So far, my battery bank has proven to be the weakest link in my off grid solar setup. I would have preferred to invest a portion of my budget in wind power, but my home is located just below a ridge line which would have meant I would need a huge and expensive tower to rise above it. That said, and with experience now as my reference, I would suggest that anyone interested in living off the grid, without an ample supply of wind, and depending largely on solar, should give much consideration to the investment they make in a dependable, and long lasting battery bank.
In hindsight, I made two mistakes in the beginning. The first was to start out with a string that was too small. The second was to add new batteries to that string after a year or two of service on the older batteries. I was advised against it, but was thinking more with my wallet than listening to the experience of others. I can’t complain too much as I’ve gotten about eight years use out of them, but the real rub isn’t that they haven’t lasted long enough, it’s that throughout the years of use they were never dependable enough to store energy for more than a day, and on cloudy days I’d always end up having to run the generator more than I should have to augment the limited strength of the batteries. The real problem? Propane has gotten expensive as well as wear and tear on the generator which can’t be overlooked.
The string of batteries I’ve been referring to consists of 16 – 6v, 220 ahr Trojan T-105 Batteries, wired for 24 volts and commonly used in golf carts. They found their way into the off grid arena some years ago and are a popular option among PV system installers. They’ve been good batteries, don’t get me wrong, I just shouldn’t have combined the old string of eight with the new eight. Also, if I had the money at the time, as well as the knowledge, I would have chosen stronger batteries.
My wish list includes either a new string of Rolls Surrette 4KS-21PS
or the HuP Solar-One Batteries.