No. 6 Dry Cell

Brooke Clarke 2007

	Too tall (6.25" body)	6.0625" body

The wet battery gave way to the dry cell opening up many portable applications that were not possible with a glass jar full of chemicals.  These first generation Zinc Carbon cells were the common type through the Korean Conflict.   They consisted of a Zinc cup which is the negative terminal just like the Zinc in a wet battery is the negative electrode.  The metal cap on the carbon rod is the positive terminal.  Some type of insulating material was poured between the cup and rod at the positive end to seal the battery.  The label was a cylinder of single layer cardboard on flashlight batteries and there was a bottom cap on the No. 6 Dry Cell.  Modern designation is LR40 for the size or ALR40 for Alkaline. The body of a No. 6 Dry Cell is 2½" diameter and 6" tall.  The terminals are #8 Thumb screws or optionally Fahnestock Clips.

The Zinc gets consumed in this chemistry so if a battery is left connected to a load or just left on the shelf, after some time the Zinc will have holes that allow the liquid electrolyte to leak out.




Maybe the No. 6 came after No. 1 through No. 5?  The No. 6 replaced glass batteries on a one for one basis in clocks, telephones and many other applications.  In the 1950s these were available in almost any hardware store.  In 2007 they are only available from specialist internet or mail order houses.

I think this drawing is from the 1980s so may be the last incarnation of a real No. 6 Dry Cell.

The simplest (lowest cost) version that retains excellent flash amps uses a single "D" cell battery holder.  Top hardware is # 6 so the optional #6 Fahnestock Clip will fit.  Internal heavy wiring is soldered to the battery holder and crimp to # 6 ring tongue terminal.

Instead of putting a terminal in the center, it's offset a little to provide a 1 ince center to center distance between the two terminals.  This is the unit shown above with the Ray-V-vac label.

The current version of the No. 6 is no longer a Carbon Zinc, but a post Mercury ban Alkaline.  This type of alkaline cell is the common type on the shelves of all kinds of stores that sell the common AAA, AA, C, D and 6 Volt lantern and 9 Volt transistor radio batteries.

The Zinc Carbon cell uses Amalgamated Zinc which means Zinc that's been treated with Mercury.  The first generation Alkaline cells also used Amalgamated metal (I forget but it may have been Zinc).  So when Zinc could no longer be used in batteries a whole new generation of Alkaline batteries was developed.  The bulk of the patents you see on any Energizer battery package are related to making a Mercury free alkaline cell.

The top button, top surface and cylindrical surface is the positive contact.  The center of the bottom is the negative contact.  This is very different than the old Zinc Carbon where only the button was the positive contact.

This can cause shorts in some applications that were designed for Zinc Carbon cells, like the PSR-1 Seismic Intrusion Detector where the battery clips can cut through the thin plastic label on a modern battery and short the positive battery terminal to chassis ground which is the negative terminal.

The No. 6 battery that's being sold today is no longer a single cell that's the same size as the old No. 6, but instead is a plastic shell that holds a couple of "F" size modern Alkaline cells connected in parallel.  The reason for connecting them in parallel is two fold. 

First by paralleling a couple of "F" cells the capacity of the modern No. 6 probably approaches that of the original Zinc Carbon No. 6.

Second by paralleling a couple of "F" cells the internal resistance of the modern battery probably approaches that of the original Zinc Carbon No. 6.

I've been studying a number of products based on electromagnets like the Self Winding Clock which was designed originally (1884 - 1930) for a couple of wet batteries, and the later clocks (1930 to 1960) were designed to be powered from two each No. 6 Dry Cells.  The Build it Yourself! a Real Electric Motor kit was designed to run from a single No. 6 Dry Cell and I think the Electro-Magnetic Toy Engine was designed to run from a couple of No. 6 Dry Cells.
The interesting thing is that the coil resistance for the two motors is a small fraction of an Ohm.  The modern No. 6 has an internal resistance of 0.1 Ohm and so will power these motors.   Note that the actual motor current is being set by the battery's resistance and so it's the key specification.   But a "D" cell has 2 to 3 times the internal resistance and so will not do a very good job.   In this case the problem is not the amp hour capacity but rather the high internal resistance of the "D" battery.

