Electronics > Beginners
19V PSU charging 12V lead acid battery
nuclearcat:
Is it ok to charge lead acid battery by PWM controlled circuit powered by 19V PSU? (no typical step-down circuitry, such as inductor/capacitor, just MOSFET switching voltage on/off).
I plan to measure the voltage on the battery using the ADC + resistor divider, and increase the duty cycle until the voltage does not exceed the allowable for this type of battery.
Of course I will use PSU with soft overcurrent protection, such way i wont exceed allowed charging current.
Zero999:
Just one question: why?
A power supply with overcurrent protection, will likely not be designed to operate in constant current mode. The actual current limit could be higher than the rating and it much simply shut down, when it's exceeded, rather than regulating the current.
You need a constant current power supply for this to work properly, but it also needs to safely work open circuit. An LED driver might be more suitable, but why not simply buy a lead acid battery charger in the first place?
nuclearcat:
You're right, I'd rather make an additional discrete circuit to limit the charging current pulse. I just fear that even in a PWM mode, in a short pulse (the average current will not exceed the maximum) high momentary current will cause some harm to the battery...
Reason of such strange solution - 3rd world country problems, mostly.
I'm not looking for a way to make an efficient charger, but i hoped PWM will be a little better than a heater in the form of a linear adjustable regulator (like it is done in cheap APC UPS).
The end device is customizable DC UPS + load control, it is based on ESP8266, so most of parameters will be adjusted in software.
Since probably underqualified electricians will install it, i am trying to make the device as simple as possible. Unfortunately LEGO from different modules will not work in such case.
A maximum of three connectors, a battery (protection against reverse polarity), a power supply (barrel jack wont allow such mistake), and load (barrel plug, no mistake possible as well).
One of the requirements to the device - inexpensive. Existing devices are excellent electronic waste generators, with lithium batteries that sometimes explode, and often just die very early, additionally there is no supply of good quality lithium batteries in this country.
I want to make a device that will work with an available common power supplies and an affordable, replaceable lead-acid battery (lead-acid batteries are recycled here). Maybe it will be some 9V supply + 6V battery. Or laptop power supply (19V mostly) and 12V battery.
AVGresponding:
Perhaps a small automotive lamp in series with the PSU output?
More information would be helpful, like the output current of the PSU, the type of lead acid battery (wet, gel etc) and its capacity
KL27x:
I say why not?
With the battery on there, you have a buck converter, essentially. Car battery is not picky. As long as the PSU handles it, I don't see any problem.
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