Making a new 15 volt AVO battery - UK Vintage Radio Repair and Restoration Discussion Forum

Mooly · 9th Nov 2011, 1:40 pm

Having read on this forum about using Lithium cells to make a 15 volt AVO replacement battery I thought I would have a go. I had wanted to make an electronic convertor but having spotted these packs of cells in our local "home bargains" at £0.99 they seemed worth a punt.

Hoping that these will last a long time, I wanted to try and prevent problems that could occur with poor contact of the cells and wires over time and so this is what I did.

I have a small plastic suction vice and so mounted that vertically and began to stack the cells. Each was cleaned with ISO and then a small piece of aluminium foil placed between each such that it might mould to the contours better. The cells on their own are not flat and contact is more of a point contact. With that done and light pressure applied via the vice I coated the rim of the cells in epoxy and left to harden.

Now for the wires...
I used a 6800uf cap charged to around 13 volts to "tag weld" them to the cell ends and then finished off with more epoxy. Hopefully that will give a reliable contact as there is nothing worse than having to keep moving or spinning cells to get a good connection. The battery reads around 16.6 volts and its nice to have the AVO "zeroed" with the pot at the bottom rather than top end of the range. Time will tell I guess...

The cells are a snug fit, wrapped in a piece of U shaped foam and pushed into the holder with wires soldered to the original connectors which on the MK5 have tiny tags already available to use.

paulsherwin · 9th Nov 2011, 2:05 pm

I must admit I just wrapped some vinyl tape around 5 2032 cells and bent the holder arms inwards to hold the smaller sized battery. So far so good, but my AVO doesn't get a lot of rough handling, and your solution is much more robust.

ronbryan · 9th Nov 2011, 2:34 pm

I found five 2032 lithium cells, a section of plastic overflow pipe, and a couple of brass end cheeks made by a friend, gave me a plug in battery for my Avo 8 MkII that has lasted from 2005 and is still going. The original idea came from a suggestion by Leon Crampin posted here a while back.

After an initial clean with IPA, the clamping pressure of the springs in the battery holder has been sufficient to maintain good contact so far.

Having looked again at the photo, it looks as if I should have made a better job of deburring the pipe edges!

A great improvement over the replacement BLR121 batteries, which had a very poor shelf life, (unless I was very unlucky).

Ron

Roger-M0TDM · 9th Nov 2011, 5:37 pm

I just held five 2032's in series in a piece of foam.
The foam is a snug fit in the battery holder on the Avo a smaal piece of copper wire protudes through each side of the foam to make contact.
Incidently I haven't used the Avo for about 6mths, checked the operation yesterday and all still fine.
Regards Roger.

Andrewausfa · 9th Nov 2011, 6:28 pm

That's a good method. I bought some 2032 batteries and used 2p peices as spacers and wrapped the bundle in tape.

Andrew

Mooly · 9th Nov 2011, 6:53 pm

Quote:

Originally Posted by ronbryan

I found five 2032 lithium cells, a section of plastic overflow pipe, and a couple of brass end cheeks made by a friend...............

A great improvement over the replacement BLR121 batteries, which had a very poor shelf life, (unless I was very unlucky).

Ron

Looks alright to me

Nice job.

I wonder what the new batteries from Farnell and RS are like. Around £7.00 I think but these lithium ones are cheaper and must far outlast an alkaline button cell.

paulsherwin · 9th Nov 2011, 7:59 pm

Lithium coin cell batteries are ideal for this application, as they have a very long shelf life. I have a 15 year old LCD watch which is still on its original lithium battery.

Mooly · 9th Nov 2011, 8:12 pm

Quote:

Originally Posted by paulsherwin

Lithium coin cell batteries are ideal for this application, as they have a very long shelf life. I have a 15 year old LCD watch which is still on its original lithium battery.

I can believe it...

I have a Casio F8 ? LCD watch bought when I started technical college back in 1978/9. It's only had one replacement battery in all that time and it still lights the backlight.

Just looked up the capacity of the 2032 and it's around 200mah give or take. So the old AVO could sit with probes shorted for around 3 months...

