We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which I
cleaned up). I measured the battery's voltage which was 1.6V, well above
that of a normal rechargeable (1.2V?).

I presume the battery is the source of the problem. I tried replacing the
battery with both rechargeable and non-reachargeable AA ones, but the unit
still didn't work.

I suspect that the original battery was much more than 1.6V - maybe 3V? But
I can't find any references to
rechargeable AA-sized 3V batteries. Can anyone suggest where to get a
replacement battery (or other ideas)?

Cheers.

"Steve" wrote in message ...
We have a solar powered alarm clock which automatically synchronises with the terrestrial time signal. The clock is marked
'PRECISION', 'SOLAR POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look inside. There was an unmarked AA size battery (leaking
blue liquid which I cleaned up). I measured the battery's voltage which was 1.6V, well above that of a normal rechargeable
(1.2V?).

I presume the battery is the source of the problem. I tried replacing the battery with both rechargeable and non-reachargeable AA
ones, but the unit still didn't work.

I suspect that the original battery was much more than 1.6V - maybe 3V? But I can't find any references to
rechargeable AA-sized 3V batteries. Can anyone suggest where to get a replacement battery (or other ideas)?

Cheers.

Any sign of damage to the PCB from the leaking electrolyte?

I think you are reading too much into the 1.5 terminal voltage with no load.

--
Graham.

%Profound_observation%

On 04/12/2010 20:35, Steve wrote:
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which I
cleaned up). I measured the battery's voltage which was 1.6V, well above
that of a normal rechargeable (1.2V?).


Was that with it in circuit of after you removed it? If it was in
circuit and being charged when you measured it then 1.6v may be correct
for a normal AA rechargeable battery.

Lithium ion batteries are around 3V when discharged and 4.2V when fully
charged. The 14500 lithium ion cells are AA sized (14500 = 14mm
diameter and 50mm long). However, beware that lithium ion cells can
burst in to flames if incorrectly charged so you want to be sure it
should be lithium ion before fitting one. If you do fit one, I would
recommend that you buy a battery with the protection module built in.

These came up after a quick Google:

http://www.ecrater.co.uk/p/9751735/t...ttery-900mah-2

http://ant-supplies.co.uk/Rechargabl...teries14500tf1

http://www.ledfiretorches.co.uk/batt...batteries.html

"Graham." wrote in message
...

"Steve" wrote in message
...
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which
I cleaned up). I measured the battery's voltage which was 1.6V, well
above that of a normal rechargeable (1.2V?).

I presume the battery is the source of the problem. I tried replacing
the battery with both rechargeable and non-reachargeable AA ones, but the
unit still didn't work.

I suspect that the original battery was much more than 1.6V - maybe 3V?
But I can't find any references to
rechargeable AA-sized 3V batteries. Can anyone suggest where to get a
replacement battery (or other ideas)?

Cheers.

Any sign of damage to the PCB from the leaking electrolyte?

I think you are reading too much into the 1.5 terminal voltage with no
load.

--
Graham.

%Profound_observation%

Thanks for replying Graham. There's no damage to the PCB. Also, I've never
seen a rechargeable with 1.5V (even under no load); the battery (I should
say 'cell' really) is the most likely cause of the problem. I may risk
conecting a couple of 'normal' AAs in series and see what happens.

Cheers

"Gareth" wrote in message
o.uk...

On 04/12/2010 20:35, Steve wrote:
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which
I
cleaned up). I measured the battery's voltage which was 1.6V, well
above
that of a normal rechargeable (1.2V?).


Was that with it in circuit of after you removed it? If it was in
circuit and being charged when you measured it then 1.6v may be correct
for a normal AA rechargeable battery.

Lithium ion batteries are around 3V when discharged and 4.2V when fully
charged. The 14500 lithium ion cells are AA sized (14500 = 14mm
diameter and 50mm long). However, beware that lithium ion cells can
burst in to flames if incorrectly charged so you want to be sure it
should be lithium ion before fitting one. If you do fit one, I would
recommend that you buy a battery with the protection module built in.

These came up after a quick Google:

http://www.ecrater.co.uk/p/9751735/t...ttery-900mah-2

http://ant-supplies.co.uk/Rechargabl...teries14500tf1

http://www.ledfiretorches.co.uk/batt...batteries.html

Thanks Gareth. The 1.6V was with the battery removed. The Li-ion ones you
identify look interesting; you may have hit the nail on the head. As I
said to Graham (previous post) I may try connecting a couple of normal AAs
in series to check if 3V does the job. If so, a Li-ion should work well.

