This is an assembled and tested version of the Fechter/Goodrum battery management system (BMS) board that was developed on the Endless-Sphere forum.

We purchase the boards from TPPacks . and assemble them to make these excellent boards available to those that don't care to tackle the complex assembly and testing process.

This board is designed to manage a 72 volt nominal pack of LiFePO4 cells - 24 cells in series. It was designed for cylindrical cells such as those sold by A123 Systems, PSI, Headway, and others.

It is also an excellent match for large format LiFePO4 cells such as those sold by Thunder Sky. We're using a 21-channel version of this board to manage the 21-cell string of 60Ah Thunder Sky cells in our X-Treme XM-5000Li scooter, for example.

The board provides individual cell low voltage cut-off (LVC) protection. When any cell reaches the LVC set point, an optically-isolated signal bus activates which can be used like a brake inhibit signal or other input to a controller in order to remove the load from the battery. It can also be used (with additional components) to active a relay for vehicles with brake lights or higher current demands.

Each cell is protected during charging with a circuit that activates when the cell is nearing fully charged. This curcuit begins to shunt energy out of the full cell in order to slow or stop the charging process for that cell. This allows the other cells in the battery pack to catch up. This helps to balance the cells during charge. The shunting circuit activates at about 3.68V and works to keep cell voltage at or around 3.7V. The individual shunting circuits work with the BMS's charger control circuit to reduce charge current as cells begin to fill. Charge current is reduced to zero and the charge circuit latches off when the last bypass shunt activates. The combination of the shunts and the active charge current control allows all cells to be fully charged without being over-charged..

The BMS was designed to manage a pack charged from fixed power supplies and inexpensive sealed lead acid battery chargers, but is an excellent match for our HiPower chargers.

We recommend using 2.1V low-voltage detection for cylindrical cells and 2.7V LVC for large format cells.

There are three options for shunt values. The 250mA shunt is an excellent match for small to medium sized packs - up to 40Ah. This allows reasonable balancing time with a minimum of heat from the large resistors. The 250mA board can be completely enclosed in a battery bag or box during charging.

The 500mA shunts will increase balancing speed for medium sized packs but are a better match to 40Ah and larger cells. Boards configured for 500mA shunt resistors should be kept in the open during the final balancing stages of charging. They should be provided with forced air cooling if enclosed in a battery box.

The larger 1000mA shunt option is also available. These bypass shunts can generate considerable heat during balancing. Heat sinks and/or forced air cooling is mandatory for the shunt resistors when this option is selected.

This board is 3.35"/85mm wide by 12"/305mm long and .6"/15mm thick.

We warranty our parts choices and workmanship for 30 days from the day the board is put into service. While we're certainly happy to provide support, the main development thread on Endless Sphere is the best option.

The board will be provided as pictured - ready for you to wire the BMS to your pack and vehicle.

Please note: While the first 8 cell portion of the board should stay together, the board can be broken into sections. This allows placement of the management boards with individual battery boxes or sub-packs. Additional sections can also be added to the BMS to manage larger packs. Each section of the board is tied to the next with six small gauge wires.

These boards are hand crafted to your specifications - please allow a couple of days for assembly and testing.

Please confirm your options. If no options are selected, we'll build a board with 2.1V low-voltage detection and 250mA shunts.