I found this info on the Eco Charge web site.:
EC-90 BATTERY SPECIFICATIONS
• 12V, 7.2A/h
• Dimensions: 6" x 2.75" x 5"
• Weight: 5.5 lbs.
I thihk Eddie once told me you could buy "replacements" from Grainger. We may have a Grainger account at work, I will check if you think that helps.