Grumpy_Mike:
Why can you not just charge a lead acid battery with a constant voltage of 14.1v
Because it will then take too much current.
You need a current limiting source until it reaches 14.1V AND then you do not increase the voltage any more.
Ok I get what your saying. But if I have a power supply that is 14.1v and supplies a maximum current of 100mA then it will be fine provided the 100mA is not more than 20% of the battery capacity? The charger might just get hot because it's working at its maximum rated capicity?