Notice the plastic shell on the left has an indentation for the battery.  That's because the outside diameter of two "F" cells side by side is less than 0.1" less than the maximum diameter of a No. 6 dry cell.  So by thinning the plastic on both sides right next to the cells the overall diameter will meet specifications.  I can not close this unit maybe because it's old the the batteries are starting to swell?   Two "F" cells side be side are wider than the outside of a 2" PVC pipe.

There are two metal ribbons spot welded to the "F" cells and an eyelet or tublar rivit type connection to the bottom of the screw terminal posts.  They are 0.005" thick by 1/4" wide and 2 3/4" long, probably nickel.  These are probably 6 milli-ohms each or 12 milli-ohms for both of them.

This cell is the same diameter as the common "D" cell but is 1 inch longer.  The "F" dry cell must have been one of the very early dry cell sizes since a pair of them fit and properly power a railroad lantern from prior to 1937.  If you know what these were called back in the early 1900s please let me know.

This is a modern post Mercury ban "F" Alkaline dry cell.  It has a single layer cardboard sleeve slipped on to act as insulation between adjacent cells.

The "F" cell has an internal resistance in the 150 to 200 milli Ohm range, so two in parallel will be about 75 to 100 milli Ohms ( < 0.1 Ohms).

The can is the positive terminal on an F cell and the cap shown at left on the top is the negative terminal.

This photo gives you the idea that the "F" cells used in the modern No. 6 Dry Cell are that same as the cells used in a 6 volt lantern battery.

It would make sense that by combining 4 "F" dry cells in series you would get a 6 volt battery.

After bending back the metal on the bottom of this Energizer 6 Volt Lantern Battery (model 529) the following parts are found:

Going clockwise.  4 each "F" cells in cardboard insulating sleeves.  Energizer sells the "F" cell with or without the cardboard sleeve.

The plastic top with two terminals and one battery to battery jumper strip.

A cardboard square with two battery to battery jumper strips.

A metal plate with the four corners bent up that pushes on the plain side of the double jumper strip cardboard.

The bottom square cardboard.

The sheet metal outer case.
Note that there are no welded straps, all the electrical joints are pressure contacts.  Also there is what appears to be Silicon grease on both ends of all the batteries and on the jumper strips and terminals.  This is an insulator, but would act to keep air away from the joints thus preventing oxidation.  This may be the same patented 5037566 type that Radio Shack sells as Lube-Gel where there is no entrapped oxygen.

23 Feb 2008 - needed a 6 volt lantern battery to work on an Adams-Westlake Railroad lantern and the above unit is no longer useful that way so got the other one.  It's an Eveready 1209.  The 1209 weighs 1 pound 3.7 ounces 19.7 oz).  Most of the parts of the 529 weigh 1 pound 15 ounces, probably over 2 pounds (32+ oz) with the  missing parts included.  The price and energy content probably are about proportional to the weight.

My Agilent E3617A bench power supply rated for 0 to 80 volts at up to 1 Amp will not power the Toy Engine.  The stock 6 volt Lantern battery does power the engine.  The resistance of the two series connected electro-magnets is about 0.2 Ohms.  So connecting a 6 volt battery might cause a current of 30 Amps to flow, but that can't happen because the current is limited by the battery.  It turns out the same Energizer battery that I took apart above demonstrated a resistance of 0.4 Ohms when powering this Toy engine which along with the resistance of the clip leads limited the current to about 8.5 Amps (way more than my bench supply can deliver).

"D" Cell

If the negative end of a "D" cell is held directly on one of the Toy Engine terminals (to eliminate one clip lead's resistance) and a clip lead is connected to the other Engine terminal and it's end held to the "D" cell the engine barley turns over.  Connecting two "D" cells in series runs the Engine at a respectable rate.

