Quiz question

On Thu, 10 Oct 2013 10:57:20 +0100, "Dave Plowman (News)"
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. That's quite a
discrepancy. It can be enough to be a nuisance if you've designed
something to last a full working day and it doesn't. So be warned;
don't believe quoted battery capacities. If you're designing something
for which the running time is important, don't believe what the
manufacturers say, but get a few samples and test them yourself.

A (good) lead acid car battery is usually spot on for its quoted capacity
when tested in the method used to determine that. But I'd totally agree
with you as regards 'domestic' rechargeable types. And the higher the
quoted capacity, the less likely it is to be close.

The particular battery that started it all was a "Dryfit" solid or
paste electrolyte type purchased through Radiospares or Farnell which
I understood was based on the same chemistry as car batteries. The
ones marked as 15Ah never tested more than 10Ah, even when new.
Similarly with other sizes. The numbers were nonsense.

Rod.

In article ,
Roderick Stewart wrote:
A (good) lead acid car battery is usually spot on for its quoted capacity
when tested in the method used to determine that. But I'd totally agree
with you as regards 'domestic' rechargeable types. And the higher the
quoted capacity, the less likely it is to be close.

The particular battery that started it all was a "Dryfit" solid or
paste electrolyte type purchased through Radiospares or Farnell which
I understood was based on the same chemistry as car batteries. The
ones marked as 15Ah never tested more than 10Ah, even when new.
Similarly with other sizes. The numbers were nonsense.

I have an (expensive) electronic tester for lead acid batteries which
gives a readout of the actual capacity in amp.hr. And having checked a
couple of car batteries by discharging them, found it extremely accurate.

I'd wonder just how long the ones you had were on the shelf. A 'dry
charged' lead acid has a very good shelf life - not so sure about an SLA
type. RS at one time did some very high (claimed) capacity lead acid
single cells - Cyclone? Didn't think much of them.

--
*Your kid may be an honours student, but you're still an idiot.

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

(Richard Tobin) writes:

In article ,
Bill Wright wrote:

They must be. And the gradients must be identical. And the players must
all weigh the same.

They use an ISO standard golfer.

Who completes each hole in par.

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.

--
SteveT

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?

--
SteveT

On 10/10/2013 14:44, Bill Wright wrote:


When I was at school everything was made from Earth, Water, Air, and Fire.

Bill

Blimey, that must have been before Phlogiston was discovered!
--
Cheers,
Roger
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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.

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.

--
SteveT

"Ian" wrote in message
...

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.

Used to work for 're-gunning' CRTs. They used to recoat the screen with
phosphor too. Not sure it would be worthwhile for a valve, or why you would
want to clean off the cloudy area.

--
Max Demian

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.

--
*The more I learn about women, the more I love my car

Dave Plowman London SW
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