WO2020021420A1

WO2020021420A1 - Battery pack for an electric bicycle

Info

Publication number: WO2020021420A1
Application number: PCT/IB2019/056218
Authority: WO
Inventors: Mauro Fantin
Original assignee: Texa S.P.A.
Priority date: 2018-07-23
Filing date: 2019-07-20
Publication date: 2020-01-30
Also published as: IT201800007408A1

Abstract

A battery pack (40) is described for a pedal-assisted bicycle (10) for generating a voltage at two output terminals. To limit the bulk, the battery pack comprises K voltage generation modules (42), K >= 2, electrically connected to each other in series to give the voltage at the output terminals, each module (42) comprising N batteries (50), N >= 2, electrically connected together in parallel, wherein for each module (42) two imaginary parallel planes are definable on which all the opposite electric poles (52, 58) of the N batteries (50) of a module lie, and the modules (42) are arranged aligned along an axis (X) of the battery pack so that said parallel planes of each module are orthogonal to the axis (X) of the battery pack.

Description

BATTERY PACK FOR AN ELECTRIC BICYCLE

The present invention generically refers to a battery pack for a pedal-assisted bicycle, and the bicycle so equipped.

Electric pedal-assisted bicycles are equipped with an electric driving motor powered by an on-board battery pack. The battery pack is usually an assembly of batteries connected in series and parallel to get the total voltage and amperage needed. Almost like a standard, nominal 3.6 V cylindrical batteries are used.

The battery pack, for reasons of space and weight, almost universally is mounted in the front tube of the bicycle, i.e. in the frame sleeve which connects the pedal box to the handlebar joint. Unfortunately, its position ends up being an inconvenience for the rider, who while pedalling finds between the knees an undesired bulk. And also the aerodynamics of the bicycle suffers because the massive shape of the front tube filled by the battery pack has a very low penetration coefficient shape. Finally, the internal wiring of the battery pack to carry out the series and parallel connections between batteries is very complex, and adds a lot of weight.

The main object of the invention is to improve this state of the art.

This and other objects are achieved by a battery pack, preferably integrated in a pedal-assisted bicycle, according to claim 1; other advantageous technical features are defined in the dependent claims.

The battery pack is used to generate a voltage at two output terminals, and comprises

K voltage generation modules, K >= 2, electrically connected to each other in series to give the voltage at the output terminals,

each module comprising N batteries, N >= 2, all electrically connected in parallel,

wherein for each module two imaginary parallel plans can be defined on which all the opposite electric poles of the N batteries of the module lie, and

the modules are arranged aligned along an axis of the battery pack so that said parallel planes of each module are orthogonal to the axis of the battery pack.

This arrangement is very spindy, modular for the output voltage and with reduced bulk.

Preferably for the K generation modules, K is 6 or 7. Preferably each of the N batteries of a module generates a voltage of about 3.6 V.

Preferably for each module N is 6 or 7.

Preferably at the two imaginary parallel planes each module comprises an electrically conductive plate for short-circuiting all the homologous electrical poles of the N batteries.

Preferably the N batteries of a or each of the K modules are equal.

Preferably the N batteries of a or each of the K modules are arranged according to the vertices of a regular polygon (e.g. a hexagon) or along a circumference, more preferably so as to surround, e.g. touching it, a battery placed at the center of the regular polygon or of the circumference.

Preferably the electrical series of the modules is achieved by placing in electrical series all the conductive plates of the modules.

Preferably each of the N batteries of the K modules has an axis passing through its own two opposite electrical poles, and in each K-th module said axes of the N batteries are all parallel to each other.

Preferably all the axes of the N * K batteries contained in the battery pack are parallel to each other and parallel to the axis of the battery pack.

Preferably the battery pack comprises a voltage boosting circuit to boost the voltage present across said two output terminals.

Preferably the voltage boosting circuit is configured to boost the voltage present across said two output terminals as a function of an electrical signal coming from the outside of the battery pack.

Another aspect of the invention concerns a pedal-assisted bike assisted by an electric motor comprising a battery pack, for powering the electric motor, as defined in one or each of the previous variants.

