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Power systems

I am trying to get a shopping list for Solar Power and wanted to get some feedback. Specifically: 

  Do the power assumptions seem reasonable?

  Any suggestions on equipment vendor, particularly charger controllers?

  Other comments, ideas?


Richard - wb6tae


Some givens:

  Average watts per radio = 3 (Based on observered draw of 2.5w and Ubiquiti's estimate of 4w

       See: )
  Total days off-grid w/no sun = 2

  Total Sun hours per day = 6 (San Francisco Bay Area)

For a one radio system:

  Total watts per system = 3
  Battery size = 25AH  (sized to not go below 50% charge)
  Solar panel size = 30 watts
  Charger capacity = 4 amps


For a two radio system:

  Total watts per system = 6

  Battery size = 50AH  (sized to not go below 50% charge)

  Solar panel size = 50 watts

  Charger capacity = 6 amps


Equipment gueses... (Vendors are "good guess" and prices are approximate)

Solar Panel =

          Renogy 30w/12v Monocrystalline @ $65


          Renogy 50w/12v Monocrystalline @ $90


Battery = AGM Deep Cycle

          Universal Battery 35AH @ $60


          Universal Battery 50AH @ $90


Charger (MPPT) = 

          Genasun GV-4 | 50W 4A  @$65


          Genasun GV-5 | 65W 5A  @$75


Cost less cables, box, frame, etc.: 

    One radio  = $190

    Two radios = $255


Note: I selected Monocrystalline panels and MPPT chargers because they are supposed to be more efficient.



Also need 12v POE injector

Unless you already have this worked you, you will also need POE injectors to run off your 12v power system.  I am currently successfully using TP-DCDC-1224 for this purpose. 

K6AH's picture
Passive Injectors

You may also get away with using a passive injector directly to a 12 volt battery.  The power requirement for the Ubiquiti devices is 10.5vdc at the CAT5 connector.  I started using the these $2 injector from China for powering nodes in my car... and now use them routinely in my solar-powered installations for cable runs up to about 30-40':

Andre, K6AH


AE6XE's picture
my solar experience...

1) solar rating.  I recommend taking a ~90% solar panel rating from STC (on the equator with a couple marketing mirrors to spin the number).  The PTC test bench #s for CA are shown for panels used in a lot of home solar systems--lucky if the panels we use will be shown on the this state site--but maybe.

2) MPPT vs PWM.   Generally MPPT yields bigger value when coupling multiple panels.  I question if the cost to go from PWM to MPPT controller is worth the little bit of extra efficiency one gets with a single panel.

3) After 10 years of using a PWM and 110W panel.  It can still generate 6A in full sun, or ~12.8v * 6 = ~77w.  Given 10 years of panel efficiency loss (and was truely only a 100W anyway), I'm still happy with the results.   I just ordered one of the renogy 100W with PWM controllers combo for ~$180--should arrive tomorrow.  I'll be interested in how it performs.  I suspect this will yield as much or more power for the same cost with MPPT controller--but prices keep coming down.

4) You'll want to put up an ipCam at your remote solar site (or wished later you had sized the solar accordingly).    If you do, then add in nominal cost and parts for a switch to plug everything together.

5) My ~77W actual generated power of my panel loads up 2 Rockets, an AirCam, and TrendNet pan-tilt cam.  It has a 3 year old RV battery--~95aH and will start dropping out at night after 3 days of clouds (12.4v low voltage shutoff).  Check the low voltage shutoff of the controller you are looking at--looks fixed at ~5% battery capacity, beyond the 50% desired.


Thanks for the comments. I am

Thanks for the comments. I am familiar with the PoE injectors... I currently have a 100AH AGM battery powering my 2m/70cm radio and a local node. However, rather than solar, I float everything on a 15 amp charger.  This works quite well and using 12v with a ~50 foot feed for my Rocket has not been a problem.  

I had mentioned MPPT charge controllers because of this bit of info I found on one reseller's web site:

MPPT's are more efficient for:

Winter, and/or cloudy or hazy days - when the extra power is needed the most.

Low battery charge - the lower the state of charge in your battery, the more current a MPPT puts into them - another time when the extra power is needed the most. You can have both of these conditions at the same time.

However, if there is not much effective difference with small (100w and under) then I guess PWM makes sense. I can use the savings to add battery monitoring,  Any particular brands/models to look at or stay away from?


