MP2759A with 4S stack - protected or non-protected cells?

Battery Management
1

Hi there,

We have designed a 4S battery pack with power path control based on the MP2759A reference design. Our development prototypes used four 5Ah protected cells in series for the 4S stack, to provide an extra level of safety during development, but we intended to use non-protected cells in the final product

Our OEM’s battery supplier says there is a danger that one of the cells in the 4S stack could start to fail and could enter a state where it should not be charged. As we are only monitoring the voltage and current of the whole 4S stack through the MP2759A (rather than each individual cell) we would continue to charge the damaged cell and could cause a catastrophic failure. They claim that we would need to use individually protected cells in the 4S stack to prevent this from happening.

Is the supplier’s concern justified, or can the MP2759A identify the potential breakdown of a cell before safety is compromised? Any advice would be welcome.

1 Like
2

That’s an interesting question. Hey MPS engineers, do you have additional info?

In my opinion:
Yes the Li ion cells can be nasty and cause such problems. Individually protected cells are the best solution (also pricey).
However, if you look at other products such as e-scooters, hoverboards, e-bikes etc.
They somehow solved this issue with either rigorous testing or stack monitoring plus fuse wire contacts.
Did you manage to solve this design issue?