19V to 12.8V Buck Converter

245

03:40:43

Possibly for charging or keeping charged a car battery.

published 7 years ago

BillyT

7 years ago

The basic ideas are good, but you need to do a bit more reseach on the voltages required for charging batteries.

jason9

7 years ago

Fully charged car batteries are 12.8V and my trickle charger for my generator is giving 14.25V open circuit voltage, so what’s the problem? This device’s open circuit voltage is 14V.

jason9

7 years ago

*13.9V, but still pretty good to me.

jason9

7 years ago

I changed the zener diode voltage so that the open circuit voltage is 14.2-14.3V.

hurz

7 years ago

I charge my lead acid with max 14.4V but mostly with max 13.5V if the voltage is below 11V i stop discharge to not damage the battery. In case the 6 cells are to different in voltage but the water and acid is ok, i charge at 15.0V to equalize/balance the cell voltage, but not to long, cuz you loss to much hydrogen. I think to keep the battery full and ready to use you have to go upto 13.5V all voltages below might not give you the full capacity. Billy?

BillyT

7 years ago

Ok after many years of looking after batteries, the following information is recommended as a guide. Basically, recommend auto battery charging voltage is14.2v with a 15.4v DeSulphation spike every10 charges. Float charge maintenance voltage is about13.8v, it is recommended to adjust this voltage to allow 1mA per Amp hour of battery capacity. This will keep a battery healthy for years.

hurz

7 years ago

For float charge i try to chrage below 13.5V which makes 2.25V per cell if fine balanced. This cell voltage seems to be a magic boarder to oxidation. So if installed in a car and always charged with 14.4V its good to take it out from time to time and do a float charged upto 13.5V over 48h and wise versa. If you do always float charge its good to do from time to time a higher voltage charge at 15V.

BillyT

7 years ago

@hurz, sounds ok to me, I've found that different batteries have different float voltages to achieve the 1mA / VA/h setting.

hurz

7 years ago

I dont agree to the cryptic unit mA/VA/h but i know what you mean something like 1mA/Ah. Currently im working with a handcrafted car battery lead acid and this thumb of rule does fit even for this battery type. It was sold as 75Ah but i measured with a fuelgaug about 45Ah this is after two days of float charge the current i get 50mA....

BillyT

7 years ago

@hurz, yes you are correct, I muddled my abbreviations.

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