Energy Systems

Nickel Iron Batteries

A Solar System Secret

As my wife Emma and I are finally piecing together a homestead of our own, we are doing our best to find the most ecological means of putting a home together. Unfortunately, building codes in North Carolina have required us to use a lot of materials we would not have otherwise chosen. Nevertheless, to get through the process legally, we have begrudgingly adhered to certain systemic situations that don’t sit right. We repurpose where we can, but sometimes the code has left little, to no wiggle room.

One place we have managed to stick to our guns, at least so far, has been solar power. More or less, the lone company serving North Carolina’s power need is Duke Energy, an enterprise that seems endlessly involved in troublesome litigation. Since we’ve been here, they’ve been in court, in particular, over coal ash pits that have contaminated local water sources. They are refusing to clean them up. In short, we don’t want to be involved with them.  We do want to use solar power, and we’ve thus far managed to reject tying into the grid, which would put us in collaboration.

Having originally planned to settle in Central America, where grid-tied solar power isn’t the status quo as it is here, we’d always assumed we’d be having solar batteries, i.e. a true off-grid system. We had no idea that it was unusual for solar power to work that way in the US, but in fact, most people, it would seem, don’t even have “battery back-up” for their panels. People who use solar panels feed the grid and essentially get a discount of normal, grid-supplied electricity when the sun isn’t shining. In fact, for my brother in Utah, it’s actually illegal to back up his own house with his solar array because he’s connected to the grid.

For us, this notion is problematic because we’d essentially still be supporting a company that is steeped in environmentally unsavoury activity business we take pains to avoid. As we’ve researched and plotted, contacted solar power providers, sought information with regards to code-compliant solar power, we’ve noticed a curiously raised eyebrows at the thought of having a battery bank. The reaction became even more skeptical when we brought up nickel-iron batteries.

No joke, the specialist—our second contact in a large local company, sent specially to deal with our situation—at a solar contractor actually recommended that we go elsewhere because he’d never heard of nickel-iron batteries. I wasn’t all that surprised: The solar power providers we’ve vetted here in NC seem to be somewhat cookie-cutter operations, and there are literally only two providers of nickel-iron batteries that I’ve found in the entirety of the United States.

To be honest, I’d not heard of them until watching a Geoff Lawton video, and aside from seeking them out, I’ve not heard of them since. That said, they’ve been around for over a century and are renowned for being “bulletproof” batteries.


Some Problems with Other Battery Back-Ups

Emma and I have been trying to find the most environmentally friendly ways of doing what we need to do. While not particularly wealthy, we’ve accepted that doing so often costs a little more. When first looking into nickel-iron batteries, the cost seemed a bit out of reach, but after factoring everything, the choice felt right, both ecologically and economically. Battery banks on the whole are pretty problematic.

  • Though increasingly recyclable, most batteries contain corrosive and toxic materials, such as lead, lithium, cadmium, and mercury. The materials used to produce lead-acid batteries are extremely worrying, and the materials in the increasingly popular and affordable lithium ion versions have problems,
  • Longevity is another issue with typical battery back-ups. A well-maintain, lightly used lead acid battery might last 10 years, but more likely less than half of that. Tesla’s Powerwall has a 10-year warranty with a guaranteed decrease in its ability to hold a charge during that time.
  • These batteries are expensive in the first place. Replacing them frequently is even more expensive.
  • Deeply discharging either lead-acid or lithium ion batteries will significantly reduce their life. Essentially, these batteries should only be drained to about half their capacity before recharging them. In other words, not only do they have relatively short lifespans in the best conditions, they are also susceptible to serious damage.


What’s So Great About Nickel-Iron Batteries?

 Nickel-iron batteries addressed a lot of our concerns about the other batteries.

  • Nickel-iron batteries don’t have the toxic chemicals that lead-acid, nickel-cadmium, or lithium ion batteries do, so their impact on the environment is less. What’s more, there is no acid, thus no concern of spills. The materials aren’t hazardous.
  • What’s more, these batteries are known to last for decades, with a minimum life expectancy of 30 years, not to mention batteries dating back to WWII but still functioning after all that time. They have thousands upon thousands of cycles in their lifespan, and what’s more, they can be rebooted to essentially start anew. Nickel-iron batteries were used in the original electric cars in the 19-oughts, and some still work today.
  • Compared to the lithium ion batteries, nickel-iron batteries are very inexpensive. When considering the number of times a lead-acid battery would need replacing next to nickel-iron, the cost is significantly less here as well. In short, they are the most economic choice in addition to being the most ecological one.
  • They have the capacity for deep discharging. While other types of batteries generally call for no more than 50% discharge, nickel-iron can regularly be taken down 80% without any depletion of its life. Discharging this way isn’t damaging to the batteries.
  • They also handle a wider temperature range than other batteries, holding strong well below freezing and at highs hotter than anywhere on the planet currently gets.


