The hAP ax3 Power Supply Output Specifications (US) is 24VDC @ 1.5A (Model:SAW36-240-1500U)
The hAP ax3 Router's input Specifications show 12-28VDC , maximum of 38 Watts, but typically 15W without POE
It is preferential to be at a higher voltage point within the 12-28VDC input Window, (24VDC)

I have looked considerably online for a reasonable 24V DC Battery Backup solution (All in one to include batteries) and have so far haven't been able to find an economical solution which would deliver ~8 Hour Run Time @ 24V 15 Watt Load.

The following is what I have come up with as a more economical solution but wanted to ask others if they had found a competitive all-in-one solution that I might have missed, or if there might be any better DIY configurations someone else may be currently using as compared to the one I have tentatively come up with below.

1) 24V 3A 72W Power Supply: ~$12.89
2) PWM Solar Panel Battery Regulator Charge Controller 10A ~$7.93 (11/26/23 ebay item 374884141603)
3) 12V 17AH Battery or 24V 7AH Battery(x2 in series) ~ $40
[Total: ~$61]

The higher Amp capacity (3A) of the 24V Power Supply (Max load demand of 1.5A) is considered for Battery Charging Allowance.
I would just connect the 24VDC Power Supply output to the Solar Panel Input of the Solar Charge Controller. The Solar Charge Controller supports Voltage & Current regulations/restrictions as well as protection circuits for Battery Cut off to prevent damage, while also supporting the discrete Load Connection (24VDC) to the hAP ax3.
I believe I could configure either a single 12VDC Battery @ 17AH or two 12VDC Batteries in Series (24VDC) ~7AH while maintaining the 24VDC Load.

Thanks in advance for any suggestions!

This:

https://www.meanwell-web.com/en-gb/ac-d ... drc--100b

And two 12V 12Ah batteries and you have no problem with achieving 8h backup time.

Thanks gigabyte091,
It appears a used DRC-100B can be had for ~$30

The DRC-100B has a 27.6V Output, which is just about the Maximum the hAP ax3 maximum indication of 28VDC... I did notice a voltage adjustment screw on the front of the DRC-100B but it only indicated a "+" so am unsure if that control would allow me to lower the 27.6VDC to 24VDC.

As far as the battery capacity for ~8 Hour Runtime at 15 Watts, I was using a online calculator at www.dotwatts.com/battery-runtime-calculator/ and it indicates that a 24V 7AH Capacity (2x12V 7AH Batteries in series) should run a 15 Watt Load for ~7.62 Hours... entering the specifications for two 12V 12AH batteries shows ~14 Hours.

In my case, I doubt that the Fiber Network Box (DC Backup) on the side of the house would support much more than 30-60 Minutes of Internet Connection anyway... so anything more than an hour would just support LAN devices of which were on AC Backup or generator.

So you can adjust voltage from as low as 23V i think. Have in mind that at the same time you adjust battery charge voltage.

So i could recommend you to set output voltage to 27V so you have charge voltage of about 13.5V per battery.

I use that PSU a lot in my field of work and over the past 4 years i had one faulty units (of about 120 of them) and that was caused by lightning strike.

I use a Meanwell tuned to 27.2V to float-change two SLA's, But my stuff is 11-30VDC.

27.2V is a bit to close to 28VDC. I would probably add a diode or L7824 or a diode (like MBR1060) to drop the voltage some.

Then it's better to add DC-DC converter instead of burning excess heat in linear regulator. But I don't think there would be any problem with 27.2V on router input.

Since I can increase the voltage, maybe it would be a better idea to go with 12V, but then I have to worry about the Low Voltage in the event of Low Battery being lower than the 12V Minimum.
This is going into a Home environment for Internet Access, so after you add the expense of some sort of enclosure box for a Din Rail, the total price becomes comparable to a all-in-one mini DC UPS that uses 3-4 Lithium batteries,,, Guess I would have needed the Enclosure for the Solar Charge Regulator solution as well... So it's looking more like an All-In-One lesser runtime solution might be the least expensive, easier solution.... Anyone had any experience with them? I see a 31200mAh unit a 24VDC for ~$66 (From China) not sure if there would be additional import duties I would have to pay for .... Maybe I will just locate the hAP 3ax at the computer where I can plug the AC Adapter into the Computer's UPS... it's not ideal as it would then be located at the fare end of the house instead of centralized.

Well for that price maybe is better for you to buy used UPS with a bad battery and replace battery.

Well for that price maybe is better for you to buy used UPS with a bad battery and replace battery.

Perhaps use with modern MPPT solar charger? I know the smaller Victron MPPT solar chargers have a load out that can go to the Mikrotik, like https://www.victronenergy.com/solar-cha ... -15-100-20
Might be cheaper than adding DC-DC regulator.

Yea, but OP doesn't use solar panels, and cheap DC-DC converter are available everywhere. But for eg. I would rather spend a little bit more money to have more reliable UPS power for my network equipment.

Personally I wouldn't trust chinese UPS with lithium batteries...

My setup involves true sinewave online UPS (2 kVA) for all network equipment, PCs, peripherals, TVs, etc.

Victron MPPT solar chargers are overkill in this application.