I want to do an experiment with a battery I have. I have 200AH 6v lead acid battery and I want to charge it with maximum current the battery can take in bulk stage, then in float or acp. stages, I want to reduce the current, but clamped the voltage applied to the battery. so I decided to use a zener diode parallel with the battery (let say also the power supply I have is the only has Constant current mode). this way I can charge the battery with max current in bulk stage and in next stages with voltage clamped to zener diode voltage (let say voltage of zener diode is 6.8V) and then I reduce the current with the voltage being constant. so I am looking into the specification of this zenar diode. since I am working with high current, I don't know how to choose the right 6.8V zenar diode? .