The hAP Lite is old enough it is listed as accepting PoE 12-30v, less than what most PoE equipment is sending (48v, 54v).

Is it true that it doesn't accept the full POE voltage range? Will it go up in smoke? Will it simply reject PoE?

48-54V is usually in 802.3af / 802.3at PoE standard.
RB952 does not support 802.3 af/at . It supports only Passive PoE (no negotiation between devices - it just sucks power)

If you feed it 48-54V over passive PoE, it might really burn as it can't refuse it or negotiate lower voltage.

If you feed it 48-54V over passive PoE, it might really burn as it can't refuse it or negotiate lower voltage.

"Might", or it might run fine. There must be some people with a network such as this..

Firstly, you must understand that standard 802.3af/at source will not start feeding power, unless it finds that power-consuming device requests the power. So you can try to connect it to 802.3af/at switch or injector. It will not work, but it should not break either (only in case of malfunction). Detection on 802.3af/at is done with low voltage (2-10V) and it will obviously fail as the device does not support this standard.

However, your question is about voltage. If you feed 48-54V directly into the 30V rated device, you are risking electrical damage or even fire and YOU are responsible for any damage caused by this action. There is nothing like "might be fine". It is against specification and no person with piece of brain would do that. If device says that 30V is max, there might be few volts tolerance but definitely not 18-24V (almost double) tolerance.
On the other hand, there are devices (hAP ac) which support 12-57V passive but not 802.3af/at. So you can clearly see that some mikrotik devices have limit on 30V while some are designed up to 57V.

Nobody reasonable will tell you to feed 48-54V directly into 30V rated device, if thats what you are asking...

Is there any specific reason behind your question? Maybe I just did not get what you ask for.

Is there any specific reason behind your question? Maybe I just did not get what you ask for.

I want to have some hetrogenous devices on my network. I want to use a 'modern' (e.g., higher-voltage standards-compliant) PoE switch and some devices that need that higher voltage level.

I want to connect that to my Mikrotik devices, including the hAP Lite, which is listed at the lower voltage levels.

I don't want to let the smoke out of the hAP Lite. Ideally, I'm hoping the magnetic transformer and PoE circuitry in the hAP Lite can operate at the higher voltage levels, or at least don't ask for any power, which means I can still run it even if I need to supply power to the hAP Lite.

I assume there are people using "higher voltage" PoE with a hAP Lite on the network, so my hope is someone can tell me if it actually works.

Otherwise I suppose I should just replace it with a hAP ac and a generic unmanaged PoE switch, or a hEX S, a well-placed cAP/wsAP ac lite/wAP, and an unmanaged POE switch. Hmm. So many options, and no real reason to replace my nicely-configured router.

I want to use a 'modern' (e.g., higher-voltage standards-compliant) PoE switch

If this means 802.3af / 802.3at compilant switch (that is just my guess as it is most common standard), then it will not get burned but it will not work either. hAP Lite is not compatible with this IEEE standard, it will not request the power, therefore switch will not supply any power to your hAP. You will have to power your hAP by yourself. Either directly by adapter or with additional mikrotik-compatible passive PoE injector. Some managed PoE switches allow you to select, what type of PoE you want to use (e.g. Unifi switches, CRS with PoE..)
If that "modern" device is not 802.3af/at compilant, or you are unsure, feel free to give example of considered device. your "e.g." is unfortunately not specific for me to be certain which standard you are refering to.

Ideally, I'm hoping the magnetic transformer and PoE circuitry in the hAP Lite can operate at the higher voltage levels

I would not risk that at all but fortunately it should not be your case

or at least don't ask for any power, which means I can still run it even if I need to supply power to the hAP Lite.

That should be right.

I assume there are people using "higher voltage" PoE

I believe this is cause of our misunderstanding. The "higher voltage" PoE is extremely broad description. There are many different types of PoE. Some are standardized by IEEE, some are proprietary but compatible across several manufacturers, some are proprietary and totally not compatible with anything else. Many of them share same voltage, despite being incompatible. Therefore you cannot identify type of PoE just by voltage.
In addition, it is not really possible to say in general if incompatible PoE will just not work or if it will cause some damage. Personally, after my experiences with passive poe, I would recommend to stick with proper IEEE 802.3af/at standard compilant switches. These should not burn anything and in worst case, your device will not get power.

Everything vecernik87 has stated here is 100% accurate.

...that said, though MikroTik (to my knowledge) doesn't make one, there do exist in-line 3af-to-passive adapters that will allow you to power (many/most) passive-PoE devices from a 3af/3at-compliant switch. It is, of course, not guaranteed that every "passive PoE" device works and accepts power exactly the same way as all others, and you shouldn't make the assumption that they do. But MikroTik and Ubiquiti gear both implement PoE in a way that is compatible with each other, and Ubiquiti manufactures and sells a device that allows you to power passive-PoE-fed Ubiquiti gear from most standards-compliant switches. It takes in 3af-compliant 48V and outputs 18V passively on the other side.

I have access both to these devices as well as to hAP ac lite routers, so just a few minutes ago, I plugged a hAP ac lite into a 3af switch (Dell 3548P) with one of these Ubiquiti in-line adapters sitting in between, and it worked perfectly. hAP ac lite powered up just fine.

The main downside that I can think of is that I think these in-line adapters retail for roughly $20 or so. So your costs just went up by $20/port.

-- Nathan

Thanks for confirmation. I just want to add that some Ubiquiti products actually have ability to switch from 802.3af/at to 24V passive PoE which is compatible not just with some Ubiquiti gear but also with Mikrotik. Therefore with some of Ubiquiti switches, you don't have to use the af-to-passive converter.
I am using these on few locations but it is mainly becaues they were purchased before i was asked to take care of it. Now it is causing more issues than expected, for example breaking ROMON network etc...

I have access both to these devices as well as to hAP ac lite routers, so just a few minutes ago, I plugged a hAP ac lite into a 3af switch (Dell 3548P) with one of these Ubiquiti in-line adapters sitting in between, and it worked perfectly. hAP ac lite powered up just fine.

The main downside that I can think of is that I think these in-line adapters retail for roughly $20 or so. So your costs just went up by $20/port.

Thanks Nathan.