I have purchased 24 reconditioned, AGM, 90A 12v truck batteries at a local, used battery store in Albuquerque, for $50 (now $65) each, and feel I have figured put a way to get the benefits of maintenance-free, durability, economy, and finally, Replaceability, as these batteries can be sourced and replaced virtually anywhere, as oppossed to the expensive, "solar" batteries.
My system is 48 V. I have 20, "175 watt" panels, and often/always shut 15 of them down because the huge battery bank is often charged up within a few hours of sunlight with only 400-500 watts of true input, and the excess energy is a tax on my system. I turn the other 15 on when I am running larger power tools (1800watt) for more than 30 minutes, so as not to use the battery life span for these tasks.