Power Shift: A New/Old Battery Bank

By , March 11, 2015

Our lead acid battery bank may—or may not—be wearing out (see Is It Time for a New Battery Bank?). Back in October or November, we decided to work toward replacing it, not just with new lead acid batteries, but a whole new—or, I should say, old kind of battery.

Back in 2013 I wrote about the “other” battery bank in the outhouse when we first arrived (see Buried Treasure?). At that time, I thought that these batteries might be Edison nickel-iron batteries.

In hindsight, I loaded that essay with misinformation. I described nickel-iron batteries as “lead acid.” They are not. They are nickel-iron, as the name implies, and their electrolyte is alkaline, not acid. I also learned later that the batteries had not frozen and broken, they had just lost their electrolyte. They are in excellent shape, but they are not nickel-iron. I asked the original owner, who referred me to the neighbor he’d gotten them from, who confirmed that they’re a variety of lead-acid battery.

When we started looking at how to replace our current batteries, we looked again at nickel-iron batteries, and decided that we should switch to this new/old technology.

Thomas Edison invented the nickel-iron (Ni-Fe) battery, often referred to as the Edison battery, at the turn of the previous century. Supposedly, some of his first production batteries are still powering a building in New Jersey, more than 100 years later!

The general consensus is that this battery is one of those inventions we all gossip about that does its job so well for so long that manufacturers stop making them, simply because no one needs to replace them when they wear out! As such, they virtually disappeared, but are coming back.

I found two suppliers in the U.S., Be Utility Free, Inc., and Iron Edison.

Nickel-iron batteries can last for years with little more than a periodic electrolyte replenishment (about every 5 years, according to our supplier). If we treat them right, this new battery bank could last the rest of our lives, and possibly Aly’s as well.

The electrolyte is a lot safer than acid, although not totally safe—it’s basically lye, the highly caustic chemical we use when we make soap. But, especially with our experience, we should have little trouble refreshing the electrolyte when necessary. And, while those chemicals are somewhat expensive, they’re less than half the cost of a new bank of lead acid 6 volt batteries. Also, it’s a fraction of the weight.

The cells come in 1.2 volt units, 10 cells combine to make, essentially, a single 12 Volt battery that replaces a similar capacity lead-acid bank. Because they allow, and apparently even work better, with an 80%  capacity draw down, we could replace our 900 Ah capacity battery bank (recall that we use 225 Ah at most) with a 400 Ah nickel-iron battery.

With this new battery, we’ll haul it in once, and probably never need to haul in any more. We won’t replace it the future, as we would a lead-acid bank, nor will we need to haul in and out each replacement.

An additional advantage of the nickel-iron battery is that cells may be added at any time. Unlike lead acid batteries, the battery does not reduce to the weakest cell in the string.

All of this makes the higher cost worthwhile. The nickel-iron battery costs about the same as three lead acid banks at current prices. However, comparing today’s prices to what we paid for our lead acids 7 years ago, we would likely pay considerably more for each of the 2-3 replacements we’d likely need in our lifetime. That being said, the cost of the Edison battery is comparable to that of a decent used car bought from a private citizen. It’s a big expenditure in our budget, not to be taken lightly, but the benefits seem to outweigh the cost.

We expect the batteries to arrive sometime in the next month. I’m sure you’ll read much more about them here as we install and learn to use them.

As we wait for the batteries to arrive, other events overtook us, leading us to expand this radical change in our power system even further. I’ll outline the rest of our new plan next time.

4 Responses to “Power Shift: A New/Old Battery Bank”

  1. Al Frascoia II says:

    Here is some intresting reading regarding batteries.
    http://www.technologyreview.com/news/535251/old-battery-type-gets-an-energy-boost/

  2. Mark Zeiger says:

    Thanks, Al, this looks like great news. Battery innovation is definitely on the rise. I recently read about Harvard’s flow-through(?) batteries that use organics instead of metals. We’re going to see some incredible leaps in technology in the near future, I think.

  3. Survival Skvez says:

    Battery technology these days is dominated by *charge density* (capacity per unit weight) because most battery use is for mobile applications (laptops vehicles etc). Nickel-Iron batteries have a poor charge density and so are not popular for most applications. Of course in your application you don’t particularly care about size or weight of the battery.

    > Unlike lead acid batteries, the battery does not reduce to the weakest cell in the string.
    All chains of batteries; no matter what the battery technology; are limited by the weakest link (cell) in the chain.

  4. Mark Zeiger says:

    Skvez, technically, you’re right, any battery is limited by the weakest cell. The difference between lead acid and nickel iron is that one can switch out a bad nickel iron cell with a new one to improve capacity, whereas it is not advisable to put a brand new lead acid battery into an older bank.

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