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Wanted: A 'joule thief' style circuit design...

... that I can use to drain alkaline cells and push the 'charge' into either a lithium-Ion cell (for a flashlight), a phone or a powerbank.

I have a combined wireless doorbell - inside/outside thermometer that I quite like. Unfortunately it won't run on NiMH cells and only uses alkalines down to 1.33v. (It's the only thing I have that doesn't run on rechargeable cells.)

The sender uses AAA cells and the receiver uses AA cells and I buy good quality (expensive) cells to get the longest run-time between changes (as it's a PITA to re-pair them and re-set the clock in the receiver too often). I though of converting the receiver to run on a single 14500 Li-Ion cell (AA size) and a buck regulator or even a wall-wart but that still doesn't solve the issue of the sender.

I dislike throwing good quality alkalines away when they still have ~65% of their capacity remaining but have had enough leak-disasters to not want to put already semi-discharged cells in remote controllers etc. where they then get forgotten about until things stop working. (I've never had an Eneloop leak and they run my remotes for about 3 years between charges.)

So I'd like to make a gizmo that takes a single alkaline and pushes out ~5v through a USB cable for as long as the cell has juice, preferably at a reasonable current. I have a few different pre-made boost modules from the usual suspects but when I tested one the output voltage curve dropped with the input so that it wasn't very successful.

If anyone has any ideas for something I can put together with a bit of veroboard or similar I'm all ears. I'm tired of having loads of half-used cells sitting around but don't want to just chuck them away. I've thought of this before but it's fresh in my mind as I've just bought a 32-pack of each size cell and they cost quite a chuck of change.

TIA.

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~
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Reply to
default

If there is room for two AA cells in the sender why not substitute a lithium pouch cell and a regulator? Then you could charge the pouch cell while in the sender and never worry again about pairing the devices? Eric

Reply to
etpm

Brilliant! Thanks.

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~

The sender uses two AAA cells and is very tightly packaged. Also it's waterproof as it's outside in the elements so I don't want to mess with it too much.

Cheers,

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~

these are cheap and will do it

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how often do you need an unreliable portable USB charger? the cost to run that thing will not be much less than the cost to run a plug-in usb charger, but the hassle will be greater.

It seems like a waste of time to use batteries, even free batteries, where mains power is available.

can you run a wire to power the door button?

maybe you can find some device to run off the partly used batteries, a portable radio perhaps.

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts

On Mon, 30 Sep 2019 15:07:18 +1300, ~misfit~ wrote as underneath :

Trouble is that the boost circuit takes a proportion of the available battery power to run, so trade off calculation required! See:

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Reply to
Charlie+

Yep. My plan probably isn't worth how much I'd 'save' by not mains-charging whatever I use this for. However I dislike waste, especially energy waste.

I'm probably better to just get a flashlight that uses 2/4 AA/AAA cells and use them up that way.

I remember over a decade ago I had a cell phone (not a smart phone) that had an alternate battery cover / adapter that took 3 x AA cells (and had a bulge in it that made the phone a bit bigger). It was designed more as an 'emergency solution' to not having a charged battery than a day-to-day option.

Anything would be better than having a drawer half-full of 65% good AA / AAA cells...

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~

I've actually already got some of those in my 'module collection'.

True.

Yeah, it's more the principle and not liking waste.

Not easily - and I rent so I don't want to go drilling holes in walls etc.

Radio? I haven't used one of those in years! However you're right, I think I'll use them in a flashlight or something that I *do* use. ;) Now I need to decide if buying a new flashlight (when I have several perfectly fine 18650-powered flashlights) works out better than wasting alkaline cells.

Cheers,

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~

My bad, just checked and I don't have those. I have some of these and at first glance I thought they were the same thing. I really need to 'index' my module collection.

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~

I just ordered 5 of these They're cheap enough and claim a higher efficiency than the one you linked. If I don't use them for this 'project' they will likely be useful down the track sometime. I can put them in my collection. ;)

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~

SEPIC

WIKI has a page on it that isn't too bad.

Reply to
jurb6006

3 AAAs are smaller than an 18650 and the voltage is about right. you can get adaptors.

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On the other hand the torch may work just fine off a single cell, I've got mostly AA/14500 torches here, they have some sort of buck/boost device.

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts

It's bad design if it requires 1.33V; either bypass the battery terminals with a capacitor (that'll lower the impedance, if it's a logic-glitch that makes it malfunction) or consider using three cells in series (if it works on 3V, it should be OK for 4.5... maybe). A redesign of the circuit might be in order, except it's a consumer-grade package with cryptic labels and 'instructions'.

Gluing it into a bigger waterproof box isn't too hard.

Reply to
whit3rd

You need a batteriser!

--
RoRo
Reply to
Robert Roland

... like I need a hole in the head. ;)

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
in the DSM" 
David Melville 

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.
Reply to
~misfit~

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