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Old 17th Jun 2020, 9:16 am   #1
Phil G4SPZ
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Default Dry battery longevity

I have just re-stuffed the large combined HT & LT battery that I use in my Ever Ready Sky King. I originally re-stuffed this battery what seemed like three or four years ago, but when I opened it up I was amazed to discover that the cells had ‘best before’ dates of 2013 and 2014 on them. I used all brand new cells at the time, so I must have done the original re-stuffing around ten years ago!

There were 54 pound-shop ‘Panasonic’ branded zinc chloride AA cells. Only one was showing significant leakage and the terminal voltage was down to roughly 1.1 volts per cell. Three ‘Maplin’ C-size alkaline cells in parallel supply the LT, and annoyingly one of these had leaked quite badly, necessitating a clean-up of its holder. All in all though, I was quite impressed with the longevity of these cells. Of course, if I had made more regular inspections I might have spotted the deterioration sooner.

I have been less impressed by a batch of ‘Maxell’ CR2025 Lithium button cells, bought from Amazon and bearing a date code of 12-2024. From my stock of ten, two were OK and eight were virtually flat. Looking at other purchasers’ feedback proves my experience is far from unique. Avoid!

Phil
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Old 17th Jun 2020, 10:54 am   #2
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Default Re: Dry battery longevity

I wonder, do batteries get 'faked' in the same way other electronic parts seem to do?
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Old 17th Jun 2020, 1:07 pm   #3
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Default Re: Dry battery longevity

Was the radio used often, for short periods? I wonder if that helps with battery life and health?
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Old 17th Jun 2020, 2:38 pm   #4
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Default Re: Dry battery longevity

Quote:
do batteries get 'faked' in the same way other electronic parts seem to do
Oh yes, there was a thing about fake Duracells (the king of leaks) a while ago. Unintuitively you are probably better off getting "pound shop" own brand than posher ones, they are not likely to get faked (no profit in that). And as "pound shops" survive by sheer bulk of sales any whiff of bad quality* would knock them for six.

*in the sense of "it does what it says on the tin" rather than a beautiful finish and superlative (superfluous!) packaging.
 
Old 17th Jun 2020, 2:59 pm   #5
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Default Re: Dry battery longevity

Yes, Bill, it’s my workshop radio, so it’s used once or twice a week, sometimes less, for maybe half an hour at a time. Zinc chloride cells are indeed reputed to last a long time in intermittent low-current, light duty applications. Thinking about it, half an hour a week over ten years is not far off 240 hours, which this type of battery was originally designed to achieve in later sets using the Dx96 range of low consumption miniature valves.

Regarding the faking of Maxell batteries, it’s hard to know for sure, but quite possible. In future I’ll buy all my batteries from CPC. Merlin, you make a good point about pound shop batteries and I’ve always used them when making replica HT/LT batteries with very few problems.
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Last edited by Phil G4SPZ; 17th Jun 2020 at 3:14 pm. Reason: Clarity
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Old 17th Jun 2020, 4:09 pm   #6
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Default Re: Dry battery longevity

...It's possible for Lithium coin cells to appear dead after a period of storage- i forget the exact chemistry but it's something like an oxide layer that needs to be broken through by asking the cell to supply a zap of greater current than it would normally be asked for in use. The cell is reanimated by this action.

(This is anecdotal, based on someone else's experience- can't remember who.)

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Old 17th Jun 2020, 4:23 pm   #7
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Default Re: Dry battery longevity

This is exactly what happened with a couple of these cells, Dave. I have a tester that draws 200mA from the cell under test. Most of the dud ones tested at virtually zero current permanently, but one or two did start off showing ‘flat’ but recovered after a second to read well into the ‘good’ category.
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Old 17th Jun 2020, 4:50 pm   #8
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Default Re: Dry battery longevity

The 4.5V Panasonic Zinc Cloride flat battery in our kitchen torch with a use by date of Oct 2010 still gives a bright light. It only gets intermittent use, but always works when it is needed.

Last edited by emeritus; 17th Jun 2020 at 4:52 pm. Reason: Typo
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Old 17th Jun 2020, 7:54 pm   #9
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Default Re: Dry battery longevity

Quote:
Originally Posted by merlinmaxwell View Post
Quote:
do batteries get 'faked' in the same way other electronic parts seem to do
Oh yes, there was a thing about fake Duracells (the king of leaks) a while ago. Unintuitively you are probably better off getting "pound shop" own brand than posher ones, they are not likely to get faked (no profit in that). And as "pound shops" survive by sheer bulk of sales any whiff of bad quality* would knock them for six.

*in the sense of "it does what it says on the tin" rather than a beautiful finish and superlative (superfluous!) packaging.
Thanks Merlin. I tend to buy Kodak's from our Poundland and occasionally Sony and Panasonic. I've never had any of these leak over the years, unlike your 'King of Leaks'. A good name. I'd put Energizers in that category as well.

