SC_Universal_Charger_Pt1.pdf

(5244 KB) Pobierz

NiC3ds

NiMHs

SlAS

LiiONs

Bike batteries

car batteries. • •

IT 5THE ONLY BAnERY CHARGER YOU WILL EVER NEED, EVER AGAIN!

Part

By JOHN CLARKE

Improved MkII version now charges Lithium-Ion and a huge

range of Nicad, NiMH, SLA and.

.-:e

-acid batteries. And

YES, you can update the MKI version if

you

wish...

SILICON CHIP

aiting for your power tool

batteries to charge can be a

drag, particularly when you

wish to use the tool immediately. This

Fast Battery Charger can have your

tools operational in a short time,

will charge your power tool bat

teries in less than 15 minutes for a

1.2Ah Nicad pack.

includes full bat

tery protection and employs end-of

charge detection to ensure that the

cells are not damaged. Along with

Nickel Cadmium (Nicad) and Nickel

Metal Hydride (NiMH) batteries, you

can also charge Lithium-Ion batteries,

6V and 12V Sealed Lead Acid (SLA)

packs and Lead-Acid car and motor

cycle batteries.

This is an improved version of our

very popular Multi-Purpose Fast Bat

tery Charger which was first published

in the February and March 1998 is

sues of SILICON CHIP.

While the original charger provided

for a host of battery types and volt

ages, inevitably there were calls from

readers who wanted to use it for other

voltages and for Lithium-Ion batter

ies. The original design also had a

tendency to prematurely terminate

charging on older batteries.

Note that if you built the previous

version, you can upgrade to the new

design by transferring all the compo

nents to the new PC board and chang

ing some ofthe wiring to the switches.

Charger features

For those not familiar with the pre

vious design, we will now outline the

features of this very flexible charger.

uses a Philips TEA11012 IC to per

form all the control functions of the

circuit.

monitors char'ging current,

battery or cell voltage and battery tem

perature (optional) and incorporates a

timer to shut down charging if other

methods of charge detection fail.

is important when fast charging

batteries that they are not over

charged. Both Nicad and NiMH types,

if given too much charge, will over

heat and be permanently damaged.

LiION, SLA and Lead-Acid types

should not be charged beyond a cer

tain voltage or they too will be dam

aged and their life reduced. Nor should

SLA and Lead-Acid batteries be un

dercharged since this will also lead to

a shortened life.

Nicad batteries should also be dis

charged before recharging in order to

consistently provide their maximum

capacity.

Our new Fast Battery Charger pro

vides accurate detection of full charge

for Nicad and NiMH batteries and pre

cise end-point voltage regulation for

LiION, SLA and Lead-Acid types.

also has various protection features to

prevent fast charge when the battery

temperature is too high or low for

Nicad and NiMH types and if the bat

tery voltage is initially low for all bat

tery types.

An added feature of the charger is

the Refresh cycle which is used for

Nicad batteries. This discharges the

battery so that each cell reaches a

nominal 1V before the charger begins

to fast charge. Nicad

NiMH batteries

are then fully charged and this is de

tected when the voltage begins to drop

off from a maximum value.

a thermistor is connected to moni

tor temperature of the battery pack,

then the charger detects full charge

when the temperature begins to rise at

a rapid rate.

Once charged with high current (fast

charge), Nicad

NiMH batteries are

topped up with a 200mA current for

about 90 minutes and then trickle

charged at 62mA to maintain their

capacity before use. This trickle charge

comprises short bursts of current

which average to 62mA. These bursts

of current prevent dendritic growth

within NiMH and Nicad cells.

LiION, SLA and Lead-Acid batteries

are initially fast charged and this cur

rent tapers off as the battery voltage

approaches 4.1V for LiION and 2.4V

per cell for SLA and Lead-Acid types.

Charging stops at these voltages.

For 12V SLA and Lead-Acid batter

ies, this end point corresponds to

14AY.

Charging automatically starts

again when the cell voltage falls to

2.2V for SLA and Lead-Acid types

and to 3V for LiION.

