Recommendation for powering network gear

[JustinLacy]

This is my first attempt at doing something with solar. My driveway is about 1500' long, with a gate at the entrance. I want to have a couple of video cams near the gate. My plan is to extend my LAN by installing a wireless bridge near the gate. I'm trying to figure out how to power this stuff 24/365. A lot of what follows is my uneducated guessing, so let me know where I'm going astray.

I haven't decided on the bridge or security cams, but assume the total power consumption for them is 50 watts, so about 1200wh per day. I assume the hardware will be running at or near this level of power consumption continuously. I live south of Houston TX, and the equipment location has good southern exposure. I don't have a gate opener. If I get one, I will power it with a separate battery/panel in order to keep the network stuff simple.

If I get a 100ah 12V LiFePO4 battery, I could run this stuff for maybe 20 hours without recharging, so I need a solar array that can provide an additional 200wh to make up for what the battery can't cover, plus enough power to fully charge the battery every day. I don't expect 100% uptime, but there are often times where there will be fairly heavy cloud cover for four or five days in a row. Does that mean I need four or five of these batteries (and a solar array big enough to recharge them in a day) to ensure 95% uptime? That seems like a lot to power less than the equivalent of a medium size incandescent light bulb.

What am I missing here?

Thanks,
JL

 

[sunshine_eggo]

300W of solar favorably tilted to a winter-weighted tilt of 45° due south in Houston:



You multiply the solar radiation values by your panel wattage. On average, 300W would produce > 1200Wh/day (all values are > 4).

400W with a 40A charge controller should guarantee near 100% up time unless you have extended inclement weather.

 

[JustinLacy]

I understand how you come up with 300w for the solar panels, but I'm trying to understand how the battery plays in all of this, especially how "big" a battery is needed. Let's say the four hours of charging starts at noon, ends at 4PM. The gear (bridge, cams, etc.) are drawing 50w continuous. I think that means that if I have a 12V 100ah battery, and if the battery is fully charged by 4PM every day, it will be [almost] completely discharged at noon the next day when the panels start generating again. Assuming the 1200w generated by the panels between noon and 4PM is enough to keep the gear running and fully recharge the battery, I can see how this works well in a perfect world.

However, it seems like any time the panels don't generate enough power to run the gear and fully recharge the battery during that four hour window, the gear will somehow get shut down when the partially charged battery runs down. I know I'm oversimplifying things, but is that what happens? I'm trying to understand what happens on "bad days".

To make matters more confusing for me, I found a "charger calculator" that says it takes a 310w to 390w panel (depending on the type of charger) to recharge a 80% discharged LiFePO4 12V 100ah battery. That implies I would need at least a 360w panel to keep the gear running and fully recharge the battery every day, and that leaves no wiggle room for less than optimum days.

 

[400bird]

I understand how you come up with 300w for the solar panels, but I'm trying to understand how the battery plays in all of this, especially how "big" a battery is needed. Let's say the four hours of charging starts at noon, ends at 4PM. The gear (bridge, cams, etc.) are drawing 50w continuous. I think that means that if I have a 12V 100ah battery, and if the battery is fully charged by 4PM every day, it will be [almost] completely discharged at noon the next day when the panels start generating again.

The panel would start charging the battery shortly after sun rise, not noon.

Assuming the 1200w generated by the panels between noon and 4PM is enough to keep the gear running and fully recharge the battery, I can see how this works well in a perfect world.

However, it seems like any time the panels don't generate enough power to run the gear and fully recharge the battery during that four hour window, the gear will somehow get shut down when the partially charged battery runs down. I know I'm oversimplifying things, but is that what happens? I'm trying to understand what happens on "bad days".

I believe the term is "days of autonomy" and you need to plan for them. The easiest math is to just count for 0 sun (no solar) (and you said you were oversimplifying! Going with 0 solar makes the math easy)

So, you'd take your 100 ah from earlier and add another 100 ah of battery capacity for each day of no solar you'd like to survive. Also if you only want 1 day, you should probably treat the battery a little nicer and not plan for 100 discharge every day. 80% discharge will help extended battery life

To make matters more confusing for me, I found a "charger calculator" that says it takes a 310w to 390w panel (depending on the type of charger) to recharge a 80% discharged LiFePO4 12V 100ah battery. That implies I would need at least a 360w panel to keep the gear running and fully recharge the battery every day, and that leaves no wiggle room for less than optimum days.

I'd double check that charge calculator. That doesn't quite sound right.

One more thing to include when shopping for parts, solar panels aren't 100% efficient. Well, the listed spec is in lab conditions. Real world results are lower, quality panels should list second, lower set of specs for more real world output. I can't remember the name, NOTC?

Also, your inverter, charger, battery, and everything else costs a little in efficiency. If you can run the components all from DC that will help the battery last longer.

 

[Any name you wish]

So I am running an 8 port PoE switch with two Ubiquiti G3 Flex, and a UAP-AC-Mesh. The non-PoE side has a garage door wireless network connection, a monitor uplink for my whole home power monitor, and a 12V PS that runs a USB charger hub, and an alarm clock. I have about 3 days of power when I am not using my computer to monitor what is going on. If I power on the computer, I get about 2 days. This is a 100Ah cylindrical cell battery at 24V with a 2kW PSW inverter. It is twice the size of a 12V 100Ah system. You might wanna go bigger.