LEAD ACID BATTERY
CHARGER KIT
Ramsey Electronics Model No.
LABC1
An educational kit that will come in handy around the shop and
garage. Build your own charger instead of shelling out big bucks
for a “store bought” unit. You might learn more than you ever
wanted to know about batteries and battery charging. Amaze
your friends with your new found knowledge. Wait . . .is that
Regis on the phone?
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No more fried gel cells!
Extends the life of your 12 volt lead acid batteries.
Automatic ambient temperature compensation.
Automatically adjusts charge voltage depending on battery status.
Bright front panel charge indicator.
Saves spending money on costly replacement batteries; pays for
itself in no time!
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Add our matching case and knob set for a professional appearance.
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Ramsey Publication No. MLABC1
Price $5.00
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
LEAD ACID BATTERY
CHARGER KIT
TABLE OF CONTENTS
Quick Battery Theory..................4
Circuit Description.......................6
Schematic Diagram ....................8
Parts Layout Diagram.................9
Parts List ....................................10
Kit Assembly...............................12
Custom Case Assembly .............15
Adjusting your LABC1.................17
Safety Considerations.................18
Troubleshooting Guide ...............19
Warranty.....................................23
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
LABC1 • 3
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Quick Battery Theory
To begin, we should cover a few facts about lead acid batteries in general.
Most traditional historians date the invention of batteries to the early 1800’s
when experiments by Alessandro Volta generated electrical current from
chemical reactions between dissimilar metals. Volta’s original ‘voltaic pile’
consisted of zinc and silver disks separated by a porous nonconductive
material saturated with seawater. When stacked in a particular manner, a
voltage could be measured across each silver and zinc disk.
Other more radical thinkers, however, believe that lead acid battery
technology has been around since the early days of the Egyptian Pharaohs!
Whether they discovered the electro-chemical process on their own or if the
‘Space Aliens’ using their pyramids as an intergalactic spaceport taught them
still requires a bit more clarification. We’ll leave that one for you to follow up
on!
While advances in construction and materials have come a long way over the
years, the basic principles still apply. Lead acid cells of all types (‘Wet’ or
‘VRLA’ ) undergo a specific set of chemical reactions while charging and
discharging. They are also formed from similar types of active materials. For
the most part, lead acid batteries are made up of lead plates submerged in a
sulfuric acid solution. The positive electrode plates are formed from lead
dioxide (PbO2) while the negative electrodes are made of sponge metallic lead
(Pb). The porous nature of the lead plates allows the electrolyte, a dilute
mixture of 35% sulfuric acid and 65% water, to efficiently contact the
maximum surface area and obtain the most charge carriers. The electrolyte
solution provides the sulfate ions formed during the discharge chemical
reaction process giving us the electrons needed for current flow into the load.
One of the byproducts created during the discharge process of freeing sulfate
ions is lead sulfate (PbSO4). As the battery discharges, the lead sulfate
attaches to the electrode plates raising the internal resistance of the battery
which in turn lowers its working terminal voltage.
To determine the SOC (State Of Charge) of a lead acid battery, the classic
voltmeter approach does not work well. The terminal voltage will vary widely
between batteries as a function of things like ambient temperature and the
relative age of the battery. A full set of temperature profile tables would show
big differences in the open circuit terminal voltage over a wide temperature
range. This is why a good charger must incorporate a temperature
compensation network to avoid ‘over’ or ‘under’ charging the battery at
different ambient temperatures. To test a lead acid battery’s SOC, the best
indicator is a hydrometer. When you test a battery’s SOC with a hydrometer,
you are actually measuring the amount of sulfuric acid left in the electrolyte
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solution. As more energy is drained from the battery, the ratio of sulfuric acid to
water decreases and the created lead sulfate byproduct begins forming on the
electrode plates. A low hydrometer reading means the chemical makeup that
generates the free electrons is diminished so not as much energy is stored for
use.
The term ‘specific gravity’ is often used to benchmark a lead acid battery’s
SOC. The specific gravity of a substance is a comparison of its density to that
of water (1.000). Imagine a one gallon bottle filled with water and a second
filled with feathers. There are equal volumes of material present in both but the
bottle with the feathers will weigh less than that containing the water. The
resultant specific gravity value of the bottle of feathers would be less than that
of the bottle of water. With lead acid batteries, the sulfur atoms break down and
leach out of the electrolyte solution as it discharges. The breakdown of the
electrolyte reduces its overall ‘weight’ as the sulfur is removed from the solution
thus reducing the specific gravity measurement. Take a look at Table 1.
