will fit the radio BUT when it comes time to charge them, you will find out that they require different chargers.
Fortunately there is a hint: The back panel of the radio (some people call this "back door" or "battery door") is different. If your radio uses the KEBT-047 battery, there is 2 silver metal contacts in the middle of the back panel (pictured on the left). If the back panel is just plain plastic (as pictured on the right), use KEBT-046 (also known as NNTN8971 or NNTN4190 or 53871)
If you get the wrong charger with the wrong batteries for your radio, you still have the option of charging the battery separately from the radio. But good luck getting the battery out of the radio, as this is tends to be difficult.