Group 24, 27 or 34 battery? Good brand? Marine/RV ?

[edbods]

Many websites call for group 24 but the CCA are low, 650 to 750

I have a Group 27 680 CCA battery...it starts my 383 up just fine. Although it doesn't get to 0°F here.

 

[73Polara360]

Original batteries were nowhere near the CCA of today's batteries. If yours needs that much to start, you might have a 1 weak starter 2 bad power or ground cable, loose connection or 3 something drawing down your battery. If you have an alternator with a bad diode, it can still sorta charge, but drain battery while parked.

Ultimately I just gave my old battery a really good deep charge, a quick 12a charge to wake it up and then a long 2a trickle charge over the course of a weekend and now it's firing up just fine. But I noticed that my neighbor's battery charger boost pack thingamajig did not start it, even on the booster setting, thus my impression was that it needed a fair amount of amperage beyond what traditional hardware store equipment provides.