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Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2

[Equipment] More power battery talk

Ok I have some silly questions. An argument between small UPSs and DC only setups.

So I have most of my sites run from small 350 and 550 UPSs and they do give good enough runtime for smaller outages like around 2 hours with about 25-30 watts power draw.

If I do some basic calculations using 2 9ah batteries in 24volt wiring I get about 6-7 hours with 25-30 watts.
I used this - »ep.yimg.com/ty/cdn/sports-import···alc.html

Is it just because UPSs are that inefficient?

Im looking for longer runtimes at a few sites but my enclosures are just big enough to hold a 550 ups and the 24 volt POE injectors.
Could get 2 9AH batteries in there and a charger/power supply.
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foobar

join:2009-04-12
Canada
A UPS is (like) an inverter, so there's loss when its running on battery. Your AC PoEs are also not as efficient, so there's loss on that conversion too.

Some higher-quality UPSes won't let you 100% discharge your battery array either, where as the calculator you linked is outputting on 100% discharge of your bats (something you want to avoid if you can to prolong the life of your SLAs)

raytaylor

join:2009-07-28
kudos:1
reply to Inssomniak
Try to never discharge the battery below 50%
A ups will typically go down to about 30%

I just run 12v DC with a laptop power supply, PWM solar controller and a deep cycle sealed 120ah battery. Radios / routers are connected to the load output of the solar controller and the laptop supply is connected to the solar input instead of a solar panel.

For a 30 watt site it will give me 24 hours of run time.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to Inssomniak
said by Inssomniak:

Is it just because UPSs are that inefficient?


Yes. I have consistently argued against use of traditional off-the-shelf AC UPS for WISP applications. Those are designed to provide hundreds of watts for many minutes, with the built-in assumption that AC outages are quite rare.

WISPs usually need only tens of watts, but for many hours, and assume power outages are more frequent. A huge mismatch in specs!

said by Inssomniak:

Im looking for longer runtimes at a few sites but my enclosures are just big enough to hold a 550 ups and the 24 volt POE injectors.
Could get 2 9AH batteries in there and a charger/power supply.

Can you post a photo? My hunch is that you could fit a 24V DC-only system with 2x12AH SLA batteries in same space. For much longer runtime, you will need a Lithium battery system.


TomS_
Git-r-done
Premium,MVM
join:2002-07-19
London, UK
kudos:5
reply to Inssomniak
The best way to achieve efficiency is to do the least number of conversions between voltages. Each conversion wastes some power.

Bring in AC to feed your site, convert it to DC, and then power as much stuff as possible off that DC. Theres little point going from AC to DC back to AC and then back to DC again.

Google and Facebook through OpenCompute are big on this kind of thing, and have servers that are crazy efficient.


Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2
reply to lutful
I will post a digikey part# later when I'm back home.
I do t want to go full Dc like with solar. There is AC there and is reliable enough but because this one particular site is very important in the network and sometimes they shut off the power to do work. I'm just looking for 6-7 hours.
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54067323

join:2012-09-25
Tuscaloosa, AL

1 edit
reply to Inssomniak
said by Inssomniak:

Im looking for longer runtimes at a few sites but my enclosures are just big enough to hold a 550 ups and the 24 volt POE injectors.
Could get 2 9AH batteries in there and a charger/power supply.

Get yourself one of these, a plug in transformer and a couple of 12 volt gel cells and you will be good to go.

»www.altronix.com/products/produc···ame=SMP5


Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2
So that outputs 4 amps, charges at 0.3 amps.
Ok. Cool! I like it. How much?
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54067323

join:2012-09-25
Tuscaloosa, AL
said by Inssomniak:

How much?

Say around $60 or so with a transformer.

This is not a recommendation of a merchant, just a quick Google search.

»www.surveillance-video.com/smp5.···odGA8AeQ

You may also want to browse around the Altronix web site and see if they offer a better choice for your application.

I picked the SMP5 just from a quick search of their catalog and yes I can recommend Altronix as they build some very basic and yet robust equipment.