Cheers

On 04/12/2010 23:50, Steve wrote:
"Gareth" wrote in message
o.uk...

On 04/12/2010 20:35, Steve wrote:
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which
I
cleaned up). I measured the battery's voltage which was 1.6V, well
above
that of a normal rechargeable (1.2V?).


Was that with it in circuit of after you removed it? If it was in
circuit and being charged when you measured it then 1.6v may be correct
for a normal AA rechargeable battery.

Lithium ion batteries are around 3V when discharged and 4.2V when fully
charged. The 14500 lithium ion cells are AA sized (14500 = 14mm
diameter and 50mm long). However, beware that lithium ion cells can
burst in to flames if incorrectly charged so you want to be sure it
should be lithium ion before fitting one. If you do fit one, I would
recommend that you buy a battery with the protection module built in.

These came up after a quick Google:

http://www.ecrater.co.uk/p/9751735/t...ttery-900mah-2

http://ant-supplies.co.uk/Rechargabl...teries14500tf1

http://www.ledfiretorches.co.uk/batt...batteries.html

Thanks Gareth. The 1.6V was with the battery removed. The Li-ion ones you
identify look interesting; you may have hit the nail on the head. As I
said to Graham (previous post) I may try connecting a couple of normal AAs
in series to check if 3V does the job. If so, a Li-ion should work well.

As I said, you do need to be sure that your clock was designed to work
with a lithium ion cell as they can burst into flames if incorrectly
charged. If you do try it, make sure you get cells with built in
protection modules and don't blame me if your house burns down.

Gareth.

snip
As I said, you do need to be sure that your clock was designed to work
with a lithium ion cell as they can burst into flames if incorrectly
charged. If you do try it, make sure you get cells with built in
protection modules and don't blame me if your house burns down.

Idiot boy questions for my education : might it have been an "ordinary"
lithium battery - i.e. not rechargeable? Unless the paperwork specified
the "solar" recharged a battery might it have been cheaper for the
manufacturer to stick a non-rechargeable in given the likely long life
with such a device - i.e. well beyond any reasonable claim for a refund
under the Sale of Gods Act?

Would the presence of a charging voltage and current from the clock
(when in bright light) be one test?
--
Robin
PM may be sent to rbw0{at}hotmail{dot}com

In message , Gareth
wrote

As I said, you do need to be sure that your clock was designed to work
with a lithium ion cell as they can burst into flames if incorrectly
charged. If you do try it, make sure you get cells with built in
protection modules and don't blame me if your house burns down.


Is it a rechargeable battery or just a lithium (long life) cell
designed(?) to run the clock for 10 years, supplemented by the solar
cell only when there is enough light? If it is the latter then there
should be no problem with recharging.
http://cpc.farnell.com/varta/craa/ba...-3v/dp/BT01078


--
Alan
news2009 {at} admac {dot} myzen {dot} co {dot} uk

Gareth wrote:
On 04/12/2010 20:35, Steve wrote:
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which I
cleaned up). I measured the battery's voltage which was 1.6V, well above
that of a normal rechargeable (1.2V?).


Was that with it in circuit of after you removed it? If it was in
circuit and being charged when you measured it then 1.6v may be correct
for a normal AA rechargeable battery.

Lithium ion batteries are around 3V when discharged and 4.2V when fully
charged. The 14500 lithium ion cells are AA sized (14500 = 14mm
diameter and 50mm long). However, beware that lithium ion cells can
burst in to flames if incorrectly charged so you want to be sure it
should be lithium ion before fitting one. If you do fit one, I would
recommend that you buy a battery with the protection module built in.

These came up after a quick Google:

http://www.ecrater.co.uk/p/9751735/t...ttery-900mah-2

http://ant-supplies.co.uk/Rechargabl...teries14500tf1

http://www.ledfiretorches.co.uk/batt...batteries.html

try LiFe cells.

Not sure if AA available.

Steve wrote:
"Graham." wrote in message
...
"Steve" wrote in message
...
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which
I cleaned up). I measured the battery's voltage which was 1.6V, well
above that of a normal rechargeable (1.2V?).

I presume the battery is the source of the problem. I tried replacing
the battery with both rechargeable and non-reachargeable AA ones, but the
unit still didn't work.

I suspect that the original battery was much more than 1.6V - maybe 3V?
But I can't find any references to
rechargeable AA-sized 3V batteries. Can anyone suggest where to get a
replacement battery (or other ideas)?

Cheers.
Any sign of damage to the PCB from the leaking electrolyte?

I think you are reading too much into the 1.5 terminal voltage with no
load.

--
Graham.

