Will A 50 Watt Solar Panel Charge A 12 Volt Battery?

Will A 50 Watt Solar Panel Charge A 12 Volt Battery? -Featured Image

So you want to know will a 50 watt solar panel charge a 12 Volt battery? Over the last few years there have been several advancements in batteries. Notably the introduction of Lithium Iron Phosphate (LiFePO4) which significantly extends battery life.

The attraction of lightweight and cheaper 50 watt solar panels is bringing off-grid power to lovers of the outdoors. But can a 50 watt solar panel really effectively charge a battery like a LiFePO4?. Can it effectively charge a larger lead-acid battery? And what about portable power stations? 

In this post I will be exploring which 12 volt batteries a 50 watt solar panel can actually charge.

Will A 50 Watt Solar Panel Charge A 12 Volt Battery?

“Yes, a 12 volt battery can be charged with a 50 watt solar panel. But it is a smaller solar panel and it’s amp output is going to be much less than larger panels . So it should only really be used as a stand alone charge solution for 30Ah batteries or less. It can also be used to charge smaller portable solar power stations up to 200 watts” 

You can use it to charge a 50Ah lead-acid battery that is normally modestly discharged. What I mean by that is to around 75% of its capacity – that would be a total discharge of 12.5Ah. Because even under 6 hours of direct sunlight a 50 watt solar panel will only produce around 17.4Ah per day. 

By only using 25% of a12 volt 50Ah battery capacity there will be some wiggle room. Because of the maximum number of amps a 50 watt panel can produce per day. Larger batteries should really only be used with a 50 watt panel to be kept topped off.

If you would like to know more about how many amps a 50w solar panel produces. You can read my article about it here; 

Related >>>>>>>>>> How many amps does a 50 watt solar panel produce?

Can A 50 Watt Solar Panel Effectively Charge A 12 Volt Lithium Iron Phosphate (LiFePO4) Battery?

Will A 50 Watt Solar Panel Charge A 12 Volt Battery? - Renogy Smart LiFePO4 Battery

A LiFePO4 battery can be discharged to 90% of its capacity with no ill effects thousands of times. Let’s be honest, the discharge ability is one of the best advantages over lead-acid. Because lead-acid can only be discharged to 50% of it’s capacity without damaging it.

If a 50 watt solar panel can produce a maximum of 17.4Ah per day (realistically more like 15Ah). It will only really keep a 15Ah LiFePO4 12 volt battery satisfactorily charged with heavy use. You might be able to push it to a 20Ah battery but that would leave you with much less wiggle room.

When it comes to larger 12 volt Lithium Iron Phosphate batteries say 50ah and upwards. You can see now why a 50 watt panel can really only be used to keep them topped off. 

Relion Say;

Performance is a major factor in determining which type of battery to use in a given application. Long life, slow self-discharge rates and less weight make lithium iron batteries an appealing option as they are expected to have a longer shelf life than lithium-ion. (Source; relionbattery.com}

Can I Connect 12 Volt 50 Watt Solar Panels Together To Achieve More Amps?

Is there a point in connecting several 50 watt solar panels together? You could connect them in parallel to achieve a higher amp production. I can see that might be an option where space is limited. Or you want to cover curves with flexible panels on a boat such as the wheel house.

But to keep a 50Ah LiFePO4 battery charged under heavy use taking into account a 90% discharge. You would need to be able to cover 45Ah per day. I know you would probably not discharge the battery down that far. But with solar you have to cover all eventualities.

Can I Connect 12 Volt 50 Watt Solar Panels Together To Achieve More Amps?

To calculate how many 50 watt solar panels you would need to cover those 45Ah. You need to add at least 25% to cover environmental factors such as cloud, haze and the season. That is a total of 56.25Ah. Which then needs to be divided by15 realistically the amps a 50 watt panel might produce in a day. 

This comes to 3.75. Meaning that you would need 4 x 50 watt panels to keep a 12v 50Ah LiFePO4 battery properly charged. Unless you are installing the panels on a boat my question is why would you do that?

When 2 x 100 watt or a 200 watt 12 volt panel would do the job quite nicely.

If you would like to know more about LiFePO4 12 volt batteries. You can read a review about the Renogy 100Ah here;

Related >>>>>>>>>> Renogy Smart Lithium Iron Phosphate Battery Review

Can A 50 Watt Solar Panel Effectively Charge A 12 Volt Lead-Acid Battery?

Varta Lead Acid Battery

As I mentioned earlier a 30Ah lead-acid battery heavily used would be suitable for a 50 watt panel to charge. Because of the 50% discharge rule you would need to cover 15Ah of discharge per day. A 50Ah lead-acid would have to be discharged modestly if using a 50w panel to charge it.

Again larger batteries than 50Ah could only be topped off with the panel. I know that there are recommendations out there saying a 50w will keep larger batteries charged. These are misleading because topping off is keeping it charged isn’t it. So they are not exactly lying, they are just not telling the whole truth.