In particular, the battery pack is installed inside the cavity of a tubular element or sleeve that forms the bicycle frame.

In particular the modules are arranged aligned inside the sleeve or tubular element so that the axis of the battery pack, i.e. that of the modules arranged in a stack, coincides with or is parallel to a longitudinal axis of the sleeve or tubular element.

Preferably the pedal-assisted bicycle comprises an electronic circuit (e.g. a microprocessor) configured to control a voltage boosting circuit, e.g. comprised in the battery pack, which is capable of boosting the voltage present between said two output terminals of the battery pack. The electronic circuit is configured to control the input/ output conversion ratio of the boosting circuit via an electrical signal, transmitted wirelessly or by wire.

Further advantages will be clearer from the following description, which refers to a preferred embodiment in which:

- figure 1 shows a side view of an electric bicycle;

- figure 2 shows a schematic view of a battery pack;

- figure 3 shows a plan view of a module of the battery pack;

- figure 4 shows a battery as seen from a side.

An electrical bicycle 10 (fig. 1) is movable on two wheels 12 coupled by struts 26, 28, front and rear respectively, to a central frame 14.

The frame 14 is formed mainly by a horizontal tube 20, a front vertical tube 16 and a vertical rear tube 18 forming a kind of triangular structure.

In the front tube 16 a battery pack 40 is mounted to supply an electric motor 32 which, together with pedals 30, provides the propulsive torque to the bicycle 10.

The structure of the bicycle 10 described herein is exemplary and should not be intended to limit the scope of the invention.

The battery pack 40 may also be installed in different zones of the bicycle 10, e.g. in the tube 18 or 20, while retaining its advantages.

The battery pack 40 has a circuit structure visible in fig. 2.

It comprises stacked modules 42 connected in series along a X axis, wherein each module 42 is formed by N 3.6 Volt batteries 50 (see fig. 3) connected in parallel. The number N of batteries 50 connected in parallel inside a module 42 may vary from what is illustrated; and preferably, for maximum modularity, each module 42 comprises the same number N of batteries 50.

The number of modules 42 can be variable according to the power required, typically the battery pack 40 will comprise six or seven modules 42. In the first case the total voltage VI across the terminals of the six modules 42 is therefore about 22 V. In the second case the total voltage VI across the terminals of the seven modules 42 is therefore about 25 V. This voltage is then boosted to a higher voltage V2 equal to about 36 V, a standard value in electric bicycles, by a voltage booster 70, e.g. a boost-topology or charge-transfer converter.

The electronic components of the booster 70 may be powered e.g. directly from the voltage VI .

The voltage of the batteries 50 may also vary from the aforementioned 3.6 V, as also can vary the number of modules 42 in series and the output voltage V2.

Fig. 3 shows in plan view a preferred arrangement of individual batteries 50 inside each module 42. Fig. 4 shows a single battery 50 viewed from a side.

There are in total N = 7 batteries 50, e.g. cylindrical, all equal and placed side by side with parallel axes. For compactness, six batteries 50 are placed at the vertices of a hexagon and surround a central battery 50. To minimize the overall dimensions, the external batteries 50 are all brought closer to the central one so as to touch it.

Each battery 50 has a same electrical pole exposed at a terminal 52 and at an opposite terminal 58.

The terminals 52 of the seven batteries 50 are connected in parallel by a conductive plate 60. An analogous conductive plate (not shown) is mounted to short-circuit the electric poles of opposite polarity present on the diametrically opposite terminals 58 of the batteries 50.

To obtain the series of fig. 2 it is enough to connect in series the plates of the modules 42.

In the illustrated arrangement all the plates of the modules 42 are orthogonal to the X axis. The plates 60 lie on two imaginary parallel planes that are orthogonal to the X axis and to an X2 axis that passes in each battery 50 through the terminals 52, 58 (see fig. 4). Each battery 50 has the X2 axis parallel to the axes of the adjacent batteries, and all the X2 axes are parallel to the X axis.

The advantages of the battery pack 40 are many, including:

- the assembly of the stacked modules 42 is a very slim and spindy object, which looks like a very long cylinder with respect to its base, like a wand. This makes it possible to thin the outer shape of the tube into which the pack 40 is mounted, bringing it back to dimensions similar to those of normal, unassisted bicycles, with immediate comfort advantages for the rider, aerodynamics advantages for the bicycle 10 and, last but not least, aesthetics advantages; - the voltage VI is achieved by setting in series the modules 42 by arranging them along a single axis. There is no need then for complex circuit connections between the modules which weigh down the battery pack and make it expensive to manufacture;

- the voltage V2 is produced with a smaller or minimum number of batteries 50. Then the weight and volume of the battery pack 40 are reduced compared to the known battery packs that generate the voltage V2 using only the series of batteries 50;

- the booster 70 allows an adjustment of the voltage V2, which remains always constant during operation. The well-known battery packs, instead, suffer the disadvantage that the voltage V2 drops when it supplies the motor 32, whose efficiency is lowered accordingly.

Another advantage relates to the possibility of supplying the motor 32 with a voltage higher than the nominal one when the motor rotates at such a speed as to generate a counter-electromotive voltage close to that of the battery. An electric motor is indeed also a generator and the counter-electromotive force it generates limits the operating range to RPM values whereby the electromotive force generated by the battery prevails.

Often, at higher motor regimes the control electronics introduces driving corrections, called "defluxing", expensive in itself from an energy point of view.

Advantageously, such electronics can control, by means of communication on a standard bus (CAN or serial Bus, for example) the boost converter 70 to increase the supply voltage of the motor 32 avoiding the defluxing.

Claims

1. Battery pack (40) for pedal-assisted bicycle ( 10) for generating a voltage at two output terminals, comprising:

K voltage generation modules (42), K >= 2, electrically connected to each other in series to give the voltage at the output terminals,

each module (42) comprising N batteries (50), N >= 2, electrically connected together in parallel,

wherein for each module (42) two imaginary parallel planes are definable on which all the opposite electric poles (52, 58) of the N batteries (50) of a module lie, and

the modules (42) are arranged aligned along an axis (X) of the battery pack so that said parallel planes of each module are orthogonal to the axis (X) of the battery pack.

2. Battery pack (40) according to claim 1, wherein for each module N is equal to 6 or 7, and the N batteries of one or each of the K modules are equal to each other.

3. Battery pack (40) according to claim 1 or 2, wherein the N batteries of one or each of the K modules are arranged according to the vertices of a regular polygon, e.g. a hexagon, or along a circumference, and so as to encircle, e.g. touching it, a battery placed at the center of the regular polygon or the circumference.

4. Battery pack (40) according to any one of the previous claims, wherein in correspondence of the two imaginary parallel planes each module (42) comprises an electrically conductive plate (60) for short-circuiting all the homologous electrical poles (52, 58) of the N batteries.

5. Battery pack (40) according to any one of the previous claims, wherein each of the N batteries of the K modules has an axis (X2) passing through its two opposite electrical poles (52, 58), and in each K-th module said axes (X2) of the N batteries (50) are all parallel to each other.

6. Battery pack (40) according to any one of the previous claims, wherein all the axes (X2) of the N*K batteries (50) contained in the battery pack (40) are parallel to each other and parallel to the axis (X) of the battery pack.

7. Battery pack (40) according to any one of the previous claims, comprising a voltage-boosting circuit (70) for boosting the voltage present across said two output terminals.

8. Battery pack (40) according to the previous claim, wherein the voltage boosting circuit (70) is configured to boost the voltage present across said two output terminals as a function of an electrical signal coming from outside the battery pack.

9. Bicycle ( 10) with pedal-assist by an electric motor (32) comprising a battery pack (40), for power supplying the electric motor, as defined in any one of the preceding claims.

10. Bicycle ( 10) according to claim 9, wherein the battery pack is installed inside a cavity of a sleeve or tubular element ( 16) which forms the bicycle frame.