Go Down

Topic: Redundant power (Read 336 times) previous topic - next topic

mattlogue

I hate UPSs. Had bad time with them growing up..
 I have a home security system using ESPS. it's all in planning and had been sine 2017.

My grid is stable.. so not biggie. But someone brought it up. Site I had some plans, but want to run it by. Depression and dumb sometimes..


In basement have two SLA battery's.
MCU controls charging.
Battery's are maintained with draining once weekly, one on Sunday, other on Weds, etc...
5V and 12V run thru house on unused Telco pair. Ground is earthed.
IP Cams, Router, MCUs, emergency lighting, and security actuators run off this power..

Is that wire sufficient for 5 or 12V?
Should I step it up with transformers?
Should I run wire?

Not a big issue. I won't do this until most of DomEStat is done. Right now it's all dead!
Just because I live in the states don't mean I care

gilshultz

In our area Telco uses a nominal 90V ring voltage so for anything less the insulation should be OK. You should determine how much load you are going to connect. The major concern for the wire is the current, that will be your limiting factor. You can consult wire tables to determine the wire resistance.  Using Ohm't law you can determine what voltage will be delivered to your load. At that point you will know if it will work. If you have more then one unit on a pair of wires you will need to calculate with the combined loads.  If you want you can also use the resistance of the wire between the devices to refine your calculations.  This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil

PerryBebbington


Quote
Battery's are maintained with draining once weekly, one on Sunday, other on Weds, etc...
Why? Lead acid batteries are best kept charged and only discharged when you need them. If you are routinely discharging them for no reason you are using shortening the service life for no reason, not to mention wasting the stored electricity.


Quote
5V and 12V run thru house on unused Telco pair.
Telephone wire insulation is fine for 12V but the wire itself is quite thin so unless the current you are supplying is quite low I'd be concerned that the voltage drop would be excessive. For 5V distribute at 12V and put a buck converter close to the load.

Don't forget that 12V lead acid batteries are not 12V, they are 2V2 per cell, total 13V2 if you are floating them, which is what you should be doing for your situation.


MorganS

Quote
IP Cams, Router, MCUs, emergency lighting, and security actuators run off this power..
That sounds like a lot of power. Can you estimate the maximum amps required? You can ignore the current used by the Arduinos and sensors but everything else on your list could be one amp each at 12V.

Phone wire is about 22 or 24 gauge? You can run 1 or maybe 2 amps through a pair but voltage drop will be high if it is more than a few meters of cable. The capacity calculation gets kind of complex with multiple pairs. Running 1A through every pair in a phone cable will probably start a fire.

"The problem is in the code you didn't post."

PerryBebbington

#4
Dec 12, 2019, 05:26 pm Last Edit: Dec 13, 2019, 01:18 am by PerryBebbington
Search for CW1308 telephone cable specification.

Resistance should be about 90 Ohms per kilometre per conductor.

[Edit] Just checking that you have actual, proper telephone cable, not that cheap CCA rubbish or worse, CCS. If you have those you might as well give up.

DebraWay

A redundant power supply is the point at which a solitary bit of PC gear works utilizing at least two physical power supplies. Every one of the power supplies will have the ability to run the gadget all alone, which will enable it to work regardless of whether one goes down.

For ordinary activity, every one of the power supplies will give half (accepting there are two) of the power that is required. On the off chance that one is fueled off for reasons unknown, the other one will promptly repay to give full capacity to the gadget so there is no vacation by any means.

mattlogue

After review of this I have determined running a 18ga wire may be better.

Not sure on battery.... I'd want maximum life around 24hr and services running could be dropped off at discretion of MCU. I want reliable and inexpensive... so maybe not SLA? Sorry - a bit dumb, I thought periodic cycling of SLAs was conducive for performance.

Just because I live in the states don't mean I care

hammy


PerryBebbington

Quote
I want reliable and inexpensive... so maybe not SLA?
If size and weight are not a problem then lead acid batteries can't be beaten for being reliable and cheap. The simple way to keep them healthy is just to apply 2V2 per cell (13V2 for a '12V', 6 cell battery) and leave it alone. No need for any fancy management, they will look after themselves like that. Occasional discharge to test their capacity, that's all.

And, as hammy says, fuses are essential. A lead acid battery can easily supply enough current to melt cables and start a fire. I have a 48V battery in my loft to keep the lights on when there is a power cut. It is comprised of 4 * 12V SLAs in series. There is a fuse between #2 and #3.


larryd

#9
Dec 16, 2019, 10:48 pm Last Edit: Dec 16, 2019, 10:51 pm by larryd
Periodically running on battery can be a good thing.

You would run on battery power until you reach a reasonable discharge voltage.

The time you take to get to that voltage will give you an idea of the holding power of the battery; raise an alarm if this time becomes too short.

Better find out if the batteries have sulphated rather than thinking you have healthy batteries. ;)




No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

Go Up