12VDC UPS what are my options? - Page 1
Forum section: electronics / general

author: Kjelt
author_rank: Super Contributor
timestamp: June 02, 2017, 07:06:44 pm
content: Hi I got an internet router that has a PSU of 12V 2A so it will use probably around 10-15W (have to measure it accurately).I need it to keep running on a power outage for about 48 hours.When I look at for instance APC UPSs the problem arises that they only build 230VAC UPS.In order to maintain 15W 12VDC for 48 hours it takes an UPS of >2000VA and $2000 which is absurd for this problem.All I need is 12VDC 1,5A for 48 hours so a carbattery with around 60Ah or 70Ah will suffice.So does anyone know of a UPS that takes 12VDC in from an external PSU and as backup a 12V carbattery with charging and maintenance charging and delivering 12V ?I found a PICO PSU but that does not charge the battery and take 15V in as minimum, that could be an option but there must be better solutions?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 02, 2017, 07:26:57 pm
content: http://www.mini-box.com/picoUPS-100-12V-DC-micro-UPS-system-battery-backup-system

author: Kjelt
author_rank: Super Contributor
timestamp: June 02, 2017, 09:59:56 pm
content: Yes I found that one also, need a different input PSU voltage and built a housing but that is not a big problem.Anyone built designed something like this themselves?

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2017, 10:11:48 pm
content: I'd measure the current drawn by the router before continuing otherwise any capacity calculation is a stab in the dark. Also I'd go for a solution which uses Li-ion batteries because these will last much longer than a lead acid battery.

author: Kjelt
author_rank: Super Contributor
timestamp: June 02, 2017, 10:17:45 pm
content: Last longer in the sense of lifetime expectancy?

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2017, 10:36:25 pm
content: Quote from: Kjelt on June 02, 2017, 10:17:45 pmYes. A lead acid battery deteriorates quickly. You can prolong this with the right pampering (trickle charging at the right intervals and charging it correctly). All in all this is going to cost some money if you want to come up with a solution which still works after 5 years without needing to change the battery twice during that time.

author: mariush
author_rank: Super Contributor
timestamp: June 03, 2017, 12:13:04 am
content: You should open up your router and see what it actually does with that voltage.The router may require 12v for optional features like having a regular mechanical hard drive inside ... so the high current requirement could be for the case when you have a mechanical drive installed).Otherwise, the router most likely will have dc-dc converters inside to take down 12v to 5v , 3.3v , 1.8v whatever voltages it needs inside... so if the voltages inside tare as low as 5v or even less, you may not necessarily require 12v. They may have chosen 12v simply for convenience or because [max 2A] adapters were cheaper.Anyway, the basic idea is that you may be able to power it directly from a 2 or 3 cell lithium battery (7.4v - 10.6v) so you could quickly use a big lithium battery and a smart charger would top up the battery.

author: floobydust
author_rank: Super Contributor
timestamp: June 03, 2017, 01:57:32 am
content: There is thisDC-12V-2A-Mini-UPSusing 18650 batteries. Maybe could be modded to work?

author: David Hess
author_rank: Super Contributor
timestamp: June 03, 2017, 03:56:23 am
content: Measure the actual power that it uses.UPSes generally always use 24 volts and higher to reduce input current requirements.If you are considering the UPS route, then a bank of AGM batteries in parallel and a charger plus a couple of diodes and the original power supply for the router will be a lot less expensive.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 03, 2017, 04:35:37 am
content: I have seen 1A 12V adapters being used for consumer level routers as far back as 802.11b. For the new multiband units, 2A or more is not uncommon. Granted, the actual power usage would be much lower under typical conditions, but the peaks can be quite substantial - some long range routers actually have rather sizable capacitors to supply the transmit amplifiers.

author: Kjelt
author_rank: Super Contributor
timestamp: June 03, 2017, 06:48:32 am
content: Thank you all for the good input.Yes you are all correct that I first have to measure the current / power to make a better choice in my options.This router is supplied by the ISP and has a couple of addons: dual optical interfaces, tv out, telephone out and internet switch. Since it is positioned in the utility closet I have disabled the Wireless transmitters so that would save power. If it is indeed under 10W there seem to be more easier options available.Opening it up to determine the smps details is unfortunately not an option, there are void stickers in place and it plays a critical role in the household.To be continued.

