I have one 230 A/h battery sitting on the floor of the powershed, and the original plan was to go ahead and connect it to my one remaining sorta-good 186 A/h battery. That battery is deteriorating so quickly I’m glad I got cold feet.
The inverter routinely shuts itself off overnight now. Day before yesterday was overcast, and I lost power at 10 PM with only one CFL on. This morning dawned overcast, and I’ve only now got enough power to run the ‘pooter. The situation gets a little worse every day. So not yoking a new battery to an old one turned out to be the right decision, because that old one is failing fast under its unreasonable load.
One thing everybody I’ve consulted agrees on is this: If you connect a big battery to a little one, pretty soon you have two little ones. And I’ve heard over and over as if it’s holy script, though I’m not sure why it should be true, if you connect a new battery to an old one it’ll last no longer than the old one.
Going back to the big town about fifty miles away a week from Thursday, and should have $160 in hand by then. I’m also bringing the two old batteries to avoid any more core charges. I just have to limp along on what I have for another week and a half, and then all should be well again.
Internal resistance of the crummier battery louses up the whole mess; the good one works harder and fails faster until its performance reaches rough parity with the bad one.
Not sure if your inverter has a low voltage setting but if it does, set it to whatever the 50% battery discharge voltage is. Probably around 12.4v or so. If you go below that a few times you might as well start saving up for 2 more batteries. When I have charge issues I just turn the inverter off till the sun comes back out the net morning.