make the harbor freight 45w solar panel charge controller useful with a simple mod.

by:Tunto     2020-04-15
Like many of us who are interested in solar energy, I spent about $150 on a 45 watt solar panel kit for port cargo with three solar panels and a charging controller.
It was an exciting moment a few months ago when I set it up to see the front panel light up.
I thought I got enough solar to charge my SLA Battery.
However, excitement is short-lived.
I stupidly thought that the lights for the first night were powered by solar and forgot the fact that the battery was fully charged before I connected the battery to the solar panel.
As many have discovered, the charging controller doesn\'t seem to work as we expected.
For example, I used to have 12 SLA batteries. 5 Volt.
During the day, the front panel shows about 13-
14 V, so I turned on the charging controller, but when I came back from work, I found that the battery was not charged at all.
In fact, the voltage will drop by about 0.
1 Volt becomes 12 volts. 4 volt.
What\'s going on?
I search for answers on the Internet as usual, but most people just complain that this particular charging controller is not efficient or can only be used as a distribution device.
In order to get a better charger, people need to invest another $100.
Basically, the solar panel kit is only suitable for the display concept (
I have to say that the charging controller looks good and strong from the outside).
Recently I had some free time and started to diagnose this charging controller and I found that while it does charge during the day, it will discharge as the sun goes down.
I suspect that when the voltage of the solar panel is lower than the voltage of the battery, it may discharge.
I am not sure about this because I have not turned on the device to view the design.
If you turn this device on, it will discharge around 30 mA at night (
The LED display uses power unless you turn off the suggested LED display).
One experiment I did was to add a blocking diode to the back of the charge controller.
I initially put the diode on the battery side, but as suggested by \"evilmunkey\", the diode should now be on the side of the solar panel.
The diode I use is 1N5822 and it happens to be in my toolbox, so I think many other diodes will work as well.
1N5822 can handle 40v 3A, so I use two of them in parallel to make sure it can handle the current from the solar panel.
Also, make sure that the cathode lead of 1N5822 should be connected to the charging controller side, while the anode should be connected to the solar panel side.
Previously, I tried to put the diode on the battery side, but I was worried that it might overcharge the battery, so now the diode is on the side of the solar panel.
My SLA Battery is better charged after modification.
Since I don\'t know the charging circuit inside the box, the effect of this added barrier diode on the charging of solar panels and batteries is not clear.
In theory, the charging controller should already have a blocking diode on the side of the solar panel, otherwise it will return all solar energy at night.
The final solution is to look at the components in the box and see what it is doing.
There are many kinds of controllers that work differently.
I think it\'s a PWM type, but I really don\'t know.
For example, does it have a micro-controller that controls the voltage?
How about current limit?
With all the unknowns in mind, I won\'t risk charging any expensive batteries.
In my case, I rescued some of the old 12v SLA batteries by refiling them with Epsom water.
I also put the battery outdoors in case it leaks.
So far, it works fine and the battery has actually recovered to a certain extent.
This is largely an experiment, so be careful not to overcharge.
Finally, make sure to add an online fuse near the battery terminal (such as 5A).
It would be better to stand on the safe side.
Please let me know if anyone has better suggestions for improving this unit.
I may open this box in the future and write another structure later.
For now, I need to continue working on the next project using desulfator.
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