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I am looking to renew the electrolyte in our Edison Nickel Iron Batteries is our 1914 Detroit.  Does anyone have experience with the Potassium Hydroxide solution?  Where to buy the chemicals?  What proportions to use?


Thank You

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  • 4 weeks later...

The desired specific gravity for an Edison battery is about 1.20-1.21, achieved with a mixture of distilled water and potassium hydroxide (KOH) in a ratio of about 1000 ml (1000 grams) of water to 250 grams of pure potassium hydroxide pellets (KOH).  That's the same as 1 lb of water to 4 ounces of KOH.  The literature indicates that slightly better performance is obtained by also adding a small (but unspecified) amount of lithium hydroxide (LiOH), say perhaps 5-10 grams per 250 grams of potassium hydroxide as a guess. Put the water (about 80 degrees F) in a large polyethylene contained and slowly add the pellets, stirring with a plastic utensil to dissolve.  The solution may get warm as you add the pellets.  Do not allow the solution to contact any metal items before pouring into the battery.  Get a polyethylene funnel at the auto parts store or supermarket.


You can buy a battery hydrometer at an auto parts store for under $10 to measure the specific gravity of the solution, but be sure to use a new one that has never been used on a lead-acid battery.  If the specific gravity isn't 1.20 with the solution at 80 °F, add a few more pellets to raise it or a little more distilled water to reduce it.  The pellets are typically sold as ">85% assay", but the other 15% is mostly absorbed water, as KOH is normally produced as a high purity material but you probably don't need extra-pure reagent grade or semiconductor grade material, just plain white pellets.


CAUTION:  Wear goggles or face shield, an apron, and long rubber gloves.  The dust and solution are corrosive and can burn your skin!  Read the MSDS information sheet from your supplier.  Your can Google for a chemical specialties supplier, e.g. Sigma-Aldrich. 


Apparently, someone is making nickel-iron batteries in the U.S. again, principally for energy storage for solar arrays.  They seem to be very expensive, but extremely robust and long-lived. 

See http://www.ironedison.com

and these documents from their web site:





Particularly pay attention to manual instructions to never let the battery get dry and to immediately refill the discharged battery when changing the solution. 

If you are lucky, and can find the Edison cell type number on your battery, page 15 of the Operation and Care booklet will tell you how many pounds of solution you will need.  The solution will run about 10 pounds per gallon, having about 2.5 lbs or 1 kg per gallon.  Pricing for KOH seems to be about $45-70 per kg (2.2 lbs).


See this interesting document about rejuvenation of abused 85 year old Edison batteries:


You may be the guy who can document Edison's claim of 100+ year life for nickel-iron batteries!


These are my best guesses from the literature, though I have no direct experience with nickel-iron batteries in cars.  I do know that my old high school in Baltimore, built in 1912, was still using the original nickel-iron batteries installed for the phone system well into the 1960s, though these were indoors and always maintained well. 




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Thank You Gary.

I stumbled into Mr. DeMar's articles just recently and contacted him directly.  A very good fellow he supplied me with copies of all of his Edison Battery material.  Your numbers are very close to the information he supplied and I am on my way.  I have purchased the Potassium Hydroxide and am awaiting the delivery of the Lithium Hydroxide.


The batteries in the car have not been maintained properly for who knows how long but with a bit of charging the car will move about quite nicely.  It's just that the charge won't last long and soon I am going through the lengthy charging process.


I have little doubt these batteries are Champions at longevity and hope to soon be proving that.


Good Luck on your Indy Stude project.

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