Battery 3 Stage Charger

Something like this↓? This is an interesting site.

Make this 3 Step Automatic Battery Charger/Controller Circuit

you can design a 3 current stages one for float charging (normal and slow speed charging with low current) medium stage and the Boost stage to charge the battery in higher speed .

Note:over current will melt or damage the plates .

I charge batteries with current-limited power supplies. They are also constant voltage. You set the voltage a little higher than what the battey is supposed to be. As the battery charges, the voltage goes up, so the current drops off. You could call that infinite steps.

Why do you want to re-invent the "wheel"? First what type of battery, flooded, gel or AGM, all require different methods of charging and maintenance. Second, what is the AH capacity (now called cold cranking amps) of the batteries. Flooded cell batteries for example can accept 50% of their AH capacity until approx 85% of capacity, then 10% until approx 95% and 1% for the remainder. Then of course you need some circuitry to detect float charge current and an occasional equalizing charge. You can buy one of these with a max 6 amp output for less than $40.00. Now if you're looking to charge from a solar panel(s), these are called charge controllers and are a lot more complex.

The first stage is to define exactly what the problem is in terms of numberical boundaries.

The second stage is to develop several options based on the parameters established above.

The third stage is to select the best option.

The fourth stage is to build that option.

The fifth stage is to commission that option.

The sixth stage is to review stages 1 to 5 and develop a better design in readiness for the next opportunity.