»www.altronix.com/

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to Inssomniak
said by Inssomniak:

So that outputs 4 amps, charges at 0.3 amps.
Ok. Cool!

Someone asked me via e-mail to comment on the Altronix SMP5 product because apparently there is some confusion.

You will need to purchase a separate 28V/175VA rated AC transformer for the 24V/4A DC output. That is also quite bulky and heavy.

It wastes more than 16 watts as heat (=0.3x49BTU/h) while supplying the 96 watts output (=24Vx4A) ... so it is not actually cool.

Finally, it only trickle charges at 300mA which means it will take more than 60 hours to recharge your 18000mAh battery bank after each 6 hour outage.


54067323

join:2012-09-25
Tuscaloosa, AL

4 edits
said by lutful:

You will need to purchase a separate 28V/175VA rated AC transformer for the 24V/4A DC output. That is also quite bulky and heavy.

Only if the OP needs 4 amps, which at 30 watts from 24 vdc is considerably lower than 4 amps, therefore that oversized transformer is not needed in this application, nor applicable...

You need to remember when sizing up power supplies to match the input to the load and as such in this case, a much smaller plug-in will do the job just fine.

Finally, it only trickle charges at 300mA which means it will take more than 60 hours to recharge your 18000mAh battery bank after each 6 hour outage.

Not sure how you came up with 18000mAh, the OP mentioned using two 12 volt 9 amp hour batteries in series which is still 9 amp hours, not 18 amp hours, in order to achieve 18 amp hours the batteries would need to be wired in parallel.

Wiring in series increases voltage while wiring in parallel increases capacity.
Expand your moderator at work

kf6ytc

join:2002-03-26
Turlock, CA
reply to 54067323

Re: [Equipment] More power battery talk

your amount of radios (5a will power about 30-40 ubnt radios) and batteries to your desire, I recomend walmart deep cycle boat batteries, they are much better than sealed agm batteries because you can service them to extend the life


54067323

join:2012-09-25
Tuscaloosa, AL
said by kf6ytc:

your amount of radios (5a will power about 30-40 ubnt radios) and batteries to your desire,

The OP only needs a hair over one amp and a 1.5 amp power supply may do the job and be less expensive, hence the reason I recommended the OP browse the Altronix catalog and decide for him/herself the best choice for the application.

The OP also posted about having a limited amount of space in the cabinet and considered using 9 amp hours of standby which is a very small battery and probably not to be found at Wall Mart.


Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2
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Here the the standard box we use at any sites that are needing an outdoor enclosure. With ups 350 as example for size scaling.
We usually use a 550 ups.

Is there a device like the above anyone know of one that is sorta plug and go? With the transformer already in it and can do at least 2 amps ? Maybe 3?
I don't really care how long batteries take to charge so charge current is not incredibly important.
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lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
I make my own but you can buy one of these UPS modules from Powerstream. They have the transformer built-in and are quite small.

»www.powerstream.com/12V-backup.htm

They have 12V/3A and 12V/6A models and also 24V models. DC voltage is adjustable. There are mounting screws for backplates.

Unfortunately, trickle charge current is only 200mA but you don't care.


Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2
THanks, looks like exactly what Im looking for. Only thing that concerned me is that the output voltage was not regulated, and ubiquiti radios to the best of my googling are not tolerable above 24 volts, BUT Im running at this one site 200+ feet of cat5 at least, and pretty sure Im losing 4 or more volts once it gets to the top.
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lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by Inssomniak:

Only thing that concerned me is that the output voltage was not regulated, and ubiquiti radios to the best of my googling are not tolerable above 24 volts ...

The output voltage is indeed regulated and it is also adjustable. However, for nominal "24V" UPS function, the output needs to be adjusted to 26-27V range to allow trickle charging the battery bank. That should be OK with 24V PoE.


Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2
Sorry I actually meant to say the output voltage was the same as the charge voltage. Im thinking it will also be OK for 24v devices
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