State of Charge as related to Specific
Gravity and Open-Circuit Voltage
State Of
Charge
Specific
Gravity
Open-
Circuit
Voltage
(approximate)
100%
75%
50%
25%
0%
1.265
1.210
1.160
1.120
1.100
12.63
12.30
12.00
11.76
11.64
Table 1.
Great care should be taken to avoid discharging a battery beyond the 75%
SOC point. Once the specific gravity drops below the 1.210 level, excessive
sulfate deposits form on the electrode plates. This process is called ‘sulfation’
and leads to the hardening of the electrode plates. If the battery is kept in a low
charge state for long a period of time, the sulfation process will eventually
reduce the ability of the battery to generate ion charge carries to the point that
it no longer provides the needed power. This point is otherwise known as a
DEAD BATTERY!
When you recharge the battery, the process is reversed and the sulfur returns
to the electrolyte solution. Proper cycling of the battery will ensure a long and
functional life. If the battery is abused by allowing sulfation of the electrode
LABC1 • 5
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plates on a regular basis or over an extended period of time, the charging
process will not be able to restore the battery to its former full potential. Time
to make a costly battery replacement!
Circuit Description
The LABC1 has been designed as a dependable workhorse to charge and
hold your 12 Volt lead acid batteries at their peak level, insuring a long life and
maximum performance. The charging procedure used when working with a
flooded ‘wet’ cell battery or one of the newer VRLA (Valve Regulated Lead
Acid – ‘Gel’ or ‘AGM’) batteries is the same. The battery being charged will
automatically set the LABC1 in one of two charging modes upon hookup. The
circuit design takes into account the battery’s current SOC (State Of Charge)
and adjusts the terminal voltage at J2 accordingly. The main charging circuit is
very simple because as we discussed before, the concept of lead acid
batteries has been around for centuries (give or take a few thousand years if
you don’t believe in the ‘Space Alien’ theory). The real secret to correctly
charging a lead acid battery system is to use a temperature compensated
voltage source that automatically varies its output in accordance with the
batteries SOC. ‘Frying’ your battery occurs when the charging unit fails to
sense that the electro-chemical rejuvenation (or charging) process has slowed
to the point that the higher voltage charging mode should end. Continual high
voltage charging will decrease the overall life of the battery.
Let’s take a closer look at the LABC1 schematic and see what’s happening.
The power supply inlet for the LABC1 is J1. The input voltage is immediately
presented to a full wave bridge rectifier consisting of diodes D1 to D4 and then
filtered by C1 to reduce the voltage ripple. Using a bridge configuration on the
voltage input allows the user more options to power their LABC1. The use of a
14 VAC or 20 VDC (positive tip) power supply will do nicely with any 12 Volt
lead acid battery. Varying your power supplies current capacity will allow you
to charge any type of lead acid battery without a problem. Most of the
standard cells require a charging current of 650mA or greater. For these
systems a 14 VAC (2 Amps or so) transformer will work very well. If your
application is to charge very small capacity batteries with a maximum charge
current of only a few hundred milliamps, using a 14 VAC @ 500mA ‘wall wart’
supply or a current limited bench-top power supply set for 20 VDC will avoid
excessive current draw that could damage a heavily discharged battery.
Internal heating from excessive charge current will also degrade your overall
battery life.
Moving on, VR1 is a voltage regulator that provides the precision terminal
voltage we need to charge the lead acid cells. Unlike a standard voltage
regulator that is designed for a fixed level output, VR1 lends itself well as a
variable voltage source. With a maximum current source capability of about
1.3 amps, VR1 gives the user the flexibility to charge even very large capacity
LABC1 • 6
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batteries. Granted, that might take a while.
The other support components on the board help VR1 to know when to adjust
its output voltage up or down to ensure the proper charging rate of the battery.
These other components are grouped into two major sections, the SOC
feedback loop and the ambient temperature compensation used during the
‘Float’ mode after the battery has been fully charged.
