My girlfriend is moving in, so electrical loads will increase. Getting an apartment sized heat pump dryer, small mini-split heat pump for backup space heating, small microwave, etc. So I need to double my array and battery bank, and am facing a number of decisions that I suspect many others, in one form or another, may be also be facing. So I’d very much like to hear people’s thoughts. I’m totally open to suggestions, advice, and accusations of ignorance or stupidity. After all, that’s why I’m posting! Here’s my existing system: *Two parallel strings of 3, 295 watt panels in series, for a 1.79 kW array with a Vmp of 135 volts *Midnite Classic 200 *Four Rolls S530 6 volt batteries in a single, 24 volt string for 10kWh of storage (3kWh usable based on a 30% dod) *24vdc loads: overhead light fixtures (led bulbs), ceiling fan, pressure pump, SunDanzer ‘fridge. *110 vac loads powered by a 2kw Samlex inverter: Staber clothes washer, notebook computers, medium sized flat screen TV, 40 watt receiver, C-pap machine, and a few lamps (led bulbs). *Meanwell 24 volt battery charger and Honda 2000eu generator for the relatively few days per year when the battery bank has dropped below 70% soc. *I consume an average of 2kWh per day. When it’s sunny the battery bank reaches float by noon. But it’s often...not super sunny. As you can see, I’m running a number of critical load on the 24vdc side of the system. I do like the fact that those loads aren’t dependent on the inverter (a.k.a. “a fancy gizmo that can fail”). The few times the battery bank has dropped below what the inverter needs to operate, those critical loads have kept right on cranking. And leaving aside the “All a.c. vs hybrid” debate, I have an investment in 24vdc loads, so even if I decided that all a.c. is the best approach, it’s too late to change. I know it makes total sense to double my battery capacity by moving to a single, series, 48 volt string. This would allow me to double the array (just repeating the current panel configuration and putting the two arrays in parallel) and keep my single Classic 200. One downside right off the bat is that I’d be retiring my current bank of Rolls betteries, which are only 2.5 years old and in pretty good shape. One approach is pretty straightforward, but expensive: *Buy eight new 6 volt batteries to make a 48 volt bank *Upgrade to a 48vdc inverter / charger (tempted by the AimsPower’s features and low price, but thinking it may be too good to be true; that is, that at such a low price it can’t possibly approach the reliability of, e.g., a Magnum or a Schneider). *Buy a dc-dc buck converter to power the 24vdc loads. But here’s the thing…there are other options. I could... *Simply replicate the system I have—array, charge controller, and battery bank—and use a great big A-B switch to run the house off one bank or the other. Result—no need to buy a new inverter and dc-dc buck converter, and I only have to buy 4 new 6 volt batteries instead of 8. Yes, I’d have to buy another Classic 200 charge controller...but you have to admit, there’s something about two completely redundant systems that adds a pretty significant degree of fault-tolerance. *Buy 4 new 12 volt, 200ah batteries for a 48 volt string of the same kWh capacity of my 400ah 24 volt string, plus a 48 volt inverter/charger. I’d then make use of the 24vdc string by charging it from the 48vdc bank with an MPPT charge controller. In this case I’d run a.c. loads from the 48 volt string, and dc loads from the 24 volt string. *Just go ahead an mix the old and new batteries into a 48 volt series string, and accept that the new ones won’t last as they would if the whole string was new. So many options...that’s what makes it challenging. But on the positive side, it’s and interesting problem. Ultimately I’ll probably end up going with a new 48 volt bank, 48 volt inverter/charger, and a dc-dc converter for the 24 volt loads. But I suspect people may well have ideas I’ve not yet hit on. So...bring ‘em on. And thank you.