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Gel Cell Battery Charger Circuit

Normal car battery has liquid inside.

Gel Cell Battery Charger Circuit uses jelly but not liquid.

Jelly make battery strong and work in any position.

To charge gel battery we need special charger.

This charger gives right power but not too much.

Too much power can hurt battery.

Special charger keep battery safe and good.

Circuit Working:

Parts List:

CategoryItemQuantity
Resistors (All resistors are 1/4 watt unless specified)470Ω, 2.2k1 each
Rx = 0.7/max current1
Preset 5k1
CapacitorCeramic 100nF1
SemiconductorsIC LM3171
Transistor BC5471
LED Red 5mm 20mA1
12V Gel cell battery1

This circuit charges gel battery with 300mA, 650mA or 1.3A.

It depends on resistor in 0V line.

To set 13.4V output, adjust 5k preset.

When battery reaches 13.4V current goes down to very low.

If we want 650mA or 1.3A then we need better plug pack.

Red LED means charging.

As battery voltage goes up the current goes down.

LED turns OFF when current drop about 5%.

After that current slowly goes to almost zero.

Formulas:

We can use this formula to find output voltage Vout for LM317 circuit:

Vout = 1.25V × (1 + R2 / R1)

where:

Note:

Adjust pin (Iadj) has very small current of 50 microamps so most time we ignore it.

That is why formula does not use it.

Use resistors with 1% tolerance for better result.

More things:

Lowest voltage LM317 can give is around 1.25V

Max voltage depends on input voltage and dropout 2 to 3V less than input

To find R1 and R2 values more steps are needed.

How to Build:

To build a Gel Cell Battery Charger Circuit follow the below mentioned steps for connections:

Design the Circuit:

Power Supply Section:

Voltage Regulator Section:

Current Limiting Section:

LED Indicator:

Test the Circuit:

Monitor Charging:

Safety Tips:

Conclusion:

This Gel Cell Battery Charger Circuit is made to charge gel battery safely.

It has transformer, rectifier, voltage control and current limiter.

It keeps battery safe and works well.

References:

Arduino gel cell charger

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