United States Patent 1191

Dahl
[54] INDUCTION CHARGING SYSTEM
[76] Inventor: Ernest A. Dahl, 3747 Breaker Drive, Ventura, Calif. 93003
3.673.485 6/1972

[11]

3,938,018

l45l Feb. 10, 1976

Vital et a]. ........................... .. 320/2

[22] Filed; Sept. 16, I974 [21] Appl. No.: 506,530

[52]
[51]

Primary Examiner~l D. Miller Assistant Examiner-Robert J. Hickey Attorney, Agent, or FirmRalph B. Pastoriza

[57]

ABSTRACT

US. Cl. ..................... .. 320/2; 320/39; 336/225

Int. Cl.2 .......................................... .. H02J 7/10

A normal 1 l7-volt, 60 cycle source is converted into a

high frequency signal resulting in radiation of a sub

stantial portion of the energy in the signal. A receiving I coil is inductively coupled to the radiation over a given distance substantially less than a wave length of

[58]

Field of Search ............ .. 320/2, 39, 40, DIG. l,

320/DIG. 2, 13; 336/110, 115, 118, 510, 225, 233, DIG. 2

[56]
1,982,689
3.253.596

the high frequency signal to provide a received signal

without the necessity of any electrical wires. The re

References Cited UNITED STATES PATENTS

12/1934
5/1966

ceived signal in turn is converted into a DC. signal and passed to a rechargeable battery for charging. The
inductive coupling can be utilized for recharging por
table electrical instruments having rechargeable bat
teries
,

Polydoroff ........................ .. 336/233

Keller. .lr. . . . . . . . .
?lclhon ~ - - - ~ - ~ ~ ' - ~ -

. . . .. 320/2 UX
v ~ ~ ~ ~ - -~ 323/7202;
. . . . . . . . . . .. _

or
.

for

charging
' ,

larger
'

rechargeable
'

batteries

mes

. . . . . . . . . . . .

3.454.012

H1969

Ruddi I I ' ~ I _ _ p . . ~ ~ _

v_v_"

320/39 X

such as used in electrically driven vehicles.

3.652.915

3/1972

Eberts ................................. .. 320/35

4 Claims, 2 Drawing Figures

D.C. Battery
| ITV A. C. '0

TT/H
Rectifier

i T l i i" l
\
29 3Q.

26/
l2

+i
A.C. TO

an
<l
Limiter
.
Rate

30 KC- T
OSC. I8 20
'4

25~ 0.0.
d
22

32"\~
_

Converter

/
'6 C2

'3 23

x Regulator <_J

\ 28

US. Patent

Feb. 10, 1976

3,938,018

DC Buttery

|l7V
A.

C.

T Rectifier
Y

T/
c2
CI

10

"
26/
'8 20 d

~4||||||||||l;27
' -

T f

"1

+I
25v 0.0.
A.C. TO
Converter

1 f \29 30 3l'v
3
2._
_

30 KC. ""2
08C.

<

\'

{
/ *

I
\L 22 M

( (
Regulator
I \

Rate
Limi'rer

I6
=-

I4
23
13

I
'

\
28

)5

C3

\24

I 2.

1
INDUCTION CHARGING SYSTEM

3,938,018
2
BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the invention will be had

This invention relates generally to battery charging

systems and more particularly to an improved method and apparatus for recharging batteries without the ne cessity of any physical conductors extending between a charging source and the battery.
BACKGROUND OF THE INVENTION

by now referring to the accompanying drawings in

which
FIG. 1 is a circuit diagram partly in block form illus trating the basic components making up a battery charging apparatus in accord with the present inven tion; and FIG. 2 is an exploded perspective view illustrating an

Normal charging of batteries either in portable elec

trical devices such as electric shavers, mini calculators, and the like, or in larger applications such as electric golf carts or electrically driven automobiles, is accom

application of the apparatus to the charging of portable

electrical devices.
DETAILED DESCRIPTION OF THE INVENTION

plished by connecting a D.C. charging source directly

with wires to the batteries involved. The source of charging current may be derived from a conventional

Referring first to FIG. 1, there is shown in the upper left portion a conventional l l7-volt, 60 cycle source 10 connected to a recti?er 11 for driving an oscillator 12.

ll7-volt, 60 cycle source by recti?cation.