AE6XE's picture

I'm currently putting in a 7KW solar system in my house and adding in the MPPT modules from TigoEnergy on every 2 panels.   Basically what these devices do is load the solar PVs to the voltage-current optimal power production.   In my case, there is a chimmy shadow going across the roof--some people will have trees. etc.  When a string of panels in series are used there are more extremes in the power production across these panels, thus more efficiency can be gained to load each panel to the voltage level that yields the maximum power output for that panel.    With one panel with relatively small surface area, clear unobstructed sun (particualarly in Southern CA),  I would like to see some data that says how much efficiency is really gained.  I have a hard time imaging it is significant for the cost.

One can also say with PWM, "...low charge of battery,.. more current goes into it...".  until they get to a float charge voltage/current.

MPPT is definately more efficient, it's the issue that it may be only 1% to 10% more efficient for 1.5x the cost or more for a single panel system.  We'd need to track down some 'data' to quantify this.   I'm very skeptical of vendor #s that claim 30% more efficiency--well, yea if it's a bunch of panels in series and lots of shadow extremes (please buy our more expensive higher margin product...).



AE6XE's picture
charge controller brands

I don't have any particular controller recommendation, I suspect these are commodities now days and cost and features (low voltage shutoff) are the primary criteria.   I've been using a MorningStar ProStar PS-30 for a long time--happy with it.  I'll be trying one of these Renogy controllers--sitting on my door step in the fedex box as I type...


k1ky's picture
Voltage requirements of the Ubiquiti devices

I was interested to read that the Ubiquiti devices require 10.5 volts.  How much voltage will they handle?  I was thinking about a 24 volt battery system into a power injector system, then use solar chargers, etc. Knowing that 2 SLA batteries in series will yield around 27-28 volts when floating, will that be too much?



a 24v battery system would be

a 24v battery system would be too high.  says the MAX is 25v and by MAX they mean "the 24v zener (acting as a MOV) is frying itself to protect the board and unless you cut the power while its in short to ground your going to blow parts"

There are a couple ways around this

1) Run a 18v battery system (3x6v) which will be below the 24v mark

2) Run a DC to  DC Switching power supply (I use the Meanwell SD25's and SD50's) they have 12v,24v and 48v input models with 12v(11-16v adjustable) 24(23-30v adjustable)[i've seen them go lower to 22 even but wouldn't recomend running out of spec] . Meanwell even has a 12v in 24v out model for use on your existing 12v battery bank when you need to go longer distance you can run at 23v on the line)   This also includes running the 24v-24v model so that you can avoid the voltage issue of 28v on the charger affecting the device.

With these units (Similar to the device posted above) you can get away from the issue of battery vs unit voltage (I actually have a node running off a 48v-24v unit attached 79kwh battery bank)

K6AH's picture
Voltage requirements of the Ubiquiti devices

Yes, too much.  24vdc is the absolute max.  I wouldn't risk going higher.   Although I've been told (but haven't verified) that there's a sacrificial zener diode that protects the device... so don't throw it out if you inadvertently let the smoke out of one.


AE6XE's picture
12v battery system

Note that a 12v battery system (sealed, lead acid, gell) are essentially at 0% capacity by the time the  measured voltage is at 10.5v while discharging.   (Open Circuit at ~11.8v = 0% capacity).   Consequently, a 12v system is the appropriate system to put into an off-grid deployment.    The full range of battery charge is fully within Ubiquiti supported specifications.  A 24v battery system would exceed the higher voltage limit of ubiquiti devices and thus require additional equipment to protect the devices (or at least have a good nights sleep to not worry you'll fry a device).


AE6XE's picture
Ubiquiti may be protecting

Ubiquiti may be protecting some device models above 24v.    Without considering the outcome, I plugged an M2 Bullet into my GS108PE switch.  this is the POE "af" standard at 48v.    The Bullet did not power on, but it also did not burn anything up.    I suspect recent hardware models now have sufficient protection?  ...ether that or the GS018PE detected a short and protected the device.

This is because of the 802

This is because of the 802.3af specifications.

Initial detection is done at 2vdc-10vdc with 802.3af on the data lines (includes the Passive POE lines we use for power) (

If the correct signature is not detected the device will NOT provide power at the 48v range.