"F" Cell

If the same setup as above is used with an "F" cell the motor is running at a respectable rate.  By holding a couple of "F" cells in parallel (no cardboard) and using a clip lead to touch each positive terminal there is not a noticeable improvement.  When two "F" cells are held in series the motor runs at a faster rate.  The spark at the comutator is brighter and stronger with the "F" cells as compared to the "D" cells.

The wire that comes with this kit has a total resistance (for motor electro-magnets and all the hook up to the No. 6 Dry Cell) of 0.08 Ohms.  The instructions for the motor say it will develop 6,000 RPM from a single No. 6 Dry Cell.  A 1.5 Volt cell with no internal resistance would deliver just under 19 Amps and a No. 6 with 0.1 Ohms internal resistance would deliver 8.3 Amps!  About the same as the Toy Engine is drawing.  Seeing this is what got me looking hard at the No. 6 specifications.  It's the only Dry battery I've seen that has specifications on internal resistance (0.1 Ohms at room temp).

At the top of this page is show a low cost No. 6 Battery Adapter.  It's made from 2" PVC pipe.
Construction of Western Union Clock Battery Packs by N7CFO.
If you're interested in getting a kit to build this adapter let me know I have way more 2" PVC than I need and also have the Rigid cutter for it.
See it in a Sweep Second Hand Self Winding Clock.

Hardware

This is some terminal hardware consisting of:
* 6-32 Brass screw that will be in the low cost No. 6 Dry Cell Battery Adapter.  They can also be used for Do It Yourself electrical circuit terminals. 
* #6 Brass Nut that can be used to pinch the top of the battery adapter or for making electrical connections.
* #6 Brass Thumb Nut for making electrical connections.  An option to the tuumb nut is the wing nut which allows applying more torque without resorting to pliers.
* #6 Fahnestock Clip for connecting to wire ends, or better as shown
* Tip Pin wire termination.  These were a very common way of terminating wires in a way that's much more rugged than just using the wire itself.  Headphones commonly used tip pins.  Western Union clocks (Self Winding Clock Co, #2) use these to make it easy for a man on a ladder to change the No. 6 Dry Cells.

Not shown but also in stock are 8-32 Screws, Nuts, Thumb Nuts and Brass Washers for both #6 and #8 hardware.

Teeth on Pliers

On most ordinary pliers there are teeth behind the jaws, i.e. closer to the hinge pin.  For a long time I wondered why they were included.  For example if you use them on pipe or any smooth round object they do more damage and typically don't grasp well enough to actually do any good.  The answer may be they are for tightening thumb screws.

The No. 6 Dry Cell is capable of very high currents, (See Flash Amps below) and a number of applications use these high currents so good electrical joints are needed.  Finger tightening may not be good enough.

The original Leatherman Tool shown at left has the teeth that look about like what I remember on everyday pliers.  Note that a homeowner in the late 1800 through the mid 1900s might have a number of devices that used the No. 6 Dry Cell and so a tool to tighten them would be a common requirement.

I've read that in Europe Wing Nuts were more popular than Thumb Nuts because you could get more torque on a wing nut using just bare hands than was possible with Thumb Nuts.

My local hardware store stocks bronze wing nuts in 6-32 and 8-32, the two common sizes for No. 6 Dry Cell terminals.  Note bronze offers both good electrical performance and mechanical strength.  The other wing nut sizes are steel.

If you know about the teeth on plires please let me know.

By using a slightly modified Equivalent Series Resistance (ESR) meter intended for use checking electrolytic capacitors it's possible to measure the resistance of a live battery.
Energizer white paper on Battery Internal Resistance.  Mentions "Flash Amps" which is the current into 0.01 Ohms applied for 200 milli seconds.

