Dry battery longevity

[Phil G4SPZ]

Originally Posted by russell_w_b

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

You’re lucky! I bought a pair of the same brand AD28s quite recently from a well-established specialist online supplier and they lasted barely a year, with virtually no use, and leaked badly to boot.

Someone started this thread about AD28s quite recently and, when I last looked, they had all but disappeared from the market. Hang onto yours, Russell, and re-stuff it when the time comes!

[MotorBikeLes]

Referring to post 16, my pal Graham figured out that he could put the primary in the switch circuit. Ran perfectly for a while until, one wet day, a friend paying a visit had a shock. His wife Margaret put her size 5s down, and he reverted to convention and excepted the cost of all those annual Watt hours.
That was around 60 years ago and they are still together. She is still the Boss.
Les.

[stainless]

Apologies for off topic - I fondly remember the clockwork operated doorbells, where you turned the gong to wind up the spring (usually when going out the front door); the push button released the mechanism and a rotary hammer struck against the inside of the gong. No battery costs, and you even got a bit of physical exercise as well!

Often mounted on the door itself.

[russell_w_b]

Originally Posted by Phil G4SPZ

'Hang onto yours, Russell, and re-stuff it when the time comes!'

I actually have two, Phil, having bought them for, and used them regularly - but just for the news of an evening - in my Ultra 'Transistor Six', over ten years ago. No sign of leakage as yet. Wonder if yours were just a bad batch?

[russell_w_b]

Originally Posted by stainless

'I fondly remember the clockwork operated doorbells, where you turned the gong to wind up the spring...'

We had one of those on the outer door when I was a kid. On the inner door we had another mechanical doorbell which was, in effect, a bicycle bell. Didn't need winding up; just a push-rod through the door from the bell-push acting via gears onto a weighted centrifugal mechanism which threw out circular hammers to strike the gong.

I did have a bell transformer, it did get a bit warm. A new PVC door and window precluded wiring up this again, so... clockwork bell, marvelous.

[winston_1]

Originally Posted by Ed_Dinning

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

There are still losses due to the magnetic hysteresis of the core. These are known as iron losses.

[Phil G4SPZ]

Originally Posted by russell_w_b

I actually... bought them for... my Ultra 'Transistor Six'... Wonder if yours were just a bad batch?

I think they must have been, Russell. Modern stuff, eh? Mine are in an Ultra Transistor 101 which is a pleasant-sounding radio. Incidentally I’ve checked again this evening and it would appear that no suppliers anywhere have any stocks of AD28s. It looks like replicas are going to be needed from now on.

The divergence of this thread into doorbells has reminded me of the mechanical one on a friend’s front door in the 60s, loud enough to wake the street up and the equivalent of the Klaxon. On electric bells, my wife’s late aunt had lived in her bungalow for over twenty years when her ‘ding-dong’ doorbell stopped working. She insisted it must be mains-powered, as she’d never had to replace batteries. I fitted a new set of C cells and jokingly said that she probably needn’t worry about replacing them ever again. She was 85 at the time... and, sadly, time proved me right

[emeritus]

I suppose you could use a battery-powered relay with mains-rated contacts to energise the transformer only when the bell push operated the relay. This would offer a saving if the relay current was significantly less than the bell current, but it's probably not worth the effort.

[SeanStevens]

** BEWARE ** Probably off topic - but related . . .

I've often thought, it must be possible to build a detector. A device that (let me get vague here for a moment) detects all the electrons it sees pass a certain point in a circuit. By counting the flow, it could keep a tally of how many mAh have passed through that part of the circuit.

Could this be done with a coil around one of the wires from a battery box? That way it would not be in circuit.....

With one of these devices you could read off how well a set of batteries performed over their life.

Again, being vague. But this would probably need its own power supply . . Another battery!


SEAN

[turretslug]

Originally Posted by emeritus

I suppose you could use a battery-powered relay with mains-rated contacts to energise the transformer only when the bell push operated the relay. This would offer a saving if the relay current was significantly less than the bell current, but it's probably not worth the effort.

