MacBook Pro crashes and reboots fully when battery gets critically low

If I allow my ~2011 MacBook battery to get close to 0% (say 2 or 3%), and then put it to sleep by closing the cover, it appears to be unable to "suspend to disk" (i.e. write the current state, running apps, open files, etc. to disk).

As a result, when I reconnect the system to a power source and try to resume, the system appears to try to restore the previous state first, but then does a full reboot and reopens the apps that were previously running, behaving as if there had been a full system crash.

Previously, the system would successfully recover from a "hibernate" state when I allowed the battery to get very low. I can't state what exactly has changed to the system, since I rarely allow this situation to occur. However, it is annoying when I cannot avoid allowing the battery to run down.

Is there a command that I can use to force it to suspend to disk when the battery gets low--say 5%?

I'm running Yosemite v10.10.5. Also, I replaced the OEM HDD, which crashed some time back, with an SSD. I'm wondering if this could be a factor.