Battery Charging Tips

Battery Charging - Remember you must put back the energy you use immediately. If you don't the battery sulfates and that affects performance and longevity. The alternator is a battery charger. It works well if the battery is not deeply discharged. The alternator tends to overcharge batteries that are very low and the overcharge can damage batteries. In fact an engine starting battery on average has only about 10 deep cycles available when recharged by an alternator. Batteries like to be charged in a certain way, especially when they have been deeply discharged. This type of charging is called 3 step regulated charging. Please note that only special SMART CHARGERS using computer technology can perform 3 step charging techniques. You don't find these types of chargers in parts stores and Wal-Marts. The first step is bulk charging where up to 80% of the battery energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger. When the battery voltage reaches 14.4 volts this begins the absorption charge step. This is where the voltage is held at a constant 14.4 volts and the current (amps) declines until the battery is 98% charged. Next comes the Float Step. This is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries but will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. Some gel cell and AGM batteries may require special settings or chargers.

Battery Charger Ideas

Here is the schematic for the automatic charger I have been using for my kids' battery cars. The charger is a small molded unit that probably doesn't supply more than an amp and this circuit would have trouble with much more. No current limit is provided by this circuit - it relies on the charger for that. The circuit could be modified to provide more current by lowering the 470 and 330 ohm resistors in the 5195's base circuit and the 10k in the collector of the 4401. A relay could also be used in place of the pass transistor.

Here is how it works: When the battery voltage is low, the voltage at the base of the first 2N4401 (on the right) is not sufficient to turn it on and the second 2N4401 is biased on by the 10k resistor. The power transistor is turned on and the LED lights. When the battery is fully charged the voltage will exceed a somewhat arbitrary "over-voltage" value slightly below 14 volts and the regulator will switch off. The 470k feedback resistor gives the circuit some hysteresis so that it will not turn back on until the battery voltage drops below about 13.5 volts. When the battery is nearing full charge the light will begin to flash on and off and after a few hours the light will only come on occasionally. This occasional over-voltage jolt sure seems to keep the batteries in great shape.


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from :: http://www.techlib.com/electronics/battery_chargers.html

How to use Battery charger

The battery charger created this time is equipped with voltage control and current control.
Usage is shown below.

First, full charged battery is prepared.
This is for setting up a voltage control circuit. If there is no full charged battery, it will charge about one day with about 300mA current or more.
Depending on the condition of a battery, it still may not become full charge.

Setup of the charging current

(1)	Make the knob for current control into the minimum (full of left).
(2)	Make the knob for voltage control into the minimum (full of left).
(3)	Short-circuit the output of a charger.
(4)	Turn the knob for current control to the right until the charging current is set to about 300mA. I think that a problem does not have even a 500mA setup. I am making it little current, in order to charge a battery for a long time.
(5)	Connect a charger to a battery.

Setup of the over charge prevention voltage

(1)	Turn the knob for voltage control to the right until the charging current is set to about 100mA. Because the latest car consumes current also in the condition where it is not used, it leaves the part.

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Charge circuit at the side of a car

When connecting a charger with the battery of a car, it is troublesome to open the engine room cover each time.
Then, I prepared the easy charger connection circuit for the car side.

I attached this connector in the frame of a windshield. I don't know what this portion is called in English.

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I am not the specialist of a battery. Therefore, I don't know what the charging current is suitable, and this over charge prevention circuit is effective, or not.
From now on, I will add a postscript, if it may be consulted by the used result.