%Profound_observation%

Thanks for replying Graham. There's no damage to the PCB. Also, I've never
seen a rechargeable with 1.5V (even under no load); the battery (I should
say 'cell' really) is the most likely cause of the problem. I may risk
conecting a couple of 'normal' AAs in series and see what happens.

Cheers


plenty of batteries of the non rechargeable sort have 3v voltage..LIPO
are about 3.7 in the rechargeable arena, and LiFePo are about 3.3.

But I don't think any 3.3v rechargeables come in AAA format.

More likely the whole unit is a con, and its a non rechargeable battery
that is actually being slightly recharged by the solar power.

However I am puzzled: for reasons of cmapitbility, most AAA cells are of
similar voltage.

"Gareth" wrote in message
o.uk...

On 04/12/2010 23:50, Steve wrote:
"Gareth" wrote in message
o.uk...

On 04/12/2010 20:35, Steve wrote:
We have a solar powered alarm clock which automatically synchronises
with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a
look
inside. There was an unmarked AA size battery (leaking blue liquid
which
I
cleaned up). I measured the battery's voltage which was 1.6V, well
above
that of a normal rechargeable (1.2V?).


Was that with it in circuit of after you removed it? If it was in
circuit and being charged when you measured it then 1.6v may be correct
for a normal AA rechargeable battery.

Lithium ion batteries are around 3V when discharged and 4.2V when fully
charged. The 14500 lithium ion cells are AA sized (14500 = 14mm
diameter and 50mm long). However, beware that lithium ion cells can
burst in to flames if incorrectly charged so you want to be sure it
should be lithium ion before fitting one. If you do fit one, I would
recommend that you buy a battery with the protection module built in.

These came up after a quick Google:

http://www.ecrater.co.uk/p/9751735/t...ttery-900mah-2

http://ant-supplies.co.uk/Rechargabl...teries14500tf1

http://www.ledfiretorches.co.uk/batt...batteries.html

Thanks Gareth. The 1.6V was with the battery removed. The Li-ion ones
you
identify look interesting; you may have hit the nail on the head. As I
said to Graham (previous post) I may try connecting a couple of normal
AAs
in series to check if 3V does the job. If so, a Li-ion should work well.

As I said, you do need to be sure that your clock was designed to work
with a lithium ion cell as they can burst into flames if incorrectly
charged. If you do try it, make sure you get cells with built in
protection modules and don't blame me if your house burns down.

Gareth.
Thanks Gareth. Noted!!!

"Robin" wrote in message
...
snip
As I said, you do need to be sure that your clock was designed to work
with a lithium ion cell as they can burst into flames if incorrectly
charged. If you do try it, make sure you get cells with built in
protection modules and don't blame me if your house burns down.

Idiot boy questions for my education : might it have been an "ordinary"
lithium battery - i.e. not rechargeable? Unless the paperwork specified
the "solar" recharged a battery might it have been cheaper for the
manufacturer to stick a non-rechargeable in given the likely long life
with such a device - i.e. well beyond any reasonable claim for a refund
under the Sale of Gods Act?

Would the presence of a charging voltage and current from the clock (when
in bright light) be one test?
--
Robin
PM may be sent to rbw0{at}hotmail{dot}com
Yes, it could have been a non-rechargeable lithium battery. However there
is a voltage from the solar cell when in daylight (2.6V, no load, not
direct sunlight) though this is not enough to drive the clock. So I
suspect the recharging mechanism is actually present.

(I can't measure the current through the clock without 'breaking-open' the
circuit (ammeter must be ins series), which I don't want to do.)

Cheers

Cheers.

"Alan" wrote in message
...
In message , Gareth
wrote

As I said, you do need to be sure that your clock was designed to work
with a lithium ion cell as they can burst into flames if incorrectly
charged. If you do try it, make sure you get cells with built in
protection modules and don't blame me if your house burns down.


Is it a rechargeable battery or just a lithium (long life) cell
designed(?) to run the clock for 10 years, supplemented by the solar cell
only when there is enough light? If it is the latter then there should be
no problem with recharging.
http://cpc.farnell.com/varta/craa/ba...-3v/dp/BT01078


--
Alan
news2009 {at} admac {dot} myzen {dot} co {dot} uk

It's nmarked (so can't tell if it's rechargeable or not). The cell in your
link may do the job.

Cheers

"The Natural Philosopher" wrote in message
...
Gareth wrote:
On 04/12/2010 20:35, Steve wrote:
We have a solar powered alarm clock which automatically synchronises
with the terrestrial time signal. The clock is marked 'PRECISION',
'SOLAR POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a
look inside. There was an unmarked AA size battery (leaking blue liquid
which I cleaned up). I measured the battery's voltage which was 1.6V,
well above that of a normal rechargeable (1.2V?).


