Best Battery
 

Got the LS3 Miata.....jesus, what a ride. One issue. Seems to drain the battery when starting. The little Miata battery doesn't seem up to the task. What is the best solution to this issue? TIA.

Have you done a voltage drop test and are seeing the battery drop too low, or is the car just cranking slowly?

I have a large Interstate battery that barely fits, b/c I thought it was the issue - turns out I had a cheap starter that would slow crank when heat-soaked. New starter seems to have improved the issue.

I've used Optima Batteries in almost everything I build and have great luck with them. Lots of cranking power and with the Yellow top it's deep cycle. with any battery, The secret to a long life and great startup voltage is to hard wire in a smart charger and keep it plugged in during downtimes. Whatever ECM you run, it needs full 12V. Meter your alternator output ( if computer doesn't show it) and like PJ says, tests for voltage drop on your loads. With the battery in the back it can be an issue. I'm upgrading to 2ga. wire from my batt to the starter as well.

Hope this helps!
KT