The Catches of the Nickel-Iron Battery Back-Up

Without a doubt, the nickel-iron battery bank does come with some unique challenges. Point of fact, the system was invented by Thomas Edison in the early 1900s, but it isn’t the premiere solar battery bank. Why? Well, these are things that we decided we could live with:

  • Nickel iron battery banks are large and heavy. For anyone who has picked up a lead-acid solar battery, the thought of something heavier is scary. In other words, if moving the battery bank around is necessary, this choice might have been troubling. We don’t need to do that.
  • While these batteries don’t have toxic materials, they do off-gas hydrogen, which is highly combustible. As a result, nickel-iron batteries require enclosures with ventilation that releases the hydrogen outside. That didn’t seem problematic since we aren’t moving the batteries around anyway.
  • They require the monthly task of adding distilled water so that the electrolysis required for charging can take place. While this does mean looking in on and dealing with the batteries regularly, we want to understand our system and look after it. This will keep us in tune with our system, and luckily not doing this maintenance with perfect timing won’t damage the battery.
  • They don’t always work with standard solar equipment. However, for the most part, they work with quality equipment, and they do have plenty of options. We had no problem finding what works, but it did mean not buying any old thing.


To Each Their Own

By no means, not even stretching the truth to its limits, are either Emma or me solar power experts. We are simply people hoping to have a relatively modest amount of electricity, enough to run some lights, a couple of laptops, WiFi, a chest freezer, and the occasional kitchen appliance. We wanted a quality system to provide that, one that would last and not cause too much damage when all was said and done. Nickel-iron is what we settled on. Because it seems to be relatively under the radar here in the US, I just wanted to share some of the information we’ve gathered.

Jonathon Engels

The financially unfortunate combination of travel enthusiast, freelance writer, and vegan gardener, Jonathon Engels whittled and whistled himself into a life that gives him cause to continually scribble about it. He has lived as an expat for over a decade, worked in nearly a dozen countries, and visited dozens of others in the meantime, subjecting the planet to a fiery mix of permaculture, music, and plant-based cooking. More of his work can be found at Jonathon Engels: A Life About.


  1. Thanks for this Jonathon,

    Have you actually been able to get Nickle Iron batteries? I have an off grid solar system, but have not been able to find nickle iron batteries in my country, Namibia. Everybody here here just says they are an old wives tail. We do not have many specialists here and most go for lithium, that are very expensive. I have unfortunately been forced to go lead acid batteries, and am already picked up battery failures, that is costing us. We are however pushing through with limited power at night, but would like to get out of that situation, by replacing with Nickle Iron.

    Thanks again. We will look into the companies mentioned, and hopefully will be able to import some at reasonable costs.

      1. IronEdison is a reseller/distributor for a Chinese made battery. Iron Edison does sell them as Iron Edison brand but they do Not make them. I have one of their batteries(6kW) and two refurbished original NiFe Batteries (3kW each). The original Edison Battery Co was purchased by a european company and moved to China around 1970 or so. The Russians have since, also, stopped production. There are several different companies in China making these batteries but some are of questionable value.
        The main use of this type of batteries is in mining operations where internal combustion engines cannot be used.
        We are 100% off grid with 12kW of solar, no grid tie at all.

  2. Some lead acid batteries also off-gas hydrogen, and require distilled water top-ups.
    Distilled water can be energy intensive to create, as it involves boiling the water. Do you have a solution for that?

    1. Yes. Not to be so fussy. You may use solar energy distillation if you read about it.

      Cheers Michael

  3. I was very interested when I read about nickle iron batteries because of their cost and longevity. The one big negative that concerns me about the nickle iron batteries is the self discharge rate. The nickle iron batteries lose stored power over time, and my understanding is that the rate at which they lose power is higher than most other battery types and faster. The self discharge rate is one thing I would look into further before considering them. Base on what I have read about solar battery storage solutions, lithium iron phosphate batteries (LiFePO) seem like they may a better choice. If you try out the nickel iron batteries I would be very interested in hearing about your experience with the self discharge rate of the batteries.

    1. They do have a higher then LifePo discharge rate, but with solar typically being a daily charge cycle its not as relevant as many people might think.

    2. Hi, I have considerable experience with NiFe batteries. They have reportedly self-discharge in 1-3%/day. This magnitude self-discharge is of no consequence for solar applications as they are charged daily by the sun. It does reduce their efficiency, but the user typically discharges 50% daily, so the self-discharge is irrelevant considering the other advantages.