The SOC feedback loop consists mainly of U1 and R6 together to form a low
voltage comparator in conjunction with R1 and R4 to set the range of the
charging voltage. Here’s how the loop functions. Assume for starters that the
battery under charge, or BUC (not to be confused with your BUT, or Battery
Under Test) is discharged and drawing enough current to set the LABC1 in
charge mode. After the current drawn by the battery drops below a certain
point, the need for ‘high’ voltage charging has ended. U1 monitors the voltage
drop across R6 to determine when to switch VR1’s output at J2 from 14.4V
(‘Charge’ mode) to 13.4V (‘Float’ mode). As the battery comes to a full charge,
the charging current it draws drops below about 150mA. The voltage across
R6 (0.47 ohms) will then fall below 0.07V thanks to Ohm’s Law, V=IxR. This
trigger point causes the V+ pin (U1:1) to toggle from its ‘Charging’ mode ‘high’
value of about 12.8V to a charged ‘Float’ mode ‘low’ value of about 0.7V.
When V+ (U1:1) toggles low, R4 is switched into the reference feedback
circuit of VR1 causing its output voltage drop back to 13.4V. The ‘Charged’
LED (D15) is turned on when the Base-Emitter junction of Q1 is thus forward
biased indicating that the battery is charged and is being ‘topped-off’ by the
‘Float’ mode operation.
Now that the battery is charged, the ambient temperature compensation circuit
comes into play. The effects of this circuit, formed by R2, R3 and diodes D5 to
D14, are used only during the ‘Float’ mode operation to adjust the terminal
voltage in accordance with the ambient temperature. If the temperature is not
factored in, you would run the risk of over-charging the battery when it’s hot or
under-charging the battery when it’s cold. Taking advantage of the thermal
characteristics of a PN diode (∆2.2mV/°C), the diode matrix (D5 to D14)
raises or lowers the reference terminal of VR1 by 22mV (10 x 2.2mV/°C) for
every 1°C change. This is just the right negative temperature compensation
we needed to properly charge our lead acid batteries!
At the start of the charge cycle, you’ll notice that the heatsink used with VR1
can get very warm if you are charging a large capacity battery. The fact that
the temperature sensor matrix is on the same circuit board and in the same
case will not negatively affect the compensation network because there will be
very little dissipated heat by the board components once the unit switches into
‘Float’ mode. The drop in charge current drawn by the battery is so low by the
time ‘Float’ mode is entered, the air cavity around the temperature sensor
diodes will re-acclimate to the surrounding ambient temperature.
LABC1 • 7
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LABC1 PARTS LAYOUT DIAGRAM
LABC1 • 9
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PARTS SUPPLIED WITH YOUR LABC1 KIT
Capacitors
ˆ 1 10 µF electrolytic capacitor [C2]
ˆ 1 1000 µF electrolytic capacitor [C1]
Resistors and Potentiometers
ˆ 1 0.47 ohm, 1 watt (yellow-violet-silver) [R6]
ˆ 1 270 ohm (red-violet-brown) [R1]
ˆ 3 820 ohm (gray-red-brown) [R3,7,9]
ˆ 1 10K ohm (brown-black-orange) [R8]
ˆ 1 18K ohm (brown-gray-orange) [R4]
ˆ 1 PC mount 1K ohm potentiometer (marked 102) [R2]
Semiconductors and Integrated Circuits
ˆ 11 1N4148 diodes (small glass diode) [D5,6,7,8,9,10,11,12,13,14,17]
ˆ 4 1N4002 or 1N4004 diodes (black with white band) [D1,2,3,4]
ˆ 1 221334 transistor (three leads TO-92 package marked 221334) [Q1]
ˆ 2 JUMBO red LEDs [D15,16]
ˆ 1 LM317 3 terminal adjustable regulator [VR1]
ˆ 1 LM334 IC (three leads TO-92 package marked LM334) [U1]
Miscellaneous Components
ˆ 1 2.1mm power jack [J1]
ˆ 1 DPDT PC mount pushbutton switch [S1]
ˆ 1 Heatsink [HS1]
ˆ 1 #4-40 3/8” screw (for HS1)
ˆ 1 #4-40 Kep nut (for HS1)
ˆ 1 2 Screw terminal jack [J2]
ˆ 2’ #24 AWG Dual (red & black) twisted hookup wire
LABC1 • 10
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RAMSEY "Learn-As-You-Build KIT ASSEMBLY
There are numerous solder connections on the LABC1 printed circuit board.
Therefore, PLEASE take us seriously when we say that good soldering is
essential to the proper operation of your battery charger kit!
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Use a 25-watt soldering pencil with a clean, sharp tip.
Use only rosin-core solder intended for electronics use.
Use bright lighting; a magnifying lamp or bench-style magnifier may
be helpful.
Do your work in stages, taking breaks to check your work. Carefully brush
away wire cuttings so they don't lodge between solder connections.
We have a two-fold strategy for the order of the following kit assembly steps.
