CA2100253C

CA2100253C - Battery tester

Info

Publication number: CA2100253C
Application number: CA002100253A
Authority: CA
Inventors: Alan Palmer
Original assignee: Duracell Inc USA
Current assignee: Duracell Inc USA
Priority date: 1991-02-07
Filing date: 1992-01-06
Publication date: 1999-07-20
Anticipated expiration: 2012-01-06
Also published as: EP0570470B1; IL100472A; NZ241118A; JP2505095B2; DK14592A; CA2100253A1; US5128616A; ES2039184B1; EP0570470A4; EP0570470A1; KR930703608A; AU651435B2; IL100472A0; DK0570470T3; WO1992014144A1; AR243703A1; JPH06505338A; MY106900A; AU1249792A; BR9205589A

Abstract

The present invention relates to a battery tester comprising a plurality of resistive elements (22, 24, 26, 28) in thermal contact with a thermochromic material (50) wherein the elements (22, 24, 26, 28) are connected in a parallel configuration.

Description

WO92/141~ PCT/US92/00t23 BATTERY .~,~

The p~af-nt invention relatQs to a batt-ry t-ster comprising a plurality of resi~tive elQoQnt- ~n t'-_ -1 contact with a thel -~'romic material. ~n partiC~ r, the prOB~ ~ invention relates to a battery tester for a 9V battery wherein the plurality of resistive elements are electrically or~e~Led in a parallel configuration.

Over the past ~eLal years a variety of battery testers employinq a resistive element in t~ ~ 1 contact with a thermochromic ~aterial have beco~e available. The ~ajority of these testers h_ve used a single re~istive element which has a contin~o~ly varying resistance ~etle one portion of the element and another portion. For example, U.S. patent Nos.
4,835,476, 4,726,661, 4,835,475, 4,702,563, 4,702,S64, 4,737,020, and 4,006,414 all ~; r~l oqe a nbow-tie~ ~Ap~A
resistive element. This ;~ ;ment has its h ~ ghe~t resistance at the narrow portion and the resistance cont~n~o~aly decreases SUBSTITUTE ~;HEEr . : .
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W092/141~ PCT/US92/~t23 ; 3 --2--to its lowest value at the outer portion6. Another - ~o~i -nt disclosed in many of these refe,er.c~s i6 a single "wedge" shaped resistive element which is e~u Lially half of the ~bow-tien ~pe~ element. A the- - -omic material i8 generally applied to the oppo6,ite side of a 6~ Le which b ar~ the resistive element. When the terminals of a battery are co.le~Led to contacts located at opposite ends of the resistive ele~ent a current flows therethrough that is ~O~G- ~ional to the voltage of th~ battery. Resistive heating ca~es the narrow portion of the resistive element to heat up first. The ther~ochromic material ~hA ~n~ color in L'e~ e to the heat ~ Led.
~~~~ ally~ a F~ fic Lh,~ te~eraLu,~ mu~t be reached before the color rhr-,e O~UL~. The extent to which heating continues down the length of the resi~tive ele~ent is a function of the battery voltage. ~D~ e ~Lion of the color ~hr-,~ ag~inct a scale imprinted on the tester gives a visual inA i c~tion of the battery voltage.

As ~;F~CEed above, ~,~se Lly aVAilAhle battery testers use a "~ed~en ~2pe~ resi~tor. While thi~ configuration is ~A~, -te SUBSTITUTE S~ cT

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w092/141~ PCT/US92/OOt23 rj 3 for 1.5V batteries it has been discovered that it is not adequate for repeated testing of higher voltage batterie6 6uch as 9V batteries. It has bRen found that the narrow portion of a wedge ~hare~ element ~burns out" aSter repeat-d testing of a sv battery due to the h~hsr power which is ~ 1rAted in this portion vis-a-vis a 1.5V battery. Addition~lly~ a wedge ~Ap element having a resistance of about 50 ohms (e.g. a typical resistance of a device powered by a 9V battery) would have a length which would make lt diSSicult to use, particularly if the tester is associated with a battery package as disclosed in U.S.
patent No. 4,723,656.

