What batterys have a 12 or 24v, 3amp capabilities?

Excuse the lack of technical speak but i struggle with it. I've recently given a pair or old Russian PNV-57a  night vision goggles, unfortunately they have to be plugged into a tank to operate. I don't have a tank... unfortunately. 
Im looking to get them attached to a battery so i can walk about with them. They got a box at the back which allows them to be powered with 12-24 Volts with an ampage of 3 to 3.5 a maximum power consumption or less. That's the information I've been given apart from their very robust and not very picky when it comes to power supply.
like i said i want to power them with a battery but don't know what battery or if i need to make any circuits. 

Any ideas?

Thanks folk 
Ben-jammin (benbeaum@aol.com)


Picture of What batterys have a 12 or 24v, 3amp capabilities?
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-max-2 years ago

Any old 3S LiPo battery will work, or 12V SLA battery.

iceng2 years ago

12v @ 3A is 36 watts

Any 12 volt battery that can deliver 3A for 3 hours ie 9 amp-hr will do.

No xtra circuit needed.

Some aircraft and tank run on 24V, so goggles can too.

See you in the dark ;-)

Your quote for the current draw, ~3 amperes, seems high to me, for an imaging device. I mean at 12 volts, that would be 36 watts, and that seems like a lot of heat to have strapped to one's head.

I dunno. I found a quote of ~350 mA = 0.35 A, here,

http://blog.gruppa-l.com/review-pnv-57e/

although that's a different model, since it ends in "e".

BTW, I've never seen one of these gizmos in real life. So to answer the question of how to power them, I just fed the words "PNV-57a power wiring" unto Google(r) Image Search.

http://www.google.com/search?hl=en&site=imghp&tbm=...

Then I'm looking for pictures that other people have taken, in the process of wiring up their goggles.

For example, this page,

http://www.airsoft-verzeichnis.de/index.php?status...

has a picture of one plugged into a Molex(r) connector of a computer power supply. Note for computer power: black is ground=0, yellow is +12 volts, red is +5V.

When you get this toy running, I suggest actually measuring the current it draws, like you know, like, with an ammeter, or your multimeter set up as an ammeter, or by by measuring the drop across a small resistor (like maybe 1 ohm) placed in series. You know, some kind of current measurement. That way you know, and then you can estimate battery life, which, coincidentally, is measured in ampere*hours (A*h).

http://en.wikipedia.org/wiki/Ampere-hour

For example a single AA alkaline battery is maybe good for about 3 A*h, and the same is true for a stack of 8 AA cells wired in series (to give 8*1.5V =12V), since in series they all share the same current.

The naive calculation says a 3 A*h battery can supply 3 A for 1 hour, or 0.3 A for 10 hours, or 0.2 A for 15 hours, or any current*time product, equal to 3 A*h, and this is approximately correct. This is sort of reminiscent of the cliche about the candle that burns twice as bright, and lasts exactly half as long.

In truth batteries tend to give more capacity at lower current draw, when they're not being stressed, as is the case for low current draw. I think asking AA cells to give you 3 A, would be stressful, but then I don't think your current draw is really as high as that 3A quote.

I am guessing it will be closer to a tenth of that, more like 0.3 A, like the quote from that link I put first, whatshisname, gruppa-l?

Ben-jammin (author)  Jack A Lopez2 years ago

Okay jack, that makes alot of sense, considering the A's are older than the E's... so using grappas number i would need a 12V battery that has approx 1.05Ah to start with? im a bit new to this

Speaking metaphorically, we learn to crawl before learning to walk, and learn to walk before learning how to dance. What this means is first steps should be simple. For DIY projects, "simple" means low cost and low hours (time cost) to put it together. Low danger (i.e. safety) would be nice too, if possible.

