Battery level low limit

It would be VERY helpful if we could set the lower limit on the battery. I don't feel comfortable allowing my battery to get to 7%. What if the charger isn't working when I get there at 7%? It would be nice if there was an option to select the low limit on your battery. I would never like to go below 20%. I can rearrange things and do it, but it's problematic and tedious.