McGraw Edison Ni-Cads (KOH electrolyte) [RE-wrenches]

Tue Jul 1 16:07:00 PDT 2003

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Hello John and John

The ED-120 cells which John has are, indeed, NiCd even though they 
have the Edison name on them. They have a nominal voltage of 1.2 VDC 
and a capacity of 120 Ampere-hours. I have run many of these for 
years.

Electrolyte specific gravity does NOT change with state of charge, 
but remains constant.

These are rugged and long lived cells. If they have not been ruined 
by operating them for long periods with high carbonate levels, then 
an electrolyte replacement will bring them back to useful life.

Please contact me off list for details on electrolyte replacement.

Richard
Home Power

At 15:06 -0700 07/01/2003, John Berdner wrote:
>John:
>
>Edison cells are normally NiFe not NiCd.
>The railroads here in the US used NiFe for years because they were so
>tough.
>The downside is they are expensive, not very space efficient, and they
>have high self discharge.
>Great for severe cycling service but not so good for remote site OV
>with low loads.
>I allways thought Edison cells would be the ideal battery technology
>for load shifting here in CA where we have time of day metering and an
>almost 3:1 cost ratio :-)
>
>The electrolyte is KOH and as you noted it is nasty - just alkaline
>instead of acidic.
>NiFe batteries have a virtually unlimited cycle life but you do need to
>change the electrolyte from time to time.
>Normally this is due to contamination due to atmospheric Carbon from
>C02.
>Some of the RR guys float a layer of oil (mineral oil I think) on top
>of the electrolyte to slow the carbon absorbtion rate.
>>From what you describe it sounds like a electrolyte swap is in order.
>
>I have never done that myself but I know the guys at Home Power played
>with Edison cells a few years back.
>Perhaps one of them will chime in.
>
>Best Regards,
>
>John Berdner
>
>
>>>>  john at gosolar.co.nz 6/30/2003 10:59:37 PM >>>
>Greetings all,
>
>I've a customer with some Edison Ni-Cads that are about 12 years old
>(or
>thereabouts) and they had very light use. The stamp on the side is
>ED-120, which I believe to be 120a/h per bank of 5 cells to make up
>6v.
>Generally the batteries look to be in good condition, hardly any
>corrosion or spills, etc.
>
>These were sold to another customer and when he tried to use them they
>would only give about an hours use. We have been told various things
>about checking the S.G. on them which was said to be about 1.20 but at
>68degrees and evidentally temperature is pretty important. Also the
>only
>thing to top them up with is distilled water.
>
>Owner A has left the country and No-one seems to know much about these
>batteries locally and I have been told various things, probably more
>heresay than reliable info. We have also heard that the KOH is nasty
>stuff and treat it just like the cautions for H2S04.
>
>I've been told that the electrolyte should be changed every 10 years
>and
>if thats the case these are overdue. And, after having changed the
>electrolyte, it will take about 20 cycles to bring them back to
>productivity (so the electrolyte can sink in, we are told)
>
>The new owner is really keen to use them as he is a great person to
>recycle and re-use and we both have heard some great things about
>Ni-Cads except how to get them to a usable state.
>
>If anyone has some first-hand experience and can help, please contact
>me
>off-list, your experiences would be greatly appreciated.
>
>thanks a lot, John V, Christchurch,
>N.Z.
>
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