I'm looking for a low cost high current power supply for a series of permanent installations with in there a Raspberry Pi 3, Teensy and 5V D-class audio amplifier. I found the Meanwell APV-16-5 (5v 2.6A), though it is of course meant for driving LEDs rather than a microcontroller, is there any reason this would not be a good choice? An alternative I'm looking at is this one, but it feels safer to get one with an enclosure.
Given that this power supply is a constant voltage source, with (5 +/- 0.25) V (the spec lists 5% voltage tolerance) it is within the specifications of the Pi. It should work. I am not sure about the high ripple of 100 mV but I would not expect too much trouble since the Pi regulates all its internal needed voltages. There's also nothing of a minimum load in the spec sheet. It lists the full range of 0 to 2.6 A so it should not be a problem to run it at lighter loads.
So I will go with: Yes, that will most likely work with the Pi.
Raspberry Pi will most likely work flawlessly with this PSU. Keep in mind it may not be as well regulated as the PSUs designed for Raspberry Pis, mobile phones and other digital devices. They may fry your board. You have to make sure that the PSU supplies "clean" voltage (without voltage spikes, both overvoltage and undervoltage) before using it. I recommend getting a known brand name PSU, because it'll still be cheaper thing to do than replacing a Pi fried by a dodgy power supply.
That said, I was successfully using a PSU designed for LEDs to power my NAS when its original plugpack failed. It was a temporary solution, before I replaced the plugpack.
The big thing to watch about any PSU you attempt to use for the RPI is the dead/no load voltage. As @goldilocks stated, I have seen a few PSU questions asked and I also think it is on topic (all-be-it loosely) to find the best PSU that won't fry our rpi.
What you will want to do if you buy any PSU is leave the 5v end unplugged. Before plugging the PSU into the wall, connect a volt meter to the 5v side. If you have a volt meter that is quick to read and has a auto "hold" feature for the highest detected reading that would be best.
Otherwise watch the meter and plug the PSU into the wall and look for a spike initially and a holding voltage that goes past the tolerances of the pi.
Many wall unit PSU's will spike. Thereby fry or weaken your rpi.
As for the PSU you found, it looks like from the datasheet that it will work but I'm entirely not sure as current drop can cause stability problems in case your Pi draws more power.
Anyways, I'll tell you what I did.
If you want to battery power your Pi, the best option according to me is buying Li-ion cells, or just scavenge them out of an old laptop battery (that's what I did), once you have the cells connect them in such an arrangement that you get more than 5 volts and more than 2.5-3 amps. For example I got 6 Samsung ICR-18650 22F cells from my laptop's old battery, each cell was 3.3V and 2200 mAh, I connected two in parallel to pump up the current and then added a third in series to increase the voltage, I then connected a 5V 3A UBEC to the battery pack and plugged it on the pins 4 (+ve) and 6 (-ve), and my Pi runs fine.
That's the cheapest way you can run the Pi on batteries as far as I know. I can post a picture of my battery pack if you want.