SE1551598A1 - A protective arrangement for a cable connector - Google Patents

Abstract

A protective arrangement for a connector (5) adapted to connect a cable (4) to a terminal (3) of a wet cell battery (1), wherein said terminal extends from a battery casing (2) of said battery. The protective arrangement comprises a washer (6) mounted around said terminal between the battery casing and the connector, forming a chemically tight seal with the terminal. A gap is provided between the washer and the battery casing and the washer has a hydrophobic outer surface to prevent electrochemical corrosion of the connector. The invention further relates to a battery assembly comprising said protective arrangement and a motor vehicle.(Fig. 1)

Description

A protective arranqement for a cable connector TECHNICAL FIELD OF THE INVENTION The present invention relates to a protective arrangement forprotecting a connector adapted to connect a cable to a terminal ofa wet cell battery according to the preamble of claim 1. The invention also relates to a battery assembly and a motor vehicle.

A hydrophobic surface is herein to be understood as a surface having a contact angle with water of at least 90°.

BACKGROUND AND PRIOR ART Wet cell batteries, e.g. lead-sulphate type batteries, are commonlyused as an electrical power source in motor vehicles having aninternal combustion engine such as trucks, buses, boats,automobiles, etc. The batteries are connected to the wiring of themotor vehicle by means of cables having connectors attached tothe terminals of the battery. Such batteries are unfortunatelyassociated with corrosion and sulphation problems affecting theaüached deterioration of the electrical connection that may ultimately lead connectors. Corrosion and sulphation cause to lost electrical contact between the terminals and the cables.Thus, evaporation of battery electrolyte from the area around the corrosion and sulphation, generally arising due to terminal, may damage the battery terminals and the connectorsand thereby shorten battery life, and potentially even createhazards to safe vehicle operation. Road dirt and salt or corrosionlead to that a products may in combination with moisture connection is formed between the terminal and grounded parts ofthe motor vehicle, which can cause a leakage current and severe electrochemical corrosion of the connector.

US5021305 discloses a protective arrangement for protecting aconnector adapted to connect a cable to a terminal of a wet cellbattery from corrosion. The protective arrangement comprises ahousing encapsulating the connector such as to prevent gasesfrom the battery from coming into contact with the connector. Awasher is provided between a casing of the battery and thehousing, in contact with the battery casing surface such that itforms a seal therewith and furthermore with the terminal and thehousing. However, the construction is complicated, and there isalso a risk that humidity enters the housing due to temperaturevariations and therewith associated pressure variations, andcondenses therein. Such condensation may lead to corrosionproblems. The deformation of the battery terminals over time, thatarises since the terminals are generally made from soft and ductilematerial such as lead, may also affect the sealing properties of the washer and make the arrangement unstable over time.

SUMMARY OF THE INVENTION lt is a primary objective of the present invention to achieve aprotective arrangement for protecting a connector adapted toconnect a cable to a terminal of a wet cell battery, which is in atleast some aspect improved with respect to known solutions. lnparticular, it is an objective to achieve such a protective arrangement which is easy to install and to replace. Another objective is to achieve such a protective arrangement which can function regardless of temperature variations.

According to a first aspect of the invention, at least the primaryobjective is achieved by means of the initially defined protectivearrangement, which is characterised in that a gap is providedbetween the washer and the battery casing and in that the washerhas a hydrophobic outer surface. The washer forms a chemicallytight sea| with the terminal of the battery and thereby preventsgases from the battery from reaching the cable connector. Byplacing a washer at a distance from the battery casing, gases thatescape from the battery casing can be directed away from theterminal, and thereby also from the connector, once the gasesreach the washer. Thus, on one hand, the washer interruptsstreams of gas and splashes of acid originating from the batterytoward the connector. The washer thereby prevents chemicalcorrosion arising due to contact between acid from the battery and the connector.

On the other hand, the washer has a hydrophobic surface and istherefore water repellent. The hydrophobic surface preventsformation of a continuous thin film of adsorbed moisture fromforming on the washer. The washer thereby interrupts theelectrochemical connection that may otherwise, in the absence ofthe washer, form between the connector and a chassis of a motorvehicle in which the battery is located. The chassis is usuallyconnected directly to the negative battery pole and serves asground for the electrical wiring, with an electric potential of O V.Such an electrochemical connection, formed by a wetting film, may lead to electrochemical (galvanic) corrosion on the connector, in particular on the positive terminal. By breaking the connection, the washer prevents the connector from electrochemical corrosion.

