Switch mode power supply as a float charger

[Mike M.]

I have a 12V 13A switch mode power supply that I'd like to connect to
a 12V lead acid automotive battery and use this combination to power
several amateur radio transceivers. The idea being that the battery
can supply peak current that exceeds the power supply rating and
provide emergency back up if power fails.

Is there anything I need to watch out for? Do I need a diode to
isolate the battery, or will the power supply rectifiers be enough? Is
13.8 V a good voltage to run the supply at? How critical is the
voltage setting?

 

[Jerry G.]

This is not a good way to charge a battery. The battery needs some headway
with current regulation. Normally the opened end voltage of a 12 volt
battery charger is about 14 to 15 Volts. The current has to be regulated.
The battery will seek it own level as it is charged. The charger must reach
a unity level, or trickle charge level once the battery is charged. It is
easy to boil over a lead acid battery if it is strongly overcharged.



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Greetings,

Jerry Greenberg GLG Technologies GLG
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I have a 12V 13A switch mode power supply that I'd like to connect to
a 12V lead acid automotive battery and use this combination to power
several amateur radio transceivers. The idea being that the battery
can supply peak current that exceeds the power supply rating and
provide emergency back up if power fails.

Is there anything I need to watch out for? Do I need a diode to
isolate the battery, or will the power supply rectifiers be enough? Is
13.8 V a good voltage to run the supply at? How critical is the
voltage setting?