Understanding lead-acid battery charge

Question

I´m trying to understand how lead-acid batteries charging work. So far what I tested:

1. If a 14 Vdc supply is connected in a 12 Vdc battery, the voltage will drop to the battery level, and start going up until it reaches the supply voltage ( Why is this happening? ). The current will start at the maximum value that the supply can provide ( if not limited ), and will drop until the charge is finished, let´s say 1% current of total capacity. But then when the charger is disconnected, the voltage drops a few volts ( Why is this happening? ).

2. If a constant current supply is connected to a 12 Vdc battery, the voltage will be determined by the battery. The current should be specified by the manufacturer, for putting values let´s say 10% of the total capacity. If total capacity is 100 Amp/H, it will be charged at 10 A.

As far as I know, the best way to charge a battery is CCCV, wich will involve a first charge with CC and then 2 step charges with CV. Can I buy a SMPS supply like the one below (15 V one), and charge a 12 V 200 A battery with constant voltage? How much current will it draw if it´s connected directly to the battery? If I want to charge it with constant current. Can I use the same supply with some type of circuit to make constant current charge? What circuit should I use ( considering that the battery has to be charged at 20A maximum and 15 V Max) ?. Obviously this is very poor data, but is only for the power, it will be around 300W.

https://qiniu.aipulnion-power.com/uploads/media/20240118/1-24011QH625122.pdf

I´m open to adding more data, it´s a very wide question, but I´m asking for general answers, not a specific charge circuit.

Answer 1

1. When you first connect your supply to the battery it is acting as a constant current supply with the constant current being the maximum current it can supply. When it reaches this current it reduces the voltage it is supplying.

As long as your supply is capable of doing this and the maximum current is within the battery charge current specification this is fine.

When a battery is removed from charge its voltage will drop this is normal for all battery chemistries. Essentially some of the voltage being supplied during charge is being used to drive the electrochemical process charging the battery.

The supply you buy should have a maximum current which matches your desired battery charge current and be capable of supplying this for extended periods of time. Its voltage output should match the batteries absorption voltage. This will give you a two stage charge you then need a method to drop the output to the float voltage for the third charge stage.