McMurdo · 9th Nov 2011, 8:38 pm

I dont know if megger still do, but at one time they used to supply a brown plastic adapter shell with the AVO 8 to replace the BLR121, it accomodated a standard 15V alkaline camera battery eg Varta V74PX or Duracell BLR154. I'd have thought this was a better idea than the useless BLR121's that you seem to get today that leak and die and are (in any case) just a stack of cheap coin cells inside. (A certain highstreet store actually sold us some new but dead BLR121's that, when broken open, were already green and furry).
Surely a shell can be fashioned from a piece of upvc minitrunking or similar sawn to fit?
When I worked for a company servicing AVOs etc we regularly used these plastic adapters when decent BLR121s from Duracell ceased to be readily available. The BLR154 seems a superior beast all round

neonlamp · 11th Nov 2011, 7:28 pm

I made a 15V equivalent using 13 mm heatshrink tube, the end caps from a dead 15V battery and a stack of 10 SR54's. BIgger than the tiddlers used in Maplin's BLR121 battery replacement.

Mooly · 11th Nov 2011, 8:26 pm

I like it... and I have the original plastic adapter too.

ThePillenwerfer · 11th Nov 2011, 9:39 pm

I joined my cells together with heat-shrink and then fitted them into a wooden adaptor.

- Joe

neonlamp · 12th Nov 2011, 5:38 pm

Yes, my heatshrink stack needs the plastic adapter.
For my trusty 8 Mk II, even the new BLR121's don't fit because the battery clips have metal foils with slots in them and a further spring foil behind the slotted foil. They were intended to hold the original battery in place which had rectangular brass terminals. The newer BLR121's have circular disk terminals, and fall out. Even using a BLR154 with an adapter did not work, so I hardwired a different socket. I cut an "N" cell holder in half, stretched it by about 4 mm and stuck the two halves onto a matching strip of plain SRBP. Then I soldered (!) the flying wires to the metal foils. HOlds a BLR154 or a coin stack nicely.

jonnybear · 21st Jun 2013, 12:32 pm

Here is a simple way of making up your own 15 volt battery for avo and many other meters using the BLR154.
Just get an old DEAD Duracell AA or any alkaline battery cut 3 cm from positive terminal with junior hacksaw, drill out carbon core, sleeve with cardboard from cornflake packet, then insert 10 x LR1130 button cells, a small hole can be drilled at the + end so that you can push out cells if replacements are required.

9th Nov 2011, 1:40 pm	#1
Mooly Octode Join Date: May 2011 Location: Lancashire, UK. Posts: 1,351	Making a new 15 volt AVO battery Having read on this forum about using Lithium cells to make a 15 volt AVO replacement battery I thought I would have a go. I had wanted to make an electronic convertor but having spotted these packs of cells in our local "home bargains" at £0.99 they seemed worth a punt. Hoping that these will last a long time, I wanted to try and prevent problems that could occur with poor contact of the cells and wires over time and so this is what I did. I have a small plastic suction vice and so mounted that vertically and began to stack the cells. Each was cleaned with ISO and then a small piece of aluminium foil placed between each such that it might mould to the contours better. The cells on their own are not flat and contact is more of a point contact. With that done and light pressure applied via the vice I coated the rim of the cells in epoxy and left to harden. Now for the wires... I used a 6800uf cap charged to around 13 volts to "tag weld" them to the cell ends and then finished off with more epoxy. Hopefully that will give a reliable contact as there is nothing worse than having to keep moving or spinning cells to get a good connection. The battery reads around 16.6 volts and its nice to have the AVO "zeroed" with the pot at the bottom rather than top end of the range. Time will tell I guess... The cells are a snug fit, wrapped in a piece of U shaped foam and pushed into the holder with wires soldered to the original connectors which on the MK5 have tiny tags already available to use. Attached Thumbnails

9th Nov 2011, 2:05 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Making a new 15 volt AVO battery I must admit I just wrapped some vinyl tape around 5 2032 cells and bent the holder arms inwards to hold the smaller sized battery. So far so good, but my AVO doesn't get a lot of rough handling, and your solution is much more robust.

9th Nov 2011, 2:34 pm	#3
ronbryan Octode Join Date: Jan 2003 Location: Guildford, Surrey, UK. Posts: 1,960	Re: Making a new 15 volt AVO battery I found five 2032 lithium cells, a section of plastic overflow pipe, and a couple of brass end cheeks made by a friend, gave me a plug in battery for my Avo 8 MkII that has lasted from 2005 and is still going. The original idea came from a suggestion by Leon Crampin posted here a while back. After an initial clean with IPA, the clamping pressure of the springs in the battery holder has been sufficient to maintain good contact so far. Having looked again at the photo, it looks as if I should have made a better job of deburring the pipe edges! A great improvement over the replacement BLR121 batteries, which had a very poor shelf life, (unless I was very unlucky). Ron Attached Thumbnails Last edited by ronbryan; 9th Nov 2011 at 2:42 pm.