Was that with it in circuit of after you removed it? If it was in
circuit and being charged when you measured it then 1.6v may be correct
for a normal AA rechargeable battery.

Lithium ion batteries are around 3V when discharged and 4.2V when fully
charged. The 14500 lithium ion cells are AA sized (14500 = 14mm
diameter and 50mm long). However, beware that lithium ion cells can
burst in to flames if incorrectly charged so you want to be sure it
should be lithium ion before fitting one. If you do fit one, I would
recommend that you buy a battery with the protection module built in.

These came up after a quick Google:

http://www.ecrater.co.uk/p/9751735/t...ttery-900mah-2

http://ant-supplies.co.uk/Rechargabl...teries14500tf1

http://www.ledfiretorches.co.uk/batt...batteries.html

try LiFe cells.

Not sure if AA available.

Lithium-Iron is available in AA, but is only 1.5V.
http://ly.rsdelivers.com/product/ene...v/1966692.aspx

Steve wrote:

Lithium-Iron is available in AA, but is only 1.5V.
http://ly.rsdelivers.com/product/ene...v/1966692.aspx

Or less than 1/3 of the RS price

http://www.needbatteries.co.uk/energizer-lithium-27-c.asp

"The Natural Philosopher" wrote in message
...
Steve wrote:
"Graham." wrote in message
...
"Steve" wrote in message
...
We have a solar powered alarm clock which automatically synchronises
with the terrestrial time signal. The clock is marked 'PRECISION',
'SOLAR POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a
look inside. There was an unmarked AA size battery (leaking blue liquid
which I cleaned up). I measured the battery's voltage which was 1.6V,
well above that of a normal rechargeable (1.2V?).

I presume the battery is the source of the problem. I tried replacing
the battery with both rechargeable and non-reachargeable AA ones, but
the unit still didn't work.

I suspect that the original battery was much more than 1.6V - maybe 3V?
But I can't find any references to
rechargeable AA-sized 3V batteries. Can anyone suggest where to get a
replacement battery (or other ideas)?

Cheers.
Any sign of damage to the PCB from the leaking electrolyte?

I think you are reading too much into the 1.5 terminal voltage with no
load.

--
Graham.

%Profound_observation%

Thanks for replying Graham. There's no damage to the PCB. Also, I've
never seen a rechargeable with 1.5V (even under no load); the battery (I
should say 'cell' really) is the most likely cause of the problem. I may
risk conecting a couple of 'normal' AAs in series and see what happens.

Cheers
plenty of batteries of the non rechargeable sort have 3v voltage..LIPO are
about 3.7 in the rechargeable arena, and LiFePo are about 3.3.

But I don't think any 3.3v rechargeables come in AAA format.

More likely the whole unit is a con, and its a non rechargeable battery
that is actually being slightly recharged by the solar power.

However I am puzzled: for reasons of cmapitbility, most AAA cells are of
similar voltage.

Triple A? Would you care to borrow my glasses?
--
Tinkerer

"The Natural Philosopher" wrote in message ...
Gareth wrote:
On 04/12/2010 20:35, Steve wrote:
We have a solar powered alarm clock which automatically synchronises with the terrestrial time signal. The clock is marked
'PRECISION', 'SOLAR POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look inside. There was an unmarked AA size battery (leaking
blue liquid which I cleaned up). I measured the battery's voltage which was 1.6V, well above that of a normal rechargeable
(1.2V?).


Was that with it in circuit of after you removed it? If it was in
circuit and being charged when you measured it then 1.6v may be correct
for a normal AA rechargeable battery.

Lithium ion batteries are around 3V when discharged and 4.2V when fully
charged. The 14500 lithium ion cells are AA sized (14500 = 14mm
diameter and 50mm long). However, beware that lithium ion cells can
burst in to flames if incorrectly charged so you want to be sure it
should be lithium ion before fitting one. If you do fit one, I would
recommend that you buy a battery with the protection module built in.

These came up after a quick Google:

http://www.ecrater.co.uk/p/9751735/t...ttery-900mah-2

http://ant-supplies.co.uk/Rechargabl...teries14500tf1

http://www.ledfiretorches.co.uk/batt...batteries.html

try LiFe cells.

Not sure if AA available.

NiZn cells are 1.65v and rechargeable.
They are reputed to come in AA size but I've never knowingly ever seen one.

--
Graham.

%Profound_observation%

(I can't measure the current through the clock without
'breaking-open' the circuit (ammeter must be ins series), which I
don't want to do.)

