Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Pages: 1 [2]

Author Topic: UPS recommendations  (Read 973 times)

WWWombat

  • Kitizen
  • ****
  • Posts: 1431
Re: UPS recommendations
« Reply #15 on: March 17, 2017, 05:52:02 PM »

I'd be a bit nervous about putting batteries in parallel in case for some unknown reason they discharge at different rates - does that even make sense / is that even possible though in this configuration? After all you did say to equalise them to begin with.

Yes, this is (or at least tends to be) a serious problem.

We have a share in a narrowboat, where the electrical supply (when not plugged into a shoreline) comes from a bank of 4 x 110Ah batteries, wired in parallel, in theory giving us access to 50-150Ah for overnight use.

The bank of batteries is one of its weak spots, even after a lot of thoughtful attention. Invariably, the bank isn't balanced, and one of the batteries gives up the ghost far too soon. We can't get them to last more than a couple of years. After that use, you need to replace all the batteries in the bank at the same time, so not a cheap failure.

This page gives some information about wiring the bank to achieve better balance:
http://www.smartgauge.co.uk/batt_con.html

That page highlights the different current that can come out of each battery (or goes into it when charging) when badly wired. All down to the small internal resistance of the batteries and the small resistance of the cables. An imbalance in the resistance means that, while the voltage is the same, the current is not.

The right wiring ends up like this:
http://erin-mae.blogspot.co.uk/2016/05/battery-balancing.html

Parallel batteries have to stay at the same voltage (since they're in parallel...), so it's safe to put in parallel any batteries of the same chemistry even if they're of different capacities.

If they are going to actually have significant current in and out, then it will pay for the batteries to be as identical as you can make them. Variation in resistances means variation in current, means some batteries will get degraded lifetimes.

As you say, though - UPS batteries tend to sit in a fully-charged state, with a float current running through them. They aren't likely to degrade much in this condition - only when they are being used.
Logged

currytop

  • Reg Member
  • ***
  • Posts: 113
Re: UPS recommendations
« Reply #16 on: March 17, 2017, 06:22:05 PM »

While I'd agree that regular, significantly high re/dis-charge loads on parallel batteries requires careful wiring and attention, I don't think the kind of load Weaver is talking about really matters. Modems are a few watts, APs about 9W, dumb switches maybe 8 watts, and a smart switch maybe 20W. So a few amps at most. Many modems and dumb switches may be run off 12v and many of for example the Ubiquiti radios run satisfactorily from 12v on shortish leads. I've never tried one of their APs on 12v but in any case Weaver uses Cisco and I know even less about those.

So if it was necessary I really don't think it's an issue in this case, especially considering when a single leisure battery would suffice for an hour or two.
Logged

WWWombat

  • Kitizen
  • ****
  • Posts: 1431
Re: UPS recommendations
« Reply #17 on: March 17, 2017, 06:25:11 PM »

I always used to buy APC UPSes but they are expensive so I bought a CyberPower one cheap in a sale a couple of years ago and its been fine.

I have a 480W cyberpower "mini tower" UPS (about £90 from Ebuyer at the moment), with limited sockets.

I also have a couple of the APC ES550 units (330W, and around £80 at Ebuyer at the mo), that have 4 sockets powered from the UPS, and 4 sockets protected from surge.

All of them seem to work just fine.
Logged

nallar

  • Member
  • **
  • Posts: 34
    • Smokeping
Re: UPS recommendations
« Reply #18 on: March 17, 2017, 06:25:55 PM »

Practically speaking, that doesn't apply to a UPS which will spend 99%+ of its time at standby at a float voltage...
Logged
Virgin Media cable, A&A and Sky DSL. pfSense router.

WWWombat

  • Kitizen
  • ****
  • Posts: 1431
Re: UPS recommendations
« Reply #19 on: March 17, 2017, 06:37:15 PM »

So if it was necessary I really don't think it's an issue in this case, especially considering when a single leisure battery would suffice for an hour or two.

I agree. My motivation was to make sure that people didn't extrapolate that situation into other, larger scale solutions. Particularly after this advice:
so it's safe to put in parallel any batteries of the same chemistry even if they're of different capacities.

followed by this response:
Thank god someone knows what they're talking about.
Logged

WWWombat

  • Kitizen
  • ****
  • Posts: 1431
Re: UPS recommendations
« Reply #20 on: March 17, 2017, 06:38:17 PM »

Practically speaking, that doesn't apply to a UPS which will spend 99%+ of its time at standby at a float voltage...

Which I pointed out in the post.
Logged

Weaver

  • Kitizen
  • ****
  • Posts: 4004
  • Retd sw dev; A&A; 3 ◊ 7km ADSL2; IPv6; Firebrick
Re: UPS recommendations
« Reply #21 on: March 17, 2017, 10:40:28 PM »

>  Modems are a few watts, APs about 9W, dumb switches maybe 8 watts, and a smart switch maybe 20W. So a few amps at most.

The power consumption is
    3 * DLink DSL-320B-Z1 modems and their DC PSUsí losses  = -unk-
    1 * Firebrick FB 2700  = 0.1 A @ 230 V = 23VA or 8 - 15 W
    2 * Cisco 1830i WAPs + POE injectors  = -unk-
    1 * 24-port gigabit switch  = -unk-

The switch is either
    24-port gigabit / HP 1820-24G  (J9980A)  = -unk-
    28-port gigabit / Cisco SG300-28  = 21W

I don't have any rough numbers to use to plug into those big holes - 3 modems, 2 WAPs and their PSUs.
« Last Edit: March 17, 2017, 10:42:49 PM by Weaver »
Logged

currytop

  • Reg Member
  • ***
  • Posts: 113
Re: UPS recommendations
« Reply #22 on: March 17, 2017, 11:41:37 PM »

I appreciate you may not find it easy to get access, but I expect the modem power bricks and the AP data plates will furnish some idea of load. You can't beat actually measuring it though as actual load is usually less than stated, sometimes by quite a margin.
Logged

Weaver

  • Kitizen
  • ****
  • Posts: 4004
  • Retd sw dev; A&A; 3 ◊ 7km ADSL2; IPv6; Firebrick
Re: UPS recommendations
« Reply #23 on: March 18, 2017, 12:22:24 AM »

I can get Mrs Weaver to photograph plates for me.
Logged
Pages: 1 [2]
 

anything