It is an ob~ect of th- p,~ ~ invention to provide an improved battery te~ter for battcries having an open circuit voltage greater than l.SV vher-ln the tester can withstand the higher power di~ip~ted by these batteries.

It is an addit~orAl ob~ect of the present invention to provide a battery te~ter for batteries having a voltage in PYc~ss of l.5V whlch ia of a cG..~nient size, Su8 ~ S ~ ~

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W092/141~ PCT/US92/~123 The features and ~dvantages of the ~P~nt invention are ~xplained below in reference to the Figures in which:

FIG. l shows a h~C~ view of a t--ter uad- in accordance with the ~e L invention; and FIG. 2 shows a f.~nLaide view of a t-ster ~ade in accordance with the ~.~se ~ ~nvention.

Referring now to FIGS. l and 2, tester lO co~prises a plurality of rectangular resistive ele~ents 22, 24, 26, and 28 located on the back ~ide 14 of ~uL~r~Le 12. ~uss bars 30 and 31 run along opposite edge~ of the r ~istive element pattern 3, whereby elements 22, 24, 26, and 28 are electrically co~e_Led in a parallel configuration. Portions 38a and 38b of buss bars 30 and 31, .~F~P ~ively, function as the electrical contact pads for co~ne~-Lion to the terninal6 of a 9V battery.

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2"~?~'3 Substrate 12 can be ~ade from a variety of materials ~ncluding, but not li~ited to, plastic, pap r, cardboard, and the like. Whichever material i8 ~elected it -~o~l~ be able to wlthstand the tempe aLu~e of the resi~tive QlQments during the voltage measurement without shrin~ing, deformlng, charring, etc.

Resistive elements 22, 24, 26, and 28 can be made from a variety of resistive materiAls and can ~e Ap~ by a variety Or different methods. For example, a coating o~ an electrically resi6tive ink can be coated or printed on the su~L~aLe in the desired pattern. Suitable resistive material~ include, but are not limited to, epoxy or ure~hAne ba~ed silver, ~ Arh~n, or mi~LuL_s thereof. Alternatively, a thin resistive layer can be applied in the de6ired pattern using any o~ the well known vacuum deposition t--hn~ -P such as vacuum vapor depositicn, cathode ~puttering, and the llke. Suitable materials r - -hle to vacuum deposition include, but are not llmited to, silver, ni~el, iron, copp~r, car~Qn~ lead, and mi~Lu~es thereof. The particular choice of material ~ on the resistivity ~e~s~
to achieve t~e desired resistance for a particular size of SU~ ~ S~E~

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W092/141~ PCT/US92/~123 ~ 1 Q ~t r~ 6-resistor. Generally, the size of the resistive ~1 - ts is llmited by the dimensions of the toster as well a~ the watt density needo~ to obtain a ~Yr~ -2 from the thermochromic material ~ir~Rs~ more fully below).

Buss bars 30 and 31 are shap-d to follow th- outside -ncions of the pattern of resi~tiv- el~ ~nts. The resistance of each of ele~ents 22, 24, 26, and 28 ~ ~ , in part, on the distance beL~ecn the .~Q_8~ in~i~e edges of each buss bar.
Thus, for .-~ le, the resistance of element 22 is a function of the distance ~-t~an the in~ide ~dge Or portion 32a of bus~ bar 30 and th- in~id~ edge of port~on 32b o~ buss bar 31. Bu6s bars 30 and 31 are pr-rerably highly ~v..~ ve so that they do not contribute --~F~-ably to the o~erall resi-~anc~ o~ the tester.
Any well known cQ~ ~ive lnk c~n be used for the the buss bars. Examples include, but ~re not limited to metallic inks comprised o~ silver, CO~L ~ n~ and the like.