First, we install parts in physical relationship to each other, so there's minimal
chance of inserting wires into wrong holes. Second, whenever possible, we
install in an order that fits our "Learn-As-You Build" Kit building philosophy.
This entails describing the circuit that you are building, instead of just blindly
installing components. We hope that this will not only make assembly of our
kits easier, but help you to understand the circuit you’re constructing.
For each part, our word "Install" always means these steps:
1. Pick the correct component with the proper value to start with.
2. Insert it into the correct PC board location.
3. Orient it correctly, following the PC board drawing and the written
directions for all parts - especially when there's a right way
and a wrong way to solder it in. (Diode bands, electrolytic
capacitor polarity, transistor shapes, dotted or notched ends
of IC's, and so forth.)
4. Solder all connections unless directed otherwise. Use enough heat
and solder flow for clean, shiny, completed connections.
5. Trim or nip the excess component lead wire after soldering.
NOTE: Save some of the longer wire scraps nipped from resistors and
capacitors. These will be used to form wire jumpers (JMP1, etc.) to be
soldered in just like parts during these construction steps.
Enough of that ... let’s get started!
LABC1 • 11
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LABC1 BATTERY CHARGER KIT ASSEMBLY
Although we know that you are anxious to complete the assembly of your
battery charger kit it is best to follow the step-by-step instructions. Try to avoid
the urge to jump ahead installing components.
Since you may appreciate some warm-up soldering practice as well as a
chance to put some landmarks on the PC board, we’ll first install a couple of
the larger components. This will also help us to get acquainted with the up-
down, left-right orientation of the circuit board. Remember that the
components will be mounted on the component side of the circuit board and
soldered on the solder side of the circuit board, the side that contains the
printed circuit traces. Have a look at the parts layout diagram to help with your
assembly.
Use the boxes to check off your progress.
Check all received parts against the parts list. The parts list describes the
various markings that may be found on the kit parts. Carefully sort the parts
into small piles, (an empty egg tray does nicely for this purpose) to aid in
finding the correct part at the required time.
ˆ 1. Install DPDT PC mount pushbutton switch, S1. Be sure it is seated
properly before soldering all 6 pins.
ˆ 2. Install J1, the 2.1mm power jack.
We’ll begin to install some of the polarity sensitive parts at this point. Use the
parts layout diagram in addition to the PC board silkscreen to orient the
diodes, electrolytic capacitors, transistors and ICs properly.
ˆ 3. Install D1, 1N4002 diode (black with white band). You’ll see a black
band on the PC board silkscreen. Line up the white band on the diode
with this black band. This is the cathode side of the diode.
Cathode
Anode
ˆ 4. Install D2, D3 and D4, 1N4002 diodes (black with white band) in the
same manner as you did D1 above. Carefully orient the banded end
before soldering these diodes.
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ˆ 5. Install C1, 1000 µF electrolytic capacitor. This part also must be
installed properly to function. In fact, this capacitor has the potential to
explode if installed in reverse polarity. The PC board silkscreen shows the
positive hole and the band on the capacitor shows the negative side.
You’ll also note that the lead closest to the stripe is shorter than the other
lead; this also indicates the negative side. Save the long leads you clip off
from this part. They’re great for the jumpers you’ll need to install later.
Next we’ll install VR1. You’ll need to locate the following parts: the LM317,
HS1 is the black finned heatsink, the #4-40 3/8” screw, and the #4-40 kep nut.
ˆ 6. Install VR1, the LM317, 3 terminal adjustable regulator. Place the
heatsink, HS1, on the circuit board, lining it up with the silkscreen so that
the hole in the heatsink matches the hole in the board. Take the LM317
and place it on top of the heatsink so that the hole in the regulator lines up
with the other two. This will show you where to bend the leads down so
that the part fits in the PC board holes and lays flat on the heatsink. This
allows maximum “bleed off” of heat from the part. Once the leads are bent
and through their PC board holes, take the screw and nut and attach the
LM317 and the heatsink to the board. It is easiest to put the screw through
the top of the components and tighten the nut on the bottom of the board.
Once the screw is holding everything in place solder the three leads of the
LM317.
ˆ 7. Install J2, the 2 screw terminal jack. The openings should face the
rear of the PC board. This is where the battery you’re charging will be
attached to the LABC1.
ˆ 8. Install R6, 0.47ohm 1 watt resistor (yellow-violet-silver). This part is
physically larger than the other resistors in your kit for a reason; it is a 1
watt part compared to the other 1/4 watt parts. That means it needs to
(and can!) dissipate more power than the others.
