Just for reference - Alza dry cell 12 volt lead acid battery. This is no jokes the price keeps increase each year i buy them the last time i got this Hyundai Dry Cell Type A was RM200 and after more than a year till now i have to replace it using GP battery and it cost RM230
Hyundai Dry Cell 12 volt 42 Amp Hours Class Type A battery
As you can see how much voltage left - just 2 volts ++ around 10.7 volts the battery is already useless. So much wasted 10.7 volts is still a lot of voltage can could power pone charger. I was thinking of making step up voltage circuit for DC to DC to get back 12 volt from the dead battery at long as the voltage still around 10 to 8 volts.
Brand new GP battery is 12.54 volts cost RM230
Battery Air Lead Acid Perodua Alza, Bezza, MyVi, Kancil