I'm probably missing the point but I'd thought that you would have
access to the terminals to which the battery was connected and so could
connect across them a resistor of (say) 470k [1] and then measure the
voltage and current when the cells are in sunlight.


[1] total guesstimate based on a Lion cell requiring a charging voltage
of ~3.6V and anything less than a few microamps not being worth the
candle

--
Robin
PM may be sent to rbw0{at}hotmail{dot}com

Tinkerer wrote:
"The Natural Philosopher" wrote in message
...
Steve wrote:
"Graham." wrote in message
...
"Steve" wrote in message
...
We have a solar powered alarm clock which automatically synchronises
with the terrestrial time signal. The clock is marked 'PRECISION',
'SOLAR POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a
look inside. There was an unmarked AA size battery (leaking blue liquid
which I cleaned up). I measured the battery's voltage which was 1.6V,
well above that of a normal rechargeable (1.2V?).

I presume the battery is the source of the problem. I tried replacing
the battery with both rechargeable and non-reachargeable AA ones, but
the unit still didn't work.

I suspect that the original battery was much more than 1.6V - maybe 3V?
But I can't find any references to
rechargeable AA-sized 3V batteries. Can anyone suggest where to get a
replacement battery (or other ideas)?

Cheers.
Any sign of damage to the PCB from the leaking electrolyte?

I think you are reading too much into the 1.5 terminal voltage with no
load.

--
Graham.

%Profound_observation%

Thanks for replying Graham. There's no damage to the PCB. Also, I've
never seen a rechargeable with 1.5V (even under no load); the battery (I
should say 'cell' really) is the most likely cause of the problem. I may
risk conecting a couple of 'normal' AAs in series and see what happens.

Cheers
plenty of batteries of the non rechargeable sort have 3v voltage..LIPO are
about 3.7 in the rechargeable arena, and LiFePo are about 3.3.

But I don't think any 3.3v rechargeables come in AAA format.

More likely the whole unit is a con, and its a non rechargeable battery
that is actually being slightly recharged by the solar power.

However I am puzzled: for reasons of cmapitbility, most AAA cells are of
similar voltage.

Triple A? Would you care to borrow my glasses?

Think I need to..:-)

Mea culpa!

..
..
"Robin" wrote in message
...
(I can't measure the current through the clock without
'breaking-open' the circuit (ammeter must be ins series), which I
don't want to do.)

I'm probably missing the point but I'd thought that you would have access
to the terminals to which the battery was connected and so could connect
across them a resistor of (say) 470k [1] and then measure the voltage and
current when the cells are in sunlight.


[1] total guesstimate based on a Lion cell requiring a charging voltage of
~3.6V and anything less than a few microamps not being worth the candle

--
Robin
PM may be sent to rbw0{at}hotmail{dot}com

Thanks Robin, but I don't have any 470k (or other) resistors to hand. Just
a multimeter
that I use for checking electrical things.

In any case, surely measuring the current though a resistor between the
terminals
would only tell me if the charging circuit was working (solar cell
delivering current to the battery).
It wouldn't tell me if current was being delivered to the clock
- to do that the meter would somehow have to be in series with the clock..

Steve

"Steve" wrote in message
...
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which I
cleaned up). I measured the battery's voltage which was 1.6V, well above
that of a normal rechargeable (1.2V?).

I presume the battery is the source of the problem. I tried replacing the
battery with both rechargeable and non-reachargeable AA ones, but the unit
still didn't work.

I suspect that the original battery was much more than 1.6V - maybe 3V?
But I can't find any references to
rechargeable AA-sized 3V batteries. Can anyone suggest where to get a
replacement battery (or other ideas)?

Cheers.


It is probably a Lithium Thionyl Chloride which have a terminal voltage of
3.6V. You can get them in both 1/2 AA and full AA sizes.
Try Budget batteries
http://www.budgetbatteries.co.uk/ind...onyl-chloride/

Phil

Steve wrote:
We have a solar powered alarm clock which automatically synchronises with
the terrestrial time signal. The clock is marked 'PRECISION', 'SOLAR
POWER' and 'RADIO CONTROLLED'.

The display became faint and eventually it stopped working. I took a look
inside. There was an unmarked AA size battery (leaking blue liquid which I
cleaned up). I measured the battery's voltage which was 1.6V, well above
that of a normal rechargeable (1.2V?).

How heavy is this?
NiCd and NiMH batteries are considerably heavier than lithium of any sort.
I would - as others have suggested suspect a 3V lithium non-rechargable
battery - simply as rechargable lithium are more expensive.