Charge The Battery
Connect a digital voltmeter to the battery. As the charger charges the battery you will notice the voltage rise. The cutoff adjustment should be made when the battery is charged. You may use our factory default cutoff of 14.5 volts or whatever your battery supplier recommends.

Find A Keeping Point And Adjust From There
The charger enters the keeping mode when the ammeter needle starts to flicker around the zero mark. If the charger enters the keeping mode before 14.5 volts go to the next paragraph. If charging continues to 14.5 volts, turn the adjusting screw slightly counterclockwise until the needle flickers around the zero mark, indicating keeping.

Wait For Equilibrium, Adjust, Repeat As Desired
Wait a few minutes for the voltage to stabilize, allowing the battery and charger to come to equilibrium, balancing current in to current out. You are now at a keeping point. If the voltage is not what you desire, adjust the screw slightly, wait for the voltage to stabilize. (The time to wait will be longer with a larger stiffer battery.) Repeat small adjustments, raising or lowering the voltage until you have the keeping voltage you desire.

Compensate For Temperature Different From 25 deg C
Our default set point is at 25 degrees C. If your ambiant temperature is higher than 25 deg C, the cutoff voltage must be reduced 4.37 mv/degC for each battey cell. If your temperature is lower, then the cutoff voltage must be corrected by adding 4.37 mv/deg C per cell.
Example: it's winter. Your ambiant temperature is 20 deg C. You must correct the set point by 5 degrees X 4.37 mv/degC per cell X 6 cells (in a 12 volt battery). This correction of 0.131 volts must be added to 14.5 (which is the cutoff voltage at 25 deg C). Thus the keeping voltage should be set to 14.63 to correct for the cooler ambiant temperature.

The Charger Is Temperature Compensated
As the ambiant temperature rises and falls, the charger is smart enough adjust the keeping voltage in the correct direction. However you might want to check the keeping voltage set point once in summer and again in winter. That way you will also compensate for changes in battery characterisitcs due to age.

Dead Battery Charging
The charger is designed not to start on a battery with voltage below 7.5 volt (for a 12 volt charger) to prevent runaway charging if accidentally connected to a 6 volt battery. Thus if you discharge your battery below 7.5 volts, the charger will not start. Note: discharging to this level reduces battery life. To start charging, apply a voltage to charger clips while they are connect to the battery. You can use a little nine volt radio battery for this purpose.

Float charging
You may adjust the cutoff voltage to be below the gassing point of the battery for long term float charging. Check the battery manufacturer's recommended float voltage. As a starting point use 13.8 volts for a 12 volt battery. When set below the battery's gassing point you may leave the charger on for long periods of time. When you draw a load from the battery the charger will turn on providing it's full output current to help meet the demand of the load, preventing battery discharge. If you find that the battery is losing water at the float set point you have chosen, reduce the float a tenth of a volt. As a battery ages you may find that the float voltage needs to be reduced to prevent water loss. When you first set up for float charging, check the water level in the battery frequently, perhaps every few days. If you have a sealed battery you have to hope that the recommendation you get from the battery supplier is correct.

Load Shedding And Long Term Storage.
The charger will draw 20 milliamps from the battery if AC power is turned off. If you plan to store your equipment for a long time with the charger connected to the battery, but unplugged from the AC, you should think about disconnecting the charger from the battery. In two and a half months you will have drained 34 ampere hours from the battery. This isn't a problem if you use your equipment regularly, but if you were to store it over a summer, with the charger connected but unplugged, the battery would be discharged after a few months.

Notes
This charger is polarity and short circuit protected. This means that if you touch the clips together there will be no sparking as in ordinary chargers. That if you try to measure the open circuit voltage at the charger clips you will find no voltage, zero. It will not turn on until the clips see at least 7.5 volts of the correct polarity. Some people will call us and say it doesn't work, there's no voltage at the clips. It takes a while to realize it was designed that way.

It is important to connect the charger directly to the battery, not to some wiring point away from the battery. Losses in such wiring will confuse the charger circuitry. Also do not shorten the charger's DC output cable.

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