Inside a simple battery tester (with schematic)

[@dougerrohmer]

I used to be an aircraft instrument guy in another life, and worked on moving coil voltmeters, etc. That "adjuster" marked with the red locking varnish is actually a jeweled bearing for the meter pointer pivots. It is varnished to prevent vibration or whatever from moving the jewel down or up, and tightening the jewels or loostening them, which could increase friction or "wobble factor".

[@RussellTeapot]

So the industry standard name is "wobble factor", I see

[@dougerrohmer]

@@RussellTeapot No, not really the industry standard, just clear understandable terminology invented on the spot.

[@RussellTeapot]

@@dougerrohmer Ahahaha I imagined, I was joking.. it made me laugh, but it's a very effective way to convey the concept

[@vladthe_cat]

@@dougerrohmer Damn well better *make* it industry standard, how else are you supposed to get through your day with all these dull terms? "Wobble factor" 😆

[@bluesideup007]

"locking varnish is ...to prevent vibration or whatever from moving the jewel down or up, and tightening the jewels or loosening them, which could increase friction or 'wobble factor'." Dang! So that's what the red spot at the base of my p3nis is. I will cancel my doctors appointment. (ok, sorry for the sophomoric humor)

[@khoroshen]

The small one was the first battery tester I got as a child, more than 30 years ago. A fresh alkaline cell can easily slam the needle to the top on mine, it was/is a fairly good indication of good, bad and in-between cells. Still use it from time to time today.

[@mrw6156]

I bought one - cream plastic - at the West Midlands Radio Rally in the UK about 34 years ago - still use it as my "go to" battery tester. It is certainly not too "generous" and I may see what values are used inside it. Interesting video.

[@IncertusetNescio]

I have that exact newer battery tester and mine has discrete resistors like the old unit, but is functionally identical. Has been very handy in knowing the state of random cells.

[@BreemanAMV]

My Dad had this exact same tester. I have many fond memories as a kid testing spare batteries to put in my toys and various electronics. I now have a different newer tester that I use for my kids toys, but I very much remember this one.

[@bernds6587]

wow, was about to write exactly this. Except these memories are "just" around 20 years ago, and I have no kids 😅

[@NotATube]

Assuming you mean the square one, I've got one too. Honestly can't remember how long I've had it- regardless, I get the impression that those are an incredibly common design that's probably been around for decades. Other than a white pointer and a slightly different design on the (stuck on) scale, mine is pretty much identical to Clive's. (It also seems a bit more generous; fully-charged batteries max out in the middle of the "good" zone).

[@Steel_Wyvern_Kitty]

my grandma too

[@termitreter6545]

Yeah we used exactly the same here in Germany. Pretty common stuff.

[@Tag-Traeumer]

Thanks for the explanation. The screws fixed with red glue are not there to calibrate the pointer to zero but to adjust the pointer shaft bearing, it's a mechanical thing. I've been using a little tester like this for years, mine is correct.

[@CanadianCuttingEdge]

I have one of those cheap testers and it's dial goes all the way into GOOD with a brand new battery and seems very reliable in my experience.

[@theclovercross]

same for me, I guess they made some with the right resistors

[@Starphot]

It could be also the stingy deflection of the meter movement as well. I have two of these testers, a white one and a black one, I have gotten free through my company's promos and I still use.

[@Mark1024MAK]

Yes, my cheap battery tester of this style also goes all the way into the green with a new 1.5V alkaline cell. I’ve had mine for a very long time. I think it came from the former Greenweld Electronics company of Southampton. Long before eBay… Clive, I think yours must have had been built with the wrong resistor(s). Maybe someone mixed up what was put in the part bin…

[@jamesplotkin4674]

@@Mark1024MAK Colorblind Chinese factory worker. What could possibly go wong with that?

[@Mark1024MAK]

While going through a box of stuff, I found another of the small battery testers. This one came from 7dayshop. It also “goes well into the green” with a good cell or battery. This has a slightly different case to the tester from Greenweld. It’s case clips together. So it had to come apart! It also uses four resistors, but in a different arrangement. The resistor values are: 1.5V load resistor is 150 ohms. There is no separate 9V load resistor. The path from the 9V battery + terminal is via a 680 ohms resistor, meter + terminal, meter - terminal, 1k resistor, then back to the 9V battery - terminal. The fourth resistor, 22 ohms, connects between the 9V battery - terminal and the 1.5V cell - terminal. Hence when testing a 9V battery, the 150 ohms in series with the 22 ohms resistor shunts the meter and the 1k resistor. The meter resistance is 180 ohm. I forgot to test the FCD of the meter though. Testing the resistance of this battery tester from the cell/battery terminals I get: 133 ohms across the 1.5V contacts. 830 ohms across the 1.5V contacts. In comparison the Greenweld battery tester has: 2.7 ohms across the 1.5V contacts. 96 ohms across the 1.5V contacts. So rather different.

