solar panel discharging battery

The most absurd work of a solar panel-discharging a battery

If you own a solar setup or if you are a outdoor person who carries around  a solar charger for your outdoor trips, it’s most likely that you would have seen the solar panel go bonkers sometime or the other.

Imagine a situation when the mobile phone battery shows up to be 30% charged, you want to be the nice guy to your phone, you connect the device to the solar charger. After a couple of minutes being connected to the solar charger it shows up to be 25% charged and you start blaming the phone for it.

The similar situation in case of a solar setup in your house, the battery connected to a solar panel has lower voltage in the morning compared to previous day night.

Sound little too familiar?

The answer is YES in either case the solar panel/ solar charger is most likely discharging the battery (There is a possibility that your smartphone is acting equally weird). I’ll get back to why it’s possible in the case of solar charger in a minute, now let us dive into solar panel.

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Can a solar panel discharge a battery?


If you found out the problem by yourself, here is a virtual high-5 to you for your observation skill. Trust me, most of them never figure it out the fact that solar panel can leach energy from the battery.

In solar home setups there are namely 2 common types of setups-Grid-tie setup and off-grid setup. In either cases this problem can occur. In one case it’s clearly visible and in other, not much.

If you own a grid-tie setup, you’ll be able to figure out the decrease in battery voltage and you’ll find out that the solar panel has been up to something.

The fishy part about off-grid setup is that, you may not even find out that the solar panel is leaching the battery. The reason being when you are completely off-grid you will use the battery’s energy in the night, say for air conditioning.

Hence the loss in energy(leaching) from the battery due to the solar panel will be masked, like a green bug on a leaf. When you get up in the morning and check out the voltage of the battery, it will seem perfectly normal but only the poor battery would know that the helper guy called solar panel is not helpful after all.

What is the reason for the leaching of the battery?


When you look into this issue you can find that, in the morning when your solar panel is connected to the battery, everything works as expected.

When the solar panel is exposed to sunlight, the photon of sunlight knocks out the electron(-ve charge) of the solar cell and hence it acts as a source of electron and hence source of current.

Due to this release of electron, the solar panel system is at a higher potential than the battery. This difference in potential between the solar panel and the battery leads to flow of current from the solar panel to the battery. Nice and clean.

But in the night or even in the morning when the solar panel is shaded due to a tree or due to clouds, the battery will eventually have a higher potential than the connected solar panel(no flow of electrons for the solar panel). Hence the solar panel will start draining the battery, the amount of draining depends on the extent and duration of shading.

Now, how to prevent the draining of battery?


If you have already bought a solar panel and you found out that it has the problem, the good news is that there are 2 solutions to this problem.

  • Using a series diode
  • Using a LED

Before you start hunting for a diode, I got to warn you that this is not recommended DIY thingy. The diode is better off when it’s pre-installed in the solar panel.

Most of the solar panels produced today have a series diode to block the discharge of the battery. Sometimes a LED is also used to block the self-discharge. LEDs allow small forward currents and very low reverse voltages.

That’s the reason why panel array should have built-in diode. If not there would be significant drain from the battery through the panels under low/medium sunlight conditions.  The diode will maintain the panel’s voltage above the battery and thus prevent the back-flow.

There is one last solution to this problem, it’s more of a quick fix than a solution and it would require work from your side everyday!. Yup everyday.

The solution is you would have to disconnect the cables connecting the solar panel to the battery everyday before you go to sleep. This solution is not recommended until you know which cables to disconnect and only if you know your way(precautions) to handle with electrical equipments.

If you are yet to buy a solar charger/panel then all you need to do is just apply the geeky tip below.

Geeky tip: Next time when you buy a solar panel or a solar charger, try asking the manufacturer whether their products have “Reverse flow protected circuitry”. That’s the technical term these kids use for connecting an extra diode to the panel.

Can a solar charger discharge my phone’s battery?


The case with the solar charger is exactly same as with the solar panel. The only difference being in the case of solar panels it was a battery which was connected, here it’s a device namely an iPhone or an iPod. The solar charger drains the phone’s battery when it’s shaded. The solution here is also the same- add a series diode or a LED.

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Did the leaching of battery energy happen to you. I would love to hear from you in the comment section below. Also don’t forget to SHARE and LIKE the article.