But for personal off-grid system charge and discharge times aren't really concerns- fast charging would only be beneficial if the amount of PV panels was grossl

But for personal off-grid system charge and discharge times aren't really concerns- fast charging would only be beneficial if the amount of PV panels was grossly oversized. And fast discharging would only mean that it would be that much easier to drain the system and be out of power. Smaller batteries would be nice, but his enclosure was already sized for lead acid, so there isn't much advantage (this system was put online in 2008). And while lead-acid may not be as long-lived, neither he nor I was able to find any batteries currently on sale that offered similar warranty without being prohibitively expensive. He ended up purchasing 8x Trojan SIND-06-920 6V [1] batteries for 735 each ($5880). Add ~$250 for fuel expenses to pick up the batteries (cheaper than trucking) and 300 on new bus-bars (new interconnects would have been needed anyway) for a total of ~6500. There are advantages to lithium, but neither he nor I was able to find any alternatives that were (1) avaliable now (2) at least somewhat price competitive. I see that Trojan now offers Li-ion batteries, but these were introduced after he made his purchase [2]. No clue on their pricing, but they don't look all that much more attractive. I challenge you to find any lithium batteries avaliable that match the performance of this bank for 2x the cost or less. They may last 10x longer, but I couldn't find any real-world usage reports to back that up. Off-grid industrial PbA is a very different beast to car batteries. His last system lasted 10 years, and likely would have lasted longer had his charge-controller not failed and cooked the batteries through overcharging (never went into trickle, just provided full panel power for 1 month before the problem was noticed). [1] https://www.trojanbattery.com/product/sind_06_920/ https://www.trojanbattery.com/product/sind_06_920/ [2] https://www.trojanbattery.com/trillium/ https://www.trojanbattery.com/trillium/