PowerFilm Solar Inc

When To Use A Charge Controller

Posted on 02/09/2018 at 12:00 AM by Daniel Stieler, Phd

When To Use A Charge Controller Blog Post Title Graphic


When do I need a charge controller to charge a battery with a solar panel?


This is a very common question and one that is absolutely crucial.


In most cases you will need some type of a charge controller to safely charge a battery pack. This prevents overcharging and reduction in the battery life of the system.


Battery technologies such as Lithium Ion, Lithium Iron Phosphate, Nickel Metal Hydride, or Nickel Cadmium always require a charge controller to safely recharge the battery pack. Lead acid batteries are the exception to the rule. If you are trying to charge a lead acid battery quickly or using a large solar module you will want to have a charge controller to keep the battery from overcharging and drying the electrolyte in the battery.  


If you are using a solar module for a low current maintenance charging this can be done safely without a charge controller as long as the solar panel output is <1% of the battery capacity. For example, if you have a 12V, 100Ah battery this could be safely trickle charged with a panel capable of supplying up to 1A at 13.4V.  

By the nature of how solar will cycle on and off each day as the sun rises and falls not all charge controllers will be safe for lead acid or AGM batteries if solar is used.  


Most notably, chargers using a three stage charging algorithm will slowly dry out the battery once it has reached a full charge. The reason for this is that when the solar starts producing power each morning the charger will start at stage 1. It will quickly switch to stage 2 since the battery voltage is high indicating a close to full charge. During stage 2 the charger will top off the battery and balance the cells by taking the battery voltage up to 14.3-14.6V, which will take a few hours. After that is achieved the charger will move to stage 3 which is a float voltage maintenance charge at 13.4V with a trickle of current.


It is the high voltage cell balancing that occurs in stage two that causes the battery to dry out and reduces its lifetime. Three stage chargers work very well when they are connected to the grid and only take the battery through stage 2 once and then hold it in stage 3. It is the repeated cell balancing in stage two that occurs due to the daily on-off cycling of the solar that destroys the battery.


Charge controllers aren’t just something that is nice to know about. They could very easily be a part of your system and one that you must utilize to avoid damaging your battery.

Do you need a custom solar solution for your application?


We would love to be a part of your next project.


We will talk through your design, setup and ensure that you get the best possible performance from your solar, battery and charge controller helping you create a fantastic system.


Let’s start the conversation today. Email Marketing and Communications Manager, Seth Hansen, at: shansen@powerfilmsolar.com.


We look forward to learning about you project and partnering with you to meet your unique needs.


Contact us or leave a comment below. 


Categories: Solar Education

Yesudas, You are most welcome! Please don't hesitate to reach out if you need anything at all.
Seth Hansen | www.powerfilmsolar.com | 04/12/2021 at 08:12 AM
Thanks for Information.
Yesudas Selvarajan | 04/10/2021 at 08:53 AM
Natalie, That is correct! A charge controller is incredibly important in keeping your batteries safe and also for delivering the most power from your solar panel!
Seth Hansen | www.powerfilmsolar.com | 07/13/2020 at 07:20 AM
Thanks for useful information you provided. It help me understand a solar charge controller is a useful component in maintaining the health of your batteries. Is that right?
Natalie Roberts | 07/13/2020 at 06:17 AM
Thanks for the kind words. It's our pleasure. Please let us know if there is another topic you would like to learn more about.
Seth Hansen | www.powerfilmsolar.com | 01/31/2019 at 07:28 AM
this post contain a huge information about how to use charge controller for solar panels. this may help those who are unknown about this matter. thanks for sharing this with all...
Inexpensive Solar | 01/31/2019 at 07:12 AM
You are more than welcome. Thanks so much for reading the post!
Seth Hansen | www.powerfilmsolar.com | 01/07/2019 at 11:10 PM
thank you for the comprehensive article, learnt a lot
zhcsolar | 01/06/2019 at 01:05 AM
Thanks so much for your comment. Can you tell me a little more what you mean by "the whole bank?" Look forward to assisting you. Please feel free to also email me directly at shansen@powerfilmsolar.com.
Seth Hansen | www.powerfilmsolar.com | 12/10/2018 at 07:19 AM
is there a charge controller that can handle the whole bank?
ironedison | 12/10/2018 at 06:37 AM
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