Nine volt batteries for 90/45 v packs - UK Vintage Radio Repair and Restoration Discussion Forum

Pete_kaye · 25th Sep 2011, 3:01 pm

I wanted to build a 45V pack myself so decided to look in the recycling box at my local Lidl store. I dropped off about 20 AA and AAA types and salvaged 6 x 9V. Initially I wanted to open and retrieve the tops to use as connectors for the ones I had bought. However, I found that 5 out of 6 were still good for 8.85V and am still using them in my various transistor radios.
I went back and got a few more and finally made up the 45V shown.

Pete_kaye · 10th Oct 2011, 3:04 pm

As a follow on for this topic, I now have retrieved about 10 'used' batteries .One thing I noticed was that that the O/c Voltage reading says little .SEveral of the lower readings (~8V) gave the best current through a 6V bulb or in my small Roberts Rambler portable .Some of the higher readings would barely light the same bulb or work the tranny. They were all different makes and non rechargeable ; can anyone explain this?

davegsm82 · 10th Oct 2011, 6:32 pm

Pete, its all down to the battery chemistry.

Different types of batteries act differently as they run down, for example;

Alkaline - The open circuit voltage drops pretty much proportionally with use, a good 9v alkaline may show 6v at end of life, but this may only drop to 5.5v on load.

Zinc-Carbon - These act more like a battery with a resistance in line. i.e, a 'Dead' battery may show 8v at the terminals, but as soon as you try to draw any power, the voltage drops off. The 'resistance' grows higher as the battery discharges.

All batteries exhibit some internal resistance, this is why alkaline and Ni-Cd are better for high drain such as camera flash and kids toys, their internal resistance is negligible over the lifetime of the charge.

This is also why some people get confused about what types of cells to use for a particular application, cheapo zinc-carbon's are just as good (or better) for TV remotes as Alkaline's, because the alkaline is likely to exceed its shelf life before the charge is used up. A Zinc carbon will give you the best Energy to price ratio in this application.

Dave.

G4XWDJim · 10th Oct 2011, 6:58 pm

I often test batteries with the 10 amp range on my AVO. Experience shows what to expect from different types. It's a cruel test but if you are quick it gives you a good idea of the state of the battery.

A Duracell D cell will send the AVO across the scale to 8 to 10 amps.

A cheapo D Cell will barely make 2 amps. The proper test of course is a variable load but it's fiddly and I've done this AVO trick for years with no apparent problems.

Jim

ppppenguin · 10th Oct 2011, 7:48 pm

Quote:

Originally Posted by G4XWDJim

I often test batteries with the 10 amp range on my AVO.

Works equally well with a DMM. Just remember to move the +ve probe back to the voltage input after you've done the test. My Fluke 87 audibly reminds you if the probe is in a current terminal without current measurement selected.

Like Jim, I've used this test for years without trouble.

60 oldjohn · 10th Oct 2011, 9:45 pm

I also flash test batteries on the 10amp range. I find that some ex smoke alarm batteries still show around one amp which aint bad for a pp3 but maybe only 8v not good enough for smoke allarms but ideal for HT batteries. I have also tested 0.5 volts and about 5amps on a D cell! John.

paulsherwin · 10th Oct 2011, 10:09 pm

Smoke alarms will generate a low battery warning when the voltage drops to 8-8.5V. It's very wasteful to use alkaline PP3s in them unless you have a use for them afterwards. People think they will last much longer than zinc chloride, but they don't because of the voltage characteristics. It makes much more sense to use Poundland Sony PP3s at two for a pound and fit a new one every autumn before the beeping wakes you up in the middle of the night.

Tim · 11th Oct 2011, 12:50 am

Quote:

This is also why some people get confused about what types of cells to use for a particular application, cheapo zinc-carbon's are just as good (or better) for TV remotes as Alkaline's, because the alkaline is likely to exceed its shelf life before the charge is used up. A Zinc carbon will give you the best Energy to price ratio in this application.

Yes but the cheap zinc carbon types often leak,(and how much is a new remote?) whereas half decent Alkalines not so prone. I still have a set in our bedroom remote that "expired" in 2006. I think they are the Ikea ones, which at that time were made by Varta. £1.90 for 10

Andy Doz · 11th Oct 2011, 12:56 pm

I grab a handful of the Ikea batteries when I'm there. They're still made by Varta.

trh01uk · 11th Oct 2011, 9:26 pm

If you want a 90V supply, isn't a lot easier just to make up a multivibrator feeding a small mains transformer in reverse? Powered from a few volts from a rechargeable battery is going to save a lot of pennies in the long run. Designs abound on the net - my favourite is at http://www.dos4ever.com/battery/battery.html.

Richard

pichacker · 14th Oct 2011, 12:32 pm

I tried this but for radio use you have to be careful to ensure that the harmonic radiation from the invertor does not interfere with the frequency you wish to listen to....

Although fair credit to the author of the link

ed731pdh · 18th Oct 2011, 2:31 pm

Last batch I obtained from a Poundland were Kodak heavy duty cells, two for a quid. No issues with them and decent cells.