author: SeanB
author_rank: Super Contributor
timestamp: June 03, 2017, 08:21:03 am
content: Ebay and get a replacement unit, and do the testing on that one, which will give as well a spare unit for testing.I ran my router for years on the UPS battery, which kept it running well for power cuts. It came with a 9VDC power supply, but I looked internally, and all this was used for was to supply a bridge rectifier ( unpopulated, just 2 wire links and a single reverse polarity protection diode), a incoming filter assembly ( also unpopulated, so I put one from another random unit in there to solve that cost cutting method), a main capacitor ( 100uF 10V, Capxon and already starting to bulge at a year, so I replaced it with a 1000uF 25V unit), and this in turn only fed a single buck converter that dropped it down to 5V, and then there were a further 2 linear LM117 regulators to provide a 3V3 and a 1V8 rail for the Realtek chipset on the board. Then powered from the battery direct, and it worked fine for around 5 years, till I wanted to use the onboard wireless, and found out the chipset was defective. No wonder it never worked from new, thought just the phone wireless was defective, but had a new phone in the interim and it had known working wireless comms. So replaced with a new Netis one, and will put in a buck converter for it some time, getting rid of that 5V wall wart it has.

author: Rick Law
author_rank: Super Contributor
timestamp: June 04, 2017, 09:34:43 pm
content: Quote from: Kjelt on June 02, 2017, 07:06:44 pmSince you are talking about your home internet instead of work, you may also want to check if it matters...My ISP is also my cable provider, their distribution point appears to draw power locally (conclusion based on observing them service their equipment at the street corner, and then I tested my theory during power outage, twice). When myhouse is out of power, their distribution point isn't working anyway. These consumer service-level stuff doesn't deliver business quality service-level too well.

author: Cerebus
author_rank: Super Contributor
timestamp: June 04, 2017, 10:05:23 pm
content: Quote from: Rick Law on June 04, 2017, 09:34:43 pmThe OP is in the Netherlands and so will come under harmonized European standards for on-net standby power. When I was actively doing this stuff in the UK (we were a licensed telco) we had to guarantee standby power for between 4 and 48 hours depending on exactly where in the whole telecoms network and what service you're talking about. I'm some years behind on the regulations so I'm not going to quote specifics as I'd almost certainly be out of date. It certainly wouldn't have been acceptable to have no standby power on any part of the network that might have to carry a voice call during a mains power outage and most broadband kit shares wires and racks with the voice kit that would have to remain powered. Certainly we were required to keep standby power on our DSLAMs.All that said, the regulations have been getting laxer and more telco friendly. I know that a few years back BT were allowed to install on-premises (customer site but telco owned) VDSL kit without standby power in a departure from what was, up until then, the normal expectation of providing standby up to and including the customer handover demarcation point. They were required to provide it as an optional extra but I've never seen an installation with it despite them using kit that had a specific connector for standby power on it.Bottom line: it's quite likely that a telco operating to EU harmonized standards will provide standby power during a mains outage.

author: Kjelt
author_rank: Super Contributor
timestamp: June 04, 2017, 10:28:44 pm
content: What is the most concern is that the alarmsystem can still sent alerts to the dispatch even if a potential burglar shorts the mains for instance on an outside lightpoint or upper floor.Another option I am considering is a second channel such as a cellphone connection (GSM modem).

author: Rick Law
author_rank: Super Contributor
timestamp: June 05, 2017, 12:21:22 am
content: Quote from: Cerebus on June 04, 2017, 10:05:23 pmQuote from: Kjelt on June 04, 2017, 10:28:44 pmGood that you guys have stand-by power rules. Hell, I'd be happy if they would notice us when they scheduled a plan outage. I had at one time a multi-hour outage for multiple days during their equipment maintenance. I had to call to report the outage before they told me "well, it was not a failure, it was a scheduled upgrade..."Cable companies ran by folks with different brains. I suppose, their thinking is, if power is out, you are not going to watch TV anyway so what is the point of stand-by power at the distribution point -- and, what is the big deal if people can't watch their TV shows for an hour or two...

author: Cerebus
author_rank: Super Contributor
timestamp: June 05, 2017, 12:24:25 am
content: Quote from: Rick Law on June 05, 2017, 12:21:22 amIn some parts of the US, heck in some parts of the UK, that would count as the end of civilization as the locals know it.

author: Kjelt
author_rank: Super Contributor
timestamp: June 05, 2017, 07:43:35 am
content: Quote from: Cerebus on June 05, 2017, 12:24:25 amThe next generations that will be internet.The kids nowadays get their "tv" shows from Youtube and other video and game streaming communities.