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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.
•
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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 Sa
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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 measur
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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)
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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 (Val
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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 con
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LABC1 • 8
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LABC1 PARTS LAYOUT DIAGRAM LABC1 • 9
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PARTS SUPPLIED WITH YOUR LABC1 KIT Capacitors 1 10 µF electrolytic capacitor [C2] 1 1000 µF electrolytic capacitor [C1] Resistors and Potentiometers 1 0.47 ohm, 1 watt (yellow-violet-silver) [R6] 1 270 ohm (red-violet-brown) [R1] 3 820 ohm (gray-red-brown) [R3,7,9] 1 10K ohm (brown-black-orange) [R8] 1 18K ohm (brown-gray-orange) [R4] 1 PC mount 1K ohm potentiometer (marked 102) [R2] Semiconductors and Integrated Circuits 11 1N4148 diodes (smal
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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 t
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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 orientati
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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 jump
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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. 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. 15.
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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. 2
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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
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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 t
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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
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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 va
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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. R
