Uses for an Old Car Battery

[Stephen Sherman]

I have had good luck with Johnson Control batteries. However every 
company can and does make cheap as well as better and good batteries. 
These are design decisions with costs associated with them. Personally I 
try for a large capacity short lifespan battery and replace it more often.

If the old one is really starting to go, not much reason to keep it 
around. You could  hack together a backup system around it, but if it is 
near end of life, it won't run things for long. And without all your 
other components running (eg AC) it may not be that useful.  Also, how 
will you charge it. Charging a LA battery gives off hydrogen gas and 
acidic fumes.  Not much fun for inside living spaces.