  4. I commend you for your opposition to the status quo when it comes to dealing with power companies. Environmental issues aside, as with any large company they are just a pain to have to deal with.

    However, I must point out that the manufacture of solar panels involves insane amounts of toxicity. It seems you are taking a stand on one thing and conveniently ignoring another. Or have you found an environmentally friendly solar-panel manufacturer? If you have, please do share in a future article!

    1. Mike, if you find yourself holding out for the perfect solution to everything then you will never ever get started. We started with refurbed NiFe batteries that were originally made in the 1940s and solar panels that were used for 3 years by a large municipal project before being replaced. The batteries were not cheap but we saved a great deal on the panels. No one says that you have to buy new to get what you need and still cut down on the waste and environmental issues. Is it the “perfect answer”, no but it is better than waiting.

  5. Thanks for your article!

    Be aware these batteries are less efficient (in terms of energy in, energy out). Meaning they won’t be able to charge all the energy you put in, with significant losses of around 30%. (to charge batteries at 100%, you need to put 130% of energy in them).

    Second catch: They self-discharge at a rate of ~1% per day. Not a big deal if you use them daily, but that’s reality.

    Still better than any other batteries in my opinion! I’m planning to buy NiFe batteries for my home next year. Since the PV panels are relatively cheap nowadays and the other battery alternatives are a no-go in many aspects. But a full article about these batteries should not hide these big important pieces of data :) Worth mentioning as a realistic catch.

  6. Hi,
    I am David Bartlett from IRONCORE Batteries in Australia. We have been selling NiFe batteries in Australia for over 13 years and we use the nickel iron batteries we sell.
    My house is fully electric with a 48volt x 1000ah NiFe battery bank. We have induction cooktop, stove, 2 freezers, fridge, clothes dryer, washing machine, dishwasher, three tv’s, computers and a 7.5kw split cycle heater/air conditioning unit.
    We have a 6.4kW amorphous solar array and we are never out of power.
    Depending on the inverter and how you set up your system will depend on how your nife batteries work. Our system is 83% efficient but this is because of how we use, charge and discharge our battery bank.
    There is a significant amount of mis-information about NiFe batteries. They work with all stand alone (battery) inverters and solar controllers however some inverters work better with NiFe batteries. They do not loose 1% of power per day. I have many customers who can attest to this however if they are used daily then this is a non issue. The cost to replace the electrolyte including good quality distilled water and KOH is less than 5% the cost of our batteries with electrolyte replacement usually between 8 – 10 years. I am currently going through the replacement of the electrolyte in my battery bank that are over 11 years old.
    We regularly replace lead acid battery banks with our nickel iron batteries with most stand alone customers having between 900 – 1200ah x 24volt lead acid batteries they throw away every 4 -6 years. These are replaced with our 500ah nickel iron batteries. Our customers tell us they have more power than they ever had even with new lead acid batteries and they don’t have to worry about overloading the batteries like they did with lead acid batteries. In most cases they are using inverters that are designed to use with lead acid batteries. They will have more usable power when they replace their inverter with one that is better suited for NiFe batteries.
    We have been able to reduce the price of our batteries by over 50% since we started selling NIFe batteries 13 years ago and we know we can reduce this price by placing bigger orders with our manufacturing partner.
    I hope this helps

  7. David,
    I think it is most important that you mention your own set up is also grid connected, not stand alone. There is a significant difference in how you manage your stored power accordingly.
    In a grid connected system, no harm is done if the batteries are depleted and the inverter switches back to grid power. (Other than your having to pay for that power).
    However, in a stand alone system, if the batteries are depleted and the inverter cuts out, computers turn off without shutting down properly, all the lights go out, the mains powered clocks all reset, microwaves lose there settings, and if a piece of electronic equipment is undergoing a firmware update at the time, they are trashed. (Ask me how I know that). And, if your generator is not auto remote start, then you have to get out of bed before sunrise on that frosty morning and go down to the garage to start the generator so you can have toast for breakfast. These all become major issues in a stand alone system.
    Having retired a set of 13 year old lead acid batteries and purchased a set of 40 nickel iron batteries from you David, and having difficulty getting them initialised, we often have very low voltage in the batteries in the early morning before the sun hits the panels. As a result, using the microwave or toaster first thing of a morning is a no no because of the comparatively high voltage drop that nickel iron batteries experience under heavy load. The sudden load will instantly drop the voltage of the batteries to below the minimum of the inverter which then shuts off before the remote auto start generator system has a chance to start.
    So the biggest negative around nickel iron batteries from my point of view is the large voltage drop under load. This I hope will become less of an issue once I get the batteries initialised, (I have been battling with that issue for 8 months). However, I don’t expect I will be able to run heavy electrical loads in the early morning until after the sun comes up. And that is a change I have had to make since switching from lead acid to nickel iron batteries.
    In my opinion, every other so called “catch” regarding nickel iron batteries are irrelevant in a stand alone stationary system where space for the battery bank is not critical.
    Regards Chris.