Battery	Ri Ohms
No. 6 Spec	0.101
Modern (old) No. 6	0.051
F cell	0.02 - 0.041
D cell3	0.06 - 0.09
6 volt lantern meas on Toy engine	0.42
Low Cost No. 6 3 V Battery Adapter w/ 2 series "D" cells	0.36 0.154
1.5 V KCC Single "D" 1900	0.22
1.5 V KCC Double "D" 1900-L	0.12
Seagull R40	0.00

Note 1 - The actual resistance for a fresh No. 6 is probably in the 0.02 to 0.03 Ohm range (i.e. two F cells in parallel plus a little).
Note 2 -  It appears that there is resistance in the 6 volt lantern battery caused by the two spring contacts, the 3 jumper bars and the 8 joints between the dry cells and the bars or terminals that amounts to the bulk of it's resistance.  Not measured using the ESR meter, since it was taken apart prior to these measurements.
Note 3 - the Energizer EN95 "D" cell is  specified at 0.15 to 0.3 Ohms.
Note 4 - 10 Oct 2007 measured on low resistance version of low cost double "D" 3 volt adapter with Duracel batteries.  Note that when two battery adapters are used in series, like in a Self Winding Clock Co. installation, you end up with twice the resistance, so in the common case of a single "D" cell in a radio shack battery holder that may be 0.44 Ohms.

A better way to measure the internal resistance would be to use a shunt resistor in series with a static load and use a DVM to measure the voltage drops around the circuit.  If a dynamic load, like a motor is the load then a scope would be needed to measure the current.

If a 6 Volt Lantern battery is used to power a motor with a resistance of 0.08 ohms and the battery had 0.4 ohms resistance and perfect wires are used then about 1 volt will end up across the motor and the other 5 volts will be in battery loss resistance.  So using a real No. 6 battery or a battery with an equivalent low resistance will work much more efficiently.

defined as the current into 0.01 Ohms applied for 200 milli seconds.  I've been thinking of how to measure Flash Amps.
A little less than 2 feet of 14 AWG wire has a resistance of 0.01 Ohms, i.e. 10 milli Ohms.  So connecting that length of bare copper wire to a battery will provide the correct load.  Soldering some small stranded wire seperated by a little less length would provide the test leads to a voltmeter so that the voltage along the wire can be measured.  If the leads were about 12 inches apart the resistance between them would be about 0.005 Ohms and if 20 amps were flowing the voltage would be 100 mv.  The HP 34401 when in a fixed range mode and turned down to 4 digits can make a measurement each millisecond and store them.  It can also be started in this mode from a switch closure input to TRIG on the rear panel.

The problem is turning on and off the current.  Bosch type automotive relays come in current ratings around 20 to 100 Amps with coil currents under 200 ma for "12 volt" units.  The contacts are rated around 20 milli ohms for initial resistance and low currents.  The Bosch type relays have quick connect push on type terminals on one end in a standard pattern and are now made by many compaines and used for many applications.  But may have too much resistance for this test.  A number of them could be connected in parallel.  By using a high voltage driver in series with a power resistor the actuation time can be made very quick (time = k* L/R).

Relay Data

Brand	Model	Peak Amps	Contact Amps	Contact  Ohms	Coil Ohms
Omron	G8JN	100	35	?	74
Tyco	T9A	na	20	0.075	144
Beuler	BU5083B	-	40	-	80

There's what's called "Universal Starter Solenoid. 4 pole, 12 volt" these are SPST N.O. relays used for the starter on small gas powered garden tractors.  Rated for 400 Amps (no more than 0.5 seconds which is fine for this.  Stancor type 120.

There are also the starter solenoids like used on cars.  These are rated 780 Amps intermittent or 85 amps continous.   Contact resistance is will below 1 milli ohm.

The IRF 6726 might be able to do this, but the RDSon is around 2.6 milli Ohms or about 26% of the allowed resistance. 

17 Nov 2007 - About Pocket Watch Ampere Meters
The early automobiles used "Ignition Batteries" which were No. 6 Dry Cells.  There were two ways of testing them, you could measure the terminal voltage or the terminal current.  Pocket watch size meters were available as either a voltmeter, amp meter or a combined meter.  A book of the time recommended that if you could only get one the amp meter was the most important.  The example given was that a dead battery and a fresh battery read very close to 1.5 volts, maybe 1.5 down to 1.2 volts a very small amount of deflection (3% of 10V) on a pocket watch size analog voltmeter.  But the amp meter would read 10 amps or less for a dead battery and 16 Amps or more for a good one.  Which would be 20% of 30 Amps.

