I bought 2 new 25 AH 48V batteries off ebay and converted them to one 200 AH 12V The price seem good $660 for both inc shipping. The tops are just screwed on and had a empty space for 4 more cell. Each cell is rated at 80 watts and there are 32. I cut the extra off both batteries and glued them together to make one big battery. reconnected the cells for 12V adding a 50 amp fuse for each cell. The BMS is external to the battery. the finished size is about 12X10X7.