Need some advice gurus .I have 2 x 40lt Engels and they run off a second battery charged by a redarc 50 amp charger,but I run out of power 11.8 volts in the morning.Is it purely a storage capacity problem so the solution is to run 2 x Delco slow discharge batteries in series or go too lithium and what size and brand if I went to doen that track? The charger soon gets then back up above 12.5 volts thats not a drama.