A battery management system for a 24 volt battery bank at 480 watts, made from salvaged laptop LiIon cells.

To avoid spontanious ignition, and to extend battery life; a LiIon stack of cells requires a BMS (Battery Management System).

Here is a pack of 4 BMS PCBs (printed circuit boards) that I bought from evay for under $7 ea.

I plan to take 48 cells (8 banks of 6 cells) that match, and put them under the control one of the BMS PCB's. This will require that I test, each cell for capacity, and use 48 cells that have the same capacity; to make each battery bank.

Since each cell is good for 10 watts, that will give me a 480 watt bank, at 24 volfs. I will combine 50 of these banks, through schottkey diodes (for lower forward voltage drop) to the central 24 volt power bus.

The negative battery connections will be connected through a TMOS Power FET. This will allow me to turn off a single bank, without affecting the other 49 banks.

The microprocessor controlling this battery system can make this decision, turn it off; and alarm me that I have a bank down. This will allow me to remove the damaged battery bank, and rebuild it; while running on the rest.

Here are some of the salvaged good batteries:

These were bought for recycling, and the bad ones were actually recycled. These good ones I am still sorting for capacity, but I have about $10 in this batch. This will do about one and a half battery banks, in my new system.

When I get close to moving in, I will buy enough new cells to finish my initial 24,000 watt main battery. I have over 8,000 watts of good cells in house now.

This bank will run my air conditioner units, for several days with no input. The system will be charging at 30,000 watts each day, initially; and more charge will be added later, as more is built and connected.

My goal is to take this grid tied house, off grid completely; using solar and wind.

Be blessed!