25th Sep 2011, 3:01 pm	#1
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Nine volt batteries for 90/45 v packs I wanted to build a 45V pack myself so decided to look in the recycling box at my local Lidl store. I dropped off about 20 AA and AAA types and salvaged 6 x 9V. Initially I wanted to open and retrieve the tops to use as connectors for the ones I had bought. However, I found that 5 out of 6 were still good for 8.85V and am still using them in my various transistor radios. I went back and got a few more and finally made up the 45V shown. Attached Thumbnails

10th Oct 2011, 3:04 pm	#2
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Nine volt batteries for 90/45 v packs As a follow on for this topic, I now have retrieved about 10 'used' batteries .One thing I noticed was that that the O/c Voltage reading says little .SEveral of the lower readings (~8V) gave the best current through a 6V bulb or in my small Roberts Rambler portable .Some of the higher readings would barely light the same bulb or work the tranny. They were all different makes and non rechargeable ; can anyone explain this?

10th Oct 2011, 6:32 pm	#3
davegsm82 Heptode Join Date: Jan 2004 Location: Blyth, Northumberland, UK. Posts: 858	Re: Nine volt batteries for 90/45 v packs Pete, its all down to the battery chemistry. Different types of batteries act differently as they run down, for example; Alkaline - The open circuit voltage drops pretty much proportionally with use, a good 9v alkaline may show 6v at end of life, but this may only drop to 5.5v on load. Zinc-Carbon - These act more like a battery with a resistance in line. i.e, a 'Dead' battery may show 8v at the terminals, but as soon as you try to draw any power, the voltage drops off. The 'resistance' grows higher as the battery discharges. All batteries exhibit some internal resistance, this is why alkaline and Ni-Cd are better for high drain such as camera flash and kids toys, their internal resistance is negligible over the lifetime of the charge. This is also why some people get confused about what types of cells to use for a particular application, cheapo zinc-carbon's are just as good (or better) for TV remotes as Alkaline's, because the alkaline is likely to exceed its shelf life before the charge is used up. A Zinc carbon will give you the best Energy to price ratio in this application. Dave.

10th Oct 2011, 6:58 pm	#4
G4XWDJim Octode Join Date: Oct 2008 Location: Littlehampton, West Sussex, UK. Posts: 1,465	Re: Nine volt batteries for 90/45 v packs I often test batteries with the 10 amp range on my AVO. Experience shows what to expect from different types. It's a cruel test but if you are quick it gives you a good idea of the state of the battery. A Duracell D cell will send the AVO across the scale to 8 to 10 amps. A cheapo D Cell will barely make 2 amps. The proper test of course is a variable load but it's fiddly and I've done this AVO trick for years with no apparent problems. Jim

10th Oct 2011, 9:45 pm	#6
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,987	Re: Nine volt batteries for 90/45 v packs I also flash test batteries on the 10amp range. I find that some ex smoke alarm batteries still show around one amp which aint bad for a pp3 but maybe only 8v not good enough for smoke allarms but ideal for HT batteries. I have also tested 0.5 volts and about 5amps on a D cell! John.

10th Oct 2011, 10:09 pm	#7
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: Nine volt batteries for 90/45 v packs Smoke alarms will generate a low battery warning when the voltage drops to 8-8.5V. It's very wasteful to use alkaline PP3s in them unless you have a use for them afterwards. People think they will last much longer than zinc chloride, but they don't because of the voltage characteristics. It makes much more sense to use Poundland Sony PP3s at two for a pound and fit a new one every autumn before the beeping wakes you up in the middle of the night.

11th Oct 2011, 12:56 pm	#9
Andy Doz Hexode Join Date: Feb 2011 Location: Gloucestershire, UK. Posts: 376	Re: Nine volt batteries for 90/45 v packs I grab a handful of the Ikea batteries when I'm there. They're still made by Varta.

11th Oct 2011, 9:26 pm	#10
trh01uk Octode Join Date: Nov 2010 Location: Ross-on-Wye, Herefordshire, UK. Posts: 1,652	Re: Nine volt batteries for 90/45 v packs If you want a 90V supply, isn't a lot easier just to make up a multivibrator feeding a small mains transformer in reverse? Powered from a few volts from a rechargeable battery is going to save a lot of pennies in the long run. Designs abound on the net - my favourite is at http://www.dos4ever.com/battery/battery.html. Richard

14th Oct 2011, 12:32 pm	#11
pichacker Hexode Join Date: Aug 2008 Location: Essex, UK. Posts: 370	Re: Nine volt batteries for 90/45 v packs I tried this but for radio use you have to be careful to ensure that the harmonic radiation from the invertor does not interfere with the frequency you wish to listen to.... Although fair credit to the author of the link __________________ 6.3v on my heaters is no longer enough to get me going in the morning!!

18th Oct 2011, 2:31 pm	#12
ed731pdh Retired Dormant Member Join Date: Jan 2011 Location: Pulborough, West Sussex, UK. Posts: 114	Re: Nine volt batteries for 90/45 v packs Last batch I obtained from a Poundland were Kodak heavy duty cells, two for a quid. No issues with them and decent cells.