Simple Circuit to keep a Battery Topped Up

Think of a battery like water tank for our device.

This Simple Circuit to keep a Battery Topped Up is like a helper.

It checks battery level and gives charge when battery gets low.

Battery stays full and is ready always which is good for backup power, solar lights and for wireless toys.

Circuit Working:

This charger keeps battery almost full.

It uses 7 parts and works with 12V to 18V DC plug pack.

Plug pack should give over 15V without load and mostly 12V packs do this.

It is good for 1.2Ah gel cell to 45Ah car or boat battery.

And can stay connected long time without battery losing water.

It gives 13.2V output which is enough to stop battery from draining.

But it charges very slowly which is not good for flat batteries.

Normal charge needs around 13.6V with higher current.

Old car batteries accumulators and sealed gel batteries are a bit different.

Gel cell does not make gas until voltage gets high that is why it is sealed with rubber caps like safety hooks.

So charge voltage must be limited and current must drop when battery is full.

Below are the formulas for keeping battery topped up:

Formula:

Vout = 12 + (0.6 × number of diodes)

Example:

= 12 + (3 × 0.6) = 13.8V

To build a Simple Circuit to keep a Battery Topped Up following are the connection steps:

Connect IC 7812 input pin to +15V DC supply.
Connect IC ground pin to ground through 3 diodes 1N4004 in series.
Connect IC output pin to batteries positive terminal through1 diode 1N4004 and two 10 ohm resistors in series
Connect batteries negative terminal to ground of power supply.

Note:

This easy and Simple Circuit to keep a Battery Topped Up keeps battery full using IC 7812, resistors and diodes.

It gives steady charge and helps battery live longer and work better.