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DaveJacko
Regular Member

Joined: 25/07/2019
Location: United Kingdom
Posts: 76

Posted: 10:18pm 02 Aug 2024

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Hi dudes, just popped over from the micro/picomite department.

I have purchased a small 12v solar charge controller off fleabay for sub ten dollars
great value no doubt
looks just the job for the deep northern hemisphere, ie Britain.
Wired it up to a PSU to have a play..

It shows 13.3 volts if I put 13v into it,
will this cause probs with real lead-acid batteries in the real world ??
took it to bits, no adjustments or pots..

thanks for any thoughts.. Dave

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 2129

Posted: 11:18pm 02 Aug 2024

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Some controllers will only produce their rated output voltage with a battery attached.

For a simple single charge rate unit the maximum battery voltage is usually about 13.6V to 13.9V. Below 13.5V won't charge it adequately. Above 14V will squeeze more charge in but if maintained for long periods may shorten the life of the battery.

A multi rate charger will vary the voltage depending on it's estimate of the state of charge of the battery.

To simulate a solar panel with a PSU put a high wattage resistor in series.
A suitable value would be the rated open circuit voltage of the intended panel divided by its rated short circuit current.
Rseries = Voc / Isc

Vary the PSU output from 0V to Voc while monitoring the battery voltage.

If you need to change the output voltage trace the circuit from the output to find the feedback voltage divider. Add a high value resistor across the upper leg to reduce the voltage or across the lower leg to increase it.

DaveJacko
Regular Member

Joined: 25/07/2019
Location: United Kingdom
Posts: 76

Posted: 08:31pm 03 Aug 2024

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Thanks, Phil,
I'll get the magnifying glass out !

DaveJacko
Regular Member

Joined: 25/07/2019
Location: United Kingdom
Posts: 76

Posted: 10:31pm 07 Aug 2024

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I had a look at these cheap modules,
in theory, they would would work great,
but the 0.3 volt error makes them useless with lead-acid, or any other technologies,
A suggested project for our micromite cousins
(do have a look, if you don't know about them, really interesting, helpful folk)
A PicoMite controlled solar charger, $4 plus a few FETs..
just a thought...

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