Why DC?

[Samgoober]

I realize I'm showing my ignorance here... Why would I want to use a DC switch? I see people talk about them often, and see that Netonix makes them, but don't know how or why I'd want to use one.

Thanks,
Sam

[sirhc]

1) you have an off grid location either solar or wind.

2) You are on grid but you want to use a battery bank and AC chargers as your backup instead of an inverter charger. That way you are not converting DC to AC to convert back to DC to power everything which means 10-20% better overall efficiency which means longer up time in power outages.

Currently I have inverter Chargers at my sites and run AC switches but even with (4) $200 AGM batteries this is only 10-12 hours up time. If I convert to DC those same batteries will keep the site up over 24 hours as my current inverter will not allow me to depth of discharge below 80-85%. With our DC switches I can run the 48V battery bank all the way down to 9V in an emergency.

NOTE: If you completely discharge your battery AGM bank depending on your battery make you will need a 10 Amp charger per battery to recover which I already have a 3 stage charger at each site anyway so I am good to completely discharge a bank in an emergency which would give me well over 24 hours of run time.

Our WS-12-250-DC Smart DC switch also allows you to tell the switch to turn off ports based on input voltages or time base to conserve power. So say you have a primary airFIBER link with a backup airMAX link and your off grid and you know that after mid-night you do not need the AF capacity so the switch can turn it OFF and you fail over to the airMAX link and then turn it back ON at say 6AM and it recovers to the primary link for daily capacity needs.

[Samgoober]

Thank you Chris.... excellent explanation!

[petecarlson]

They are great for a mini-pop. A din rail 24V PS and a 24V DIN rail battery charger is all you need to run a system with two 12V telco batteries. We also add some packetflux gear for monitoring but it all fits cleanly on a rail. I also like that it takes away the ability to just plug some more crap in so I know that what is running at a site is the load I designed it for so when I get a power alert at 1 AM I just go back to bed and schedule someone to take a look at it the next afternoon.

[sww]

All of my sites are 100% DC using car batteries for backup. UPS's suck!

[wispwest]

I personally love to chime in on these type of questions. We have over 40 towers and around 3700 customers. In the past, we had standard APC backups, which lasted around 4-12hrs depending on how many radios we had on the tower.

Over the years, we started noticing we were constantly going to sites that completely went "OFFLINE" out of no where, for no apparent reason, only to find the APC went into an "overload" state, or whatever. RED light was on, and the APC needed to be reset. So then we yanked them out, wired multiple 12V AGM's to a TrippLite power inverter+battery charger. This extended our runtime greatly, but however we STILL had these power surges that tripped the TrippLite (lol) into overload/protection mode. I also found it wasn't a surge all the time, but simply a power "flicker", if you quickly cut power and restored in a 1/2 second, it would also trip it.

So, currently we completely yanked them out, leaving the batteries, and NO backup at this time, as its more reliable not even having them in, due to all the "lock-ups".

All our equipment (AP's, backhauls, and MIkrotik routerboards), is DC-powered. WHY would we want to go from AC<>DC? Then when on backup, go from DC batteries<>AC inverter<>AC switch<>back to 24/48VDC to the radios? I'd rather have a DC switch, and go from the batteries<>Tycon 48V power supply+battery charger, straight to the DC switch<>radios. Longer runtime, less clutter, no more APC lockups!

[wtm]

Get on EBAY, and pick up some DC-DC Upconverter Power units. They cost about $5-9 each. They have them from 12 v. to 24 v. and 12 v. to 48 v. outputs.
Each one will do about 5-6 amps out, and they are fused and adjustable output. They can be paralleled through diode blocks to provide the needed amps at the site.

We have gone back to a complete 12 volt DC Battery Bus, with standard deep charge batteries. Using standard chargers now !

The PS units allow us to have 12 v., 24 v., and 48 v. DC available for every device. They have run the Netonix switches with Mimosa B5c's on them, and have made it through the heavy lightning monsoons this year without even a hiccup!

If needed, the 48 v. unit can be turned up to 56 v. if I remember ?

[Dave]

As a note, you do not need to use the up-converters, just feed battery's directly to netonix DC switch. The up-converters will just cost you additional % efficiency loss that the up-converter adds, plus the extra wiring & expense!

[lligetfa]

As a note, you do not need to use the up-converters...

Unless you are powering a WS-6-MINI or a WS-12-DC, both of which need 48V. All other DC models would see no benefit.

[wispwest]

Another quick note, if your towers are in an area that gets COLD during the winter, I recommend using an insulated and heated NEMA box (powered off 120VAC). You WILL LOSE up to 80% capacity/runtime if the temp gets below zero and you have a power outage. I keep my batteries warm (50-60 degrees), and they WILL retain the heat when the power goes out, and give you more runtime.