Additionally, metal foil can be used i~ it i8 cut to the shape shown ~n the Figure~ and att~rh~ to the resistive elements using any of the ~ethod~ of attachment well known to the artisan.

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W092~t41~ PCT/US92/~123 2 ;~ vs 2 ~ ~?

It is preferred that a dielectric coating ~not shown) is applied over the resistive elements and the bus~ bars with the exce~Lion of contact pads 38a and 38b. The ~L~ ~e of the dielectric layer i8 to protect the circuit ~rom phy~ical A- ~ge a~ well as from ina~ve~-ent ~hort-circuiting of any port~on of the circuit. Any well known dielectric ink, paint, film, or the like is suitable for this ~ ose. Example~ include, but are not limited to, epoxies, acrylics, and ure~h~ne~.

Imprinted on front side 16 of 6ubstrate 12 i5 voltage ;n~io~tion scale 40 which is rectangularly ~h~pe~ and comprises w~ndc~ 42, 44, and 46. Windows 42, 44, and 46 are co~n~id with the position o~ resistive e~- Ls 22, 24, and 26, L~ ively, on the opposite side of su~D~,a~e 12. Voltage ; n~; s~tion scale 40 can be printed, for example, in a dark color and each window can be printed in ~ bright c~nLL~ting color, such as yellow.

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', . ,. ' W092/14l~ PCT/US92/~1 ~ ;J;)~ -8-A ther~ochromic layer 50 is located ov~r all three windows Preferably, layer 50 comprises a ~ omic ink which turns from opaque to clear above a certain th~ ol~ t~perature, ~r ~he ink preferably has a color at room t-~pe~Lu~e which i6 similar to the color of scale 40 ~nd ~h~ to clear at a temperatura above Tr Thus, w~n~ 42, 44, and 46 are blocked from ~iew at room temperatur- but become visible during te~ting de~~ ~i ng on the voltage of the battery Generally, a parti'cular watt density must be re-~he~ in each resistive element during testing before the tem~e.~Lu~c of the element Lea~ ~ Tr The watt density i8 a function of th- resistance Or the resistive _1- -nt, the surrace area of the element and the voltage applied across th- element The re~i~tance and surface area of each element become fix-d for a given design 80 that the applied voltage becomes the sole determin~nt of whether the watt density i8 achieved that is n~- ~' to trigger the thermochromic ink While th~_ - h~omic inks are the preferred thermochromic materials, an alternative, less preferred ~h~ omic material includes the class of materials known a~ liquid crystals SUBSTITUT~ SffEET

Wo 92/14144 PCI /US92/00123 Graphics 48 and 49 are printed ~longside scale 40 to indicate "Replace" and "Good" or any oquivalent message c~~oerning the condition of the battery being t~ ~e~.

As described, resistive element 28 is not in thermal contact with the tbermochromic l~yer. The ~ se of resistive element 28 is to act as a shunt and lower the total resistance of the parallel c -- ~ed resistive elements. Resistive element 28 i5 not a~ne-e~--ry -~ -r~ ~ of the ~.e~~~t invention, h- wc~er it is desirable to include it when the total resistance of tbe other "voltage ~n~ic-ting~ resistors is h;~h~r than desired.
For example, the r-sistanc- of ~ typical device ~ d by a 9V
battery is L~t ~r ~bout 50 and 60 ohms 80 tbat this is tbe desired resistanc- range for a 9V b~ttery tester. If the re~is~nceF of elenent~ 22, 2~, ~nd 26, _ ~ ~ed in parallel, give a total re~i~t~nc- Or 1-~ th~n about 60 ohms then element 28 is not ll~e~e~ , if the total resistance of elements 22, 24, and 26 i8 greater th~n ~bout 60 ohms then element 28 is included to lower the tot~l resi~t~nce of the circuit. The desired resistance of -1 -r~s 28 i8 determined using Ohm's Law and the resistance ~alue~ of elQ~ents 22, 24, ~nd 26. This is ~-~c~ese~ more fully below in conne~ion with the description of a sp~ci~ic ~ ~D -iment.

