Quiz question

On Thu, 10 Oct 2013 14:22:34 -0500, "Steve Thackery"
wrote:

Ian wrote:

There was an advert in Craigslist a few years back for a valve.

The owner had taken it apart to clean off the cloudy area at the top
of the inside, and was confident that it would be fine when
re-assembled.

The ad was widely circulated on the net.

Yeah, but I bet it was done as a joke. Anyway, how would you get a
valve apart, normally?

I'm sure that somewhere in this sequence videos of the making of an
Audion vacuum tube there was a section on doing just this in order to
retrieve the part consumed getters which I think should give you one
answer at least.

http://www.youtube.com/watch?v=oSgVGwqJ2Jk

Enjoy! :-)
--
Regards, J B Good

On Thu, 10 Oct 2013 15:05:11 -0500, "Steve Thackery"
wrote:

Paul Ratcliffe wrote:

On Thu, 10 Oct 2013 17:46:25 +0100, Dave Plowman (News)
wrote:

A 'dry charged' lead acid has a very good shelf life

Could you explain that term please. Not sure I've heard it before.

Well, it's as if you fully charged the battery and then tipped the acid
out. At that point the battery is dry, and charged (or rather, will be
charged when the acid it tipped back in again). The big advantage
being that it will stay like that for years. Put the acid back in and
it'll go straight into normal service.

Mind you, I don't suppose they actually do that. Presumably they make
the plates from new with the chemical compositions they would have in a
fully charged battery.

That's exactly right! The plates are preformed by packing red led
paste into the positive grid plates and pure sintered led into the
negative grid plates used in the assembly. Once the mechanical
assembly is completed a dilute acid fill will result in a pre-charged
battery that's ready for immediate service.

A dry charged battery is simply one that postpones the final
electrolyte fill for the end consumer to complete (normally the
battery will be sold with a bottle of the right amount of dilute
sulphuric acid for this purpose).

A dry charged battery can have a very long shelf life if the
filler/vents are left sealed to prevent atmospheric borne moisture and
other pollutants from accumulating on the plates. Once filled, there's
no way back to its original dry charged condition.
--
Regards, J B Good

On Thu, 10 Oct 2013 14:20:09 -0500, "Steve Thackery"
wrote:

Roderick Stewart wrote:

In most cases, the Ah capacities we were able to obtain from real
batteries were only about two thirds of the figures quoted in the
catalogues and printed on the batteries themselves.

Indeed - a lot depends on the discharge rate at which you measure the
capacity. I bet they used something like the 100 hour rate, or some
such nonsense.

That 100 hour rate can sometimes be quoted but, more often than not,
it's usually a 20 hour rate (very rarely might they quote the more
useful 10 hour rate figure).

With Lead Acid cells, the number of hours has a very strong influence
on how many AH can be usefully extracted due to an effect known as
Peukert's Law.

With other cell chemistries, this effect is far less pronounced (to
the extent that an 1100mAH NiMH cell might well take 11 hours to
discharge at 100mA yet still manage an effective 1000mAH at 1000mA for
a full hour's endurance.

Otoh, an identically rated Lead Acid cell for a 10 hour discharge
cycle might sustain a drain of 105mA but only achieve 30 or 40 percent
of this when discharged at 1000mA.
--
Regards, J B Good

On Fri, 11 Oct 2013 00:32:51 +0100, "Dave Plowman (News)"
wrote:

In article ,
Paul Ratcliffe wrote:
A 'dry charged' lead acid has a very good shelf life

Could you explain that term please. Not sure I've heard it before.

It is in a fully charged state chemically speaking but with the acid
removed. Add acid of the correct SG, and you have a battery ready to go
after an hour or so 'settling'. It's also a safe way to transport a
battery with the acid in a separate sealed container - that's how most
mail order batteries arrive.

I think you meant to say: "that's how most mail order Flooded Cell
Lead Acid batteries arrive. The 'dryfit' types (AGM or Gel types) are,
quite obviously, supplied in a ready for service state so should be
excluded from this particular safety aspect of mail order
transportation.
--
Regards, J B Good

On Fri, 11 Oct 2013 01:13:34 +0100, Johny B Good
wrote:

Roderick Stewart wrote:

In most cases, the Ah capacities we were able to obtain from real
batteries were only about two thirds of the figures quoted in the
catalogues and printed on the batteries themselves.

Indeed - a lot depends on the discharge rate at which you measure the
capacity. I bet they used something like the 100 hour rate, or some
such nonsense.

That 100 hour rate can sometimes be quoted but, more often than not,
it's usually a 20 hour rate (very rarely might they quote the more
useful 10 hour rate figure).

With Lead Acid cells, the number of hours has a very strong influence
on how many AH can be usefully extracted due to an effect known as
Peukert's Law.

With other cell chemistries, this effect is far less pronounced (to
the extent that an 1100mAH NiMH cell might well take 11 hours to
discharge at 100mA yet still manage an effective 1000mAH at 1000mA for
a full hour's endurance.

Otoh, an identically rated Lead Acid cell for a 10 hour discharge
cycle might sustain a drain of 105mA but only achieve 30 or 40 percent
of this when discharged at 1000mA.

The test load on our homebrew battery capacity meter was two 5 Ohm
metal cased resistors bolted to the biggest heatsink we could find,
and because we'd be testing a variety of sizes, from vehicle batteries
of 60Ah or more down to little 1.6Ah nicads, I made it possible to
switch them in series or parallel. This gave two possible test
currents of 1.2A and 4.8A from nominally 12V batteries, and they
measured pretty close to those values.