A take-over circuit could be arranged with a couple of diodes gating the relay to run off rectified transformer output instead of battery, so that the battery only needed to provide a brief initial blip of actuation current. Devise an unlatching circuit, then next the battery could be replaced by a suitable "supercap"and top-up circuit- and a slide into the syndrome of over-engineering....

[jez_145]

An interesting thread. I've just found this Friedland bell transformer in my parts dump so thought I'd run a few measurements on it. It's a typical mains primary with nominal 3V + 5V secondaries unit installed in their thousands back in the day.

Readings were as follows:-

Mains supply: 241V
Secondaries (no load): 4.11V + 7.03V
Primary current: 15.9 mA (no secondary load)
Power Factor: 0.79


That adds up to around 3.83 VA or 4.85 Watts. A bit more than I (we ?) were expecting!

Therefore, 4.85 W * 8765.813 (hours/year) gives an annual consumption of around 42.5 kWh

In Mooly's case (posts #12 and #15), running this particular transformer for 67 years would add up to around 2.85 megaWatt hours. Eeek!

When it comes to doorbells - definitely stick with batteries I say.

Just think of all those other little things you have around the house that are drawing mains current continuously. Plug in adapters for Wifi routers, telephones, clock radios. Mains sockets with built in USB charging ports (on regardless of whether you're using them or not). It all adds up.

Jerry

[Jon_G4MDC]

Real power can't be more than apparent power.
I think 3Watts or?

[kalee20]

Originally Posted by The Philpott

...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.

That's interesting! I'm in correspondence with a friend, who's considering using long-life lithium cells for grid bias. Obviously, bias needs to be highly reliable, especially for output valves.

Lithium cells are used for memory back-up, where reliability is also pretty important or data vanishes. I'm wondering, are the solder-tagged variety different chemistry, or better reliability?

[AC/HL]

That must be the difference between a minute current and zero current then, as backup batteries normally work reliably for years at a time.

[broadgage]

A bell transformer often uses one or two watts, forever off load.
I measured over two watts a few years ago, I used a cheap plug in power and energy monitor.
These are not very accurate at low loads, but I had access to numerous bell transformers and measured the load of about a dozen connected together.

Just over 2 watts would be about 20,000 watt hours a year, or 20KWH. At 15 pence a unit that will cost about £3 a year.
A set of batteries will cost about that much, but last several years.

Battery operation has the merit of working in a power cut, not common in most places, but still an advantage.

The most economical system of all is probably a rechargeable battery that is already required for some other purpose and that can also supply the door bell at zero extra cost.
I have a home made 12 volt battery backed PSU that supplies various circuits including the door bells.
The losses are probably worse than a bell transformer, but the PSU was required in any case for other purposes and the extra losses from also working the door bell are zero.

[emeritus]

Post #29 was prompted by a circuit I designed some 30 years ago for multi-way control of the external light for the shed at the bottom of the garden from the house without needing a long run of exterior-grade mains cable for the remote switch . It uses three inexpensive Octal plug-in relays, one with a 240V coil to switch the lamp, and two with 12V coils to control the 240V relay. I think the operation is easy enough to follow from the circuit diagram: the things that might resemble FETs are in fact either normally-lON or normally-OFF push button switches or relay contacts. SW1 and SW2 are MK gridswitch momentary contact switches for turning OFf and ON from inside the shed. SW3 and SW4 tun OFF and ON from the house via approx 100' of telephone cable. Futher switching points could be provided by further pairs of push-to-make switches connected in parallel with SW3 and SW4. Basically, briefly pressing SW2 or SW4 energises RL3, which is held ON via contacts C3A. Momentarily pressing SW1 or SW3 makes RL3 drop out, turning off the light.

Only very brief pulses of battery current are consumed, and no mains current is consumed when the lights are off.

As it is a bistable latching arrangement, not suitable for bell operation as it stands.