It is likely the NiMH rechargeable batteries. The MJ270 also takes three AA alkalines. As ttp suggested, a sure way to determine if the rechargeable batteries have reached their end of life is to try fresh alkaline cells.
The average lifespan of NiMH rechargeables is between one to three years. It largely depends on how they are charged and used over time. Fortunately, replacement batteries for the MJ270 are not expensive. Plus, you have the option of using disposable batteries, which makes the MJ270 a more versatile radio than those that require proprietary battery packs.
Here are several options for replacement rechargeable battery packs for the Motorola Talkabout MJ270.
Motorola Rechargeable Battery Upgrade Kit (53614)
Motorola Talkabout Replacement Battery (KEBT-071-B)
Empire 3.6V 1500mAh NIMH Battery (KEBT-071-B)
As stated earlier, you don’t have to use rechargeables, the alkalines should work just fine. However, rechargeable battery packs will be more economical in the long run.