For mid range batteries from about 10-25Ah it was feasible to test at
both current values to see if there was any difference in capacity,
but there wasn't much. If I had found that our nominal 15Ah batteries
which had only tested at about 9.5Ah on the 4.8A test load gave
something like the full 15Ah at the lower test current, I'd still have
been disappointed but I'd have understood, but it was nowhere near,
maybe about 0.5Ah to 1Ah higher at the most. I'd have thought a 10-12
hour discharge time to cover a working day was reasonable though; it's
no more than we expect from our computers and phones.

Rod.

In article ,
Johny B Good wrote:
On Fri, 11 Oct 2013 00:32:51 +0100, "Dave Plowman (News)"
wrote:

In article ,
Paul Ratcliffe wrote:
A 'dry charged' lead acid has a very good shelf life

Could you explain that term please. Not sure I've heard it before.

It is in a fully charged state chemically speaking but with the acid
removed. Add acid of the correct SG, and you have a battery ready to go
after an hour or so 'settling'. It's also a safe way to transport a
battery with the acid in a separate sealed container - that's how most
mail order batteries arrive.

I think you meant to say: "that's how most mail order Flooded Cell
Lead Acid batteries arrive.

No I didn't. Not in the context of talking about dry charged lead acid.
The principle doesn't exist with SLA types.


The 'dryfit' types (AGM or Gel types) are,
quite obviously, supplied in a ready for service state so should be
excluded from this particular safety aspect of mail order
transportation.

Sealed lead acid is the correct name. Although it has been hijacked by
some for use with semi-sealed wet types. Which still have a means of
filling concealed beneath a sticker or whatever.

--
*Rehab is for quitters

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...

Sealed lead acid is the correct name. Although it has been hijacked by
some for use with semi-sealed wet types. Which still have a means of
filling concealed beneath a sticker or whatever.

What I want to know is, what *exactly* have they done to car batteries so
that they don't need to be topped up any more. I know that they are supposed
to use a different lead alloy for the electrodes, which supposedly reduces
the amount of 'gassing' (conversion of water to hydrogen and oxygen by
electrolysis) during charging, but what about loss by evaporation?

Are they relying on charge regulators in cars being better? Is the casing
able to stand a small gas pressure to prevent loss by evaporation?
CMWTK.

Maybe it's just that we never really had to top up batteries all that often
in the past. Though batteries do seem to last a *little* longer nowadays, if
the car is in regular use.

--
Max Demian

On Fri, 11 Oct 2013 16:32:01 +0100, "Max Demian"
wrote:

What I want to know is, what *exactly* have they done to car batteries so
that they don't need to be topped up any more. I know that they are supposed
to use a different lead alloy for the electrodes, which supposedly reduces
the amount of 'gassing' (conversion of water to hydrogen and oxygen by
electrolysis) during charging, but what about loss by evaporation?

Probably the same as anything else these days that is regarded as
"maintenance free". You just throw it away before it needs any.

Rod.

On Fri, 11 Oct 2013 16:32:01 +0100, "Max Demian"
wrote:

"Dave Plowman (News)" wrote in message
...

Sealed lead acid is the correct name. Although it has been hijacked by
some for use with semi-sealed wet types. Which still have a means of
filling concealed beneath a sticker or whatever.

What I want to know is, what *exactly* have they done to car batteries so
that they don't need to be topped up any more. I know that they are supposed
to use a different lead alloy for the electrodes, which supposedly reduces
the amount of 'gassing' (conversion of water to hydrogen and oxygen by
electrolysis) during charging, but what about loss by evaporation?

Try this article for a start:
http://en.wikipedia.org/wiki/Car_battery

Lead-acid batteries for automotive use are made with slightly
different construction techniques, depending on the application of
the battery. The "flooded cell" type, indicating liquid electrolyte,
is typically inexpensive and long-lasting, but requires more
maintenance and can spill or leak. Some flooded batteries have
removable caps that allow for the electrolyte to be tested and
maintained.

More costly alternatives to flooded batteries are valve regulated
lead acid (VRLA) batteries, also called "sealed" batteries. The
absorbed glass mat (AGM) type uses a glass mat separator, and a "gel
cell" uses fine powder to absorb and immobilize the sulfuric acid
electrolyte. These batteries are not serviceable: the cells are
sealed so the degree of charge cannot be measured by hydrometer and
the electrolyte cannot be replenished.

More information about AGM and gel cell types he
http://en.wikipedia.org/wiki/Lead%E2...rbed_glass_mat



Are they relying on charge regulators in cars being better? Is the casing
able to stand a small gas pressure to prevent loss by evaporation?
CMWTK.

Maybe it's just that we never really had to top up batteries all that often
in the past. Though batteries do seem to last a *little* longer nowadays, if
the car is in regular use.


--
Peter Duncanson
(in uk.tech.digital-tv)

In article ,
Max Demian wrote:
What I want to know is, what *exactly* have they done to car batteries
so that they don't need to be topped up any more. I know that they are
supposed to use a different lead alloy for the electrodes, which
supposedly reduces the amount of 'gassing' (conversion of water to
hydrogen and oxygen by electrolysis) during charging, but what about
loss by evaporation?

The physical design of the battery is designed to 'condense' things back
into the cell.

Also alternator regulators are better designed to prevent over-charging.

--
*I get enough exercise just pushing my luck.

Dave Plowman London SW
To e-mail, change noise into sound.