9 Month Off-grid Update on $1300 used battery pack

H2SO4_guy

After living with the used Panasonic AGM VRLA batteries for 9 months, I have to say they are wonderful. I got 56 of the 2 volt cells rated at 1040 AH @ the 8 hour rate for $1300 not including trade in of lead by weight. These things weigh 145 pounds each and I did have help moving them to the final rack, which is a standard pallet rack custom made to be narrow with rails that will hold 7700 pounds per shelf. They hold 12 cells per row, so in an 8 foot span I have all of them plus a dozen 2 volt 600 AH VRLA AGM’s, but that’s another story. (Those work great too, just couldn’t get enough of them)

During the day when I am not there I put between 4k – 5k of panels on them with no load whatsoever. That duty goes to 2 strings of flooded 8 D batteries for about 330 AH @ 8 hour rate which are hooked up to about 4k of panels. If I am home and using power I can put about 9k all on the large batteries. I usually run a 24 year old deep freeze (About 2 KWH per day unless it’s summer and then it’s more), 1 dorm size fridge (About 1.5 KWH per day unless it’s summer), and sometimes a lab grade frig (Hey it was $80) with digital readout. It uses about 2 KWH per day unless it’s summer. It will keep veggies longer because the temp can be regulated very closely.

I heated most of the winter with electric, but I did use about $30 worth of propane which also heats the water. Only when the batteries were getting low did I heat with the propane as well and it wasn’t more than 10 times probably. So I lived pretty cheap this last winter. Later, I intend to use the Whiz Bang Jr’s to preheat water for the on demand propane fired water heater and then the propane usage will probably go down even more. Might as well use otherwise wasted power.

I ran AC all summer too on these. When there was extra power I got the living quarters to 62 degrees when it was 96 degrees and humid.

The batteries are set up as 2 strings of 1040 AH per string at 48 volts for a total of 2048 AH. I run them in parallel. There have not been any issues, but they are up to 5 amps different per string sometimes. Mostly they are in float. There are 6 cells in a 12 volt pack kept charged as spares for when any cells fail there will be spares charged and ready to go that are of the same age. When I got them I chose cells that were within .001 of a volt of each other. I should keep at least one string going for quite awhile with all of the potential spares.

I decided to spend way more on panels and go cheap on batteries, cause you know, better batteries are right around the corner, right?

So would I do it again? You bet. I have had great luck with these, and not so great luck with other used batteries. The way I am set up I can move power around if a battery subsystem fails and keep loads going for quite awhile. Mostly I have had great luck with AGM VRLA batteries. They charge quickly, very efficiently, no mess, don’t leak, and are very easy to care for. I never run them down to below about 60% charge, but usually less.

Thanks for everyone’s great help on this forum and NAWS where I purchased much BOS. They have been great to work with.