Battery Low SD Card unmounting and no service when low battery.

A long time ago, I began to notice that i would randomly lose service at around 2 - 3% battery. I didn't think much of it, just thought that there wasn't enough juice to power the radio or something. Some time after, the sd card started unmounting when low battery, still just thought it was not enough energy to power the sd reader. Recently, it's been happening at higher and higher battery percentages (it did this with 30% last week). When the sd card stops working the storage section in settings causes a force quit, and using the mobile network thing to manually connect gives an error. I'm pretty this has something to do with hardware, as my rom or kernel has no effect. Rebooting doesn't fix the problem (phone usually dies before theres time to scan sd or look for service), but recharging or switching the battery fixes it. I'm curious to see if there is a way to fix the problem without swapping batteries as sometimes I might not have one and recharging usually takes a long time.

Things I have tried:
- rebooting
- typing mount -a in terminal (returns a file or folder fstab doesn't exist error)

Device: Samsung Galaxy SII i9100
Rom: Jellybam 4.1.0 (Android 4.1.2)
Kernel: Siyah 5.0.1