These posts are very good. A fully charged battery should read 13-13.5v. Run your engine and check the charging voltage and see what you get. Should be 13.8-14.25. No more than that. Also check it with your accessories on. Turn on the lights, heater or a/c, stereo and what else you have and see if it drags it down below 13.10v. If it is below that you have a weak alternator and needs replacing. Go with a High Output one. Extra amperage is a good idea as it gives you a reserve capacity incase you need it and pervents you running at max output all the time and then shortens your alternator life. The voltage regulator will prevent over charging your battery. Gives you brighter lights too. Also a battery with a bad or weak cell can cause what you are having. Been there, done that more times than I want to remember. I would recommend the Optima battery. The yellow top is the best. Even the red tops are a great battery. They are a gell cell and can't spill even if mounted sideways. Lots of cranking power! I had them in my Suburban Diesel. I remember the days of the old generators I used to have with the external regulators. Use to put in brushes in them and back on the road again. I bet 53moneypit remembers those! If your volts are high enough when running your battery is probably going out and does not have the amperage needed to do the job. Starter drag will drain your battery when its hot and won't start. If it weak you have to wait till its cool before starting. Also I would insulate the starter from heat and wrap the exhaust near it with heat wrap used on headers. This is a great help to eliminate starters going out too soon. Or you can put in a heat shield next to the starter or both which is what I would do. You may have a drain problem where something is pulling your battery down. Check the battery fluid level as it may be too low. Put in electrolite to fill it up. Electrical stuff is the PITS! Worse than mechanical stuff sometimes. I hope this helps. Henry ... BTW, make sure you have extra heavy duty battery cables. 4/0 is a good size. Check the connection to the starter and the ground. A rusted, caroded or bad connection can drive you nuts trying to find out what in the world is going on. I wire brush them and solved many problems that way. Can run you ragged. Just some more ideas.