Thus, the protective arrangement according to the inventionprotects the connector from both chemical and electrochemicalcorrosion without the need to build the connector into a housing orthe like. The protective arrangement is thereby very easy to installby simply mounting a suitably designed washer with a chemicallytight fit around the terminal and apart from that leaving theconnector exposed. Of course, grease may be used to furtherprevent the connector from corrosion, but the amount of greasemay be reduced in comparison with battery assemblies in which no protective arrangement is used.

The protective arrangement is also easy to replace upon serviceof the battery. lf the terminal deforms over time, the washer maysimply be adjusted or replaced to maintain the function of theprotective arrangement. Since the protective arrangement is notconstructed to form an hermetically sealed housing around theconnector, problems with moisture condensing on the connectorare reduced, and the protective arrangement can thereby function also as the surrounding temperature varies.

The hydrophobic outer surface of the washer may be achieved bymaking the entire washer from a hydrophobic material, byproviding a washer with a hydrophobic coating, or by otherwisetreating the surface of the washer such that a hydrophobic surface is obtained.

The gap between the washer and the battery casing can be tuned depending of the hydrophobicity of the outer surface of the washer.

A chemically tight seal between the washer and the terminal canbe achieved either by selecting a suitable washer material able toform a tight seal, or by incorporating a ductile sealing material around a center hole of the washer.

According to an embodiment of the present invention, the outersurface of the washer has a contact angle with water of at least 100°. Wetting of the washer is thereby efficiently prevented.

According to an embodiment of the present invention, the washeris made from a plastic material. By “plastic material” is to beunderstood a synthetic material comprising organic polymers. Forexample, polypropylene and polytetrafluoroethylene are suitableplastic materials with hydrophobic properties to use for thewasher. Plastic materials are lightweight and possible to tailor such that the washer obtains desirable properties.

According to another embodiment of the present invention, thewasher is made from a hydrophobic material. Preferably, thematerial is a hydrophobic plastic material. By making the entirewasher from a hydrophobic material, the manufacturing processbecomes cost efficient and the hydrophobic surface is lesssensitive to damage than in the case of a separate hydrophobiccoaüng.

According to another embodiment of the present invention, the washer is made from polytetrafluoroethylene. This is a hydrophobic plastic material with a water contact angle of morethan 100° and which is also inert to sulphuric acid, commonly usedas the electrolyte in wet cell batteries. The washer is in thisembodiment protected against damage from sulphuric acid as suchacid evaporates or otherwise leaks from the battery. This improves the lifetime of the protective arrangement.

According to another embodiment of the present invention, thewasher is dimensioned so that it has at least the same extensionas the connector in a direction parallel with an upper surface ofthe battery casing. Sulphuric acid from the battery, which isdirected away from the connector by means of the washer, is thusguided past the connector and it is prevented that the acid reaches the connector.

According to another embodiment of the present invention, the gapbetween the washer and the battery casing is at least 0.5 mm. Thisdistance is usually sufficient to achieve the above discussedadvantages.

According to another embodiment of the present invention, thewasher has a lower surface directed toward the battery casing,which lower surface is provided with a surface pattern. The surfacepatterning, in the form of e.g. grooves, ridges, indentations, orprotrusions, helps preventing formation of a thin film of adsorbed moisture on the washer.

According to another embodiment of the present invention, thewasher is colour coded to indicate a polarity of the battery terminal. For example, the washer of the protective arrangement for the positive terminal is red coloured and the washer for mounting on the negative terminal is black.

According to another aspect of the invention, the invention relatesto a battery assembly comprising a wet cell battery, a cable, andfurther ln such a battery assembly, a connector, comprising the proposed protective arrangement. the connector or connectors are protected from corrosion as discussed above.

The invention also relates to a motor vehicle comprising the proposed battery assembly. The motor vehicle is e.g. a wheeled motor vehicle, such as a truck, a bus, or a passenger car.