[@GadgetBoy]

This is rekindling my interest in an old project I gave up on a while back

[@frogz]

awesome, always wondered how these worked, sleepy time now...its nearly 5 am, wish me luck fixing my ebike when i wake up, explosion containment pie dish at the ready!

[@Conservator.]

Did you have to use the ‘explosion containment pie dish? (I hope not, unless you would have been filming the ‘repair’ of course 😉)

[@samholdsworth420]

Just work on it before you go to bed

[@134StormShadow]

PLEASE Do NOT charge indoors

[@frogz]

@@Conservator. multiple times! note: dont tear down a 500 wh battery indoors, the same battery went up on me TWICE, filled the entire house with acrid smoke

[@frogz]

@@samholdsworth420 THAT was my main problem, tiredness and trying to just get it done in a hurry, when ripping large batteries apart to re-cell other batteries, make sure there is NO way they can accidently short, even for second

[@joshbrucksch]

This video made me feel so nostalgic! Also grew up using one of those little square ones. Thanks for sharing!

[@SeanBZA]

Mistake in your maths is that the unused section resistors actually load the meter movement, so the coil resistance is lower, and the full scale current is higher. Without taking this into consideration you get the pessimistic readings, you need to actually calculate combined resistance for the unused side, and the new full scale current, to get a more accurate reading, which would mean each of those range resistors would likely be the next value down on the E24 series, or at least that plus a small padding resistor.

[@COBARHORSE1]

Good point. But I thought that the jaw has a switch in it to use one circuit or the other.

[@markfergerson2145]

@@COBARHORSE1 Nope, no switch. If there was one the wiring would be different. Our Clive would not make that mistake and leave it out of the circuit drawing.

[@wingerrrrrrrrr]

I can just use my DMM with an attachment to connect a load resistor selected for the battery being tested, but these testers make it more convenient by making it a bit easier to connect, even if being less precise about it. For lithium coin cells I made a holder from a wooden clothes pin and two screws in the jaws to let me just clip onto the cell. Regular spring loaded battery holders for cylindrical cells.

[@gblargg]

@@wingerrrrrrrrr Yes, convenience is the main goal. There are $100+ battery testers but mostly you just want to be sure you have a fresh/charged cell, or determine whether a device not working is due to low batteries or failure of the device.

[@TheEmbeddedHobbyist]

You forgot that there is a second series pair of resistors in parallel with the meter, tempting a few pixies away from the meter. You never know how many of those pesky pixies might be tempted ;-)

[@BB-iq4su]

You are correct.

[@johndododoe1411]

But it's a fairly large value that probably drowns in the series resistor tolerance.

[@rexsceleratorum1632]

@@johndododoe1411 The entire 1.5V side is a low value comparable to the resistance of the coil, so it will feature prominently when calculating how much current the coil gets when 9V is applied. But they probably went with trial and error.

[@zh84]

This was a familiar exercise in Higher Physics during the 1980s. Given a meter with such-and-such FSD, design a circuit to turn it into a voltmeter or ammeter with a given range.

[@johnjordan3126]

I have one of each of these on my desk at the moment, though I modified the long one (w/ through-hole resistors) to test 14500 Li-ion cells. I like that they put a load on the cell. Nice video.

[@dave1066]

I'm an avid watcher of your videos, appreciating your often quite cutting humour, especially when it comes to the top quality, extremely safe Chinese electrics. So I had to smile when you referred to the PP3 as a good capacity 'cell' at 1:05 :) Keep 'em coming Clive!

[@jamesplotkin4674]

Your photograph was so realistic with almost 3-d reality. The lighting makes me want to reach out and touch it. With permission, of course ;-)

[@a.k.4550]

A good tester to sell batteries with, assuming no one checks the new batteries! Once upon a time, in order to justify hoarding components, I fabricobbled one of those 1mA gauges onto a tractor with roughly 15v centering the needle in "good" so I'd know whether the alternator was working or not. Two years later and it still works if it hasn't been rained on recently, sure helps justifying the drawer space that gauge occupied for 10 years.

[@carneeki]

When I first saw the poor meter, I was reminded of a pot plant indicator my grandmother used to have, a very similar dial for dry and moist. I wouldn't be surprised if it's a very similar circuit inside and a metal spike sampled the soil's resistance as a function of dryness. Thanks for the trip down memory lane :D

[@rolfs2165]

That's what they do, yes. Same for lumber testers to see how wet/dry your wood is.

