Ramsey Doctor_NiCad_DN-1 User guide

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Dr. NiCad

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BATTERY CONDITIONER/

RAPID CHARGER

Ramsey Electronics Model No. DN1

Stop shelling out a fortune on batteries ! Enjoy full performance
from your NiCad batteries or battery packs with this sensational

• Quick charges batteries for laptop computers, hand-held radios
and scanners, cordless/cellular phones, camcorders, RC models
and more ! Charge many batteries in less than an hour !

• State-of-the-art battery monitor IC safely watches both battery
voltage and charge time while fast charging your batteries !

Dr.Nicad is your best
for nicad batteries!

R

x

• Eliminate “Memory Effect” common to NiCads - uses unique
constant current circuitry.

• Safety First: circuit has “built in” timers and voltage sensors that
monitor the cell for safety - it won’t let you charge a bad cell !

• Stop “cooking” and start conditioning your rechargeable batteries,
no more leaving the charger plugged in for days on end !

• Charges single cells as well as NiCad packs from 1 to 10 cells !

• Automatic “top off” charge keeps batteries at their peak power until

use.

• Unit runs on 12-15 volts DC.

• Convenient flashing LED indicates charging modes and eliminates

guesswork.

DN1 • 1

RAMSEY TRANSMITTER KITS

· FM10A FM25B FM Stereo Transmitters

· FM100B Professional Quality FM Stereo Transmitter

· TV6 Television Transmitter

· AM1, AM25 AM Transmitters

RAMSEY RECEIVER KITS

· FR1 FM Broadcast Receiver

· AR1 Aircraft Band Receiver

· SR2 Shortwave Receiver

· AA7 Active Antenna

· SC1 Shortwave Converter

RAMSEY HOBBY KITS

· SG7 Personal Speed Radar

· SS70 Speech Scrambler

· TT1 Telephone Recorder

· SP1 Speakerphone

· MD3 Microwave Motion Detector

· PH10 Peak hold Meter

· LC1 Inductance-Capacitance Meter

RAMSEY AMATEUR RADIO KITS

· DDF1 Doppler Direction Finder

· HR Series HF All Mode Receivers

· QRP Series HF CW Transmitters

· CW7 Keyer

· QRP Power Amplifiers

RAMSEY MINI-KITS
Many other kits are available for hobby, school, Scouts and just plain FUN. New
kits are always under development. Write or call for our free Ramsey catalog.

DOCTOR NiCad BATTERY CONDITIONER KIT INSTRUCTION MANUAL

Ramsey Electronics publication No. MDN1 Revision 1.1a

First printing: March, 1994

COPYRIGHT

14564. All rights reserved. No portion of this publication may be copied or duplicated without the

written permission of Ramsey Electronics, Inc. Printed in the United States of America.

ã

1994 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York

DN1• 2

Ramsey Publication No. MDN1

Price $5.00

KIT ASSEMBLY

AND INSTRUCTION MANUAL FOR

Dr. NiCad
NiCad BATTERY
CHARGER/CONDITIONER

TABLE OF CONTENTS

Introduction to the DN1 ................. 4

How it works .................................. 6

Parts list ........................................ 8

Schematic diagram ....................... 9

Parts Layout diagram .................. 11

DN1 Assembly instructions ......... 12

Setup configurations .................... 16

Troubleshooting ........................... 21

Ramsey kit warranty .................... 23

DN1 • 3

RAMSEY ELECTRONICS, INC.

590 Fishers Station Drive

Victor, New York 14564

Phone [phone]

Fax [phone]

www.ramseykits.com

INTRODUCTION

With today’s ever changing technologies, more appliances depend on battery
power to enable their use. While this gives us greater freedom, it is often at
the high cost of purchasing portable energy, or batteries, to run our portable
electronic gismos. Consider the cost of energy from our local electric

company, about 8
penny. On the other hand, that 500 mA-H NiCad that you just purchased for
about $1.75 can only supply 2250 joules of energy; that's about 13 joules for
1 cent. So it’s fairly easy to see that energy costs about 35,000 times more
when it’s in a battery.

Nobody likes the idea of throwing all those batteries into a landfill. That's the
reason for the recent emphasis on using “green” rechargeable cells. If a set
of NiCad cells lasts you for a few months, they can save the equivalent
volume of themselves many tens or hundred times in the trash. This is not
only good for the environment, it’s also great for the wallet!

