I am planning on purchasing a 400W HQST 40A MPPT system with possibly a 2500 watt pure sine inverter. I just purchased 4 - 3.2v 176AH lithium cells to run my travel trailer. I was curious I am replacing my two super Start 27DCMJ Deep Cycle Marine batteries with that one 176AH Lithium 4 cell battery, if I needed more capacity could I connect the lithium battery in series with the flood acid deep cycle marine battery for more capacity? or do I have to connect lithium to lithium? Will, by the way, I think your youtube/ website is really very help full, you explain things in a manner that a less than normal/ less educated person like myself can follow. thank you for all you do.