Years ago I invented a feeder light that seemed to work great. The light used both green and red LEDs to become a very bright orange light that hogs could not see. But the bright light still spooked the wise old boars and sows. So I decided to add a fade-in option that allowed the light to slowly become fully bright in about 3 minutes after motion is detected.
Another company copied my idea but they have problems. I could not afford to patient it.
I had to quit making the light due to medical problems.
A friend decided to take my idea and improve on it. He is now selling it on his website.
Check it out, I think you will be greatly surprised.
There are options including an 8 watt and a 20 watt solar panel
His website is in my signature line. swine-n-tines.com
You can also check out his Facebook page to see several videos.
Of course I am biased, but I think this is one of the best feeder lights one the market.
Take a look

Years ago a company out of Canton, TexasBoars, made similar lights. In fact, after checking his site he still sells them. I bought 3 over the years and all 3 still run great. I've killed lots of hogs using them and still do. The lights don't have to come on slowly, just turn them on, hunt, and turn them off when you leave. I leave mine run for days at a time. All hogs walk into the light, even the bigger smarter ones. Last time I talked to Kevin, he said the light business was not as good as it used to be and he thinks it's due to NV and thermal. Regardless, I wish your buddy all the best. Whatever kills more hogs, I like.

Will take a look

Lots on the market
We use solar lights from a landscape company work great bright and cheaper