Cell Monitor Pack Design Considerations

What is the max Ah that a LongMon (Cell Monitor) can handle and what is the recommended?

We recommend 200-300Ah, it is subjective as others have used them on 800-1000Ah.

Typically we adopt the logic that if a battery is totally out of balance (all full with one empty or vice versa) the system should be be able to automatically equalise within ~1 week. Hence if a LongMon can sustain 5W or ~1.2A bypass and there are 168 hr in a week this results in approx 200Ah.

Reality is if you go larger and it will take longer.

Remember that this is worst case and most of the time its negligible balancing on a daily based when the pack have been balanced. This requirement is only required when recovering from a problem or on initial commission if people do not pre-balance. Our customers typically don't pre-balance hence why we have suggested sizing.

At 1000Ah will take 5 weeks, for some this is acceptable but we do not think it is ideal.

If you have large capacity on many cells, consider multiple strings, this has other pros and cons.

Example of all cells full with 2 still need to be balanced up to the same SOC%. 

Battery system in bypass

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