Nickel-Iron Battery/User Reviews
Truth About Batteries
- First-hand reviews and experience - generally overwhelmingly positive - 
- Data from a user - 
- Maintenance - weekly topping off with distilled water, and electrolyte must be completely replaced every so often, which is laborious. .
- as a user of these batteries I can tell you they are NOT what we hear about day in and day out. I purchased mine from one of the best Chinese Factories (city is Mayang) . I purchased set of 20 for 400 Ah each cell for PV backup. What I learned to my surprise, they do not hold energy at their rated maximum few weeks after usage. - comment at [. Note that this is expected, and the user has incorrect expectations of NiFe - they discharge 1%/day 
- Batteries still need to be developed, they are the holy grail to renewable energy but are being oversold? 
- Fast nickel iron proven in lab - [https://news.stanford.edu/news/2012/june/ultrafast-edison-battery-062612.html
- Useful review- [I'm happy enough, spent the $$$ already, and re-rejuvenated the electrolyte this last summer, still going and I never worry about sulfation destroying them in a week. But they are inefficient thirsty bastards - 
- "I'm currently using NiFe off-grid. Just changed over from lead-acid. Lead-acid are not actually cheaper despite what people keep saying. The capital outlay is more for equivalent *quoted* Ah. The problem with lead-acid is that you can't effectively use more than 20% of the quoted capacity. But with NiFe you can use all of it. So NiFe is 5x more useable capacity straight off. Not to mention that lead-acid plates disolve pretty damn quickly. They can be dead in 1 yr with daily cycles. I've been quoted at least 15 yrs for my NiFe by the manufacturer.
- Also, if anyone needs to reduce the voltage to their inverter by 1 or 2 volts, a method I use is to add 2 or 3 forward biased diodes between the batteries and the inverter. It's not a particularly efficient method but it works. I charge my (38) batteries at 66v from either solar or genny and 3 diodes drop the voltage to 63.75v to the inverter, since my inverter cuts off at a little over 64v." 
- Electrolyte replacement - ' NiFe only goes 10 years, then you have to refresh the electrolyte That cost me a couple grand for lab grade chemicals (lab grade needed if you want a long life.)' - ? 
- Good experience with NiFe- . Video.
Specifics of Usage
- I have been driving mine to 0% SOC all winter now. its only the last few days as we come out of the worst of winter than II have been able to get multiple days of charge in and not use near 100% You don't need to be all nice like with these batteries, you have to be a little rough with them they like it that way. The problem with only ever using 20% is memory just like Ni-CAD batteries, you will diminish your capacity and one day they will let you down. Cycling them their full voltage range 9.5V to 17V will snap them out of that fairly quickly however. Just be careful not to go below 9.5V. You can see my data in my thread posted above. -from 
- Efficiency - Coulombic eff is apparently higher than lead acid, as the latter operate largely near full - 
- Must top them off - more than lead acid. Auto watering solves this.
- Electrolyte must be replaced decennially - tridecennially.
- See Minimum Viable Night Time Power.
- Say we have a minimum 1kW pack and go with the suggested 60% depth of discharge - then 600Whrs powers a pellet stove overnight. If all loads are run during the day with an oversized PV system - that appears to be a viable solution. Compressed air, if made more efficient with good air engines - can likely do a decent job to top off the needs in a lifetime design system. Biofuel or hydgrogen may need to be integrated here. Only a systems solution can work - there is no easy fix.