[@PunakiviAddikti]

@@rolfs2165 There's a joke here somewhere...

[@christophermaciulaitis7745]

@@PunakiviAddikti It's too small. I can't find it.

[@firesurfer]

@@christophermaciulaitis7745 Do an image search for short skirted resister. :)

[@1622steve]

In the case of soil testers, the probe is a battery (note the two metals) and the soil is the electrolyte.

[@terryloveuk]

Question: I'm not techy and it's been years since my school physics but aren't the all the in a parallel circuit of sort no matter which battery type is being tested? If so does that affect the calculation? And what about the tolerances of those resisters?

[@Mike-H_UK]

Yes, this produces a significant but got game-changing difference to the calculated numbers.

[@TheGreatAtario]

Yes, current flows through every path available to it. So in any case you'd see current in each of those three vertical paths on the schematics

[@SeanBZA]

@@TheGreatAtario Yes it does, and you would have to calaculate it as well, so each of the series resistors probably would have to be the next lower value in the E24 series, with another series resistor to get a correct value, or just a single 220R pot in series with the movement, adjusted for full scale with 1V5 applied. But for a quick check of "flat, dead and only standing because it is nailed to the perch" or "still ticking" it works out well enough.

[@Chris_Grossman]

You are correct. Ignoring the parallel paths is a reasonable approximation for the load current since the parallel paths are much higher resistance than the load. However ignoring them is not a good approximation for estimating the meter deflection since the current in the parallel paths is not insignificant.

[@factorylad5071]

If you had bothered going to the 2nd lesson they would have explained Kirchoffs equation so you can separate the parts but if you ain't tech savvy you might not want to know about it.

[@frankowalker4662]

I've got a big old orange battery tester from the early 80's. It has a half pipe type thing where you put the battery, (AA/C/D), and you push the base up to test on a graded scale, and two prongs sticking up for a 9V. It's very accurate.

[@utubeuser1024]

I had the square one growing up (in white though) and always wondered why it was so harsh on the battery capacity - a 680 ohm resistor in place of the 1.2K one would make it a lot more accurate - that way a fully charged NiMH cell would get a full deflection.

[@SimonJ57]

Not saying I'm a Mathimatical, and even less of an Electrical astute person. But to reduce the required 1.9mA to 1.5 mA, which would be about half of one Resistor, you basically Halved one of the resistors?

[@andygozzo72]

then it'd go over range for a 1.5v cell .... theyre designed and 'calibrated' for 1.5v , on my cream square one (quite old) 1.2v is in middle of the green area,

[@utubeuser1024]

@@SimonJ57 680 ohms might be a bit low - but remember, the battery is also placed under load when being tested, which would reduce the voltage from open circuit (last time I measured a "full" alkaline, it came up as 1.63V open circuit).

[@johndododoe1411]

The reference to test for full deflection is a zinc-carbon "heavy duty" battery. This is what Duracell claims to last 6x longer than.

[@wingerrrrrrrrr]

That's the problem using a meter reading current rather than a high impedance volt meter, having to juggle resistances for load and full scale indications. Using a high impedance DMM for the reading, you can apply whatever load you want for the test and read voltages correctly from no load to full load. My Schumacher BT-100 battery tester uses a 0.12 ohm load, so even though it uses a panel meter, it's relatively insignificant in comparison.

[@DGFig]

Holy crap! I've had exactly one of those (the small one) for more than 30 years now. It still works. It has always worked relatively well.

[@anameofsomesort959]

This is about exactly what I expected, happy to see my assumptions were correct. Great Video as always!

[@lepus6511]

Perfect timing Clive! I've been working on repairing/modeling a vintage gauge that uses this same mechanism to move its needle. I'd been reading up on it but was still confused. You just cleared some stuff up for me and gave me some ideas!

[@JSGregg]

I have an old Radio Shack RC car battery tester that is very similar to this but tests 6V, 7.2V, and 9.6V battery packs as well. Good to know what's inside. Great content, thanks Clive!

[@angeldelvax7219]

Are you shure the painted screws are for calibration? I was told that they are locked because they hold the coil on to the needle bearing, and they are locked in a position where the bearing has least friction while still holding on to the needle as precise as possible. Especially since you can easily change calibration, as you showed. (Not saying you're wrong, just questioning what explanation is the correct one..)

[@JUANKERR2000]

I think that you are right, zeroing is done, as Clive showed, using the little lever to alter the position of the fixed end of one coil spring.

[@iamjadedhobo]

The friction deployed by the screws can ensure that 1mA gives a full scale deflection. The manual adjust is for the zero point.

