If the battery shows less voltage or won't take a charge, it's time to get out the hydrometer. This device checks the proportions of sulfuric acid and water in the electrolyte, which is a precise indication of the level of charge.
Common causes of cat hair loss, or alopecia, can range from allergic reactions to hormone imbalances to an infestation of some pest or another. Although the different causes can be difficult to pinpoint, most are fairly easy to address and remedy.
One possibility is contact dermatitis -- an allergic reaction from something your cat has rubbed against. If the hair loss is limited to the lower legs, for example, it could be a reaction to a new rug. You may have to do some detective work to figure out the cause, but once you remove it, the hair should grow back. Your vet may prescribe a hydrocortisone spray to stop the cat from scratching. Alopecia can also signal a more serious problem, such as a hormone imbalance. Cats with either hypo- or hyperthyroidism (an under- or over-active thyroid) may experience patchy hair loss, and an excess of the hormone cortisol can cause thinning hair in a symmetrical pattern on your cat's trunk. These conditions must be diagnosed with a blood test.