My daughter handed me one of those big torches the other day saying it
had stopped working - she'd put it on charge but it now doesn't work!

I found a 6v lead acid battery in it - warm after my attempts to
charge it but reading only 4+ volts. Clearly a cell down. I take it
that this is due to leaving it on charge for too long - the charger is
just a walwart transformer type.

Rob

robgraham wrote:
My daughter handed me one of those big torches the other day saying it
had stopped working - she'd put it on charge but it now doesn't work!

I found a 6v lead acid battery in it - warm after my attempts to
charge it but reading only 4+ volts. Clearly a cell down. I take it
that this is due to leaving it on charge for too long - the charger is
just a walwart transformer type.

Rob

Lead acids on a proper constant voltage charger (2.25v per cell) will
regulate their own current and tolerate continuous float charging.
A faster charge at 2.35v per cell needs to be taken off charge after
charge is complete.
If the charger is a voltage source with a resistor, then you can
possibly kill the batteries mainly be heating/drying out and cells venting.
Normally sealed lead acid die from not being charged often enough and
the cells go high impedance. Some life can be regained by charging from
a high voltage (say 5-10v per cell) with a filament lamp rated at that
voltage in series. The supply should be rated at the lamp current or more.
When the lamp starts to glow, some current is flowing and charging
should begin. Then switch to a 2.25v/cell constant voltage.

Bob

robgraham wrote:
My daughter handed me one of those big torches the other day saying it
had stopped working - she'd put it on charge but it now doesn't work!

I found a 6v lead acid battery in it - warm after my attempts to
charge it but reading only 4+ volts. Clearly a cell down. I take it
that this is due to leaving it on charge for too long - the charger is
just a walwart transformer type.

If you can get at the battery to measure the voltage, it's probaby a
standard type, available by searching for the type number printed on it.
Otherwise, if you measure it, then Maplin have a reasonably large range
of SLA batteries, or your local model shop may be able to get one that
will fit.

It'll probably be cheaper to buy a replacement rechargeable torch, though.

--
Tciao for Now!

John.

On Tue, 19 Feb 2013 16:43:33 +0000, John Williamson
wrote:

I found a 6v lead acid battery in it - warm after my attempts to
charge it but reading only 4+ volts. Clearly a cell down. I take it
that this is due to leaving it on charge for too long - the charger is
just a walwart transformer type.

If you can get at the battery to measure the voltage, it's probaby a
standard type, available by searching for the type number printed on it.
Otherwise, if you measure it, then Maplin have a reasonably large range
of SLA batteries, or your local model shop may be able to get one that
will fit.

It'll probably be cheaper to buy a replacement rechargeable torch, though.

Yep. I have a couple of fairly expensive yard torches and bought a new
battery last year for €17 for one of them. I'm now fed up with the
high death rate of teh filament bulbs and have decided to treat them
to an LED upgrade, with a XML-T6 in each, and associated driver. This
is partly stimulated by the money already laid out on that battery and
I've no desire to simply bin it. Apart from that, both have large
reflectors and I think those will make good use of a nice bright LED.
Even so, to buy the equivalent torches now, already fitted with a
modern battery, LED, etc from the same makers wouldn't leave me much
change out of a 100quid, so I'm quids in, whatever way I go.
When the SLA batteries finally turn their toes up, I'll fit them with
some 18650s in bundles.

On Feb 20, 1:42*am, Grimly Curmudgeon wrote:
both have large
reflectors and I think those will make good use of a nice bright LED.

The LED upgrades I have seen (e.g. for Maglites) effectively don't
benefit from the reflector at all, because all the light from the LED
is directed forwards and never hits it.

Richard.
http://www.rtrussell.co.uk/

In article
,
Richard Russell wrote:
On Feb 20, 1:42 am, Grimly Curmudgeon wrote:
both have large
reflectors and I think those will make good use of a nice bright LED.

The LED upgrades I have seen (e.g. for Maglites) effectively don't
benefit from the reflector at all, because all the light from the LED
is directed forwards and never hits it.

I have an LED replacement in my Maglite 2D and certainly there is focussing
of the beam when I twist the front. I happened to try it last night.


Richard.
http://www.rtrussell.co.uk/

--
From KT24

Using a RISC OS computer running v5.18

On Wed, 20 Feb 2013 02:33:30 -0800 (PST), Richard Russell
wrote:

On Feb 20, 1:42*am, Grimly Curmudgeon wrote:
both have large
reflectors and I think those will make good use of a nice bright LED.

The LED upgrades I have seen (e.g. for Maglites) effectively don't
benefit from the reflector at all, because all the light from the LED
is directed forwards and never hits it.

Richard.
http://www.rtrussell.co.uk/

Depends on the positioning of the LED, and the shape of the reflector.
This is basic optics, man.

On Feb 21, 4:14*pm, Grimly Curmudgeon wrote:
Depends on the positioning of the LED, and the shape of the reflector.

And, rather importantly, the polar diagram of the LED.

This is basic optics, man.

In which I specialised when I did my Oxford physics degree!

Richard.
http://www.rtrussell.co.uk/

In article
,
Richard Russell wrote:
On Feb 21, 4:14 pm, Grimly Curmudgeon wrote:
Depends on the positioning of the LED, and the shape of the reflector.

And, rather importantly, the polar diagram of the LED.

This is basic optics, man.

In which I specialised when I did my Oxford physics degree!

Richard.
http://www.rtrussell.co.uk/

All the LEDs I've seen have a lens on the front. I suppose you could have
an LED which throws back into a reflector, but is there any point?

--
*Never miss a good chance to shut up *

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

On 21/02/2013 17:25, Dave Plowman (News) wrote:
In article
,
Richard Russell wrote:
On Feb 21, 4:14 pm, Grimly Curmudgeon wrote:
Depends on the positioning of the LED, and the shape of the reflector.

And, rather importantly, the polar diagram of the LED.

This is basic optics, man.

In which I specialised when I did my Oxford physics degree!

Richard.
http://www.rtrussell.co.uk/

All the LEDs I've seen have a lens on the front. I suppose you could have
an LED which throws back into a reflector, but is there any point?


There is if you want to be able to focus the beam using external optics
(not that you need to throw it backwards if the reflector is designed
correctly).

On Thu, 21 Feb 2013 09:04:55 -0800 (PST), Richard Russell
wrote:

In which I specialised when I did my Oxford physics degree!

Hmm... handy.
I'll be happy enough to get a useable beam and some side spill.
Even the klutziest conversion on one of these lamps should yield
something useful. Roughly, I envisage slicing off the rear 7~9mm of
the reflector(s) and thermal glueing a T6/heatsink on the back with
the LED pretty close to the plane the filament was in. Sure, it's not
a point source, but should be adequate and more importantly, gives the
handlamps a new lease of life. Having paid some serious enough wonga
for the pair of them, admittedly a few years ago, and also having
shelled out for a new battery for one not so long back, I'm not
chucking them out.

In article om,
dennis@home wrote:
All the LEDs I've seen have a lens on the front. I suppose you could have
an LED which throws back into a reflector, but is there any point?


There is if you want to be able to focus the beam using external optics

That would be easier with a second lens in front of the LED.

(not that you need to throw it backwards if the reflector is designed
correctly).

A tungsten lamp emits near 360 degrees fairly uniformly. I've not seen an
LED which does the same. So a reflector designed for tungsten is not going
to be ideal for an LED.

--
*What are the pink bits in my tyres? Cyclists & Joggers*

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