Nicad rechargeable batteries have been around for years, but there are a few
real disadvantages in their use. They usually require a long time (sixteen
hours) to recharge. This “trickle charge” arrangement is quite common
because it is much cheaper for the original product manufacturer to produce
(the entire battery charger is typically a couple of rectifier diodes and a
current limiting resistor), and works well given the draw back of a long charge
time.

Another disadvantage to the “plug-in wall transformer charger” is that the
charging cutoff action is regulated by the heat produced by the cells’
chemical reaction when recharging. If you’ve ever opened up a rechargeable
pack you have probably seen the thermal shutoff “mystery part” connected
and mechanically touching one cell of the battery pack. While this will help if
you leave your appliance charging for several days, notice that it is sampling
only one cell in the pack, and assuming that the rest of the batteries are
“behaving” in the the same manner. Also, since the ambient temperature can
change (i.e.recharging your cordless drill in the cool garage or basement, or
your two way radio on the hot seat in the car), this heat sensing approach
can vary considerably from undercharging your pack to overcharging until
you “cook” the electrolyte solution right out of the battery.

Often times we cannot wait for the full recommended charging time or do not
use the batteries until they’re completely “dead”. When this is repeated, the
uncared for battery or pack can seem to “run out” rather quickly. This effect is
caused by not completely discharging the cell before it is recharged and is
known as the memory effect, since the battery appears to memorize the
amount of energy it is called upon to produce.. By not completing the

¢ for a KW hour, or about 450,000 joules of energy for a

DN1• 4

oxidation reduction or “redox" chemical reaction in the cell, we effectively
decrease the chemically active surface area inside the cell. The lower this
surface area, the shorter the battery’s life. Since you don’t try to recharge
conventional batteries, you’ve never noticed this property until you started to
use rechargeable NiCad batteries.

To keep your cells working like new and to eliminate this memory effect, we’ve
built in an automatic discharge circuit that will properly discharge the cells
before their recharging.

So, you can see recharging a NiCad battery correctly can be a tricky business.
How can we charge the battery to its full potential, but not too much? The
answer is to watch the ∆V or change in voltage over time. As shown in the
graph, the battery voltage continues to rise while charging but drops slightly
when the cell is completely charged. By recognizing this point on the graph, a
charger can put just enough charge into the cell. By virtue of this voltage -vs­time checking, it is also possible to charge the battery at a much higher
charging current - and significantly reduce the battery charging time. Once this
point is reached, it is best to “top off” the battery with a charge burst every now
and then.

Positive "Slope"
or + dV

dT

Full Charge

Slope = Zero

Negative "Slope"

or - dV

dT

Terminal Voltage
vs
Time
for a NiCad Cell

VOLTAGE

TIME

Enter the Benchmarq BQ2003 NiCad battery charger IC. This cell monitoring /
charging IC performs all of the previously mentioned functions, and then some.
This smart IC is the “doctor” in our NiCad recharging unit.

DN1 • 5

We designed our kit to change quickly and easily adapt to a variety of cell or
battery pack types for anything from video camcorders to cordless phones.
You can configure it for the number of batteries in your pack, discharge and
charging rate. We’ll discuss this later as we’re assembling these sections of
the circuit.

DN1 CIRCUIT DESCRIPTION

Before we get into the technical jargon, let’s take a walk around the BQ2003
Integrated Circuit . We’ll start with some definitions of the abbreviations
written on the chip in the schematic diagram.

Benchmark BQ2003 pin designations:

Pin No. Abbreviation Function

1

2

3

4,5

7

8

9

11

13

14

15

16

CCMD Charge command

DCMD Discharge Before Charge Command

DVEN

- ∆V Enable Input

TM1 & 2 Timer Mode Outputs

BAT Single Cell Voltage Input

VSS Ground

SNS Charging Current Sense Input

MCV Maximum Cell Voltage Reference

CHG Charging Status LED Output

MOD Current Switching Control Output

DIS Discharge Control Output

VCC 5 Volt input

The BQ2003 charger IC handles many of the functions related to our
charger. Without trying to sound too much like a technical manual or data
book, here’s a closer look at some of the accompanying circuitry. Have a
glance at the schematic diagram and follow along.

