USB instead of batteries?

[Anonymous]

[Anonymous]

I have a device (Elgato Eve temp/air quality sensor – first generation) which runs on 3 AA batteries. It chews up alkaline batteries rapidly – NiMh even more so. No wonder they came up with a second generation model.

Is it possible, with appropriate wiring to each end of the battery chain, to run this from a USB charger …. either directly or with a series resistance/diode?

[not done it yetParticipant @notdoneityet]

Security alarms are battery operated during mains failures? Float chargers are common for many applications, but most batteries cannot put up with over-charging indefinitely – and some won’t tolerate it at all.

Anything is possible, but perhaps not quite so simple as you suggest.

[Michael GilliganParticipant @michaelgilligan61133]

Very likely that a series diode would suffice.

Silicon diodes drop about 0.6 volts, which seems just right.

MichaelG.

[Anonymous]

NDIY … sorry, I wasn't very clear there. I don't mean to run it with batteries installed (although I can see why you would think otherwise from my post). I'd be using USB instead of batteries.

Michael …. seems to make sense. Thanks!

[Michael GilliganParticipant @michaelgilligan61133]

Thinking a little further about it, Peter … You might do well to buy a couple of ‘USB Power Banks’

One powering the device, and one available.

MichaelG.

.

I bought a couple of these when they were on offer at £5 each

https://www.ryman.co.uk/intempo-power-bank-portable-charger-4000mah

… but there are plenty of alternatives available.

 

Edited By Michael Gilligan on 14/12/2020 23:47:41

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Michael Gilligan on 14/12/2020 22:36:13:

Very likely that a series diode would suffice.

Silicon diodes drop about 0.6 volts, which seems just right.

MichaelG.

+1 for this, you beat me to it. A 1N4001 (or 2/3/4/5/6/7) or similar silicon diode in series with a USB supply or power pack will work fine to replace 3 AA cells

Robert G8RPI.

[Howard LewisParticipant @howardlewis46836]

Since it is powered by 3 x AA batteries, there should be plenty of cheap 3 pin socket type DC supplies which will power the device. If your device does not have a 3.5 mm socket for such a feed, you may need to install one. It should only entail drilling one hole and a few minute work with a soldering iron.

Since most such sockets include a switch facility, plugging in the charger feed will disconnect the internal batteries,

Howard

[Anonymous]

Thanks for all this guys. Since I have an existing USB charger in the immediate vicinity with unused outlets, I think I'll stick to the original idea using the diode (got a few of those around too). In its simplest form I can just cut one end off a USB cable, drill a hole in the case and wire it in.

What I don't have is spare mains power outlets for (yet another) unidentifiable, wal-wart.

I already have a (one) lithium power bank, Michael, although I'm not sure exactly what it would buy me (in my situation). I'll think about it. I don't need portability (at least right now, though it could happen) It did occur to me though, that some enterprising outfit could make a similar device in the shape of 2, 3 or 4 AA-cells (or AAA) as a drop-in replacement for alkaline batteries in many devices …. rechargeable from the now ubiquitous USB chargers. Sort of a super-Nicad/NiMh pack.

 

Edited By Peter Greene on 15/12/2020 16:16:01

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Peter Greene on 15/12/2020 16:11:20:

[…]

I already have a (one) lithium power bank, Michael, although I'm not sure exactly what it would buy me (in my situation). I'll think about it. I don't need portability […]

.

Hopefully insignificant, but it did occur to me that the power bank might be a more stable source of 5V than a USB charger.

MichaelG.

[Author]

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