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~ SU~ ~E S~tEET

W092/141~ PCT/US92/00123 ;s ~ rt'~ ~) The principle of operation of test-r lO i~ a~ follows The te. ;nals of a "fresh" sv battery are ~.~u~1t into contact with pads 38a and 38b Current flow~ th~g1 bus~ bars 30 and 31 as well as through resistive elements 22, 24, 26, nnd 28 Element 22 heats up ~astQst hec~ e lt has th- ~alle~t ~ize whoreby it is first to reach the ne~ ry watt density to trigger the ~he, -- nomic ink A~ view-d fro~ th- front of the tester, portion 52 of thermochromic layer 50 turns from ~F~ to clear revea~ling colored window 42 In se~ ial f~ n, resistive ele~ents 24 and 26 achl-ve th- threshold watt density to trigger the thermochromic ink wh-reby window 44 foll~d by window 46 are revealed (element 28 al~o heats up but sinc- its function is not for voltag- ~n~c~tion per se it i8 not di~cus6ed here) Each resistive eleoent will reach an e~ hrium tem~Ll~Lu~
where the heat ,~r~a~ed by i2R heating is egual to the heat 108t to the ~u~v Atn~ When the ei~ hrium temp~ u~ of a resistive e1- ~ i8 above Tr the ink which i~ coin~ with such resistive el ~ will turn from o~r~ e to clear revealing the colored window beneath Thus, for example, a ~fresh battery" will cause element~ 22, 24, and 26 to heat sufficiently so that portions 52, 54, and 56 of thermochromic layer 50 will turn clear revealing colored wi-~ b'~ 42, 44, 46 on the other SUBSTlTUTE S~EEl-... .
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W092/141~ PCT/VS92/~1 hand, if the battery is near its end-of-life only element 22 will heat sufficiently to reach tho ~pon~e t~mpe ~u.e of the ink and only window 42 will be r-vealed. At ~ome intermediate cond~tion of the battery only wi n~ 42 and 44 will be revealed telling the user that the battery will soon have to be replaced.

The ordering of resistive elements 22, 24, 26 and 28 on substrate is designed to provide a particular visual effect during testing. Ac described above, element 22 heats up fastest d~ring testing followed by elements 24 and 26. This causes a ~, ~ntial visual effect in the the~ - ~romic material on the front of the tester. ~'~w_~er, other orderings of parallel col,..e--~ed resistive ele~ents are po~hle for providing different visual effect~. Further, while shunt resistor 28 i8 shown located immediately beneath contA~ts 38a and 38b it could be located at the oppoEite end o~ the resistor ~v~ e, or anywhere else, provided a parallel co\~e_Lion o~ the resistive elements is maint~i n~ .

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Immediately following is a specific description of a battery tester for a 9V battery. It is to be lln~ ood, ~ w_~er, that other design6 are po~ible which are al-o w$thin the scope of the present invent$on.

The "trigger" voltages for the three resist$ve elements are ~elected as follows. The voltage -'-~- to ~ cAte that a 9V
alkaline battery i8 ~good~ is about 8 volts or ~ore ~ince ~i~c~Arge at, or above, this voltage in~icAtes that the battery has the majority of its capacity still available. m erefore, resistive element 26 i- dosignQd to trigger the ther~oc~romic ink at, or abovo this voltage. The voltage ,-_ to ~ nA i cAte that th~ battery ~hould be replaced is _bout 5 volts or less ~ince ~t~chArge at, or b-low thi~ volt_ge, ~n~Atos that the battery is almost completely ~3-harged. There~ore, resistive element 22 i~ -d to trigger the thermochro~ic ink at about 5 volts. An int-r~ediate voltage which ~ nA ~ rateg that a 9V
battery ha6 had a ma~ority of its cA -~ty removed is about 6.5 volts and this i~ the ~trigger~ value selected for resistive element 24. The voltages ~ho~ will ~ of cou. e, ! ~- ' on how ~any resistive el ments are used. Additional ~intermediate"
voltages would be ~elected if more than three resistive elements are used in the circuit.