Quote:
Originally Posted by The Philpott View Post
...It's possible for Lithium coin cells to appear dead after a period of storage- i forget the exact chemistry but it's something like an oxide layer that needs to be broken through by asking the cell to supply a zap of greater current than it would normally be asked for in use. The cell is reanimated by this action.

(This is anecdotal, based on someone else's experience- can't remember who.)

Dave
I've experienced this with car keys. The one in the wardrobe stops working after a few months, I open it up, test the battery and its fine (no load test) but pop another in and it works.

I blamed the contacts in the past but then found if I hold the lock/unlock button down for several seconds it starts to come back to life. So I alternate them now and don't have the problem.

The oxide layer thing is something I read about somewhere in the distant past and I also have a recollection of reading that some coin cells are more suited to usage such as key fobs than others in that they don't suffer this issue so much.
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Old 29th Jun 2020, 3:38 pm   #10
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Default Re: Dry battery longevity

I'm just about to change the C cells in our doorbell as the present ones have finally died. They have only just started to show some whiskers around the negative end. They are, or were, Sainsburys Long Life Alkaline and dated coded 05-91. Not a bad life, maybe we just don't have enough visitors.

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Old 29th Jun 2020, 3:52 pm   #11
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Default Re: Dry battery longevity

Another vote here for Sainsbury's own brand alkaline. The 4 C cells in our doorbell were installed in 1987 & still working with no sign of leakage. On my crude test of short into the 10A range of a multimeter, they still deliver 3-4A so should be good for a few years yet.

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Old 29th Jun 2020, 4:00 pm   #12
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Default Re: Dry battery longevity

Doorbells are an interesting study...

I don't know the exact numbers but I would guess a mains transformer for a bell consumes about 1 watt which is nearly 10kW over a year. We've one, powered up in 1953 and still running a bell.

Do the sums, the batteries work out much cheaper overall, even if replaced quite frequently.
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Old 29th Jun 2020, 4:25 pm   #13
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Default Re: Dry battery longevity

I make that 8.76 kWh which works out about £1.25...but does it really consume 1W when not energising the bell, assuming an older AC type (i.e. no DC rectification, bleed or switch mode stuff) - I'm genuinely interested in this.
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Old 29th Jun 2020, 5:58 pm   #14
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Default Re: Dry battery longevity

I’m guessing that the bell transformer is probably pulling rather more current but at a very low power factor. Based on my observation that such transformers run slightly warm, one watt is not a bad estimate. The old rule of thumb, that “one watt, running continuously, equates to one pound per year” is a bit outdated now, but it’s a fair starting point.
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Old 29th Jun 2020, 6:30 pm   #15
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Default Re: Dry battery longevity

Like Phil, I figured 1 watt a reasonable estimate. It runs 'not cold' rather than warm. It's also pretty large so I figure any core losses are quite low.

2020 back to 1953 is 67 years. 67 * 8.8kW is 590kW which would take you a couple of thousand miles in a Nissan Leaf (back of packet guestimations...)

Actual energy used at say five 1.5 second bell pushes a week is 7.5 seconds a week or (rounding up) 400 seconds a year. Seven minutes use.

67 years of that would be 469 minutes or 7.8 hours.

Lets say the transformer was 100% efficient and the bell drew 1 amp at 12 volt (no idea what the voltage is tbh but the current bell can use 4 C cells).

That's 12 watts for 7.8 hours which is 93 watts over 67 years vs 590kW for the transformer.


From memory it looks a bit like this:
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Old 29th Jun 2020, 6:51 pm   #16
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Default Re: Dry battery longevity

In a porch with a decent push switch you could put it in the transformers primary side and save that £1.25 a year.

But transformer run bells ofter have an illuminated bell push which would prevent that and increase that £1.25 a year anyway.
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Old 29th Jun 2020, 7:28 pm   #17
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Default Re: Dry battery longevity

You would also be running the mains through your bell push and associated wiring, which isn't really a good idea - even if it's safe when you first install it, doorbell installations stay in place for many decades and multiple occupants. My (battery) doorbell was installed by a previous house owner sometime in the 70s, and is untouched apart from battery replacement and contact cleaning.
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Old 29th Jun 2020, 8:56 pm   #18
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Default Re: Dry battery longevity

Hi Folks, if the bell push is not illuminated then there will be no sec load on the transformer and it will only be drawing primarily reactive current (low power factor).
The domestic electricity meter is generally only responsive to "real" power, so the low PF consumption will not be recorded

Ed
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Old 29th Jun 2020, 9:11 pm   #19
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Default Re: Dry battery longevity

The 'Eveready' AD28 6V battery in my Bardic handlamp is still going strong and it is dated 'Best Before 01 2010'.

I only really use the handlamp in winter, and not for prolonged periods. And I have fitted an LED replacement bulb in it, but still...
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Old 29th Jun 2020, 9:32 pm   #20
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Default Re: Dry battery longevity



Can I put in a plea for kWh or Wh in those calculations for actual energy used, kW or just W is the rate at which the energy is consumed.
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