The method was to line up the available No. 6 Dry Cells on the counter and holding the pocket meter in one hand and the test wire in the other hand make a firm connection to the battery terminals (observing polarity) and as soon as the meter needle was steady remove the meter and remember the reading.  I doubt that there was a "Flash Amps" specification at the time.  The spec was probably made to reflect what was being done.

A loose-leaf book titled "Battery Engineering Data" by the National Carbon Co., a division of Union Carbide and Carbon Corp. has data sheets on the what may be the full line of Eveready batteries.  At the time the book was written National Carbon Co. maintained a research lab with equipment to test the RF and audio characteristics of battery powered radios so that batteries could be developed to optimally power the radio.  There were different ways of using the "A" and "B" batteries and different problems associated with either a weak "A" or weak "B" battery in different designs of radios.  When the internal resistance of the "B" battery is excessive (the battery is going bad) the radio "motor boats".   So far I have not found a date anywhere in the book, but there is quite a discussion about "B" batteries made up of flat cells instead of cylindrical cells and references papers with dates as recent as June 1941.

The book mentions that measuring the terminal current of a battery does NOT tell you much about how much charge is remaining.  The book about early automobile was from the late 1800s so by 1941 Measuring Flash Amps was not as popular. 

The Battery Engineering Data book shows the terminals on Eveready No. 6 Dry Cells as 8-32, not the 6-32 that's common on the Chinese battery.  The Brentronics military unit has the proper #8 hardware.
15 Dec 2007

Measured Flash Amps

Using the Conn Tel & Elec Co Inc Flash Amp meter.

	2 F cells Parallel		F  cell
	2 x F	Seagull	F	2 x D series	2D Series	2D Parallel	1900L 2 x D parallel	1900L single D
Flash Amps	29	26	23	16	14 - E95 17 MN1300	23 - E95 24 - MN1300	11	7

More Flash Amp Measurements

Made on batteries close at hand, condition unknown

Battery	ZTS1	Flash Amps	ZTS
Duracell MN1300 "D"	3	4	4
Duracell MN1400 "C"	3	4	3
Duracell MN1604 "9 V"	5	9	5
Energizer E91 "AA"	4	13	4
Energizer E95 "D"	5	13	4
"	5	12	5
"	-	15	3
"	5	12	3
Energizer "F"	4 2	19	4 2
Radio Shack 23/872A "AA"	5	19	4
Powerizer (China) Ni-MH	4	19	4
Kirkland (Costco) "AA"	4	8	4

Note 1 ZTS reado 0 to 5
Note 2 the ZTS is not designed to measure an "F" cell so it's not suprising that it gives a wrong answer.

The open circuit voltage is 1.5 Volts (nominal for a fresh No. 6 Dry Cell or for a single Alkaline cell like a AA, C, D or F cell). 
The voltage across the Flash Amp load resistance of 0.01 Ohm is V = I * R or V = (FlashAmps) * 0.01.
For example two "F" cells in parallel show Flash Amps of 29 Amps, then the voltage across the load is 0.29 Volts.
The drop due to the battery internal resistance is 1.5 V - 0.29 V = 1.21 Volts.
The internal resistance is R = V/I = 1.21 V / 29 A = 0.0417 or 41.7 milli Ohms.

Optimum Power Transfer occurs when the load resistance is equal to the source resistance.  So to get the most power from a battery the load should have a resistance matched to the batteries resistance.  Primary cells like the No. 6 came in various versions depending on the load.  For example a No. 6 for telephone use would be designed to supply a small current for a very long time (a few years).  But an ignition battery would need to supply very high current pulses.  So while the optimum power transfer load works, it also can not be maintained for very long since the drain is maximized.

