Ramsey Electronics Battery Charger LABC1 User Guide

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?  
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!  
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  
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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  
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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.  
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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!  
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!  
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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  
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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.  
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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 Krispieswith 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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This page intentionally left blank.  
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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