# Charge controller not charging battery



## watsonlarson (Jun 22, 2020)

Hi everyone,

This is my first post so apologies for any noob questions.

I have a very simple setup of 1x 100w solar panel with a pwm charge controller which came with it.

The panel works just fine and outputs 20v when I measure it but once the controller is connected and the battery is connected to the controller, I only get 12.2v from the battery terminals of the CC. Is that normal? Surely it should be more than 13v for it to be able to charge the battery? Currently, the battery is at 70% charge.

Many thanks for any help


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## Chiefster23 (Feb 5, 2016)

What is the battery voltage measured disconnected from the charge controller? If the battery is slightly discharged and the voltage only measures 11.5, then 12.2 would be fine for charging. But the charging voltage should go up as the battery charge approaches 100% until the charge controller senses the battery is fully charged, then it should stop charging completely.


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## Back Pack Hack (Sep 15, 2016)

Agreed... if your battery is discharged, the voltage may only be 11.8v or less. In that case, the controller is sensing that and only 'letting it have' 12.2 volts to bring it up. Once the voltage of the battery starts to rise, the charger should increase the voltage.


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## Elvis (Jun 22, 2018)

Back Pack Hack said:


> Agreed... if your battery is discharged, the voltage may only be 11.8v or less. In that case, the controller is sensing that and only 'letting it have' 12.2 volts to bring it up. Once the voltage of the battery starts to rise, the charger should increase the voltage.


Actually with the PMW type controller he has the controller is feeding the whole 20v through but the battery sucks the voltage down and the roughly 8v difference between the 20v the panels are putting out and the 12v the battery is wasted. That is why when using a PMW type controller it's important that the panel not be rated more than about 180% of the battery voltage. The extra voltage is wasted because a PMW controller can't take the extra voltage and convert it to extra amperage. 
Since a 12v battery needs about 15v to fully charge the 20v his panels are putting out is about perfect for efficient charging of a 12v battery.


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## MisterMills357 (Apr 15, 2015)

Hmmmm.....this might as well be written in Sanskrit....cause I don’t know what any of it means. 
But I figured that I would venture away from General Talk......and now my head hurts. :vs_rain:


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## Elvis (Jun 22, 2018)

MisterMills357 said:


> Hmmmm.....this might as well be written in Sanskrit....cause I don't know what any of it means.
> But I figured that I would venture away from General Talk......and now my head hurts. :vs_rain:


Yea, it took me a while to figure this solar stuff out beyond the Harbor Freight level. Just trust me when I say I understand the solar stuff. Below is a bit of information from my old business website using an alternator instead of a solar panel to make the electricity that may help you understand.

Imagine that your 12v alternator is a pump and the faster it spins the more water (or watts) it pumps and it pumps at higher pressure (or higher voltage). If it pumped it straight up a pipe it would pump it up well over 100' (or 100 volts) before it reached the end of it's abilities but at 100 feet (or volts) something would probably break or burn out because the system wasn't designed for that much pressure or voltage. What if at 13.6 feet up the pipe we put in a huge water tank ( battery). It would hold the water level (voltage level) at about 13.6 feet or 13.6 volts for a long time until it filled up. The water tank (or battery) is your "load" holding the voltage around the desired 13.6v. But once the water tank is full the water would keep going up making higher pressures (or voltage) unless we put a switch box with a valve to send any water (or electricity) over 14 feet (or 14volts) up the pipe out a hole in the pipe so that the water (or voltage) can't get over 14 feet (14 v) protecting the system from too much voltage. The switch box would be called a load controller and it reads your battery voltage and when it sees the voltage getting too high because the battery is full it sends the extra electricity to a load dump which like the hole in the pipe 14 feet up dumps extra water (or electricity) away. Most systems use electrical heating elements for the dump load to dissipate the extra electricity as heat. Sometimes you may use electricity from the battery lowering the voltage and the controller switches back to sending the electricity from your alternator to the battery refilling it for you.

In this very simple example voltage is like water pressure. The higher up the pipe the water goes the more pressure created. Watts are like water volume. A watt is a watt just like a gallon is a gallon. It may be under more pressure (higher voltage) but it's still 1 watt. Amps are a measure of the total flow (watts / volts = amps) through the wire or pipe. Higher pressure would move the water faster increasing the total amount of gallons (or watts) moving through the pipe and higher voltages (higher pressures) will move more electricity through a wire. Too much power will burn a wire out.

If you use a 12v battery the system will settle at about 13.6 volts. With a 24v battery the system will settle at about 26.8 volts until the batteries get full and the extra energy needs to be dumped. Most of the charge controllers I sell can be set for either voltage (even 48v) protecting your battery.


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## Weldman (Nov 7, 2020)

And the higher the voltage the more efficient a system can be as to not loose amperage down the line. Marine wire has more wires than strands per gauge than SAE wire or any household wire which also helps with efficiency as heat is a energy sucker. Want to jump down a rabbit hole go visit Midnite charge controllers website, it has a forum included there along calculators for their charge controllers. 
So what’s the 100 watt panel for, keep a battery tickle charged?


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## Elvis (Jun 22, 2018)

Weldman said:


> And the higher the voltage the more efficient a system can be as to not loose amperage down the line


No. Higher voltage minimizes watt loss and allows you to use smaller wire because higher voltage means lower amps for the same amount of watts.

Don't mean to sound negative but remember. Volts X Amps = Watts.


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