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Voltage regulator issue?

Jagalag

Jan 9, 2021
3
Joined
Jan 9, 2021
Messages
3
So I'm trying to keep my car battery charged while it's in storage for a year at my mechanics lot.

I got a 20w solar panel to function as a trickle charger, and a voltage regulator. (Both pictured) The panel puts out upwards of 25 volts in full mid day sunlight. This would be bad for the car battery and gas it out, so I got the voltage stabilizer to supposedly keep it at 12 volts.(IN: 5-32v, OUT: 12v 3 amp MAX) The idea was to splice it inline on the alligator clip leads.
It was evening when I tested it. I shone my car's high beams on the face of the panel. Direct source voltage was reading 18.3 volts on the alligator clips. I attached the clips to the input leads on the regulator/stabilizer, and tested voltage on the output, and it only read 3.2 volts.

My concern is that the regulator might only convert to a trickle 12v voltage in the mid day sunlight when the panel is producing 25+ volts, which is not a long time to maintain charge. Is this an wrong assumption? Did I test the setup incorrectly? Should I go with a different solar product and return both of these? I'll try it again tomorrow afternoon.e7f4c69f-bca3-49ee-8b0d-226c4ed6e7c9.9585435e8babc19c9af5e95c1c40fcf7.jpeg 51jTFogHzwL._AC_SY780_.jpg
 

crutschow

May 7, 2021
520
Joined
May 7, 2021
Messages
520
!2V will not maintain the charge on a lead-acid battery (who's nominal full-charge voltage is 12.6V).
From Battery University:
The recommended float voltage of most flooded lead acid batteries is 2.25V to 2.27V/cell. Large stationary batteries at 25°C (77°F) typically float at 2.25V/cell. Manufacturers recommend lowering the float charge when the ambient temperature rises above 29°C (85°F).
Thus you need about 13.5V to 13.6V to maintain a 12V lead-acid battery.

Can your regulator be set to that voltage?

If not, an easy way to regulate the voltage is with an LM317 regulator set to the desired output voltage.

It was evening when I tested it. I shone my car's high beams on the face of the panel.
That puts out only a fraction of the optical power that sunlight does (your eyes have a logarithmic response to light and are a poor judge of absolute brightness).
Do the test with sunlight.
 

Jagalag

Jan 9, 2021
3
Joined
Jan 9, 2021
Messages
3
I bought a Harbor Frieght voltage regulator. Seems to be charging the battery on my other car when I tested it in broad daylight. Going to hook it up on the stored vehicle and hope fo the best.
 
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