ˆ 9. Install U1, the LM334 IC (three leads TO-92 package marked LM334).
Also, keep a few more of those scrap leads handy as we will need a few
more jumper wires later.
ˆ 10. Install C2, 10 µF electrolytic capacitor. Watch that polarity!
ˆ 11. Using a scrap component lead, form a jumper wire and install in the
JMP3 holes. Jumpers act like electronic “bridges” that carry power or
signals over active traces on the circuit trace side of the board. Solder
both ends of the jumper into place.
ˆ 12. Install R3, 820 ohms (gray-red-brown).
ˆ 13. Take another scrap lead and install JMP2. It helps to pre-bend the
wire into a staple shape before inserting into the PC board.
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Take a moment now to check your previous solder joints for “opens” where
the solder did not completely flow around the connection, or solder bridges
between closely spaced pads. It seems the best time to identify these
problems is now when you’re focused on this section of the board, saving you
time trying to retrace your steps later.
ˆ 14. Install R2, the PC mount 1K ohm potentiometer (marked 102). It only
fits on the board one way; just be sure it is seated flat before soldering.
ˆ 15. Install D17, one of the 1N4148 diodes (small glass diode with black
band). This part will be mounted in a stand-up fashion with the body of the
part placed in the PC board silkscreen circle and the black band up. The
lead closest to the band is bent over to fit into the other mounting hole. Be
gentle with this fragile part and double check the orientation before
soldering.
ˆ 16. Install R8, 10K ohms (brown-black-orange).
ˆ 17. Install Q1, the 221334 PNP transistor. This transistor appears to have
two flat sides, one with writing on it and a larger flat side without writing.
The pin orientation of Q1, the 2N3906 (221334) transistor, is incorrect on
your LABC1 circuit board The larger flat side with no writing is the one
pictured on the silkscreen; orient the part using this as the correct flat side.
with the flat side (no writing) facing the front of the board towards the D5-
D14 diode matrix. Solder all three pins.
2 2 1 3 3 4
o n b a c k
B
Q 1
B
Q 1
C
C
E
E
E
B
C
ˆ 18. Install R1, 270 ohms (red-violet-brown).
ˆ 19. Install the last jumper wire, JMP1. Form and solder as you did the
other jumpers. You can start throwing away your clipped off leads now!
ˆ 20. Install R4, 18k ohms (brown-gray-orange).
You’ll see a designation on the silkscreen for R5. Now that I’ve brought it to
your attention, ignore it. This part is not needed for your LABC1.
ˆ 21. Install R7, 820 ohms (gray-red-brown).
ˆ 22. Install R9, the last 820 ohm resistor (gray-red-brown).
Next we’ll install a group of identical parts, the diodes D5 through D14. They
all must be installed in the correct polarity but if you can get the first one in
LABC1 • 14
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right, you can do it with the rest. These will all be mounted in stand-up fashion,
just like D17 was a few steps ago. Again, the body of the part is placed in the
hole with the circle around it and the other lead is bent up and around to fit
into the other hole. The banded end should be facing up. If you don’t want to
spend time desoldering later, check them carefully now. It might help to pre-
bend all the diodes so that you can just grab them one at a time and place
them on the board.
ˆ 23. Install D5 through D9. Be sure you solder them all.
ˆ 24. Install D10 through D14. Notice that the orientation has changed.
Now we’ll install the two LEDs. One indicates “power on” and the other
indicates what mode your charger is in, whether charge or float mode. Both
are oriented the same way and should be left sitting up off the circuit board so
that they can be bent over to fit through the holes in the matching case.
ˆ 24. Install D15 and D16. You’ll see that the LEDs have a flat side and so
does the PC board silkscreen. Orient the flat sides correctly and slide the
diodes into their mounting holes. One lead is shorter than the other, just
like the electrolytic capacitors we installed earlier. This indicates the
cathode or negative lead of the LED and should correspond to the hole
closest to the flat side. Get them both lined up so that they are about the
same height above the circuit board and bend the leads on the back of the
board to hold them in place before soldering.
Leave leads approximately
3/4 inch in length
LED
Leave leads approximately
3/4 inch in length
LED
Flat
Flat
PC Board
PC Board
Front View
Front View after Bending
CONGRATULATIONS !
