Hi there John and welcome
This is one of the drawbacks of long exposure, it drains the battery as its basically taking a photos constantly for the time you are doing this. It is not a fault with this camera, all cameras suffer from this. The strength of the batteries will not help.
What I suggest is get a pack of rechargeable batteries with a charge and use these instead. Take a number of these and then you can switch batteries and then recharge in order to take a number of long exposure shots. But it is just one of the disadvantages of long exposure. It really makes the camera work hard as its processing all the images and that takes the power out of the batteries.
If you would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.