is there a big diffrence with 27 series and 31 battries

The biggest difference (other than cost) would be weight. Could be upto 20 pounds depending on brand.Your MK (as well as the mg digitals) is pretty energey efficient. As long as you dont plan on using the 2 – 3 days without recharging the 27s will be fine, just make sure you recharge after every use.I would suggest going to sealed/maintence free batteries (AGM or voyagers). This is to prevent damage when you forget to check the battery levelsJimYour Signature …

I bought the Sears Platinum AGM 31s. They are big, heavy and $$$$$, but zero probs in 2 years. I run them in my P4 with 82#MG. Probably overkill, but they rock. The 29s would probably do fine.