Great job! You’ve made it through the circuit board assembly of your LABC1
kit. We know you’re anxious to “fire it up” but take a moment to look over your
work now, checking for imperfect solder joints, misplaced components and
correct orientation of polarity sensitive parts. Even if you have to fix
something, you’ll be glad you found it now and not after you turn on the power
and let the magic smoke out of one of your parts!
LABC1 • 15
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ASSEMBLY INSTRUCTIONS FOR CUSTOM CASE
The enclosure is a key element to the overall pride you will have upon
completing your Ramsey kit. The enclosure will show how you were able to
“build from scratch” a commercial piece of high-tech electronics. For some of
us, the enclosure will also hide a number of “not-so-pretty” assembly
mistakes. Once the kit is enclosed, your friends will never know that you were
new to soldering. Finally, the enclosure case will protect your electronics from
many possible causes of damage so that you can receive years worth of
enjoyment using, talking about, and remembering the fun you had building
your kit. In short, TAKE YOUR TIME when assembling the enclosure. This is
the part that you and your friends will look at and admire for years!
ˆ 1. Lay the front and rear plastic plates over their corresponding labels to
verify which sticker goes with which panel. You’ll want to work with one
panel at a time to avoid possible mix-ups.
ˆ 2. Remove the backing material from one of the stickers and line it up
properly on its pre-punched panel. Make sure that they are aligned
correctly before allowing them to touch the plastic plates. They stick the
first time; line them up right!
ˆ 3. Use a sharp hobby knife to cut out the holes in the labels along the pre-
punched holes. A short sawing motion works well around the inner
circumference of the holes.
ˆ 4. Repeat the above steps for the other panel.
ˆ 5. Insert the board into the case with the knobs and LED extending
through the holes in the front panel.
ˆ 6. Raise the rear portion of the PC board and extend the jacks through the
rear plastic plate. Insert the plate into the grooves on the base tray.
ˆ 7. Secure the PC board to the bottom base tray with 4 short Phillips head
screws.
LABC1 • 16
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ADJUSTING YOUR LABC1 BATTERY CHARGER
Now that you have finished the assembly stage there is only one more step
before you start charging your batteries. The necessary alignment is to adjust
R2 for the proper ‘Float’ voltage with reference to the current air temperature
around diodes D5 to D14. In order for the temperature compensation network
to function properly and automatically adjust the ‘Float’ voltage as needed,
you will need to know the air temperature in the room you are in. Note that this
adjustment only needs to be done once. When R2 has been set, the unit will
automatically track as needed from there on out.
To adjust R2, take a temperature reading for the current room temperature
with a thermometer. Set your voltmeter on the 20VDC scale and attach the
probes (Red = +, Black = -) across the output of J2. Trim the pot (R2) to get a
reading of 13.4 VDC (+- 0.01 VDC) at a room temperature of 25°C (77°F) with
no battery attached. If your room temperature is above or below 25°C, you will
need to account for the difference by offsetting the alignment voltage by 22mV
(10 x 2.2mV/°C for each of the sensor diodes) for every 1°C of difference. See
Table 2 for examples.
If you do need to adjust for any temperature differences, here are a few
helpful hints to point you in the right direction:
·
If the temperature is higher than 25°C (77°F), reduce the alignment
voltage at J2 by 22mV for each 1°C difference.
·
If the temperature is lower than 25°C (77°F), increase the alignment
voltage at J2 by 22mV for each 1°C difference.
Handy formulas: °F = (°C x 1.8) + 32 or °C = (°F – 32) x 0.556
‘Float’ Mode voltage settings of R2 for
different example temperatures
Temperature
J2 Terminal Voltage
12V Battery
27°C (81°F)
25°C (77°F)
23°C (73°F)
13.356 VDC
13.400 VDC
13.444 VDC
Table 2.
LABC1 • 17
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SAFETY CONSIDERATIONS
All lead-acid batteries produce Hydrogen and Oxygen gas during the electro-
chemical recharging process. The production of these gases is increased if
overcharging occurs, commonly caused by too high of a charge voltage.
Sealed battery designs plan on the recombination of Oxygen at the same rate
it is produced, therefore eliminating the explosive mixture. Any Hydrogen
which is produced will diffuse through the plastic container and as long as the
sealed battery is not in a sealed enclosure, the hydrogen will harmlessly
disperse into the atmosphere.
It is good practice to use adequate ventilation even with sealed batteries due
to the possibility of unforeseen problems. Should something happen, the
battery may vent as needed to prevent pressure build up.