Timer

LED indicators

The charger incorporates a timer

which stops fast charge after a set

period (called time-out). This prevents

overcharging should the end of charge

detection methods fail. Normally,

time-out is about 1.6 times the ex

pected charge time of the battery, as

Main Features

•

Fast charges Nicad, NiMH, UlaN

Suitable for 1 2V 24V 3 6V 4

,SLA and Lead-AcId batteries

. , . , . , .av,

6V, 72V

4V 96V 12V

from 1.2Ah to 4.2Ah plus UlaN 36V 72'V' . , "

14.4V batteries

Ch'

. ,.

14.4V

arges either 6V or 12V SLA batt . f

Charges 6V or 12V Lead-Acid

batt;~:ss

o;om 1.2Ah t? 4Ah

any capacity above 1.2Ah

Includes a discharger for N' d b '

Ica attenes

Top-off charging at end of fast char e I

Voltage limited charge for SLA

L g d

pUlsed,tnckle charge for Nicad

NiMH

Volt

ea -AcId battenes

age drop

temperature rise (dT/dt) f II h

Under and over-temperature cutout for

b~tte~yarge

detection for Nicad

NiMH

Over temperature cutout for charger

Short circuit battery protection

Time-out protection

Fuse protection

Multi-LED charge indicators

Specifications:

• Fast Charge Current

nominally 6A

• Top-off current (Nicad

NiMH)

200mA

• Trickle current (Nicad & NiMH)

62mA

• Refresh current (Nicad)

1V per cell

• Refresh discharge end-point

• Battery-low detect (Nicad

NiMH)

0.3V per cell

• Battery-low detect (UION)

0.9V per cell

• Battery-low detect (SLA & Lead-Acid)

0.45V per cell

2V per cell

• Battery-high detect (Nicad & NiMH)

6V per cell

• Battery-high detect (UION)

• Battery-high detect (SLA & Lead-Acid)

2.97V per cell

2.4V per cell

• Charge voltage end-point (SLA

Lead-Acid)

• Charge voltage end-point (UION)

4.1 V per cell

• Recharge voltage after end-point (SLA & Lead-Acid) ..2.2V per cell

• Recharge voltage after end-point (UION)

3V per cell

• Voltage peak detection (Nicad

NiMH) .. 0.25% drop in top value

0.25%

• Temperature rate detection level (Nicad

NiMH)

12° C

• Under-temperature cutout (Nicad

NiMH)

50° C

• Over-temperature cutout (Nicad

NiMH)

• Charge over-temperature cutout

80° C.

• Fast-charge time-out

15, 30 or 60 minutes (nominal)

• Top-off charge time (Nicad & NiMH)

about 90 minutes

determined by the capacity and charge

current.

W?en charging Lead-Acid batteries

the tImer. is reset at regular intervals

~r~vent

tIme-out. This is because Lead

Cld. batteries have a large capacity and

~qulre

a .much longer time to charge

tI:ner can accommodate.

Vanous mdicating LEDs show the sta

tus of the Fast Charger: Refresh Fast

Protect, 100% and No Battery'

.The REFRESH LED

indicat~s

when a

N.lcad battery is being discharged. Th

function is initiated by

mg the adjacent Refresh pushbutt n

Refresh is only available when tOh .

charg

IS set to charge Nicad or NiMH

~a~enes

a.lthough it is not necessary to

e esh

.N~MH

batteries since they do

not exhIbIt memory effect.

~h~

A~T

LED shows that the charger

IS e Ivenng a maximum of 6A to the

?attery under charge. After the batter

cha~ged>

the 100% LED is turned y

o~.

WhIle this LED is on the Ch

. "T

ffU

, a r g e r IS

opo

mode which delivers a slow

c arge at 0.15 of the full fast current

After

To~o~f,

the LEDs are all off and

th~

c~arger

IS m trickle mode for Nicad

NIMH batteries

bu~

there is no further

ch~rge

current for LIION, SLA and L d-

ACId types.