The talk on forums I linked to, mentioned rumor of powering these night-vision goggles from just a 9-volt battery, which sounds to me like the easiest, and cheapest, thing to try first. I'm not sure if I actually believe the stories about using just a 9V battery, a little boxy thing with two tabs on the top, used to power smoke detectors, the reason being 9V batteries are notoriously weak. But it would very easy to try, and the cost is the cost of a new 9V battery.

I think the next easiest, cheapest, thing to try is going to be a 12V battery made from 8 AA batteries, in a 8xAA battery holder. Actually, you asked about this specifically, and I provided some links in a separate reply.

Other answerers who say: 12 V lead-acid battery, or 3S LiPo, etc. Those will likely work too. The answer may depend somewhat on what parts you already have, or what is available in the local marketplace.

In the former US, there used to be a retailer called Radio Shack(r), and they sold battery holders, like the 8xAA, 4xAA. I don't know if they're still around in your town or not. They might have been replaced by the online parts-mongers, who have better selection, better prices. The only trouble with the online stores, is you have to pay shipping, and wait.

Regarding what I was saying before about measuring the current, with an ammeter, so you'd know how much, how many milliamperes (mA) or amperes (A), your device is drawing... if you did not follow what I was saying about that, that's OK.

If you find a battery that works, eg. if a little 9V battery works, then note how many hours (minutes?) of useful battery life that actually gives you. If it is not long enough, then you need a bigger (larger A*h capacity) battery.

It seems like no one knows how to use a multimeter to measure current. Maybe I write an Instructable to show everybody how to do that? Maybe.

I always believed you could only short a voltage source with a current meter or hook it up correctly in series with the load.

But then HR hired a newly degreed PHD, while I was on a trip, to work as an EE for my dept.

This PHD actually found a third and improper ammeter hook-up then I thought really existed.

Ben-jammin (author)  Jack A Lopez2 years ago

in the uk most of the electronics and large battery's seem to be shipped from the U.S. and China for ridiculous postage costs so I'm happy to start with the smaller batteries.

As for the battery holding box I could probably make something out of electrical tape or frankinstien a few old touches?

Would using a large a*h capacity not damage the internals. Or would the transformer save them do you think. Say a 12v battery with 9ah as a friend of mine has quad bikes So their readily available

Would I need a battery to use an ammeter?

I think a 12V, 9A*h, battery would work. 12V car battery, 12V motorcycle battery, I think these are all good.

A battery pack for a toy RC car, or cordless drill might work too, provided it has an output voltage kind of close to 12 volts.

Regarding what I was saying about measuring electric current, I think that explaination will require pictures, and that will take some minutes to put together.

I'll post that as a reply to this post.

The important thing about measuring current is the ammeter is placed in series with the battery and the load.

BTW, if you are wondering what I mean by "in series", and how that is different from "in parallel", there are free textbooks out there that explain how this stuff works. Here's a page from allaboutcircuits.com,

http://www.allaboutcircuits.com/vol_1/chpt_5/1.htm...
which explains series versus parallel.

The first picture I have attached, a hand drawing on notebook paper, is a circuit diagram, which is just a symbolic representation of the actual wires and electrical stuff shown in the next four pictures.

Lines represent wires. Solid black dots represent electrical connections. The battery, the ammeter, the load, these are labelled clearly, I think.

The big circular arrow with a capital "I" next to it, represents an electric current which flows through, the battery, the ammeter, and the load. "I" is the traditional letter physicists and engineers use for electric current. Or at least that's true int the tradition I was raised in.

When I look at this diagram, I imagine this electric current, I, is flowing through the wires (lines) and circuit components (symbols). However, drawing a circular arrow right on top of those lines (wires) would be hard to draw, and confusing. So the convention is to draw an arrow next to the wire, and this is understood to mean there is a current in the wire. The diagrams drawn by the authors of allaboutcircuts.com, look similar.

Probably the only other confusing thing is this component I have labelled "LOAD", and that is a symbol that stands in for a bunch of different things. In the attached pictures, the load is (1) an open circuit (nothing connected), (2) a dim light bulb filament, (3) a bright light bulb filament, and (4) a red LED in series with a resistor.