Remember, the gases that form while charging lead acid batteries are
extremely explosive! Never charge a battery around an open flame or
anything that may cause a spark that may ignite the venting gas!
Another point to enforce is that a battery should never be left to charge
unattended. Any charging battery should be considered an explosive fire
hazard and deserves full attention of the person charging it. The battery’s
sulfuric acid can cause bodily harm to you and the environment around you
should an explosion occur. If you should hear excessive bubbling (kind-of like
a bowl of Rice Krispies with milk) coming from the battery, cease charging
immediately and investigate the situation. Your safety is your responsibility
and the end use of your LABC1 or any other charger is up to you to use
responsibly.
Always wear safety glasses and protective gloves while working with lead acid
batteries. You might even find it beneficial to wear your father’s ‘polyester
leisure suit’ (yep… you finally found a use for that old thing!) to protect
yourself from corrosive acid that might ruin a " normal human’s” clothing!
Notes on Operation
1) First and foremost, the LABC1 has been designed to work with 12 Volt
Lead Acid Batteries only. Modification for other voltages is not encouraged.
The easiest way to check to see if your battery is compatible with the LABC1
is to carefully read the information stamped on the battery itself or in the
manufacturer’s datasheet. Since a 12V battery is composed of six 2 Volt cells
in series, count the number of vent covers on top of the battery as a quick
check! An example would be: three vents equals 6 Volts equals no good!
2) The value of R4 has been conservatively set for 18K to avoid the possibility
of excessive Hydrogen gas build-up while charging. Remember from before
LABC1 • 18
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that R4 is used in the SOC feedback loop that varies the charging terminal
voltage in accordance with the battery’s present state. Lowering the value of
R4 to 15K or less will have the effect of increasing the mode differential
voltage. Initially the battery will be charged at high current levels and the
terminal voltage of the charger will be pulled low by design. When the battery
begins to draw less current, the terminal voltage will gradually increase to the
maximum determined by the value of R4. Using a higher ‘Charge’ voltage will
decrease your charging time but you must keep in mind that cell gassing
normally begins at 14.4V and higher at 25°C, so doing this is risky. Great care
should be taken to avoid possible gas build-up inside the battery. See the
Safety Considerations section before operating your LABC1.
3) Another point to cover is the type of hook-up wire used to connect your
LABC1 to your battery. The wire provided with your kit works well for hobbyist
type batteries but you may wish to increase the wire gauge if you plan on
working with large capacity batteries or longer wire runs. Make certain to color
code any wire you intend to use to avoid polarity problems. The colors Red
(Positive Battery Terminal) and Black (Negative Battery Terminal) work well
and help to ensure no harm will come to you, your battery, or your charger by
hooking the system up backwards.
LABC1 • 19
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TROUBLESHOOTING GUIDE
If your LABC1 does not work correctly after construction, recheck the
following:
•
•
•
•
•
•
correct orientation of VR1, and U1 (see PC board layout diagram)
correct polarity of electrolytic capacitors
correct orientation of diodes D1 to D17
correct orientation of transistor Q1
No shorted traces on the bottom side of the circuit board
all solder connections.
Hints
Erratic or unstable operation is generally caused by faulty solder joints or
•
cable connections.
Replacement components may be ordered directly from Ramsey Electronics,
Inc. but records show that failure rates for these parts are extremely low.
Please understand that it is nearly impossible to “troubleshoot” by phone. Any
specific questions should be documented and sent to us by email or snail-
mail. Email questions should be sent to [email protected].
LABC1 • 20
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CONCLUSION
We sincerely hope that you enjoy the use of this Ramsey product. As always,
we have tried to compose our manual in the easiest, most user-friendly format
that is possible. As our customers, we value your opinions, comments, and
additions that you would like to see in future publications. Please submit
comments or ideas to:
Ramsey Electronics Inc.
Attn. Hobby Kit Department
590 Fishers Station Drive
Victor, NY 14564
your observations to other kit enthusiasts as well.
And once again, thanks from the folks at Ramsey!
LABC1 • 21
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Don’t you hate it when people do this? Why don’t they just admit that they ran
out of things to say!
LABC1 • 22
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The Ramsey Kit Warranty
Please read carefully BEFORE calling or writing in about your kit. Most problems can be
solved without contacting the factory.
Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too!
All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual
is your assurance that a team of knowledgeable people have field-tested several "copies" of this kit
straight from the Ramsey Inventory. If you need help, please read through your manual carefully.
All information required to properly build and test your kit is contained within the pages!
