Most of the residential keypad locks are not designed for gates where both sides of the local are exposed to the elements- typically the side with the battery can’t be exposed to water. You need a mechanical keypad lock. You can get them in many configurations- levers, deadbolts, always locked, keypad on both sides…

Other options are available but this is the type that I am referring to.

Thank you, that looks like it would work!

I don't think it's possible to install a lock like that on such a gate. It would be very complicated and costly, so I don't see the point. The best solution to this problem is installing a slide lock to open from both sides. In general, you will need the help of a specialist. However, a good locksmith is very difficult to find now. It is easier to teach yourself how to do it, especially now that it is easier than ever. You can find more information on the Internet, which will help you with this. I hope you find a solution to your problem. I wish you good luck!

@HALLETT & Co. You would need a rain guard for a battery-operated keypad, such as this one:

https://www.amazon.com/Plastic-Rainproof-Waterproof-Protect-Controller/dp/B07RKXQQY3