Power redundancy

[mlow]

Hi, quick question.. designing a battery backup system and want to run everything DC, but the budget cannot handle a purpose-made DC UPS such as http://solarcraft.net/dcups-power-supply/

So we'll use a generic smart charger, and want to keep our load disconnected from the batteries while there is power from an external 24V PSU, to minimize cycling of the batteries.

How long can either the WS-12-250-DC or WS-6-MINI last when supply voltage lost? Thinking about using a SPDT relay which will allow the external power supply to power the switch until power is lost, then the relay will transfer over to the batteries. Don't yet know what the transfer time of that will be, but I need to know what to aim for..

[rebelwireless]

zero seconds.

Just look at a tycon 2424 charge controller. pretty cheap, and will automatically switch to DC power. Feed your 24V supply directly into the controller solar/wind/dc input, batteries to the battery leg, and PoE out to your netonix.

a TP-SCPOE-2424HP is about $80 and will do nicely. You can feed it with any 24v supply you like. I do this and I build a multi-input supply from RocketM5 24V1A supplies, just add a 1ohm resistor and a zenner diode on the - leg of each supply and tie the legs together to feed the charge controller. SUPER cheap, very effective, and you can get a 2A redundant supply with 3 cheap ubiquiti PoE injectors...

[mlow]

Thanks for the input! I took a look at the Tycon adapters, they look pretty nice. Not sure how I'd power a WS-6-MINI + radios with one.

The relays we were looking at had a very fast release time (which is the time taken to switch to batteries), from 2-15ms. Cheap APC UPSes have transfer times of 5-10ms. Though in that scenario your equipment is powered through a AC-DC power supply that might bridge that gap. We'll use a 24-48V DC-DC converter that may bridge it as well.

After thinking about it, I don't think I really care if equipment reboots when power goes off and we switch to batteries, and when comes power comes back. A very small amount of people on our service have automatic transfer switches, most people would be running to pull out the generator, if they have one at all.

[Chris@edgarhighspeed.com]

Hi
I actually bought all the equipment to run a 2424hp on a poorly accessible tower site but I haven't installed it yet. I was looking to use the ws-6-mini also but I think I am better off going to a dc model.

I do have 1 question for rebelwireless, when the batteries start getting low, does the 2424hp drop voltage one the Poe output side or does it completely shutoff the Poe port, it does say it's regulated 24 volt. Because if I used a dc netonix switch I would want to be able to alert on low voltage. In your setups do you tie the 2 outputs together.(Poe and the rear ouput)

Also on the 2424hp you need a 48 volt Poe to charge the batteries, charge light wouldn't even come one when I put 24 v to it. Unless maybe I didn't have enough amps.