1. DEFECTIVE PARTS: It's always easy to blame a part for a problem in your kit, Before you
conclude that a part may be bad, thoroughly check your work. Today's semiconductors and passive
components have reached incredibly high reliability levels, and it’s sad to say that our human
construction skills have not! But on rare occasions a sour component can slip through. All our kit
parts carry the Ramsey Electronics Warranty that they are free from defects for a full ninety (90)
days from the date of purchase. Defective parts will be replaced promptly at our expense. If you
suspect any part to be defective, please mail it to our factory for testing and replacement. Please
send only the defective part(s), not the entire kit. The part(s) MUST be returned to us in suitable
condition for testing. Please be aware that testing can usually determine if the part was truly
defective or damaged by assembly or usage. Don't be afraid of telling us that you 'blew-it', we're all
human and in most cases, replacement parts are very reasonably priced.
2. MISSING PARTS: Before assuming a part value is incorrect, check the parts listing carefully to
see if it is a critical value such as a specific coil or IC, or whether a RANGE of values is suitable
(such as "100 to 500 uF"). Often times, common sense will solve a mysterious missing part
problem. If you're missing five 10K ohm resistors and received five extra 1K resistors, you can
pretty much be assured that the '1K ohm' resistors are actually the 'missing' 10 K parts ("Hum-m-m,
I guess the 'red' band really does look orange!") Ramsey Electronics project kits are packed with
pride in the USA. If you believe we packed an incorrect part or omitted a part clearly indicated in
your assembly manual as supplied with the basic kit by Ramsey, please write or call us with
information on the part you need and proof of kit purchase.
3. FACTORY REPAIR OF ASSEMBLED KITS:
To qualify for Ramsey Electronics factory repair, kits MUST:
1. NOT be assembled with acid core solder or flux.
2. NOT be modified in any manner.
3. BE returned in fully-assembled form, not partially assembled.
4. BE accompanied by the proper repair fee. No repair will be undertaken until we have received
the MINIMUM repair fee (1/2 hour labor) of $25.00, or authorization to charge it to your
credit card account.
5. INCLUDE a description of the problem and legible return address. DO NOT send a separate
letter; include all correspondence with the unit. Please do not include your own hardware
such as non-Ramsey cabinets, knobs, cables, external battery packs and the like. Ramsey
Electronics, Inc., reserves the right to refuse repair on ANY item in which we find excessive
problems or damage due to construction methods. To assist customers in such situations,
Ramsey Electronics, Inc., reserves the right to solve their needs on a case-by-case basis.
The repair is $50.00 per hour, regardless of the cost of the kit. Please understand that our
technicians are not volunteers and that set-up, testing, diagnosis, repair and repacking and
paperwork can take nearly an hour of paid employee time on even a simple kit. Of course, if we find
that a part was defective in manufacture, there will be no charge to repair your kit (But please
realize that our technicians know the difference between a defective part and parts burned out or
damaged through improper use or assembly).
4. REFUNDS: You are given ten (10) days to examine our products. If you are not satisfied, you
may return your unassembled kit with all the parts and instructions and proof of purchase to the
factory for a full refund. The return package should be packed securely. Insurance is
recommended. Please do not cause needless delays, read all information carefully.
LABC1 • 23
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LABC1 LEAD ACID BATTERY CHARGER KIT
Quick Reference Page Guide
Quick Battery Theory ....................... 4
Circuit description ............................ 6
Schematic diagram .......................... 8
Parts layout Diagram ....................... 9
Parts list ........................................... 10
Kit Assembly .................................... 12
Troubleshooting guide ..................... 19
Warranty .......................................... 23
REQUIRED TOOLS
•
•
•
•
Soldering Iron
Ramsey WLC-100,
Ramsey RTS12
Ramsey RTS05
Ramsey RTS04
Thin Rosin Core Solder
Needle Nose Pliers
Small Diagonal Cutters
<OR> Complete Soldering Tool Set RS64-2801
ADDITIONAL SUGGESTED ITEMS
•
•
•
Optivisor Magnifier Headband
Holder for PC Board/Parts
Desoldering Braid
Ramsey OPMAG
Ramsey RTS13,
Ramsey RTS08
TOTAL SOLDER POINTS
Price: $5.00
Ramsey Publication No. MLABC1
Assembly and Instruction manual for:
90
ESTIMATED ASSEMBLY
TIME
RAMSEY MODEL NO. LABC1
Beginner ........... 2 hrs
Intermediate .........1.5 hrs
Advanced .............1 hr
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
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