40% charge of your batteries should be closer to 11.8 volts
I would return the PD 9270 and get a PD 4655 WFCO upgrade kit. Works great and we use a lot of power when dry camping. ( you know-roughing it!)
Usually takes about 3 hours to get over 90%. I added a little amp meter when I put in the 4655 to see how much power was being out putted.
DROKŪ Micro Voltmeter Current Meter Digital Voltmeter Gauge 100V /50A DC Current Meter LED Display Auto/Car/Eletronic Voltage Meter with Transformer (50A) https://www.amazon.com/dp/B00YBX1M18..._PP9oxb1T3YBSE
2014 Evo 2850 "Woodstock"
2011 Toyota Tundra "Clifford"
2014 Stealth Evo 2850- "Woodstock"
2011 Toyota Tundra Rock Crawler TRD 5.7- "Clifford"
2013 Honda Accord Coupe V6 w/Track Pack- "Julia"
Just glad to get away