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WOs2/141~ PCT/~S92/OOt~

2 ~ !) Ul ~ ~ 3 The 6ubstrate is a piece of polye~ter film that i~ 0.005 inch thick, 0.7 inch wide, and 2 jn~hes long. The resistive elements 22, 24, 26, and 28 each co~pri~e a ~ub~tantially uniform layer 0.0006 inch thick o~ an epoxy based cA-hon ~heFQ~ Colloids Co., Port ~uron ~h~7~) havin~ a re~istivity of 300 ohms/square at thi~ thic~ ~9. Element 22 i~ 0.3 inch wide (the width being the dimension parallel to the short ~i ~ncion of the substrate) and 0.45 inch long: element 24 i6 0.4 inch wide and 0.45 inch long; ele~ent 26 is 0.55 inch wide and 0.4 inch long; and element 28 is 0.4 inch wide and 0.4S inch long. These dimensions er.~~L~ that the .~cessAry watt density will be re~he~ in each resistive element at the predetermined ~trigger" voltages descrlbed above.

Buss bars 30 and 31 are printed on the ~urface and along the outer edges of the resistive elements using a silver ink (a~h~sQn Colloids Co.) having a resistivity of 0.01 oh~s/square at a ~h i C~n~5s of 0.6 mils. Each buss bar is .6 ~ils thick and .06 inch wide ex~e~ for contact pads 38a and 38b which are about 0.1 inch wide. The inner edges of buss bar portions 32a and 32b are 0.2 inch apart, 34a and 34b are 0.3 inch apart, 36a and 36b are 0.4 inch apart, and contact pads 38a and 38b are O.35 inch apart.

SIJBSTITUTE SltEET

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WO92/141~ PCT/US92/~1 As mentioned previously, the resistance of the resistive elements depends, in part, on the di~tance bct~acn the 0~03e~
inside edges of the buss bars attached to each resistive element. The resi~tance of eleoent 22 i- about 150 ohm~, the resistance of element 24 is about 250 0~08, th- resistance of element 26 ~s about 325 ohms, and the resistance of element 28 i5 about 250 ohms. According to Ohm's ~aw these resistors, conre~-Led in parallel, have a total re~i~tance of about 55 ohms.. The effect of including element 28 in the circuit is evident by calculating what the total resistance would be if only elements 22, 24, and 26 were con~ Led in parallel. That calculation gives a value of about 70 ohms. Thus, including ~1 f - - L 28 in the circu~t lowers the ovorall resisLah~c to a value which i~ closer to that of an r_t~l device. It is possible that by choos~g a different resistive ~aterial the resistance of ele~ent~ 22, 24, and 26 could be eh~ 0 that shunt resistor 28 is not r.ea - . Y ~.el, thi~ can be difficult to achieve exactly with three resi~tor6. Greater flexibility is provided by using a shunt resistor to "fine tune" the total resistance after ele~ents 22, 24, and 26 are designed.

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WO92/141~ PCT/US92/~123 ~ I 'J'~ 3 The thermochromic ink used in this exa3ple i~ Type 47 made by Matsui Internation~l co , Inc which h~ a .~
temperature, Tr~ of about 47 C The watt den~ity -~'~d in each of the above described resistivQ elements to reach the L. ,~ temperature of this ink i- _bout l 5 watts/in2 A dielectric layer of an acrylic ~'~50~ Colloids Co ) 0 0006 inch thick i8 applied over the r sistivo eloments and buss bars with the ~x~o~Lion of contact pads 38a and 38b The front surSace 16 of sub~trate 12 is fir-t printed over with a green ha~ ~J.~d color A bright yellow stripe is printed onto the green ~- ~J~VU d _nd the voltage i n~ication scale 40 co~prising w~nd~__ 42, 44, and 46 is printed in black over the yellow ~tripe such that yellow is only visible h.~uyl.