9th Nov 2011, 5:37 pm	#4
Roger-M0TDM Pentode Join Date: Aug 2009 Location: Sheffield, South Yorkshire, UK. Posts: 167	Re: Making a new 15 volt AVO battery I just held five 2032's in series in a piece of foam. The foam is a snug fit in the battery holder on the Avo a smaal piece of copper wire protudes through each side of the foam to make contact. Incidently I haven't used the Avo for about 6mths, checked the operation yesterday and all still fine. Regards Roger.

9th Nov 2011, 6:28 pm	#5
Andrewausfa Octode Join Date: Dec 2010 Location: St Ives, Cambridgeshire, UK. Posts: 1,180	Re: Making a new 15 volt AVO battery That's a good method. I bought some 2032 batteries and used 2p peices as spacers and wrapped the bundle in tape. Andrew __________________ Invisible airwaves crackle with life. Or they should do. BVWS Member

9th Nov 2011, 7:59 pm	#7
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Making a new 15 volt AVO battery Lithium coin cell batteries are ideal for this application, as they have a very long shelf life. I have a 15 year old LCD watch which is still on its original lithium battery.

9th Nov 2011, 8:38 pm	#9
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,274	Re: Making a new 15 volt AVO battery I dont know if megger still do, but at one time they used to supply a brown plastic adapter shell with the AVO 8 to replace the BLR121, it accomodated a standard 15V alkaline camera battery eg Varta V74PX or Duracell BLR154. I'd have thought this was a better idea than the useless BLR121's that you seem to get today that leak and die and are (in any case) just a stack of cheap coin cells inside. (A certain highstreet store actually sold us some new but dead BLR121's that, when broken open, were already green and furry). Surely a shell can be fashioned from a piece of upvc minitrunking or similar sawn to fit? When I worked for a company servicing AVOs etc we regularly used these plastic adapters when decent BLR121s from Duracell ceased to be readily available. The BLR154 seems a superior beast all round __________________ Kevin

11th Nov 2011, 7:28 pm	#10
neonlamp Retired Dormant Member Join Date: Sep 2010 Location: Tavistock, Devon, UK. Posts: 84	Re: Making a new 15 volt AVO battery I made a 15V equivalent using 13 mm heatshrink tube, the end caps from a dead 15V battery and a stack of 10 SR54's. BIgger than the tiddlers used in Maplin's BLR121 battery replacement. Attached Thumbnails

11th Nov 2011, 8:26 pm	#11
Mooly Octode Join Date: May 2011 Location: Lancashire, UK. Posts: 1,351	Re: Making a new 15 volt AVO battery I like it... and I have the original plastic adapter too.

11th Nov 2011, 9:39 pm	#12
ThePillenwerfer Octode Join Date: Mar 2011 Location: Sheffield, South Yorkshire, UK. Posts: 1,453	Re: Making a new 15 volt AVO battery I joined my cells together with heat-shrink and then fitted them into a wooden adaptor. - Joe Attached Thumbnails __________________ "Experts are only good at one thing: explaining why something will not work!"

12th Nov 2011, 5:38 pm	#13
neonlamp Retired Dormant Member Join Date: Sep 2010 Location: Tavistock, Devon, UK. Posts: 84	Re: Making a new 15 volt AVO battery Yes, my heatshrink stack needs the plastic adapter. For my trusty 8 Mk II, even the new BLR121's don't fit because the battery clips have metal foils with slots in them and a further spring foil behind the slotted foil. They were intended to hold the original battery in place which had rectangular brass terminals. The newer BLR121's have circular disk terminals, and fall out. Even using a BLR154 with an adapter did not work, so I hardwired a different socket. I cut an "N" cell holder in half, stretched it by about 4 mm and stuck the two halves onto a matching strip of plain SRBP. Then I soldered (!) the flying wires to the metal foils. HOlds a BLR154 or a coin stack nicely.

21st Jun 2013, 12:32 pm	#14
jonnybear Octode Join Date: Nov 2010 Location: Cullompton, Devon, UK. Posts: 1,435	Re: Making a new 15 volt AVO battery Here is a simple way of making up your own 15 volt battery for avo and many other meters using the BLR154. Just get an old DEAD Duracell AA or any alkaline battery cut 3 cm from positive terminal with junior hacksaw, drill out carbon core, sleeve with cardboard from cornflake packet, then insert 10 x LR1130 button cells, a small hole can be drilled at the + end so that you can push out cells if replacements are required.