Step up from 12V to 48V?

[tbob]

I'm working a a solar wifi project and I want to supply 48V POE to the wifi radio.

For the power supply, I'm using a DC-DC converter/POE injector that steps up from 12V to 48V.

This is the first time I've worked in a step-up scenario, so I'm trying to reality check my solar panel/battery sizing requirements.

My question: when stepping up from 12V to 48V would I do the usual battery/panel sizing calculations as if I was using a 48 volt battery? If that's the case, and the step-up efficiency of the converter is 80%, do I just add 20% to the system requirements?

[Mike90250]

If your power budget is not tight, and you can afford the 20% losses, go for it. If you have to go to more than 1 panel, you could save 20% and just go with a 48V battery bank. 2 high volt panels, 30 - 35V range, in series, with an MPPT controller .

[tbob]

RE: Step up from 12V to 48V?

OK, so you're saying I would be correct in sizing battery storage requirements/panel size as if I had a 48V system (assuming I have no choice but to do the 12V - 48V step up?)

For example, my radio needs 5 watts.
5/48 = 0.104 amps.
I need it to run 24 hours on battery backup (50% discharge) so 24 hr X 0.104 amps X 2 = 5 amp hr battery needed.

So, if I use a 12V, 5 amp hour battery I would have 24 hours of backup power with the radio using 48V via the step-up DC to DC converter?

[Mike90250]

5w @ 48V = 0.104166A So that's not much power at all.


5w @ 12V = 0.4166A, A regular group 24 (80AH) or 27 (105AH) size "deep cycle" or "marine" battery could run for days. if you had a nice 20 or 50 w panel, and a charge controller, you are all set - even adding in the upconverter losses, for this size, just one inexpensive ($90), beefy battery should do fine. Even a week of rain and clouds, it'd still keep going.

A 12V 10 AH battery however, would be very strained after one night (12 hours of drain) , is 5AH, and is 50% drained. 50% is too deep of a cycle to schedule regularly.

[tbob]

RE: Step up from 12V to 48V?

Sorry, my example wasn't very good, actually since the numbers were small.

In reality, my wifi node needs to go 24/7, 365 days a year. Based on experience at my location I need 7 days of battery storage to be safe.

In that case, it will make a huge difference in the battery capacity required if I can verify whether or not I'm sizing based on 48V (the stepped up to voltage) or 12 volts (the actual battery/system voltage). Again, assume I don't have a choice - I must use a 12V battery.

So my question is more about an electrical principle rather than specific numbers on how big a battery I need...

[btsforklift]

Better late than never...

I'm working a a solar wifi project and I want to supply 48V POE to the wifi radio.

For the power supply, I'm using a DC-DC converter/POE injector that steps up from 12V to 48V.

This is the first time I've worked in a step-up scenario, so I'm trying to reality check my solar panel/battery sizing requirements.

My question: when stepping up from 12V to 48V would I do the usual battery/panel sizing calculations as if I was using a 48 volt battery? If that's the case, and the step-up efficiency of the converter is 80%, do I just add 20% to the system requirements?

A company called PanOptic Technology may have just what you need:
streakwave.com/ItemDesc.asp?ic=IPA2112-I01

[Sunking]

[QUOTE=btsforklift;24929]A company called PanOptic Technology may have just what you need:
streakwave.com/ItemDesc.asp?ic=IPA2112-I01 smell SPAM. Dragging up 2 year old post, shame on you.

MODS can't you automatically lock post after no activity in 60 days to keep the hucksters from mining them out?

[Mike90250]

[QUOTE=Sunking;24931]

A company called PanOptic Technology may have just what you need:
streakwave.com/ItemDesc.asp?ic=IPA2112-I01 smell SPAM. Dragging up 2 year old post, shame on you.

MODS can't you automatically lock post after no activity in 60 days to keep the hucksters from mining them out?

No, posts are archived.
The IPA2112 converts 48VDC POE to 12VDC and Data, enabling non POE devices to be powered using POE.
Input Voltage 36V to 57V DC (for higher power operation an input voltage of
48V is recommended). Pin assignment is comply to IEEE
12W @ 12V 85% eff.

Well, there are other DC-DC converters that are more efficient, but they cost more.

[btsforklift]

Sorry, I thought it was relevant and helpful.

[john p]

hmmmmm I say give him benefit of the doubt this time.