BMS-Heart of the Battery

Let’s get to know about the BMS in battery packs of an Electric vehicle:

Its known as a Battery management system, BMS-Heart of the Battery the name itself tells us the function. It manages all the properties of a Battery pack like charging, discharging, cell balancing, SOC, SOH all these data are acquired with the help of a BMS.

The need for BMS in a battery pack:

To know about the need for BMS in a Battery pack we should get to know about the design of batteries.

Let’s take the design of a lithium-ion Battery pack of an Okinawa praise (72v,37.5 ah):

To design the lithium-ion pack of this specification we require the following components:

1. 7v 2500 mah lithium-ion cells – 300 pieces
2. Lithium-ion cell holders 2*2 — 300 pieces
3. Pure Nickel strips  — as required
4. Heat shrink wraps and packing materials– as required
5. Connection Wires — as required
6. 72v min 40A lithium-ion BMS

The cells are assembled in holders in series and parallel connections and using nickel strips and the spot-welding machine they are welded together then wires are taken from each series connection and connected to the BMS and then they are packed together with a heat shrink wrap and tested for the output voltage.

Now let’s get to the use of BMS, we are using 300 cells in this pack where all are welded together. The problem arises when we charge this pack. When we charge this pack without a BMS the voltage to all cells will not be evenly distributed. So, to ensure even distribution of voltage to all the cells BMS is used. If the battery pack is used without BMS then the life of the Battery is affected drastically.

When a BMS is used we could determine the SOC (State of Charge), SOH (State of health) of the Battery pack and many other properties of the Battery pack could be easily determined.

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