In all such prior art charging systems, a direct con nection has been used. Thus, in the case of portable electrical devices, it is necessary for a user to plug in or connect wires from the charging unit directly to the device and when the charging is complete to effect a
20

By way of example, the oscillator 12 provides a high

frequency A.C. signal of, for example, 30,000 cycles

per second. However, the high frequency signal may
vary from 10,000 to 40,000 cycles per second or even

higher or lower frequency values depending upon the

speci?c application.
A transmitting coil means takes the form in the par ticular embodiment illustrated of ?rst and second coils
13 and 14 connected together at ?rst ends as at 15 to a common connection 16 from the oscillator 12. The outer ends of the coils l3 and 14 in turn connect to the
30

physical disconnection. For the case of larger applica tions, such as golf carts or electrically driven vehicles, the device itself must be kept stationary and an electri cal line plugged into suitable receiving terminals con

nected to the battery to be charged.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention contemplates a battery charg

ing system working on the principle of induction cou pling to the end that no physical wires need be involved between the charging source and battery to be charged. With this arrangement, the electrical device in the case

output leads 17 and 18 of the oscillator to provide a two-phase transmitter. As shown, the coils include powdered iron cores 19 and 20 disposed at an angle to each other to'direct the path of the generated electro magnetic ?eld in a desired manner. A single phase transmitter could be used. Shown spaced a given distance d from the transmit ting coil means is a receiving coil means 21 which may
also include a powdered iron core 22. The positioning '

of portable units can simply be automatically charged when placed in its normal place of temporary storage
without the operator having to worry about plugging or unplugging various connections. In the case of electri

is such as to provide for maximum ?ux coupling of the

electromagnetic ?eld 23 provided from the angular

40 arrangement of the transmitting coil means over the

cally driven vehicles, charging of the batteries therein

can be accomplished again without any physical con nection of wires and in certain embodiments, while the vehicle itself is in motion. Brie?y, the method of the invention contemplates the steps of converting a normal I l7-volt, 60 cycle source
45

given distance a. Preferably, both the transmitting coil

means and receiving coil means may be resonantly

tuned to the given high frequency by capacitors C1, C2 and by capacitor C3, respectively. The distance d is
substantially less than one wave length of the given high frequency radiation so that inductive coupling ensues. A meter M may be connected across the receiving
coil means 21 to provide a visual indication of the

to a higher frequency A.C. signal resulting in radiation

of a substantial portion of the energy in the signal; degree of coupling. inductively coupling to the radiation ?eld over a given 50 As shown, the receiving coil means 22 connects to a distance substantially less than a wave length of the regulator 24 in turn connecting to an A.C. to D.C.

higher frequency signal to provide a received signal;

converting this received signal into a D.C. signal; and passing the D.C. signal to the battery to charge the
same.

converter means 25. The A.C. to D.C. converter 25

provides a D.C."charging signal on line 26 to the re

55

The preferred apparatus includes an oscillator means for connection to the charging source for converting the source into a signal of given high frequency and a transmitting coil means connected to the output of the

chargeable D.C. battery designated 27 which may con stitute the rechargeable battery in either a portable
type device or in an electrically driven vehicle. The arrangement is such that charging is accom plished with a constant current. The regulator circuit

oscillator means for radiating the signal. A receiving

coil means incorporated either in an adapter arranged to be permanently connected to a portable electrical device or in an electrically'driven vehicle is strategi

24 permits charging up to about 80%. The charging

60 signal is then converted to a constant voltage or trickle

type charge.
A rate limiter 28 connects between suitable sensor

means in the battery 27 as schematically indicated at cally positioned for inductive coupling over a given 29 and the regulator 24 and A.C. to D.C. converter 25. distance with the transmitting coil means. An A.C. to 65 The rate limiter 28 is responsive to the temperature,
D.C. converter means is connected between the receiv

ing coil means and the battery for converting the induc tively received signal into a D.C. charging signal.

voltage and gas pressure in the battery 27, these three parameters being provided as indicated schematically
on the input lines 30, 31 and 32 to the rate limiter 28.

3,938,018
Referring to FIG. 2, there is shown a speci?c applica tion of the inductive charging system as might be used for a portable electrical device. Thus, there is shown a box structure 33 defining a cavity 34 dimensioned to
cradle an electrical device such as a mini-calculator 35

4
motion. In this respect, a series of transmitting coils could be built into a curb or into special sections along a highway adjacent to which the vehicle would travel

wherein the device 35 incorporates a rechargeable

battery.

and thereby inductively pick up the transmitted radia tion while the vehicle is moving. An important feature of this invention is the provi
sion of a shaped electromagnetic ?eld to optimize cou pling between the transmitter and receiver. As shown in the preferred embodiment described this shaped

The oscillator means and transmitting coil means are

housed in the box structure 33, the latter being indi

cated by the dotted lines at 36. ,

?eld is provided by angulating the transmitting coils.

