Marc - great stuff! Thanks for posting, we seemed to be struggling a bit with this one before you chimed in. Much appreciated.
In general, for my money and the minimal added weight, I'm happy to carry 2 6v 7AH SLAs vs. an Ecocharge EC-90.
2 x 6v/7AH SLAs + XLRs = $45 and 6.2 lbs
1 x 12v/6v/7AH EC-90 = $190 and 5.5 lbs
Granted, the EC-90 gives you the option of 12v and/or 6v - a great value to some folks - but that's not a feature I need.
At any rate, it's good to know why John's times were much longer so everyone can make their own decisions about buying or making their own, etc. An informed decision is always a better decision.