[@I967]

Yes, you're right, that's what my book on analog measuring devices from the 1970s says.

[@kevinmartin7760]

@@iamjadedhobo Friction does not determine the full scale deflection, the strength of the coil spring does (as well as the strength of the magnet, number of turns of wire in the coil, etc). Friction in the bearings just makes the meter sluggish and unresponsive to small current changes.

[@goodun2974]

I own one of these recent testers. I also own a much earlier version, in a white case but otherwise almost identical, that I have had for over 30 years! The older one has a better- damped meter and its resistance load is lower ---- I think I measured it at 70 or 80 ohms, versus 130 ohms for this one here. The 30+ year old battery tester puts a heavier test load on the batteries and gives a better overall indication of battery quality.

[@calumbaxter9946]

I still use my Japanese made “Sesco” branded battery checker (model SBC-30 no less). Bought in 1984, it still has the price label of 295 Belgian Francs on the box so must have cost me 2 weeks pocket money. A sound investment and a reliable friend; it still works perfectly today.

[@TechNoPhobiaGirl]

I've ALWAYS wanted to know that!!!! Thank you SO MUCH! You're an AWESOME YTer! Cheers, mate!

[@dentakuweb]

That old one has pretty much what I expected to see in it so I guess I've learned something from watching these videos. :)

[@alanbritton3326]

I recently got one of these BT-136 battery testers from Amazon (this one didn't have the Eiger Electronics logo on it). I had been previously using a cheap yellow multi-tester that my (late) Dad used, but I found the probes a bit of a fiddle to stick onto the battery terminals (as Clive clearly demonstrated here). Fascinating to see how they work, and how much more of a judge of battery life they are from the old ones!

[@TheSpotify95]

Interesting, I'd be tempted to re-tune the old one by changing the resistor values to match the requirements of a 1.5V cell. Even a fresh alkaline battery (1.6V) or a fresh Lithium AA battery (1.8V) isn't going to reach the far end of the scale if it's set for 1.9V!

[@GrimResistance]

Might as well just get the digital version for like $7 honestly.

[@gblargg]

@@GrimResistance The digital versions tend to not even load the battery. They're basically like hooking a voltmeter to it.

[@SystemX1983]

@@gblargg there are DVMs that have a special mode for batteries (1.5/9 V) they use a load resistor in parallel to the voltmeter.

[@joelquaintance9025]

Excellent. If everyone made videos as honest and informative (for novice) as you, KZbin would be called KZbin UNIVERSITY.

[@aardvarkmaker1021]

Great vid, I’m inspired to make my own battery state indicator using an old moving coil meter that’s been on my bench for years. I’ll enjoy working out the correct resistors.

[@matthewbeddow3278]

I've got the tester which is the same as the one grant sent, I've had it for many years and it's pretty good for a quick check if I can't be bothered to put them across one of my multifunction meters. I've also got a very good coin cell tester that tests many of the coin cell types and gives a number of LEDs rather than a voltage so it's good again for a quick test. Thanks for the video, it was interesting.

[@NicksStuff]

These should be better than a multimeter since they *load* the battery

[@onecreativecriminal]

I have the same battery tester and I love it! It's just simple and awesome!

[@seandempsey7351]

Very interesting, the eiger tester , I have that but with a LCD display cost about a tenner from Amazon,I keep it in my camera bag , It a handy and useful tool to have . Great video as always Clive 👍👍👍❤️

[@seandempsey7351]

Just an idea Clive , the small square battery tester,? You could easily improve the acuitsy simply by adjusting the screw on the needle and test three battery’s star with a new fully charged one once you have a full deflection, then test a partially use one then a dead one . ? , it no different to adjusting the zero on a analog multimeter.

[@jonathanfairchild]

This is excellent! I’ve had the same one of these since I was a little kid. I’ve always wondered how they worked but never wanted to damage mine by taking it apart.

[@alansmith4734]

As a kid, the best 9V battery tester, was my tongue! =P

[@GWorxOz]

I have two testers like you old one. They both always show good for new batteries. Now I have a single battery box with heavy gauge wire connected permanently to one of my multimeters.

[@Vamptonius]

Glad you found the one I just bought for AA & AAA rechargeables well suited.

[@spelunkerd]

As a guess I'd say the coil resistance would be the least accurate one to estimate during the design phase, possibly even changing as current warms the coil. As usual, engineering is full of competing interests and compromises, especially when one considers how this needs to work on wildly differing input voltages with no switches, and to be robust enough to withstand the occasional overvoltage. It is testament to durability to even have this working thirty years later. We all have one of these kicking around, somewhere. Thanks for the glance under the hood!