DN1• 6

Since we want the voltage appearing at the IC to be equivalent to one cell,
we first must “divide” the cell voltage by the number of cells in the pack.
The ladder resistors R2 -R24 form an effective voltage divider circuit so that
the BAT (pin 7) voltage will be about 1.25 V per cell. The switch can increase
or decrease the BAT voltage by adding or subtracting “rungs” from the
voltage divider ladder. Another divider network consists of resistors R14 and
R16. This voltage sets up the MCV voltage for the BQ2003 IC. This should
measure 1.8 V when in operation.

Seeing how you’ll want to charge your batteries quickly, you need a high
charging current power supply to back you up. Transistors Q2, Q1, and
components D1 and L1 form the “high current” portion of our “switched­mode-regulator” circuit. When the MOD output goes “high”, transistor Q2 is
turned on, like a switch. This current then flows into the battery. Resistor R29
(and/or R27) is in series with the current flow and the voltage drop across it
is sensed by IC pin 9, the sense pin. When the sense pin reaches its trigger
point, the transistor is abruptly turned off. When this occurs, the magnetic
field around the coil quickly collapses and causes a reverse voltage “spike”
which is routed through the “catch” diode D1. This energy is recovered and
delivered to the battery cells being charged. This is what provides us with the
high current to quickly charge the cell, but does not dissipate power in the
FET or NPN transistor, making the switched power much more efficient than
a conventional pass transistor type of supply. Another contributing factor to
the charging circuit is the charge rate setup, which is configured using
resistors R26 and 27, as well as test points A - F.

Transistor Q3 is the integral part of our constant current discharging circuit.
When the chip sees a positive going pulse at the DCMD pin, it initiates the
DIS discharge output. With switch S1:10 closed diodes D2 and D4 are
forward biased, causing 1.4VDC to be present at the base of Q3. With 1.4 V
at the base, there is .7 VDC at the emitter, a diode drop in potential lost
through the transistor. With the emitter at .7 VDC, the current through
resistors R10 and R22 is about 140 mA, regardless of the cell voltages. If
switch S1:10 is opened the potential increases to 1.4 VDC. increasing the
current to 280 mA. This will continue to discharge the batteries until they
reach a potential of about .9 volts per cell. The Benchmarq chip then initiates
its own charging sequence.

A few final points concerning the TM1 and TM2 time-out, which are
configured using points G - J. They are dependant on the charge capacity, or
“C” of the pack. We’ll discuss this in more detail when it comes time to
configure these jumpers.

DN1 • 7

DN1 PARTS LIST

RESISTORS

 1 270 ohm [red-violet-brown] (R12)
 2 .5 ohm ½ Watt [green-black-silver] (R26, 27)
 3 10 ohm [brown-black-black] (R 2, 10, 22)
 2 470 ohm [yellow-violet-brown] (R3, 7)
 4 1K ohm [brown-black-red] (R1, 5, 9, 25)
 2 10K ohm [brown-black-orange] (R11, 20)
 1 10K ohm 1% [brown-black-black-red] (R16)
 1 17.8K ohm 1% [brown-violet-grey-red] (R14)
 11 47K ohm resistors [yellow-violet-orange] (R4,6,8,13,15,17,18,19,21,

23, 24)

CAPACITORS

 3 1uF electrolytic capacitors (C1,C3,C3A)
 3 10 uF electrolytic capacitors (C2, 5, 6)

INDUCTORS

 1 Axial lead inductor [enameled wire wound on ferrite core] (L1)

SEMICONDUCTORS AND INTEGRATED CIRCUITS

 3 1N4148 diodes [glass case with black band] (D2, 4, 7)
 2 1N4002 diode [epoxy case marked 1N4002] (D5, 6)
 1 1N4937 fast recovery diode [ epoxy case marked 1N4937] (D1)
 1 Light Emitting Diode [LED] (D3)
 1 NPN small signal transistor [2N3904 or equivalent] (Q2)
 1 NPN power type [marked TIP31C] (Q3)
 1 Power FET [marked 7035] (Q1)
 1 78L05 voltage regulator [marked 78L05] (VR1)
 1 BQ2003 16 pin IC (U1)

MISCELLANEOUS PARTS AND HARDWARE

 1 2.5mm power jack (J3)
 1 10 position DIP switch (S1)
 2 DPDT pushbutton switch (S2, 3)
 1 DN1 printed circuit board
 1 TO-220 heatsink (HS1)
 2 #4-40 screws and nuts
 1 Insulated jumper wire
 1 6” piece of two conductive wire (blk, red)

DN1• 8