Yes you can do it with grub. But you must install grub at the sata disk first.
Do this in the order of sequence:
1. Install Grub at the sata (sda1 or sda2) I have not tried setting up grub outside any system, but just try it. You might be able to trick Grub by creating an empty folder at the root of partition "/boot", that is all that Grub Setup will seek. If it doesn't work then you must have at least a minimal installation of Ubuntu at sata (anywhere parition) to hold Grub.
If you cannot boot at the current IDE disk where your Ubuntu is located you can boot from the Ubuntu LiveCD, while running liveCd you can "setup grub" at any partition you like, then "grub-install /dev/sda" this will write grub to the mbr of SATA. You have to specify Stage 2 for grub to have enough space for the records just in case.
2. When grub is installed in both, IDE and SATA, you can boot any of it and still point to your current IDE-Ubuntu system, just edit the device.map at /boot/grub/device.map at the SATA drive. To shorten a long story, I have no time to explain further, just read this well written tutorial
for grub in order to get enough background before you start doing the instructions above.
Another solution is:
If you have not enough time to tinker about this temporary vicissitude, you'd better go out buy a battery which is very cheap and the problem is gone. But I'd prefer though for you to read that tutorial still for contingency in the future.
Hope this helps.