Electromagnet Idea

An application would be making an electromagnet where you are restricted to use only a single "D" cell battery.  Since the Flash Amps for a good "D" cell are around 15 A the voltage across the load is 0.15 Volts. The drop across the internal resistance is 1.35 V and the internal resistance is about 0.090 or 90 milli Ohms.  So the load should be 90 milli Ohms.  If the core of the electromagnet is a "C" shaped soft iron 1/4" diameter and is 2" long (with the ends cut off in the same plane so the air gap to the soft iron keeper is minimized) then the best winding would be one layer deep and covering all of the "C".  Different wire sizes might be used, but the wire size the results in a 90 milli Ohm resistance (including the leads to the battery) is the best choice.  It turns out that winding more layers results in lower amp * turns since the resistance goes up faster than the number of turns.

I ordered these from my local Interstate Battery store as their Dry1725 expecting it to be made like the Energizer EN6 or military BA-23 using two "F" cells.  But it's a real No. 6.  They weigh 28.5 oz  a lot more than the 16.4 oz for the plastic two "F" type.
I tried to measure their internal resistance with the modified ESR meter, but it reads ZERO.

Joseph Henry was the first person to make what today we call an electro-magnet which made the DC motor/generator possible.  The unit of inductance is named Henry after him.  His coils were optimized to use a single wet cell or a small number of cells.  The tests I've done on 1 liter type Leclanché Cells indicates that they have very low internal resistance.  Henry came up with the idea of winding multiple coils on a common soft iron core then connecting them in parallel to a single wet cell.  Many of the electro-magnets he made in the 1900s use large diameter wire and are intended for low high current use.  Henry was the first secretary of the Smithsonian Institute.

I'm trying to determine if Henry was the first to use insulated wire for an electro-magnet.  Schweigger's galvonometer multiplier used bare wire and it may be that Sturgeon's electromagnet was wound on an insulated horseshoe rather than by using insulation on the wire.  I think Henry used his wife's spinning wheel to wrap silk on "bell wire" (copper wire used to ring servant's bells in large houses my mechanical movement, not electricity).  By insulating the wire powerful electromagnets can be made.

The first application was for ignition of explosive engines.  The 1893 the Columbia No. 6 had a rectangular center post and was labeled as an ignition battery.  They were shortly thereafter used in Lanterns as a more user-friendly source of power than lead acid storage batteries.  The early telephones (patents, phones) used what's now called local battery operation where each phone had it's own battery and the No. 6 Dry Cell was used in a large number of phones to replace wet cells.

Battery

The key patents were:
G. L. Leclanché Patents for a wet battery that does not use acid for the electrolyte 1866, 1867 for key patents, more later.
Columbia Ignition No. 6 Dry Cell made by National Carbon Co. shows a patent date of April 11, 1893.  The only patent issued on that date applicable to the No. 6 Dry Cell is:
495306 Galvanic Battery, C.J. Coleman, Apr 11 1893, 429/133 ; 429/249 - 

Meter

1148218 Battery Tester, Emerson L. Clark, National Carbon Co. Jul 27, 1915, 324/145 ; 324/72.5 - a cylindrical flash amp tester with a micrometer like calibration

1205343 Apparatus for Testing Dry Cells, J.H. Goodwin, F.A. Adamski, Nov 21 1916, - 4 minutes each hour for 10 hours/day for 6 days a week for  . . . .
327908 Electrical Measuring Instrument, E. Weston (U.S. Electric Lighting Co), Oct 6 1885, 324/93 ; 324/144 - maybe the first moving coil meter at least the oldest patent in class 324/144
334145 Electrical Indicator, E. Weston (U.S. Electric Lighting Co),- under glass dome
340399 Electrical Indicator, E. Weston (U.S. Electric Lighting Co),
------------ Edward Weston has a bunch of meter patents------------

619679 Galvanometer, A.A. Dittmar, Feb 14, 1899, 324/147 - pocket watch size
686561 Battery-Gauge, Charles R. Underhill (1/2 to Varley Duplex Magnet Co), Nov 12, 1901, 324/144 - pocket watch case
839637 Pocket Ammeter Dec 25 1906, 324/144 - 270 degree pointer movement, pocket watch case
854709 Electrical Measuring Instrument, J. Abrahamson, May 28 1907, 324/146 - slotted dial to pass pointer, pocket watch case

Eveready Pocket Amp Meter

966421 Portable Electrical Measuring Instrument, W.E. Beede(American Ever Ready Co ), August 9, 1910, 324/145 - moving vane gets pulled into coil



0 to 35 Amp scale.