said wi~ As ~ t ~bove, wi-'~ 42, 44, and 46 are positioned so that they ar- co~nc~d-- t with resistive elements 22, 24, and 25 Gr~r~c~ ~8 and ~9 are printed along scale 40 The above descr~bed t-ster can be used as _ rree g~an~i ng tester or it c~n b- ~ade an integr_l p_rt of the r~ e used for the displ_y ~nd sale of the batteries Sincç the total L flowing th.~agh t~e tester during t-sting is split among four resistors the heating proble~ Acsocj~ted with a single wedge sh~re~ element is avoided SUBSTITUTE SHC~
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W092/14~4~ PCT/US~2/OOt23 ~ 16-While the above d-~cribed '~ L i~ pr~rerred, there is another, althovgh less pre~erred, ~cbodiment vhich al80 uses parallel ~: - Led re~istive el~m-ntG Thi~ ~ bodi~ent e~ploys r-si~tiv~ element~ having the 8~0~ rL-r ln~d resi~a ce and a di~ferent ~- - h- o~ic ~aterial in th-r~al contact with each rQsistive ele~ent For exampl-, a~sume ~leuent~ 22, 24, and 26 all have the s~me resistance Portlon 52 oS th-rmochromic layer 50 would compri-e a theroochromic ink which would .~Y~--' to the watt density reculting rrO~ applying 5 volts acro~s the re~istive elements Portion 54 o~ omic layer 50 would oomprise a ~ dlr~erent th- D ochromlc lnk whlch would .~ ~ ' to only ~ higher watt den~ity r-~ulting ~ro~ applying 6 5 volt~ across the reslstive ~leoents Port~on 56 of theroochromic lay-r 50 would co~pri~e a third dirre._n~
thermochromic ink which would r-spond to only a watt density r sulting rrO applying 8 volt~ the r ~i~tlve ~lements Thus, th~ s~ce voltage ~n~c~tion would be ~ d as with using the pre~erred embodlnent A di~n~a Lage to this less preferred embodi~ent $8 that two additional ~anuracturing steps would be reguired ~or applylng the oecon~ and thlrd thermochromic ink~

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W092/141~ PCT/~S92/~123 2 1 ~ '3 ~ ~i 3~

While the above described design relates to a tester for ~V
batteries, the present invention can be used for testers designed for cylindrical 1.5V cells ~uch a D, C, AA, and AAA
~izes. Materials other than those de~cribed in the Fpe~i fic example can be used to fabricat- te~ter~ within the scope of the ~ nt invention. The Fp~clfic exa~ple is for $11ustrative purposes only and is not intr~ to li~it the scope of the invention as claimed.

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Claims

What is claimed is:

1) A DC voltage tester comprising a substrate; an electrical circuit located on one side of the substrate and comprising at least two resistive elements and a pair of electrical contacts, wherein the resistive elements and the pair of contacts are connected in a parallel configuration and thermochromic material in thermal contact with at least two of the resistive elements.

2) The voltage tester of claim 1 wherein the thermochromic material is a thermochromic ink.

3) The voltage tester of claim 1 comprising three resistive elements, each of said elements being in thermal contact with a thermochromic material.

4) The voltage tester of claim 1 wherein each resistive element is in thermal contact with an identical the thermochromic material, and each element has a different predetermined resistance.

5) The voltage tester of claim 1 wherein at least two resistive elements have about the same predetermined resistance and each are in thermal contact with a different thermochromic material.

6) The voltage tester of claim 1 wherein there are three resistive elements, each in thermal contact with a thermochromic material, and further comprising a fourth resitive element not in thermal contact with a thermochromic material.