Other advantageous features as well as advantages of the present invention will appear from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will in the following be described with reference to the appended drawings, in which: Fig.1 schematically shows a battery assembly including aprotective arrangement according to an embodiment ofthe invention, and Fig. 2 schematically shows a motor vehicle comprising the battery assembly.

DETAILED DESCRIPTION OF EMBODIMENTS OF THEINVENTION A battery assembly 10 according to an embodiment of theinvention is schematically shown in fig. 1. The battery assembly10 comprises a wet cell battery 1 having a battery casing 2. Aterminal 3 extends from the battery casing 2. The terminal 3 hasthe shape of a truncated cone, thus being wider at the batterycasing 2 than at a top of the terminal 3. The battery assemblyfurther comprises an insulated cable 4 and a connector 5connecting the cable 4 to the terminal 3. The battery assembly isfurther provided with a protective arrangement comprising acircular washer 6 mounted around the terminal 3, between thebattery casing 2 and the connector 5. The washer forms a tightseal with the terminal 3, either by means of an additional ductilesealing material or by itself. A gap having a width w, preferably ofat least 0.5 mm, is provided between the battery casing 2 and thewasher 6. The washer 6 is dimensioned so that it extends outsideof the connector 5 as seen in a plane parallel with an upper surfaceof the battery casing 2. The washer 6 has a hydrophobic outersurface and is preferably made from polytetrafluoroethylene. Thewasher can also be formed with extensions (not shown) extendingfrom a lower surface of the washer, directed toward the batterycasing. The extensions set the distance to the battery casing 2 andforce the washer to be parallel to the upper surface of the battery casing.

When in use, the washer 6 prevents splashes of sulphuric acidH2SO4 from the wet cell battery 1, and gas leaking out from around a base of the terminal 3. Furthermore, the hydrophobic outer surface of the washer 6 prevents formation of a thin film ofadsorbed moisture which can otherwise create an electrochemicalconnection between the connector 5 and a chassis of a motorvehicle in which the battery assembly 10 is located. For a 24 Vbattery, there is a potential difference of 24 V between the positiveterminal 3 of the battery 1 and the ground. ln the presence of athin film of adsorbed moisture, such a potential difference drives electrochemical processes leading to corrosion on the connector.

Fig. 2 very schematically shows a motor vehicle 20 comprising abattery assembly 10 according to the invention. A chassis 21 of the motor vehicle 20 serves as ground.

The invention is of course not in any way restricted to theembodiments described above. On the contrary, many possibilitiesto modifications thereof will be apparent to a person with ordinaryskill in the art without departing from the basic idea of the invention such as defined in the appended claims.

Claims (10)

1. A protective arrangement for a connector (5) adapted toconnect a cable (4) to a terminal (3) of a wet cell battery (1),wherein said terminal (3) extends from a battery casing (2) of saidbattery (1), said protective arrangement comprising a washer (6)mounted around said terminal (3) between the battery casing (2)and the connector (5), said washer (6) forming a chemically tightseal with the terminal (3), characterised in that a gap is provided between the washer (6) and the batterycasing (2) and in that the washer (6) has a hydrophobic outer surface.

2. The protective arrangement according to claim 1, wherein theouter surface of the washer has a contact angle with water of atleast 100°.

3. The protective arrangement according to claim 1 or 2, wherein the washer (6) is made from a plastic material.

4. The protective arrangement according to any one of the preceding claims, wherein the washer (6) is made from a hydrophobic material.

5. The protective arrangement according to claim 4, wherein the washer (6) is made from polytetrafluoroethylene.

6. The protective arrangement according to any one of the preceding claims, wherein the washer (6) is dimensioned so that it 11 has at least the same extension as the connector (5) in a direction parallel with an upper surface of the battery casing (2).

7. The protective arrangement according to any one of thepreceding claims, wherein the gap between the washer (6) and the battery casing (2) is at least 0.5 mm.

8. The protective arrangement according to any one of thepreceding claims, wherein the washer (6) has a lower surfacedirected toward the battery casing (2), which lower surface is provided with a surface pattern.

9. A battery assembly (10) comprising a wet cell battery (1), acable (4), and a connector (5), further comprising a protective arrangement according to any one of the preceding claims.

10. A motor vehicle (20) comprising a battery assembly (10) according to claim 9.