Redflow NEWS & EVENTS, page-1763

That’s not what round trip efficiency means.

How much energy did you put in? That’s value A. How much did you get back out? That’s value B. Tally those numbers over a long period of time, not just one cycle, and that will give you the round trip efficiency (B/A).

If you only ever discharge to 50%, the amount of energy you put in will also be reduced. It reduces the amount of energy that you can store, but not the efficiency of the storage.

And by the way: the footprint of my LiFePO4 is significantly less than the ZBM. The lithium fits into a standard rack cabinet. 45 RU will hold about 50 kWh of modules; I would need to stack the ZBMs three high and use significantly more floor space to get that much capacity. Even if I had just two or three ZBMs, the floor space required would be more than a single rack cabinet.

Which, let’s be fair, isn’t always a concern. If you have ample space available, low energy density is manageable. But considering that the ZBM cost me $10k, versus about $3k for a ~5 kWh lithium module, the economics are struggling for a justification. (I’m not sure what the ZBM goes for now, and it’s a moot point for a home user anyway now; these are just illustrative examples.)