In addition 802.3af devices likely (as you mention) have a short detection system which would when the zener shorts to ground would I suspect cause a trip causing the port to shut down before the zener can overheat.

A passive injector has no such limitations and would happily provide power.

PoE remote reset

  Does anyone know specifically how Ubiquiti PoE Remote Reset is implemented?

  I've moded one LAN port of a WRT54 for 12v passive PoE to a Loco M2, which works
OK, for short cable runs. This frees up one PoE as spare, and provides a PoE/ DTD
combination with the WRT54 for local distribution, which it is good at.

    Having remote reset would be good if it is not too much problem to emulate.


Just cary a spare POE

A common item in the WISP(Wireless ISP) industry for this is that the system administrator/ network tech carries one of the POE injectors with a RESET button in their field kit.

All deployed nodes (at homes/office buildings/etc) have the POE w/o the reset button to discourage users from resetting the nodes configuration.

A similar concept can work well for a HAM deployment in many cases, such as where its a hilltop node, or a hospital type node where all configuration details are documented and there is no need to do the 5 second reset to regain password access.

I use this method myself for my field deployed nodes, I just keep the one with reset button in my truck so I can reset a node in the field as needed (extremely rare and I'm on the BETA team.)

AE6XE's picture
A 2011 post in ubnt forums:

A 2011 post in ubnt forums:


Only the Ubiquiti 24V 1A PoE supply has a remote reset button. It is provided with Rocket and PowerBridge radios, and is available as an accessory.

Most other Ubiquiti radios are provided with a 24V 0.5A PoE supply; it does not have a reset button.

Only the 'M' series radios are capable of remote reset. It is done by superimposing a dc voltage on one of the data leads. It has the same effect as pushing the
local reset button on the radio.


Here's the link to the circuitry of the PoE reset (I can not confirm the accuracy):


Thanks Joe, that's what I was

Thanks Joe, that's what I was looking for. Reset looks pretty straightforward.

The Ubiquiti 24v 0.5A PoE here model GP-A240-050 has a reset, small paperclip hole near the RJ-45 end; this must have changed since 2011.

I've managed to diode-OR the PoE output with an extrernal 12v supply (gel cell) and it works fine. Ethernet connectivity through the PoE does not depend on its being powered, but the reset function is lost in that condition, not a big deal.


KE0RSX's picture
Dragging up an old thread...

I'm dragging this up because we're considering setting up a node using solar/battery power in Iowa/Illinois. It would power one node (either Ubiquiti Rockets or TP-Link CPE/WBS210's). The setup that I currently have is a 12V SLA Battery (only because I didn't have access to a Lithium at the time), a cut-off switch that's set to 11.4 V to cut off and 12.1 V to reconnect, a buck-boost converter that raises the voltage to 24V and an adapter for PoE and Data.

We're looking for ideas on how to accomplish this. The expected time without adequate sun is 5 days. Going off of the Solar Turbine calculator at we get around 4.7 hours of sunlight a day for a fixed panel and up to 6.9 hours with a two-axis panel. 

I plugged a CPE210 into a Kill-A-Watt and it's averaging 2 to 3 watts. I know that in my setup above, the WBS210 averages 0.02 Amps at 24V, so around 0.04 amps at 12V. So, I'll calculate everything at 9 Watts to factor in the 50% discharge and overhead for the cutoff switch and buck-boost converter. 

Daily use= 216 Watts
5 Days without adequate sunlight = 1,080 Watts
aH of the battery needed (figuring a single 12V battery) = 90 aH (45 if I put two batteries in parallel), so probably a 100 aH battery for overhead.

So a bare minimum setup would be a 50-watt solar panel array. The worst case of not having sun for 5 days would be a 250-watt array. If I'm calculating this correctly. We were already talking about needing a 100-watt panel at the minimum. So, I'm guessing 100-watts for best case and 300-watts for worst case. This should also cover the 216 watts needed to run the equipment for the day, as well as charge the batteries.

1. Does my math add up?
2. Is there anything that I'm forgetting? I've tried to oversize everything to accommodate anything I'm missing.
3. Are there any good examples of a deployment like this in the mid-latitudes (around 40-degrees)?
4. In the original post, he factored 2 days without adequate sunlight. Where did you come up with that value (meaning is there a site that shows an average, or did you just pick the number)?

Thank you, and sorry for dragging up an old thread. This fit my scenario perfectly, in my eyes at least.

