Hi,
I am wanting to use an RB922 with 4G Cellular modem to provide internet connectivity to a monitoring device powered via the on board USB port. I have a working system in the office powered via a 24v 1.2 amp UBNT POE injector which works really well.
The ultimate goal is to use the solution out in the field where there is no mains power so i need to come up with an alternative that, ideally would give me around a weeks worth of up time.
Has anyone had any experience of doing anything like this, my initial thought is to use a motorcycle 12v battery wired up to a std barrel power connector plugged into the RB, no idea of what that would provide as far as run time is concerned but wondered if anyone had any other thoughts… or even advice if that would actually work
@RogerWilco, Thanks for the feedback. This is a temporary install and will be moved to various locations every week or so. We did look at Solar but decided that with it being in one place for such a short time the installation and removal of a panel woudl be a pain.
However for longer installs a solar panel would maybe benefit by helping to charge the battery. Just of of interest what size panel are you using?
140w Victron Energy Panel - my install is in the woods under trees. When in full sun, a 50w panel is fine for the RB912 + SW MC7304.
At the moment, I’m using a 14aH AGM battery (about a week of power without panel). My 38aH Lifeline battery died after being dropped in the river
Seriously.. why waste your time answering if you have nothing helpful to add.. I have never said i want to use a panel, in fact i said the exact opposite. @RogerWilco was simply being a helpful forum member and providing info that was actually very useful
Battery Size - Stated in my first post if you actually read it - 12V.. which i know you didn’t or you would have known i didn’t want to use a panel.
Location - I guess you are referring to panel position so I’ll answer with “something that gets sunlight”
Needs - not sure how to answer this one.. i guess i need it to work!
An RB922 takes about 4w power + LTE Module you are about 6w power draw
Batteries can only be discharged to 50%, if you discharge more, your battery will stop working soon
14ah /2 = 7ah usable
6w / 12v = 0,5A
7ah / 0,5a = 14h
Your system runs 14h without killing the Battery
And about 20h until you are under 8v and RB stops working
And now? This is far away from a week…
And what you called spam, you want help, I can give you help, if you want to run it solar powered I need to know where this system is located, it makes a huge difference if it is in Northpole or in the middle of Africa!
And if you want to run it without Solar only Battery powdered your needed Battery Size for one week is :
168h x 0,5A = 84AH used, so your Battery needed is 150 to 170ah!!
@RogerWilco
You take a view to the Glas sphere and call other spammers?
Your knowledge is about try and error!
You lost Battery by river? Looks like your system only stands
on Earth without needed cases!
Looks like you’ve just gone off the PDF sheets that state the MAX power and don’t have any actual first hand knowledge… the RB912 + LTE modem draws 2-3w in use and as low as <1w when idle. What I said is not “trial and error” as you claim - this is from what I’ve measured over a 6 year period (as stated in my 1st post).
BATTERY SIZE:
72 watt hours per day == 6aH per day for a 12v system
6amp * 4 days of power reserve = 24aH of storage
24aH * 0.8 (80% discharge for an AGM battery) = 30aH battery
Your formula seems a little off - 150aH battery for 7 days usage… No, doesn’t happen for the RB912 + mPCIe LTE modem. Again, real-world knowledge over 6 years comes in handy.
You need approx. 30aH for 4 days when the modem/wireless is active 24/7. If it is idle 50% of the time (like mine at night or at work, etc), a 14aH battery will be fine. The voltage should also not drop below 12V as only an idiot would be connecting a 12V battery directly to any electronic device without some sort of regulator/battery protection.
As for a panel (which the OP doesn’t care about) and assuming a location with low solar light:
288 watts (4 days of power usage) / 3 hours of light * 1.4 (fiddle value for variance) = 135 watt panel
You can also factor in panels still generate up to 25% power when raining or overcast (again, depending on light/area).
I didn’t “loose battery by river” - I’m not sure what to make of that. I said I dropped it in the river. The battery and river have nothing to do with the amount of power or solar. Again, I’ve no idea what the rest of your sentence means.
But he is talking about rb922 it draws more then RB
912!!!
An these are real draws we have about 20 Solar Systems Most with Airfibers and a lot of Mikrotik
AC Boards needs more power, if 802.11n is enough he better go with 912
Position 2 is Netbox 5 (RB911G)
Position 3 is MAN15S (RB921GS)
Both in idle at moment only some kbytes in the air… in the evening hours both over 4w
both with low output power only 30dBm Eirp allowed
The First thing for Solar is to know where the system is located…
There is not so much sun in every country…
We had 10 hours of sunshine in Germany for the whole month of December 2017.
