Re: [EVDL] Ni-Cad wear out life/refurbishing/and electrolete info. - DIY Electric Car Forums
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Old 02-16-2009, 01:15 PM
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Default Re: [EVDL] Ni-Cad wear out life/refurbishing/and electrolete info.

Hello Storm,

The KOH electrolyte stays mostly constant between 1.2 to 1.25 SG. As you
put more cycles through this electrolyte which is just a carrier, it gains
more cadmium particles that make it more conductive. This is why we were
instructive to replace the KOH as per Mil Specs TO.xxxx.xxxx.

You can get technical KOH from any chemical supply house like from Fisher
Scientific. If you only need a small amount of it, you can get medical
grade KOH from drug stores. This type of KOH is in flakes, nut the pellets
or solution type.

It takes about l lb of KOH to one gallon of distill water. Back in 1988 it
cost about $40.00 for a 3kg or 6.61 lbs. 12kg ran about $125.00 for four
3kg packages.

Mixing one lb of KOH to 1 gallon of water will become about 1.25 sg because
it becomes warm during the time of mixing. You only want to add a little
bit of KOH flakes to the water at a time.

You then let the electrolyte cool down to room temperature first before you
test the SG of the electrolyte. If it reads between 1.2 and 1.25 sg, that's
ok. If higher than that, that add a bit of water stirring the solution at
the same time. If lower, then add a bit of KOH.

To measure the KOH specific gravity, use a baume hydrometer that is use for
liquids heavier than water, as the standard hydrometer use for h2so4 lead
acid electrolytes. You can change out the boume glass unit that floats
inside the standard hydrometer case and replace it with precision sg baume
that would read between 1.000 and 1.220 sg.

You can use the baume hydrometer alone which is normally use in mixing up a
big batch of KOH electrolyte. Just let it float in the solution which
should be inside a large glass or corrosion proof container.


----- Original Message -----
From: "storm connors" <>
To: "Electric Vehicle Discussion List" <>
Sent: Monday, February 16, 2009 10:50 AM
Subject: Re: [EVDL] Ni-Cad wear out life/refurbishing

> Roland, If the electrolyte doesn't change, why were you replacing it??
> [quote] Roland Wiench <> wrote:
> > Hello Mark,
> In a Ni-Cad battery, the KOH electrolyte does not change or very little
> change as it's discharge like a lead-acid battery. The KOH is only a
> carrier of electricity like a conductor, not a chemical exchange like the
> 5H2O + 3H2SO4 that is a lead battery.
> Storm
> _______________________________________________
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