But you will notice that these recommendations never talk about what battery capacity the panel will recharge. But now you know that the 50w will produce between 15ah and 17ah and that is in perfect conditions. It is not suitable for recharging higher amp hour batteries.

Again you could connect the solar panels in parallel to up the amps. But as I explained before when talking about LiFePO4 batteries. What would be the point unless in special circumstances. If you think differently let me know in the comments section below

What Solar Charge Controller Should I Use With A 50 Watt Solar Panel To Charge A 12 Volt Battery?

The solar charge controller is one of the most important pieces of kit in any solar setup. It is best to use a 10A solar charge controller with a 50 watt panel. Some people say less like a 5A but it is best to be cautious. Taking environmental and inefficiencies into consideration is wise.

PWM Solar Charge Controller

Solar charge controller sizing is calculated by dividing the input wattage (50) by the voltage (12). Then add 25% this would equal 5.20 which you then round to the nearest whole number. Which in this case is 5 this means you need a 5A solar charge controller.

This is why some experts recommend a 5A controller for use with a 50w panel. But wait, what about LiFePO4 batteries? Not all solar chargers can handle Lithium. This is true so it’s best to check the manufacturer’s specifications.

Remember a poorly made cheap solar controller can damage your battery. There are lots for sale out there so think before you buy. Is this controller too cheap?

Should I Use An MPPT or PWM Solar Charge Controller
This is a video about the Rover Lithium MPPT Solar Charge Controller

MPPT stands for Maximum Power Point Tracking and PWM stands for Pulse Wave Modulation. Both work very well with a 50w panel and 12 volt battery. MPPT controllers are better than PWM because they are more efficient.

At the time of writing you can source a 5A MPPT controller but it doesn’t have an outside case. It is a PCB board with components surrounding it. You can get a 10A controller with a surround and digital display.

The efficiency benefits of an MPPT controller over a PWM are not that great using a 50w panel. The substantial efficiency benefits are usually seen in larger systems so a PWM controller might suit better, 

You can source a 5A PWM controller with an outside casing. Some even have LED’s to show they are charging. There are lots of 10A controllers available and many have LCD displays.

So all in all  MPPT controllers are more efficient but more expensive than PWM controllers. So it will ultimately come down to your budget.

If you want to know more about solar charge controllers. You can take a look at my Renogy controller review here;

Related >>>>>>>>>> Solar Charge Controller Review (Renogy MPPT And PWM)

Portable Solar Power Stations
Renogy E.Flex 50 Portable Solar Panel and Pheonix 200 Watt Portable Power Station
Renogy E.Flex 50 Portable Solar Panel and Pheonix 200 Watt Portable Power Station

Just a quick note about portable solar power stations. If you are going to use a 50 watt solar panel to charge one of these. You do not need a solar charge controller because they usually have one built-in. Their battery chemistry is normally lithium based. As I mentioned earlier you can use a 50w panel to charge a 200w station or less

My Closing Thoughts

A 50 watt solar panel is not the most powerful in the world but it will charge a 12 volt battery. It will charge both lead-acid and lithium based batteries. But it’s charging capacity is limited due to the number of amps it can produce per day.

It can only be used with larger amp hour batteries over 50Ah to keep them topped off. Which in itself can be useful. But in cloudy conditions or low light conditions the 50w is going to struggle to produce amps and volts. 

If you would like to take a look at some 50 watt solar panel specifications and descriptions you can do here:

I hope you enjoyed this post and have found it helpful. If you have any questions about 50 watt solar panels and 12 volt battery charging. Or want to leave your own personal review, please feel free to leave a comment below.

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4 Comments on “Will A 50 Watt Solar Panel Charge A 12 Volt Battery?”

  1. I’m a total noob when it comes to solar panels but I’ve been seeing a lot of advertisements about solar energy and how using solar panels can help the environment. I’m thinking of giving this a try but most articles I’ve seen used complicated terms a noob like me can’t follow through. So far this article is by far the easiest to understand. Thanks 

    1. Yes new people to solar power can be confused by the language used about solar panels. This is because many times the technical terms and there meanings are used in the explanations.

      Rather than it does this because of this. Most most people don’t want to know what the terms actually mean. They just want to know how it works and not the why it works. 

      I am glad that you were able to follow the post it can be difficult to describe what you need to calculate in an easy way. But most of the calculations for solar are quite simple multiplications and divisions. 

      If you have any questions please don’t hesitate to ask



  2. I have a small orchard project right now and we have been considering installing solar panels to power the house, irrigation system and other things. This article was very helpful. I really did not know much of anything about solar power, but I know more now. I had no idea about the “50% discharge rule” or any of the other points. I have saved your site and will return when discussing it with my family.

    1. Hi yes 50% rule only applies to Lead-Acid batteries. Lithium can be discharged to I say 10%. But you can go to 0% without damaging it. 

      If you have any questions please don’t hesitate to ask 



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