    1. What knid of inverter are you using? You need an inverter with a wide voltage range. X40 cells x 0.9v = 36v. When nickel-iron batteries charge they require 1.7v per cell. x40 x 1.7v = 68v. So your inverter needs to cover 36v to 68v in order to utilise the batteries correctly. Most inverters don’t cover this range. Mpp solar have some inverters that almost cover this range.

  8. Hi I purchased nickel iron batteries like a decade ago. They were new with no electrolyte in them / dry. Now l want to use them and need to know how to fill them with fluid and will they work .they came with bags of stuff to add but I don’t have the recipe please help it wou5 be greatly appreciated steve

    1. Steve, did you buy your batteries from ZapWorks? I have what you need to include a current email address
      for one of the former owners. The moderator has my permission to give you my email address.

  9. My problem with NiFe battery is they are not compatible with available solar charge controllers rated at maximum of 14.8V. They cut off even before the batteries are fully charged.
    I decided to connect directly i.e bypass solar controller to make it work but yet no problem noticed.
    The same issue happens when I use standard chargers. I have to charge 1.2v x8 – 9pcs at a time if I need to get my bank at 100% full charged.
    My bank consists of 12V 800ah.
    Please offer an advice if any.

    1. You need MPPT (Maximum Power Point Tracking) charge controllers lik Outback MX80s with adjustable set points. We have a set that had been great.

      We have 1280 watts of panels wired in series parallel which feed into the controller at 76 volts. The battery bank is 500 amp hours at 24vdc.

      Look into a better controller!

  10. Changing of Ni-Fe battery electrolyte. 10 years is suggested at several locations but do not go into any detail as to when exactly. Does some kind of internal battery effect show up? Like not being able to take a charge. Or not getting to charge voltage? 14.5 to 17 volts. And according to Be-Utility-Free; I added a layer of oil, around 0.25 inch, to the top of my batteries electrolyte to prevent premature electrolyte decomposition. Be-Utility-Free is out of business as near as I can tell. So I am wondering how much life I will get from my Ni-Fe battery electrolyte, having used mineral oil on top of the electrolyte. Do I even need to concern myself with the electrolyte; using the oil topping? I am wondering if the electrolyte will last as long as the batteries using the oil topping on the electrolyte? No signs of deterioration of the electrolyte yet. But anyone who has used the mineral oil topping on the electrolyte for and extended period of time; please advise. I purchased my batteries, 100 amp hour Ni-Fe battery cells from Be-Utility-Free in 2009 or 2010 and added the oil topping a year later. I have 60 each Ni-Fe 100 amp hour cells; 6 rows of 10 batteries providing 12 volts when discharged and up to 16.5 volts when fully charged. Response requested to email: [email protected]. The plan for the Ni-Fe batteries was as a back up when ever commercial electrical supply is off. Which has occurred once a year for 1 to 2 hours; or has not been a problem. I am looking forward to another 80 years of Ni-Fe battery use as backup! I did purchase extra electrolyte in liquid form, but do not think I will need it.

  11. And a battery charger. I have used a Schumacher model SE 4022 since 2009 or 2010; and has worked wonderfully; until this year has gone part time with no obvious reason why. The model SE 4022 is no longer manufactured and the automated battery chargers do not appear to work, having tried two different ones. So I have been looking for a manual battery charge equal to the model SE 4022; but have not found it yet. Any recommendations from anyone? So, newer is not necessarily better is the judgment so far on battery chargers! Response requested to email: [email protected]. I did have a solar array of 8 panels but used it to heat my basement with a DC heater. The electrical transfer devices were too expensive in 2009 to consider a purchases. Why the basement heating with a DC heater from a solar array. I live in a northern climate. The basement does not get to 70 deg F except in August and is as low as 45 deg F in February. I charge my Ni-Fe cells twice a year and occasionally use the battery charger for a vehicle low or dead battery. Charging one row at a time lately with the part time battery charger for 5 days nominally to get to full charge at 10 to 12 amps continuous from the battery charger. The battery charger needs several days to a week of non use before it will work again. I need a new battery charger. Suggestions please!

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