[@fivish]

Thanks for that. I have had the smaller of the two testers for many many years. I did not know that the supposed simple voltmeter was actually pulling quite a high current from the battery.

[@COBARHORSE1]

That's the difference between a voltmeter, and a battery tester.

[@FrontSideBus]

I was always mesmerised, as a small child, by those little strips that came with some battery packs (which later was integrated into the battery itself).

[@bigclivedotcom]

Conductive and thermochromic ink.

[@AMDRADEONRUBY]

Lmao I have so many battery tester happy to see a video on battery tester Clive.

[@gem-squared]

Never knew battery testing had to load the battery for good results. Explains the insides of my trusty analog multimeter. Love the little thing. Doesn't use battery unless resistor testing.

[@gblargg]

Batteries have internal resistance, which increases with wear. Unloaded it can look fine. This is also why a light load on a battery can get more capacity out of it, because the internal resistance has less impact on the usable power. And it's why alkaline and lithium are preferred for high-drain, as they do better than dry cell ("super heavy duty") with regard to internal resistance. Battery University has a good page about internal resistance.

[@ilhuikar]

I've had one of those square ones in my battery drawer for probably almost twenty years by now. I've even fixed it once when the needle came unglued. However, mine goes well into Good with a full battery, so maybe they have made different versions over the years.

[@MsNubble]

I have the same one to for probably about 30 years, i kind of want to take it apart and see what value resistors are in it now!

[@djmips]

@@MsNubble or perhaps the meter is different

[@brianmiller6320]

Your calculations were slightly off Clive, you forgot to note that the other 2 resistors are also in parallel with the meter movement thereby reducing the meter sensitivity this would probably affect one side more than the other. The values used in the first meter would be accurate if the other side of the tester were not present.

[@KeritechElectronics]

Especially important when analyzing the 9VDC tester part of circuit. On the other hand, from the 1.5V side point of view, the 8k2 current limiting resistor is much larger than the meter's resistance, so it can be neglected.

[@d.t.4523]

In the old days at Square D, we used Glyptal, aka glip, as a calibration set material. We used it on pots and adjustable caps. It locks in a tune so the boards can be waxed. It easily breaks loose, if more turning is needed. I recommend you replace the meter with 2 leds. One for ok and one for "it only lights and led". Good luck!

[@dooronron69]

I've used the same as you for years, love it

[@tomwilliams8675]

Good to know, that's the same battery tester that came with my battery storage case. 🤝🤝👍👍👍😊🇺🇸

[@TimHollingworth]

Clive I would very much have liked to see you calculate the needed resistors and to put them in to make the meter work properly.

[@daveys]

I have one of these (or similar) and IMHO it works pretty well. I note that if a battery powered item starts to fail, one of the cells will invariably read in the yellow or red - so I trust the one I have.

[@10p6]

I can tell you from experience the BT-168 is pretty durable. Smashing it into the ground will pop it open, but all the parts will reassemble nicely.

[@libertarian1637]

I’ve had an old one of these branded “Radio Shack” that’s work3s quite well for decades; it stays in the battery drawer just as a quick check of “new” batteries which aren’t always so “new”. If the new batteries don’t peak it out I check them with a multimeter; I’ve actually found a whole bad package of batteries which were all under 1V. If I didn’t check batteries I may not have figured out the bad package quick enough to return it.

[@1kreature]

Due to the way the 9v resistors is in parallel with the coil 1.5v on the input actually delivers 0.74 mA to the coil. 64uA takes a detour through the 9v resistor array. Assuming we want 1mA through the coil we need 0.736v over it but that also passes 87uA through the 9v resistors as well. Total current passed through 1200 Ohm resistor from 1.5v terminals is thus 1.087mA making the voltage required 1.3044 + 0.736 which is 2.0404 v! Voltage not found.

[@William_Hada]

Very Interesting! I wouldn't be surprised that in the case of the crappy one, it was just a matter of the factory running out of the correct resistors and sticking one in that was close in value. LOL!!!!!

[@grahamparsons3406]

I've had the small one for many years. It's a "rough guide" tool, especially for button cells. My multimeter comes out when I have to be more sure of the voltages.

[@LongPeter]

We had one identical to that when I was a child. I recall that it too never measured anything above the yellow line. I also remember that you needed BigClive hands to operate it using the little shoulder button. The spring was immensely strong for no good reason. Great for pinging AAAs across the kitchen.

[@LiamB1708]

I've had the smaller black one, which is '7dayshop' branded, for maybe close to 10 years now and it's always seemed accurate for all battery types. Does appear to put quite a load on the batteries though. The dial quickly goes down, especially for lower capacity button cells. I'll open it up tomorrow to see what value resistors mine uses.