Have a great day, and Merry Christmas (Happy Holidays, Happy Thursday/Friday if you don't celebrate). :)

AE6XE's picture
Patrick,  I've been running a

Patrick,  I've been running a 24x7 solar system for several years now in SoCal.  I'm using 2 x 110Ah walmart deep cycle batteries with a ~320W solar panel.   There are 3 Rocket nodes, 2 ipCams, and 1 raspberry Pi.   Some of my observations:

1) I put in this higher Watt panel, because it can run the site under cloud cover -- worse case it goes out at night, but can stay running with days/weeks of cloud cover during the day.  It can also stay running in the Day when the batteries are past their useful life.
2) I found with the prior 110W panel, that when there were days or weeks of intermittent clouds, in winter, it might take a week+ to get the batteries back up to a full charge.   If there is a week of intermittent clouds, then the battery over several days may slowly be charged to a lower level during each successive day. The  calculations assume the battery is keeping up with a full charge every day, and doesn't always happen in practice.
3) Being conservative on the power consumption, I am running everything on 12v system, which needs a charge controller that can handle the 320W panel's current at 12v.   Thus, I have no loss to convert to 24v.     One exception is the Pi, which is a typical 12v to 5v car adaptor.   However, I don't have long cable runs up a tower.  This might cause me to rethink going to a 24v system. 
4) The batteries are cheap in comparison to lithium, gel, other.   They are lasting 4 maybe 5 years, already replaced them once, now ~2 years old and going strong.   I capture the charge controller data each minute on the Pi.  I bring the data into excel occasionally and create charts to see the voltage profile of the batteries over time.  I can see the discharge and charge rates over time to see how the batteries efficiency is degrading.  Eventually, when they need to be replaced, the site will start to go out at night.



I ran this thru my solar spreadsheet and came up with the same answer. A 215AH at 12V battery and 202-405W of panel (5% to 10%C charge rate) with 4.5hr of sun and 5 days of 'backup'. So yup, Joe nailed it.

-Size the battery to your load and dark/backup run time.

-Then size the panel to charge the battery at the proper rate. Most battery failures are due to chronic undercharging. 10% of the capacity in AH is ideal. (ex: 200AH would be 20A). You can go down to 5% and up to around 13% at least for a flooded battery. AGM's and Lithium might go higher, just check the specs, and be aware of different charge profiles.

You can't go too big on a panel... well you can reach a point where it's not cost effective anymore, but most people have cheap'd out long before that! Also be sure you get a "24V nominal" panel, not a 12V one. You probably won't find any 12V above the 200W+ level, but just something to watch for. This is to allow the charge controller room to drop the voltage to the correct charging voltage (~14V). A 12V panel may end up at 12V and will run your equipment but never charge the battery no matter how long it's connected.

If you need to ease into it, you might start with a 125AH battery and add a second if you find the sun not cooperating. On a 300W panel the charge rate would still be ok into 125AH. It's much easier to get the panel out of the way up front and add battery vs re-engineering panel mounts, wiring, etc.

AE6XE's picture
Year on Year flooded lead

Year on Year flooded lead acid batter degradation

Looking at the data on my solar system year on year over 4 day period in Dec 2019 and 2020, I see the following:

Full charge voltage
2019 just after sun down:  ~13.1v
2020 just after sun down:  ~12.9v

Lowest voltage level
2019 just before sun rise:  ~12.1v
2020 just before sun rise:   ~11.9v

Thus, about .2v year over year degradation.   since the battery is considered at 0% charge at 11.8v, I may only get 3 years out of these batteries :( .   It will be interesting to see if 1-year from now, they can stay running through the night.


Image Attachments: 
K6CCC's picture
Where did you get that number Joe?

since the battery is considered at 0% charge at 11.8v, I may only get 3 years out of these batteries :(

Where did you get that number Joe?  For flooded cells, 0% is generally considered to be 1.75 volts per cell - or 10.5 volts for a 12 volt battery.  Granted, you never want to run it that low, 11.8 volts is leaving a LOT of energy in the battery.

AE6XE's picture
This higher voltage is

This higher voltage is reported as open circuit voltage for state of charge.  Probably the 10.8 would be under load?  Since the load is ~small, using open circuit gives me a little margin.

here's a couple references:

joe AE6XE


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