~lscharge

push~

Vbat

Vstb

Rrel

OSC

fast

lOP

standby load

charge

off currenl current

1.251R re l

3~ 10~

CHARGE CONTROL

AND

OUTPUT DRIVERS

PROTECTION

osc

PWM

LS'

SET

I , I

NTC

present

banery

low

Tm1n

r---t--+-

PWM

+1i2.7~

end

refresh

MTV --j-9-+_--l

1.325

VNsib

1.37

1.63

1.9

1.9 V

NICd

NIMH

1111

L1lon

SLA

no-

banery

_'--~10~

.. RFSH

-------------ti-IB

PSD

NTC

~~==:::t-----+---_-.J

DNAD

CONVERTER

TIMER

AND

CHARGE

STATUS

INDICATION

LED

POD

PTD

Vsl

GND

Ig.l: Inside the Philips TEAII02 b

SILICON CHIP

attery management

Ie:

This versatile chip forms the heart of our fast

MGC.>.

c arger.

0 - -

TRANSFORMER

AND

240VAC

RECTIFIER

0--

BRI

I--

STEp·DOWN

SWITCH MODE

FIlTER

CONVERTER

I--

Ql, 01, l1, 02

GND

DISCHARGE

(REFRESH)

PWM

RESET TIMER

IC2, IC3, SA

VSUPPLY

REFRESH

BATTERY

MANAGEMENT VBAT

ICI

VOLTAGE

SELECT

S5, S4

T1M:~UT ~

FCT

BATTERY

Fig.2: th e various functional

elements of the charger are

shown in this block diagram.

Full ope ration is explained in the

text.

The PROTECT LED shows when a

battery is shorted or has low voltage

after a certain period of charging. It also

lights with over or under-temperature

if the thermistor in a battery pack is

connected.

The NO BATTERY LED only lights

when Nicad

NiMH battery types are

selected and if the thermistor is not

connected to the charger. It simply in

dicates that the battery is either not

connected or has a high impedance.

When using the battery charger it is

important to select the correct setting

on the front panel for the particular

battery under charge. You will need to

select the battery type (Nicad, NiMH,

LiION, SLA or Lead-Acid) and the bat

tery voltage. Also the timer must be set

to give a suitable safety time-out for the

capacity of battery connected.

NTC

TYPE

S3, S4

THERMISTOR

Battery management

As noted above, all of the charging

features are provided by a single bat

tery management IC, the TEA1102 from

Philips Components. Its block diagram

is shown in Fig.l.

It comprises analog and digital cir

cuits which are divided into six sepa

rate sub-sections, as shown on the block

diagram. The charge control and out

put driver section comprises a current

source, battery selection, oscillator,

comparators, amplifiers and a pulse

width modulation (PWM) and analog

control output.

Battery voltage is monitored at the

Vbat input (pin 19) and this is com-

pared against the Vreg voltage which

sets the end-point voltage for charging

the selected battery type. Options are

for Nicad

NiMH, LiION and SLA.

Note that· there is a different Vreg

selection for each type of battery but

these do not refer to the voltage to

which each cell is charged. The VlVstb

(Vstb means Voltage at standby) for

Nicad

NiMH batteries refers to an

option of either voltage regulation at

end of charge or trickle charge. The no

battery selection automatically switches

in when the Vbat voltage is above 1.9V.

The comparator monitoring Vbat and

Vreg controls the constant current

source transistor which is supplied with

one of four currents: fast charge, top

off, standby and load. When power is

first applied, the TEAll02 is reset and

fast charge is selected. Fast charge is set

by a resistor at Rref (pin 20) to select the

current flow to the lB output at pin 2.

The current from the IB output pin

flows through an external resistor to

develop a voltage monitored by the

two internal op amps, Al and A4. Al's

output is amplified by A3 to give an

analog control output at pin 18. Al's

output is also compared in A2 against a

triangle waveform generated by the os

cillator at pin

14.

A2's output is ap

plied via a flipflop to provide a pulse

width modulated (PWM) output to

drive external circuitry to control the

charge current.

Refresh (Nicad discharge) is initi

ated by momentarily connecting the

RFSH output (pin 10) to ground. This

turns off the current

source and op amp A4

BATTERY

.,.