[@Bartok_J]

Coincidentally, I also had one of theirs (based in the Channel Islands to avoid UK VAT: they sold things like camera film, printer ink, photographic and computer accessories etc). ISTR it was reasonably accurate.

[@LiamB1708]

@@Bartok_J I bought it alongside their own-brand high capacity AA batteries that were good value and well recommended at the time. Half of them are still going strong for times they're needed now and then. (And turns out I didn't actually get round to opening up the tester tomorrow.)

[@werhold]

I have the very same battery tester (the old black one) I have had it for over twenty years and you are right its gives a very sketchy reading but it at least gives you an idea the state of the battery - I think I bought it from Argos all those years ago, I every time I need to use it I always promise myself to buy a better one but I never get around to it, perhaps this is the push I need

[@brucereichert6509]

"For your pleasure" what a wonderful choice of words. I'm guessing, since you have the meter apart. You can convert it into a solar cell tester with a variable resistor with marks of cell size.

[@preston963]

The red paint on the meter is for locking the jewel screws after adjustment not zeroing the meter. I've had 2 of your new battery tester for many yrs & 1 of the has a digital lcd display not a meter.

[@pilkjaer]

We need a DIY video from you, Clive, on how to make a good battery tester ourselves. Preferably with a digital display.

[@Petertronic]

When I was a kid (80's) I had a Ronco battery tester. The way it worked was weird - a circular dial that was rotated under spring pressure by a little dc motor!!

[@byronwatkins2565]

You could inject f.s. current and measure it; don't forget to subtract the parallel load current. You could simultaneously measure the required voltage to calculate the network resistance. Thus, you could solve for the meter resistance. Using the other port, you could verify your work. They should agree within the resistor tolerance and measurement accuracy. (For ultimate precision, you could measure the resistances and use these values.)

[@caodesignworks2407]

I got the old square one, except mine has a corporate branding on it. I think it was just a promo thing at some point. Works fine in general. I've never had an issue with it in terms of not recognizing cell power, but I also don't use any rechargeable AA or AAA batteries. They always seem to drain real quick in the devices I need them for. That being said, putting an Energizer "lithium" AA battery on that thing sends the needle crashing to the other side.

[@Ranger_Kevin]

My guess would be that the old tester was built that way so that people would buy more new batteries, since the tester would show them that the old ones are "on their way out". Or whoever designed it just did not do the maths.

[@markfergerson2145]

Since you know the circuit and the individual resistor values for this kind of meter you can measure the resistance at either set of test terminals and derive the coil resistance for your larger meter. (In your schematic at ~4:34 we see that the 1200 ohm resistor and the 736 ohm coil form a voltage divider in parallel with the 4.7 ohm load resistor; the actual load on the 1.5V cell is therefore more than that from the 4.7 ohm resistor. (Obviously the coil displays the current through it but that also will tell you the voltage across it.) Worse, the sum of the 220 ohm and 8200 ohm resistors for the 9V measuring part of the circuit are also in parallel with the coil making the total real load on the 1.5V cell still more complicated. The same considerations apply to the load the 9V battery will see.) I have one of the smaller meters branded Radio Shack- they used to give the meters away with battery purchases. I don't think I'm being overly cynical when I combine the meter's apparent under-read with Radio Shack's desire to sell more batteries.

[@tomschmidt381]

My go-to battery tester is an old EICO 585 kit I built years ago. Has a rotary switch for different battery voltages and load currents. Not much use these days for the higher "B" battery voltages. It has front panel terminal strips for custom voltage and load current resistors. Guess I could determine values to test button cells but we have so many flavors floating around probably not worth it.

[@GreatJoe]

The windings of an inductor have a real resistance. Its impedance only becomes a factor for signals and AC, at which point its inductance shifts the phase of the signal, forming reactance, which is a factor of its impedance.

[@roysigurdkarlsbakk3842]

I just got one of these BT-168s and I also have an atmel-based multicomponent tester, driven by a 9V battery. The 9V battery in my tester was old and the tester itself measured its voltage to 8.65V while the new one I just replaced it with, shows 9.53V. The multimeter alone in voltage mode, without a lod, shows 9.01V for the old one and 9.61V for the new one. Still - the battery tester shows close to full power for both batteries. The old battery is just 1mm left of the new and good battery, both on top of the top-most green scale. I haven't tested 1.5V batteries yet, but I guess it should be doable to hack this to something a wee bit better…

[@CybermodsCoUk]

wow we have owned that battery tester for 30 years :D

[@michael1234252]

I have that generic black square one. My parents had it for at least 23+ years now. It works really well but sometimes it can be a bit tricky to fully show that accuracy of the battery's charge that's left. But with the indicator for the the needle when checking a AA cell and it's in the red zone. That doesn't really mean that the battery is no longer good.

