Re: (ET) Bumping up the charge voltage a tad

["David Roden" <etpost drmm net>]

On 17 Jun 2015 at 21:28, CZ wrote:

>  I run the NiCDs, and I really should charge them to 45
> volts, not 42 to blow the oxygen off the plates every once in awhile.

"Blow the oxygen off the plates"?  Never heard of such a thing.  Last I 
heard, oxygen was a gas.  Gases don't usually stick to stuff.

Here's how NiCd batteries work :

http://www.evdl.org/docs/nicad-principles.pdf

NiCd batteries are wondrous critters.  Unlike with lead batteries, the 
electrolyte is just an ion carrier, it doesn't participate in the 
reaction, 
so its SG change from flat to full is practically nil.  Thus a flat 
battery 
won't freeze.  In fact you can leave NiCds flat for years; they have no 
equivalent of lead's sulfation.  

They stand up better to overcharging than lead batteries do.  

They last a long time. Not as long as Edison's legendary NiFe batteries, 
but 
way longer than lead.

Their discharge voltage stays flat for most of their discharge cycle.

As I say, wondrous critters.  Bloody shame the big'uns are so hard to come 
by these days.

You aren't harming yours by undercharging them.  In fact you're probably 
extending their already long lives.  If they have enough capacity to do 
what 
you need done, don't mess with success.

BTW, as I mentioned in another note here, it's likely that your charger is 
pushing those batteries higher than 42 volts already.  Don't measure the 
charger output open circuit, it'll fool your meter.  Measure how high the 
battery voltage gets at the end of the charge.

> Change the capacitor a bit? 

If you really insist on bumping up the voltage, yes, raising the 
capacitance 
will raise the voltage.  I don't know how far you can go with this.  Note 
that it will also worsen the quality of the voltage regulation.

Here's a pretty good description of how a FR transformer works.

http://www.electroncoil.com/ferroresonant_transformers.php

> How about a boost transformer on the input (I could try a variac I
> have around). 

Nope.  The transformer's ferroresonant design holds the transformer's 
secondary voltage in a relatively narrow range while the primary voltage 
ranges wider.  Typically you get around 2% variation at the secondary for 
10% at the primary.  

So you probably don't want to poke up primary voltage.  Instead, you might 
try a boost transformer on the GE transformer's secondary.

Possible problem: IIRC an FR transformer's output waveform can be pretty 
wonky.  I don't know what it would do to a conventional transformer, or 
how 
it would come out on the secondary, or how well the waveforms would add in 
series.  You'd just have to try it, I guess.

But as I said, I really don't think you need to do this.


David Roden - Akron, Ohio, USA

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