UNDER

drives an external tran

CHARGE/

sistor connecting across

DISCHARGE

the battery. The current

is set by a series current

detecting resistor and

the 100mVsource at the

non-inverting input to

A4.

The DA/ AD con

verter monitors battery

voltage when charging

Nicad

NiMH batter

ies. As the battery is

charging, the voltage

gradually increases and

at a regular period, the

AD converter samples

the voltage and stores it

as a digital value if the

voltage has increased

from the previous read

ing. When the voltage

begins to fall, the lower voltage is not

stored but compared with the analog

voltage resulting from the digital stored

value. A fall of 0.25% indicates that the

battery is charged and the charger will

then switch to trickle mode.

The DA/AD converter also monitors

the thermistor voltage via the NTC in

put at pin 8.

the thermistor is con

nected, the DA/AD converter switches

off fast charge when there is a sudden

rise in temperature of the battery which

also indicates full charge. Note that the

fast charge will be switched off if a low

or high temperature is detected by the

Tmin and Tmax comparators.

By the way, NTC stands for the Nega

tive Temperature Coefficient of the

thermistors fitted into Nicad and NiMH

battery packs. As the temperature rises,

the resistance of the thermistor drops

(ie, negative coefficient) and this is

monitored by the circuit.

The "NTC present" comparator de

tects the connection of the thermistor,

while the T-cut-off comparator switches

on for a 0.25% rate of rise in tempera

ture. The MTV input (pin 9) can be

used to calibrate the thermistor tem

perature at Tmax.

The Control Logic section monitors

and sets the operation of the various

blocks within the Ie. Voltage on the

FCT input (pin 11) selects the type of

battery to be charged. The Supply Block

takes its supply at the Vp pin and pro

duces a reference voltage at the Vs out

put (pin 16). This reference provides

an accurate and stable source for the

JUNE 2001

With the exception of the power transfonner, bridge rectifier, thennistor and the front panel controls, just about everything

else mounts on a single PC board. The complete assembly and wiring detail will be presented next month.

battery end-point voltages. The Ysl out

put is used to switch on power to exter

nal indicating LEDs. These LEDs are

driven by pins which serve a dual pur

pose and are seen in the Timer and

Charge Status Indication block.

Pins 4, 6 and

are used both as

programming pins for the timers and as

LED drivers. These pins are initially

monitored at power on to check what

options are set before the LEDs are lit.

rectly (ie, essentially unfiltered) to the

switchmode step-down converter com

prising transistor Ql, inductor Ll and

diodes Dl and D2.

In effect, the battery under charge is

fed with chopped and unfiltered DC.

This allows a considerable saving on

electrolytic filter capacitors andreduces

power losses in the main series pass

transistor, QL

Circuit description

Fig.3 shows the full circuit for the

Multipurpose Fast Battery Charger.

Power for the circuit comes from

Tl, an 18Y 6A transformer which feeds

the bridge rectifier BRl and two 101JF

100VW polyester capacitors. These sup

ply the peak current to the switchmode

supply comprising transistor Ql, di

Block diagram

Fig.2 shows how we have used the

TEAII02 battery management IC in

our charger circuit. Thansformer Tl and

bridge rectifier BRl provide an 18Y DC

supply for the charger circuit. This is

lightly filtered to provide DC for the

control circuitry but is fed through di-

SILICON CHIP

ode Dl and inductor Ll.

The Pulse Width Modulation output

at pin 15 of ICl drives transistor Q3

which operates as a pulsed "current

sink" to provide 34mA base current to

Q1. Ql switches current through

inductor Ll and diode D2 into the bat

tery load. When Ql switches off, diode

Dl enables the energy stored in the

inductor to flow into the battery. Diode

D2 prevents battery current from flow

ing back into the switchmode circuit.

The 100llF capacitor across the bat

tery is there to filter the supply when

no battery is connected so that the

"no battery" detection will operate

within ICL

Fig.3 (right): the complete circuit

diagram of the fast charger.

Plik z chomika:

gasma

SC_Universal_Charger_Pt1.pdf

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: