What Size Charge Controller For 150w Solar Panel? (Solved!)

Connecting a right size regulator or charge controller with the solar panel is essential to get the maximum output from the solar panels and to make the solar system safe.

Don’t know what size charge controller you need for a 150w solar panel? so in this blog post, I’ll share with you what size charge controller you need, how to calculate the charge controller size, and some more buying tips

For a 12v 150w solar panel 15A 12v charge controller is needed and 10A charge controller for 24v 150w solar panel. By dividing watts (solar panels) with Volts (batteries) and adding 25% you can calculate the charge controller size for any size of the solar array

i recommend Victron 15A MPPT charge controller which can handle 12/24v solar system.

First of all, let’s see what a charge controller does and why it is needed?

Why do i need a charge controller?

Solar panels convert the sunlight into DC current and we store that DC power in batteries.

Batteries come in different volt sizes, for 150w solar panels a 12v 120Ah battery is needed

But a 12v solar panel will produce about 18 volts at peak sun hours so if you’ll connect your solar panels directly to the batteries it can damage the batteries because of their limited 12v capacity

so a charge controller decreases the voltage to match the battery’s voltage.

How do I choose the right size solar charge controller?

We measure charge controller size in amps, most of the experts advise that the amps of charge controller must be higher than the solar panel’s

There are different formulas available to calculate the size of any charge controller but to make things simple use this formula

solar panel’s watts / battery’s volts = amps + 25% = charge controller size

e.g for a 12v 150w solar panel the calculations will look like

150/12 = 12.5 amps + 3.1 = 15A

for 24v 150w solar panel

150/24 = 6.25 + 1.5 = 8A to make it round i recommend 10A charge controller

the extra 25% is because of some safety factors, most of the experts recommend extra 25% amps for the charge controller than the total amps produced by solar panels when charging a battery.

the extra 25% will take care of voltage variations and it will increase the lifespan of the charge controller.

a charge controller can get damaged in case of any sudden voltage high fluctuation, this is why we recommend that extra 25 %.

MPPT or PWM, Which one should you use?

There are two most popular charge controllers available in the market right now PWMc & MPPT charge controller

How does PWM charge controller work? PWM charge controller uses the modulation method to adjust the voltage to charge the battery.

if the solar panels are producing higher voltage than the battery voltage requirement then a PWM charge controller will decrease the voltage to the battery voltage but the amps will stay the same

for example if your solar panels are producing 18 volts which a typical charge controller will produce at idea sunlight conditions but the 12v battery only accepts max 13-14 volts.

150/18 = 8.3 amps

So at peak sunlight conditions 12v 150w solar panel will produce about 8.3 amps so a PWM charge controller will decrease the voltage to 13 volts to match the battery volts

so to calculate the total watt power we use this formula watts = amps*volts

8.3 x 13 = 107

so a PWM Charge will cause about 40 watts of power loss from 150w solar panels in peak sunlight hours. which makes them about 30% less efficient in the peak sunlight hours when the solar panels are producing higher volts.

Video – How to set up PWM Charge controller?

How does the MPPT Charge controller work? MPPT charge controllers have built-in programmed devices that adjust the voltage about the battery voltage limit and will also increase the amps

which will not cause a loss of power. so an MPPT charge controller is recommended then the PWN charge controller

The MPPT charge controller can be a little bit more expensive than the PWM charge controller but they are worth the investment because of their 30% efficiency.

Video – Difference between MPPT & PWN charge controller

Other important instructions

Do not connect the Appliance with the charge controller directly connecting AC appliances directly to the charge controller can damage the charge controller or AC appliance

you can connect your batteries or DC devices only directly to the charge controller

Use an inverter for lower voltage devices. if you connect the lower voltage device with the charge controller it will decrease the voltage and the rate of amps will increase within the charge controller which can damage the charge controller or device

place the charge controller as close to the batteries as you can the longer distance between the charge controller and batteries means you’ll use a longer wiring size which will cause power loss because the wires will cause loss of some amount of amps

i recommend a 16 AWG for a 10A charge controller and 12 AWG for a 15A charge controller

Invest in the MPPT charge controller as I have discussed earlier the MPPT charge controllers are more efficient than the PWN Charger controller but are more expensive but they are worth the investment because in the coming time you’ll get more power from the MPPT charge controller than the PWM charge controller

Check the voltage upper limit of the charge controller every charge controller has its upper voltage limit so make sure to check it before connecting them in series or parallel.

The Victron MPPT 15A charge controller has an upper limit of the voltage of 75, which means it can handle 75 volts only.


The most underrated component in the solar power system is the charge controller, we mostly focus on the solar panel’s wattage and the batteries

but choosing the wrong size charge controller can cause many problems it’s worth knowing what size of charge controller is suitable for your solar panel array.

I hope this blog post is helpful for you, reach out to me if you have any further queries mail me at contact@dotwatts.com. Thank You!

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Chris Tsitouris is a renewable energy professional with 10+ years of experience as Director of Engineering at Solar Spectrum, previously working as Project Manager at SunPower and Energy Analyst at the National Renewable Energy Laboratory. As a thought leader, Chris has authored numerous articles and research papers.

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