Checking Battery Capacity of Used Valence U27-XP

[Cloudsbegone]

I bought 2 used Valence U27-XP batteries rated at 138Ah 1766 Wh. Being used I wanted to check their capacity. Using Will’s chart for Battle Born batteries I don’t want to take my charge below 20%. So voltage charged 14.4 to 12.9 is 80%. Which 80% of 1766 Wh is 1412 Wh X 2 = 2824 Wh.
Calculating 20% lose in conversion from DC to AC, 2824 Wh - 20% = 2259 Wh or 2.25 KWh. I plugged in a Kill A Watt meter and a load and let inverter run until the voltage dropped to 12.9 v on the inverter display. The Kill A Watt meter showed 2.2 KWh. So are my calculations correct and my used Valence batteries are still close to full capacity, or did I miss calculate?

 

[Craig]

Your numbers seem correct. But I think 20 loss in conversion. Seems high I would hope for less than 10%

 

[Cloudsbegone]

Your numbers seem correct. But I think 20 loss in conversion. Seems high I would hope for less than 10%

Your probably right, I have a Xantrex Pro Watts 2000 Inverter. I’m going to install a shut and then I’ll be able to be more accurate. But mainly wanted to see if I was correct on my calculations. Thank you very much for your help.

 

[Goshishi]

Wondering what others are getting with either kill-a-watt AC numbers or DC meter numbers. Mine seem to have about 80ish% charge. Mine showed 25 cycles and 510177 WH.