	The crown has a socket for a short wire that's missing.  The meter works, but does not give the same reading as the Conn Tel & Elec meter.  It might be possible to make the plug for the crown and the cable to go with it. See the Flashlight web page for a photo of this meter with a few pocket flash lights, all Eveready barnded. 1906 to 1909 Made by National Inst Co, Hartford, Conn
	Cloth pouch for Pocket Flash Amp meter. This is wha't called a moving vane meter.  The scickle shaped vane is pulled into the 8 turn coil more and more as the current increases.  The wire is 0.051" dia or 16 AWG which has 3.1845 Ohms/Kft or 3.1845 Milli Ohms per foot.  For 10" of wire that's about 2.65 milli Ohms.  But the total load resistance of the test will also include the resistance of the:  top solder joint metal case from the top solder joint to the top terminal post joint between case and top terminal post (on this meter it's very high since the post can easily be turned) top terminal post joint to test lead plug, solder joint, test lead, solder joint, terminal, contact to battery post bottom solder joint strap from bottom solder joint to hole for bottom terminal post joint between strap and bottom terminal bottom terminal & contact to battery post
	1914 This may be the newest of the pocket amp meters.

1012209 Testing Apparatus,Union Switch & Signal,  Dec 19, 1911, 324/418 ; 324/157; 338/148; 338/176 - more the size of a flashlight
1184536 Portable Electrical Measuring Instrument, May 23, 1916, 324/145 ; 336/130; 336/223; 336/45 - coil a sheet metal stamping, window to see current

1199829 Battery-Meter, Walter  M. Scott, Sterling Manufacturing Co, Oct 3, 1916, 324/115 ; 324/146; 324/149 - frame saves parts and labor The dial face reads: Simmons Hardware Co., Inc., Mfrs and Distributors, U.S.A.  The eBay auction shows the meter face and the pointer is a little above zero.  When the meter arrived in a ReadyPost Photo Document Mailer with no padding the meter needle and other parts were loose inside the case.  Terminal 3 was loose in the mailer and external insulator 23 was missing, although shown in the eBay photo.  Very poor packaging.


The meter movement is about 4 milli Ohms, but the wire is 230 milli Ohms.  Yet the wire (patent drawing # 4) appears visually to be OK, it has a serious problem.
Using this wire, not the wire that came with the Conn Tel & Elec meter the Seagull battery read 15 Amps and the crimp terminal got very hot.
After doing this the wire resistance is 55 milli Ohms.  A close look at the crimp shows that is was made with the insulation still on the wire!  This appears to be a regular closed barrel ring tongue terminal, although there is a gap in the barrel with the insulation showing the full length.

1223306 Electrical Measuring Instrument, 324/146
1315816 Pocket Flash-light Battery and Bulb Tester, R.E. Cole, Sep 9, 1919, 324/444 - uses  bulbs and ammeter
1337160 Battery Tester, G.H. Riebeth, Apr 13 1920, 324/437 ; 324/537; 429/90 - connects to the top of a No. 6 dry cell and reads the current 0 - 30 Amps

Conn Tel & Elec Flash Amp Meter

15 Dec 2007 This meter arrived DOA.  Once the back was off (Kroil helped when prying the back) the problem was that a Mica washer was used between the terminal lug on the end of the green wire and the case as an insulator.  The terminal that screws into the outside has what amounts to a shoulder washer to keep it from touching the case.  Mica is fragile and the washer had broken.  It's inside the back cover on the right.   I just cut a small square of 3 x 5" card and used that on the inside as an insulator as a temporary fix and the meter is  now working.

The connector at the top on the green wire and the connector at the bottom of the meter have cup shaped ends.  Just the thing for putting on the threaded terminal posts of a No. 6 Dry Cell.

