The charge controller’s job is to regulate the voltage and current coming from the solar panels according to the battery. which keeps the batteries safe and will increase their lifespan. The Watt limit of the charge controller is the number of watts it can handle.

if you have a charge controller or looking to buy a 40 amp charge controller, in this blog post i’ll let you know the watts limit of it and what size solar panels will be suitable for them

**Upper watt limit of 40A charge controller**

**40 amp charge controller can handle 500 watts in a **12v solar system, 1000 watts (1kWh) in a 24v solar system, and 2000 watts (2kWh) in a **48v solar system**

Keep in mind that these are the maximum limits of watt you should connect with a 40A charge controller, but most of the experts recommend leaving an extra 20-25% room for safety factors.

which means you can connect 400w solar panels in 12v with 40a charge controller and 800w in 24v with 40A charge controller by leaving the 20% then its upper limit.

By leaving the extra 20% it can increase the lifespan of the charge controller and reduce the chances of damaging batteries and solar regulators.

40A charge controllers are mostly used in 24v solar panels systems. I recommend this Renogy rover 40A charge controller which can handle 12 & 24v solar panel system

Now let’s discuss how you can calculate the watt limit of any charge controller

## Video – Explaining the input/output watt limit of a charge controller

**How to calculate the watt limit of the charge controller?**

to calculate the watt limit of the charge controller we’ll use ohm’s law **charge controller Amps x battery’s volts = charge controller watt limit**

now let’s assume that we have a 40A charge controller and a 12v battery. as we know some of the 12v batteries can handle about 14 volts, but let’s make it 13v. so a 12v battery can handle 13v on average.

so a 40A charge controller will be putting 13 volts into the battery

40 x 13 = 520 watts

for 24v battery

40 x 26 = 1040 watts

This is the upper watt limit of the 40a charge controller. if you try to connect an 800-watt power of solar panels in a 12v array the charge controller will only pass 520 watts to the battery

which will cause a power loss and also can damage the charge controller or batteries

**40A charge controller watt limit (Examples)**

Now let’s see which brands offer 40A charge controllers and what their output watt limit

**Renogy Rover 40A**MPPT charge controller which can handle 12 and 24v solar arrays and the watt limit is 520 watts for 12v array and 1040 watts for 24v solar array**EPEVER**40A MPPT charge controller which can handle 12/24v system with the maximum watt limit of 520/1040 watts**RICH SOLAR 40 Amp**with the volt capacity of 12/24 DC input capacity and can handle 520/1040 watts of power**AIMS Power SCC 40A MPPT**which is can handle 12,24,36 and 48 volts of input which makes it upper watt limit for 12v 520 watts, for 24v 1040 watts, for 36v 1560 watts, and for 48v 2080 watts**AMPINVT****40A MPPT charge controller**can handle the input of 12/24/36/48 volts and the watt limits will be 520/1040/1580/2080 watts.

You get the idea, some of the charge controllers come with higher volt limits which will increase their watt limit of them accordingly

**Why does the input Voltage of charge controller** **matters?**

Every charge controller has its own input volt limit which will determine the watt capacity of a charge controller it can handle.

checking the input volt of the charge controller will give you an idea of whether you can use it for your solar array or not. choosing the right size volt charge controller is also important.

make sure to check the input volt of a charge controller or connect your solar panels in parallel or series according to the voltage limit of your charge controller.

i have explained in detail about connecting solar panels in a series of parallel **Read More…**

to make it quick, connecting your solar panels in parallel will add the amps and voltage will stay the same, and connecting your solar panels in series will add the voltage and amps will stay the same

if you have the same voltage of solar panels and the same voltage of battery then you can use a PWM charge controller but if you have different sized voltage solar panels than battery voltage i recommend using an MPPT charge controller which will adjust the amps and volta according to the battery

but still, if you have a large array of the solar panel then i absolutely recommend using an MPPT charge controller which is 30% more efficient than the PWM charge controllers

**What size solar panels for the 40A charge controller?**

As we have discussed earlier the watt limit of the charge controller in any given volt array. so you can use a 500w of solar panels with 12v and 1000 or 1000 watts of solar panels in a 24v array with a 40A charge controller

**Reminder!** these numbers are the maximum watts of solar panels you can connect with a 40A charge controller. but as the most of the experts recommend leaving 20-25% extra room in your charge controller for more safety

which will make the numbers (400w solar panels in 12v array and 800w solar panels in 24v array)

so you can connect two 200w 12v Renogy portable solar panels you can connect them in parallel for a 40A charge controller and if you have 4 of them so you’ll have to connect them in series which will make the total number of volts 48v which means now your charge controller can handle up to 2kWh of power.

**Conclusion**

By knowing the watt limit of a 40A charge controller you can select what size of solar panels you can attach with it and also what size battery you can charge with the help of a 40A charge controller

the values will depend on volts of solar panels and battery the solar panels connected in a 24v array will double the watt limit of 40A charge controller than what it can handle on a 12v array

*I hope you’ve gained some knowledge from this post, ThankYou!*