[AusNOG] Redflow/Zcell experience?

Ross Wheeler ausnog at rossw.net
Thu Nov 24 16:55:45 EST 2016

Thanks everyone for the huge number of replies (especially offlist).
I was put in touch with Simon Hackett directly, and got all my questions 

To the many who asked for an update, I offer a brief summary.

Firstly, let me say that the Zcell (ZBM2) is a very interesting device 
which I'm sure will appeal to a lot of people.

The ability to sit at any SoC for very long periods and instantly be 
called on is very attractive, as is its ability to discharge to 0% over 
and over without any significant loss of capacity. The non-flamable, 
non-explosive characteristics are significant safety considerations.

Depending on your use and budget, it has some downsides - which ultimately 
resulted in me not continuing to persue	them for my use.

If (like me) you want it for an off-grid installation, the non-negotiable 
shutdown of the cell every (roughly) 100 hours of operation for over 2 
hours is a real problem. Sure, you can add a second unit...

The maximum charge rate of a single "battery" is only around 0.2C, and the 
maximum continuous discharge rate is around 0.3C - for my needs, both of 
these are too low. I'd need two units... and probably a 3rd to carry me 
for the period one or the other is doing its maintenance cycle.

The cycle efficiency is listed as "up to" 80%, which is close to FLA (but 
nowhere near the 95% I'm seeing with my currentl LiFePO4 bank), and 
indications are that that 80% will drop to 70% or less as the ZBM2 ages. 
When you're charging from over-panneled PV, that probably doesn't matter 
much - except in poor weather when you have to charge from genset - then 
that represents an extra 20% fuel burn, which adds up!

At around $1.3/WH, that's a hard sell against LiFePO4 at around $0.4/WH, 
especially since you can't self-install, so all the extras add 
significantly more.

If I had an unlimited budget, or cost simply wasn't a consideration, 
there's no doubt I'd have a bunch of 'em. If you want to have the coolest 
kit on the block, go for it! If you're constrained by real-world 
economics, probably best to hold off a bit - Simon reckons they'll come 
down "over time". Perhaps they'll be what I replace my LiFePO4 bank with 
in 10 years or so :)


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