[@JUANKERR2000]

I have a rather novel cell tester that seems to use a small D C motor which winds up a spring, so that a disc attached to the motor shaft rotates to differing degrees dependent on the state of the cell; interesting and quite clever. I have so far resisted the temptation to do a Big Clive on it.

[@NOWThatsRichy]

Is that one made by 'Ronco'? I had one of those back in the early 1980s, & yes it had a Small DC motor inside which rotated against a spring, which rotated half a turn to move the indicator disc, I took it apart years ago out of curiosity, the only bit I still have is the motor!

[@JUANKERR2000]

@@NOWThatsRichy I don't recall seeing a name on it, but suspect that it was badged and sold by several different outlets.

[@frankjackson2439]

Wow thanks for showing the resistor values, I have the same battery meter that I accidentally left in my pocket that got sent through the washer and dryer. The regular 1.5v part still works fine but the 9v battery side of the meter stopped working after that. I’m guessing it’s just a broken wire but now I know what the resistor values are if I ever end up needing that function back.

[@ernstoud]

Ah, the moving coil meter. In engineering class we had to prove that it has a linear scale. My answer that the proof was on a page in our book was not enough during the exam.

[@UpLateGeek]

Finally got my second pair of anyloops back from my parents. It only took just over a month, although I was sick for three weeks of that time. Anyway, now I can play my Game Boy Color almost indefinitely without having to revert to alkalines. It doesn't have a battery level indicator, but it does have a power LED that gets very dim when the batteries are low, and the background humming noise from the speaker gets louder when it's right about to die. If I'm not too engrossed in my game and paying attention I can press the pause button, swap to the other pair of cells and resume my game, as it saves the state if powered off while paused. Otherwise I lose my progress on the level and have to start from the beginning.

[@Evergreen64]

On the meter, I think you will find with the screws covered in red paint, that each one of the ends of the screws are conical. That is, inverse cones. And the ends of the meter deflection are pins. You adjust the screws to mount the meter in place and to adjust how much resistance the needle gives. I'm not sure of all the correct terms to use for the parts. And I wish I could just draw you a picture! But these comments don't let you.

[@rokushou]

I have a battery tester that looks exactly the same, though I'm sure there's a thousand clones of this design around. It's actually pretty generous and I consistently get it into the green with Ni-MH. A new alkaline will nearly max it out.

[@FerralVideo]

I have a DMM with a low-impedance input "battery test" feature. Haven't measured how low yet though. One range for 1.5v, and one range for 9v. I use the 9v extensively for anything that's anywhere more than 1.5v, including Li-Ion, since the 1.5v range can't read anything higher than, well, 1.5v. I've also just used common analog voltmeters, since while the load is not quite as low resistance as these, it does the job better than a high impedance digital.

[@veeeks2938]

Ah, the battery tester you took apart brings back memories. I had loads of them in the 80s and 90s when I was a young'un and wanted to test the batteries in my R/C cars (ie 9v battery for the controller and the 7.2v Ni-Cad power pack I had more than one occasion where the battery failed (ie on the transmitter) which lead to the r/c car being stuck at high speed lol (these were the days of mechanical speed controllers so if it lost signal you were screwed as it was stuck on the last known throttle position). I still miss my R/C cars, especially Tamiya Hornet and Monster Beetle.

[@LoveClassicMusic0205]

I have that same larger meter myself. From what I've observed, the 9 volt will go all the way to the right on a fresh battery, but the 1.5 volt tester will only go about half way into the green on a brand new battery.

[@kwinterburn]

remember the two resistor networks are in parralel anyway so that affects the current through the meter

[@onfire4Jesus2]

"Let's get out the kink palculator". Cracks me up every time he says that.

[@xzx4696]

Oh God this brings back memories when I would find a bunch of batteries and have to go get the battery tester out the 9-volt batteries were the easier ones to do but the smaller the battery the harder they were to balance properly

[@CptnKremmen]

Just got my simple battery meter (identical to yours - probably from 7-dayshop) out of the drawer and it's a bit more generous than your one so no need to change any resistors. I generally find this its a handy go to tester to get a general idea for AAs; for PP3s as a kid we'd just lick the terminals.