It will thus be appreciated from the foregoing that the present invention has provided a unique and valuable improvement in the art of charging rechargeable bat
teries. 7

A small adapter casing 37 in turn incorporates the receiving coil means indicated by the phantom lines 38
and also the A.C. to DC. converter. This adapter cas

ing is arranged to be plugged into the normal inlet charging socket for the mini calculator 35 as indicated
at 39 such as by means of the male plug 40. The ar

What is claimed is: 1. An apparatus for charging a DC. rechargeable

rangement is such that when the adapter casing 37 is

secured to the portable electrical device 35 and the

battery without physical conductors extending between

a charging source and said battery, comprising in com

device itself cradled in the cavity 34 of the housing 33, the receiving coil within the adapter will be in ?ux coupling relationship with the transmitting coil 36 in the housing 33.
The oscillating means within the housing 33 for the transmitting coil means 36 is energized from a suitable recti?er and plug 41 arranged to be received in a con ventional l l7-volt, 60 cycle outlet.
25

bination:
a. oscillator means for connection to said charging source for converting said source into a signal of given

high frequency in the range from l0,000 to 40,000 cycles per second;
b. a transmitting coil means including powdered iron
core means connected to the output of said oscillator

OPERATION
In the case of small portable electrical devices such

means for radiating said signal, said transmitting coil means being tuned to said given high frequency;
0. a receiving coil means including a powdered iron

core spaced a given distance from said transmitting coil

means substantially less than one wave length of said

as described in conjunction with FIG. 2, the adapter 37

may be simply plugged into the device itself or the

portable device may be manufactured initially with the

necessary receiving coil means and A.C. to DC. con

verter built in. The transmitting coil and associated

oscillator in turn would be provided in a mating base or housing structure such as described at 33 for support ing the portable electrical device when not in use. The

given high frequency so as to be inductively coupled with said transmitting coil means including ?rst and second coils connected together at ?rst ends to provide a common connection, said coils with their powdered
iron core means being disposed at an angle to each

other to direct the path of the generated electromag

netic ?eld in a direction for maximum ?ux coupling arrangement would be such that the transmitting coil with said receiving coil means over said given distance; means and receiving coil means were spaced relatively and close to each other for maximum inductive coupling. 40 d. A.C. to DC. converter means connected between If the portable device is in constant use, it is feasible said receiving coil means and said battery for con to maintain the transmitting coil means continuously verting the inductively received signal into a DC. energized so that every time a user replaces the porta charging signal.

ble device in its receiving housing, automatic charging

of the battery will take place. By utilizing a rate limiter as described in FIG. 1 incorporated in the adapter or

45

2. An apparatus according to claim 1, including regu lating means connected between said receiving coil
means and said converting means; and rate limiting
means connected to said regulating means and to said converter means and responsive to the temperature,

the unit itself, overcharging is prevented.

In the case of electrically driven vehicles, the trans mitting coil means and associated equipment would be permanently installed at a designated area in various

recharging centers analogous to gasoline stations. The driver of the vehicle would then simply position the
vehicle over the designated area such that optimum

voltage, and gas pressure of said battery to control the DC. charging current passed to said battery. 3. An apparatus according to claim 1, in which said charging source comprises a l 17-volt, 6O cycle source
and a recti?er connected between said source and said oscillator means. 55

inductive coupling would obtain between the receiving

coil means carried in the vehicle and the transmitting coil means at._the particular station. The battery of the vehicle could then be charged over a period of time similar to that required to ?ll a vehicle with gasoline. A

4. An apparatus according to claim 1, in which said

oscillator means and transmitting coil means are

simple monitoring system would provide an indication

of the amount of charging current used and the vehicle
operator could utilize a credit card in the same manner

housed in a box structure de?ning a cavity dimensioned to cradle an electrical device containing said D.C. re
60

chargeable battery; and an adapter casing incorporat

ing said receiving coil means and converter means for connection to said electrical device in a position such that when said electrical device is positioned in said

as is presently used in gasoline ?lling stations. Since the charging system of the present invention does not require any physical wire connections be
tween the charging source and vehicle battery, the vehicle battery may be charged while the vehicle is in

cavity, the receiving coil means is inductively coupled

65 with said transmitting coil means whereby the re

chargeable battery in said electrical device is charged.

* * * * *