powering my networking at 9V, 12, and 24V

[mattadata]

I am building a small system to power my networking equipment in the house. I have 4 devices, and of course they all use different voltages.
Modem is 12V
Switch is 9V
2 Wifi POE injectors at 24V

Is it best to get a 24V battery so I can power the 2 Wifi POE injectors directly, then use 2 small voltage reduces to power the 12V modem and 9V switch?

Thanks!

 

[DThames]

If you want to stay with DC and avoid an inverter, yes most likely. However, there are step up DC to DC converters just like there are step down DC to DC converters. If your 12v load was very large compared to your 24v load, you might want to do 12v and step up to 24v. It just depends.

Added....depending your power requirements and what type solar panels you use, the battery might be better off at a given voltage because of charging options. Large commercial type panels are nice but you normally can't use the low end cheap controllers for a 12v battery and a panel that outputs 40v open circuit (for a 24v battery)

 

[Diysolar123]

when it comes to battery voltage sizing it is always best to look at what the expected loads will be. In addition...and this is a warning...
do NOT think that a 24v battery is something you can just plug a "24v DC" device into!!!
Battery voltage will vary by quite a bit as part of their normal charge/discharge life and many DC devices are not just "around 24VDC"...but EXACTLY 24VDC (+/- a few percent).

modern buck/boost converters are quite efficient so I would not worry to much about that for small loads. fyi, they do make combination buck+boost converters which means they can take in vary wide range of DC voltage (e.g., anywhere from 5-30V) and produce exactly what you need on the output, very handy to have so you can maintain a stockpile of the little critters for whatever comes up.

unless you are sure a device is designed to work with the rather large voltage ranges associated with being directly connected to a battery, you should put a regulated supply in front of each of your required voltages.

you have not exactly said what type of system you are designing, is it: just a grid powered ups, a couple solar panels on roof, single solar panel with sun tracking, etc.???
measure/figure out your power demands first to make sure you know what you will need... its not about the voltages, its about the power needed, type 3 POE devices can use upto 50-60watts PER PORT!!

fyi, I would ALWAYS start out with a minimum of 24V for any system I design unless there is a serious cost/space/weight constraint.
For some reason, all power projects seem to demand more before you can finish them...clearly some type of universal intelligence is involved in messing with the plans as you start to finish laying things out.

 

[mattadata]

@Diysolar123 - Yep, you are correct about the battery voltage +- 24 volts. Not sure how I forgot about that. Thanks.
Sounds like I should get 4 of the buck+boost converters for most flexibility.

I will measure my 2 POE devices. They are wifi APs, so don't think it will be much.

I would like to build an UPS for my networking equipment that will be mainly feed by the grid. Solar is for the extended power outages. Hoping one panel is enough to charge battery to keep networking powered for 24 hours. Next step is todo the math.

Thanks for the tips.

 

[DThames]

Search Youtube for "DIY router UPS" and you might get some ideas.