The wire connects to the meter using a tappered pin on the wire that fits a tappered socket on the top meter terminal.  It works like the Morse Tapper used in machine tools like lathes and drill presses.  You push and turn the connector and it makes an extreamly good joint.
The meter is about 8 milli Ohms and the wire 9 milli Ohms and when both are measured it's about 15 milli Ohms. 
Measuring from the wire connector to the meter connector when they are mated reads zero =/- 1 milli Ohm.  It's a very low resistance type of connection, far better than a PP15 series Power Pole.
The negative battery terminal connector on the test lead shown at the left is the same as the batery positive terminal connector on the bottom of the meter.  They have a hollow pocket that allows holding the connector on top of the threaded terminal on the No. 6 Dry Cell.

The wire measures about 10 milli Ohms and the meter is about 8.2 milli Ohms.

But the wire which appears to be stranded 18 AWG has broken strands.  18 AWG is specified at 6.6 milli ohms per foot and so 9½ inches should be about 5.2 milli Ohms so it's twice as high as it should be.


The interesting end is the tapered pin.  It fits a tapered socket on the top of the meter.  To make the connection you press and turn the pin.  The resulting connection has extreamly low resistance.  To remove just pull and turn.

The two round parts are some sample shoulder washers that have a hole about the correct size to replace the broken mica washer, but I'm liking the card stock more and more.

Just grabbing a number of cells that are nearby shows Flash Amps when making the connection directly to the battery (no battery holder) as shown:
D cell: 4 to 15 Amps
C cell: 6 Amps
AA cell: 18 Amps
9 Volt: 10 Amps
18650 ¹: pegs the needle > 30 Amps
LIR123A ¹: 28 Amps and going down scale quickly
Note 1 When testing these batteries the contact was made and released in less than a second.  The needle does not peg so much as hits the peg at full scale and bounced back and forth.

The readings from different batteries varies a lot more than a voltage reading.  Since the internal resistance of a battery is an indicator of it's state of charge the Flash Amp reading may have more than a passing relationship to State Of Charge.

See more Flash Amps data above measured with this meter.

Dual Range Pocket Voltmeter

This is a Voltmeter for checking what were then common battery voltages which were: 1.5, 3, 4.5 and 6 on the low range and 22.5, 45 and 90 on the high range.  Stamped into the case at the bottom adjacent to the left probe is 90 and adjacent to the right probe is 7.7.  Half way between them is the ground schematic symbol, meaning a test lead from the top threaded terminal is the ground connection.

The low range is about 1,000 Ohms per Volt and the high range is about 10,000 Ohms per Volt.

The readings on the low range are way off, yet the high range is quite close.

Meter	1.5	3	4.5	6	7.5	22.5	45
Actual	1.33	2.48	3.81	5.12	6.54	21.4	42.2
Error %	-13	-21	-18	-17	-15	-5	-7

After removing the two screws on the back the back cover does not want to come off.  Applied a very small amount of Kroil and will check again over the next few days.  Maybe the reason for the large error on the low range can be seen.

Note if the error was the same when this no name meter was new it's easy to see why the pocket amp meters were much prefereble to a voltmeter.  The error is close to the difference between a full battery and a dead one.

Yankee Volt_Ammeter

0 to 50 Volts and 0 to 50 Amps.  Marked pat. appld for, made in U.S.A.   At the bottom there's a circular cutout in the dial and what looks like a notch where a stylus could be inserted to set the zero.  Both Volts and Amps are operational, although like the meter above far from what today would be called calibrated.  The glass is broken so needs to be replaced.  The ground lead is attached to the meter and so is here.  The only other ground lead is the meter that came in a leather case.  The lesson seems to be if there's no place to store an accessory, even a critical one, it will get separated and that means lost.

There are a couple of people who make No. 6 battery adapters that make use of "D" cell batteries.  There are thumb screw or Fahnestock Clip terminals.

	Ken's Clock Clinic -  makes a number of battery adapters aimed at clock use.  In addition he makes an hourly synchronizer for the Western Union clocks.
	Dennis Hallworth - is making a very nice looking replica in either Working ($17 + s/h) or Display Only ($12 + s/h) versions and with either simulated tar top or simulated phenol top. He also has a number of very nice color labels. These are aimed at telephone use.