In each picture, the ammeter (which is actually a multimeter configured as an ammeter) shows the magnitude of the current it is measuring.
For the open circuit load, I1 = 0
For the dim filament load, I2 = 0.50 A = 500 mA
For the bright filament load, I3 = 1.48 A = 1480 mA

The last picture, with the LED and resistor as load, is included to demonstrate an example of a current too small to measure, on this scale of the multimeter. I claim the LED in this picture is on, and I4 is approximately 5 mA. The meter says 0.00

The battery in these pictures is a 12V, sealed lead-acid, black brick. There's a close up of the label for the last picture. Coincidentally this brick also has a capacity of 9 A*h. Or at least it says it does.

Regarding your question about, is it possible to choose a battery with A*h capacity that is too big?

The answer to that, is the load draws as much current as it wants to, needs to... Perhaps better language would be to say it draws as much current as it is designed to draw, since it is an artifact, and it sort of does what it was designed to do.

So pretty much any 12 V battery is good.

Assuming your load really does do what is was designed to do. There's some faith involved I guess, trusting the designers of your device to draw as much current as it is supposed to. Actually, I think that's why Seandogue was suggesting putting a fuse in series with it. That's kind of what fuses are for, for when something in the design goes wrong. I mean the kind of wrong-going that results in too much current.

measuring-current-00-circuit-diagram.jpgmeasuring-current-01-open-circuit.jpgmeasuring-current-02-dim-filament.jpgmeasuring-current-03-bright-filament.jpgmeasuring-current-04-resistor-and-LED.jpg12V-SLA-battery-label-close.jpg
Ben-jammin (author)  Ben-jammin2 years ago

or possably a series of smaller batteries wired together to make a 12V battery, is that what you were saying about the AA cells?

Yes. Eight AA cells wired in series makes a 12 volt battery.

Also this is a trick used often enough that there exist battery holders made to hold exactly this, 8 AA cells wired in a series, to make a 12 V battery.

Here is an example of a 8x AA battery holder:

http://www.adafruit.com/product/449


I found it via a Google Image search for "8x aa battery holder"

http://www.google.com/search?hl=en&tbm=isch&q=8x+a...

Ben-jammin (author)  Jack A Lopez2 years ago

Ah okay, thanks for you help jack :)

Regarding the high current draw, it is older Russian.

Well, in Siberia it probably gets cold at night. So maybe it helps to keep the wearer's head warm.

;-P

I forgot to include the link to the Wiki article on battery sizes.

http://en.wikipedia.org/wiki/List_of_battery_sizes

This is helpful for answering quick questions about capacity, like: What's the A*h capacity of an alkaline AA battery? (2700 mA*h) Or how much more capacity does a D cell have compared to a AA? (12000/2700 = 4.44 times as much)

For deeper battery knowledge, you can look up the manufacturer's data sheet for the battery in question. Even the humble AA has a data sheet, here:

http://data.energizer.com/PDFs/E91.pdf

seandogue2 years ago

12V is the minimum voltage they will work with, 24V is the max voltage they'll work with.

They require 3-3.5A, depending on the operating voltage (12-24V)

So any battery in the range of 12 -24V will do the job, if it can supply ~3.5A of current.

To initially test, you'll want a fast blow fuse rated for 4A, inserted inline with the positive supply lead for overcurrent protection, although ideally you'd use a variable voltage supply with a current limiter for quicker response during testing, so you can be comfortably assured of the results without trashing your neato purchase.

The goggle draw a considerable amount of power for battery powering, so you might want to use a car battery to run them, then make very sure to

a) monitor the battery voltage using a voltmeter and discontinue use when the battery voltage droops below ~10.5-11 VDC, and

b) recharge the battery as soon as humanly possible after powering the goggles to prevent lead salt formation on the battery's electrodes (lead acid batteries in a state of low charge from lead salts on the electrodes, resulting in permanent damage to the battery)