7) The voltage tester of claim 1 adapted to test a 9V battery wherein said thermochromic is material has a response temperature, T r, which is above room temperature and said circuit comprises first, second, and third resistive elements wherein, when a voltage of about 5 volts or less is applied to the electrical contacts only said first element will heat up to a temperature greater than or equal to T r; when a voltage of between about 5 volts and 8 volts is applied to the electrical contacts only said first and second elements will heat up to a temperature greater than or equal to T r; and when a voltage of about 8 volts or more is applied to the electrical contacts said first, second, and third elements will heat up to a temperature greater than or equal to T r.

8) The voltage tester of claim 1 wherein each resistive element is a rectangularly shaped deposit of a resistive material and said elements are aligned in a row parallel to the length dimension a rectangularly shaped substrate, and said electrical circuit has a total resistance of between about 50 and 70 ohms.

9) The voltage tester of claim 1 further comprising a pair of electrically conductive buss bars, wherein one buss bar is connected along one edge of each resistive element and the other buss bar is connected along an opposite edge of each resistive element and wherein an end portion of each buss bar functions as an electrical contact.

10) A battery tester comprising a substrate; an electrical circuit located on one side of the substrate and comprising at least three resistive elements, a pair of electrical contacts so positioned as to be capable of alignment with the terminals of a battery, and electrical connection means for connecting the resistive elements and the pair of contacts in a parallel configuration; a voltage scale located on the other side of the substrate in a position coincident with the position of the resistive elements; and thermochromic material on the same side of the substrate as the voltage scale and being in thermal contact with at least three of the resistive elements.

11) The battery tester of claim 10 wherein each resistive element is rectangularly shaped deposit of a resistive material and said elements are arranged in a row parallel to the lengthwise dimension of the substrate .

12) The battery tester of claim 11 wherein a first resistive element has a predetermined resistance less than the predetermined resistance of a second element, and the second element has a predetermined resistance less than the predetermined resistance of a third element, and said second element being located in the row between said first and third elements.

13) The battery tester of claim 12 wherein said voltage scale means is a rectangularly shaped pattern having three windows, wherein one window is centered over each of said resistive elements.

14) The battery tester of claim 13 wherein said thermochromic material is a thermochromic ink having a response temperature, T r, which is above room temperature, whereby said ink is opaque below T r and turns clear above T r, and said ink is applied in a layer over each of said windows of said voltage scale

15) The battery tester of claim 13 wherein a first of said windows is revealed when a voltage of about 5 volts or less is applied to said electrical contacts, said first window and a second window are revealed when a voltage of between about 5 volts and 8 volts is applied to said electrical contacts, and wherein all three windows are revealed when a voltage of greater than about 8 volts or more is applied to the electrical contacts.

16) The battery tester of claim 11 wherein there are first, second, third, and fourth resistive elements; said first, second, and third elements being in thermal contact with thermochromic material and said fourth element not being in thermal contact with a thermochromic material.

17) The battery tester of claim 16 wherein said electrical connection means comprises a pair of metallic buss bars, wherein one buss bar traverses the row of resistive elements and is connected to each resistive element along an outermost edge thereof, and the other buss bar traverses the row of resistive elements and is connected to each resistive element along the opposite outermost edge thereof.

18) The battery tester of claim 17 wherein the portion of each buss bar associated with the fourth resistive element functions as an electrical contact pad.

19) The battery tester of claim 18 wherein said elements are arranged in the row with said first element between said fourth and second elements and with said second element between said first and third elements, and wherein said first element has a predetermined resistance less than the predetermined resistance of said second element and said second element has a predetermined resistance less than the predetermined resistance of said third element whereby the total resistance of said first, second, and third elements connected in parallel is greater than about 60 ohms; and wherein said fourth resistive element has a predetermined resistance sufficient to lower the total resistance of all four elements connected in parallel to a value of less than about 60 ohms.

20) The battery tester of claim 19 wherein said the resistive material is selected from the group consisting of epoxy or urethane based carbon, silver, nickel, and mixtures thereof.