[@loukashareangas4420]

I have the digital version of the "clamp" type meter, with an LCD. When I disassembled it to find out if it loads the battery, I found out that it didn't. So I added 4 resistors with 4 microswitches (the holes for the switches go exactly where the "BT-168" marking is on yours) to add 4 ranges of current loading. One thing I found out is that it takes some samples and then holds the voltage it has concluded on, on the LCD, so you have to hold down the switch before contacting the battery. There is 'just' enough space inside for this mod.

[@Ni5ei]

It works without an internal battery and uses the battery you're testing to power the circuit and display. So it does put a load on the battery.

[@joinedupjon]

For search optimising... That style seems to be called BT168 whatever the brand name is on it... The similar looking unit with a digital meter is the BT168d.

[@pilkjaer]

Thank you for making this video. I thought i could just use my multimeter for this.

[@McTroyd]

We used the square one at Church for wireless mics, but for me, I went straight to a multimeter. (Overachiever that I am. 😁) Lately, I've been using the "Lo-Z" mode on Dave Jones' BM235 meter. It places a 2K (or so) load across the probes, putting the battery on a small load. Found that works "a treat" for testing battery state of charge. 👍️

[@ronniepirtlejr2606]

Big Clive, I have a Strange antique panel that I purchased from an antique store. I think it was a panel to monitor telephone/ Telegraph power stations but, I don't know...it Could be for anything like an old crane? The panel is 3 ft X 1 ft & 1 inch thick. (Sorry no metric conversion) it is made out of some kind of ceramic / concrete & painted black. It is super heavy ! It has an antique amp meter DC made by WESSON model 273 Day storm. Amperage is 0 - 7,500 amperes D.C. Printed on the board below it says....DISCHG. The voltage gauge is exactly the same type of meter. It reads 20 - 30 Volts D.C. printed on the board below that it says- BAT. there are two strange big relays made by Western Electric. One relay says 260 BM. High 25.25 V. Low 22 V. Underneath that relay printed on the board it says HLV Now for the other relay. says.... 260 BU. High 23.75 V- 24.5V Low 21.25 V.- 22. V. Printed Below it ...EM CELL There's also two copper shunts and a ground connection on the board. I also have a smaller version with two relays & an analog voltmeter 0 - 50v. They're all beautiful & relays. I thought about shipping one of these relays to you so you can figure out how they operate. Each relay is about the size of a can of soup. They definitely don't make relays like this anymore! I will try to find a picture of one of these relays and send a link to you down below.👇

[@ronniepirtlejr2606]

I posted the links big clive but, KZbin deleted them!

[@ElvenSpellmaker]

What happens if you put a 9V and a 1.5V on at the same time? Also nice to see the Kink Palculator back again.

[@bertkooijmans4769]

Fire? Glowing meter?

[@ElvenSpellmaker]

@@bertkooijmans4769 Haha

[@imre5311]

Nekem ez a kockaalakú van ,amit évvel szelektálok az mind oké! A másik típus az alá lehet méretezve .Mind a kettő jó ,van egy digitális az meghalt . Magam is csináltam egyet azt javítanom kell ezek után ! jó egészséget

[@JohnCline]

In the case of the 1.5 volt input, there's also an additional 8,420 ohms in parallel with the 736 ohms of the meter. In the case of the 9 volt input, there is an additional 1,205 ohms in parallel with the meter.

[@Chris_Grossman]

Ignoring the parallel path is OK for the current draw because the parallel resistance path is so much higher. That is not true when calculating the meter deflection. The parallel path reduces the meter deflection and is part of the reason your old meter read low. I have a dual banana plug with a resistor across it that I plug it into my multimeter input as a load for battery testing. I also have a small dedicated AA NiMH/alkaline tester with a 5 led readout I use to check strobe batteries when I am photo trips. The key to testing all batteries is that they need a load.

[@Electronics-Rocks]

Great I noticed the readings in my own battery testers which did cause confusion with others in the house.

[@acmefixer1]

Scary thought: the 1/4 W load resistor for the single cell is dissipating nearly a watt and it could overheat and burn up if the cell was tested for a long time. I think you could have added resistors in parallel to bring the meter needle out of the questionable and into the green range. The cheap cell tester I have has a boost circuit in it to drive the LEDs it uses. Thanks for the video, Clive.

[@andygozzo72]

you're only really meant to test quick, anyway 😉

[@onenewworldmonkey]

I always wanted one and found one in an old car I just bought. It says battery cell tester, has a zero in the center 1,2,3 to the right and the same to the left. Its sealed rubber has a red and a black wire coming out of it and a hole where it looks like there used to be another wire. Its very interesting which is how I ended up here. Mine is much different than yours but thanks for the effort.

[@TheMisphit]

Used to have one of these since the 1980s when I was a child

[@BjornV78]

i have the BT-168D (LCD display) version for many years and this works well.