Is there a free anti-virus from the internet that is not just for a trail period?

I use Avast for anti-virus, which is free, and to compliment that, I use Malwarebytes Premium.  I pay a yearly subscription fee to use Malwarebytes Premium, but Malwarebytes protects more against malware, spyware, and ransomware.

Malwarebytes is free, but with premium you get 4, real-time shields that protect you at that moment.  So if I accidentally click a link I didn't want to click, and that link has malware that is a browser hijack, Malwarebytes Premium will stop the connection before it even happens, and I won't get infected.

With the free version of Malwarebytes, you won't know if you're infected until you run a scan.  But Malwarebytes I have never seen as being an anti-virus program specifically, which is why I run Avast and Malwarebytes.  Plus, Malwarebytes Premium runs a daily scan.

And no, running both of these programs does not slow down my computer.

here are some free ones - Avira, Avast and AVG, although there are plenty of others they are the ones I have used in the past, presently I use Malwarebytes Premium, I have a lifetime licence because I bought it many years ago when they gave people lifetime licences

I saw Windows Defender on a bike trail recently.

A large number of antivirus are available and are free to use. They are also very good at protecting your computer: Avast antivirus,Panda antivirus,Kaspersky antivirus, Comodo antivirus, and Sophos home antivirus.

avast is free , thats the one i use .

Yes. Malwarebytes. And it is very good. You can also buy the deluxe version of it which offers more protection, but the basic version is free. 

There are many free ones available which aren't just for trial periods but are fully functioning versions of the paid-for program and use the same databases. Some are already mentioned here. 

The paid versions offer extra functions which may or may not matter to you. The protection which comes built-in to Windows is now better than it was but still not up there with the others, mainly because it does not update frequently. 

Yes. AVG and Avast are free antivirus. But I would suggest to go with paid one for more security.

You plan on using it when you hit the trail?

Assuming you are running Windows 10, it already has a build in anti-virus.  There is no need to add an additional anti-virus to the computer.  All it will do is slow your computer and not make you any safer.