100W UPS - Page 1
Forum section: electronics / projects

author: kxenos
author_rank: Frequent Contributor
timestamp: April 13, 2013, 05:25:52 pm
content: I need a small UPS to power my ADSL router because it is also used for my VOIP telephone line. I couldn't find a UPS around 50W so I'm thinking to build this.It's basically a 12V NiMH battery charger circuit found on the net, altered to provide around 0.9A current to charge a 7Ah or 9Ah battery. Then it uses an inverter circuit (also found in the net) to invert battery voltage into 230VAC mains voltage. The transition is done with a DPDT relay.I know I can skip the inverter part and just use a DC-DC to power directly the router as it uses a wall SMPS adapter but I might need to plug a cordless phone or whatever.Suggestions or thoughts are welcome.Thanks

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 13, 2013, 08:24:11 pm
content: I really wouldn't use an inverter, that makes it less efficient (not to mention more complicated), thus less battery time, and there is essentially no switch over time to cause issues with things, just make it a plain DC UPS for a sealed lead acid battery, stick a small SMPS on it for your router and another one for the phone (if it is a different voltage).Also, go Sealed Lead Acid, they last for a good long while in this application, whereas NiMH will probably crap itself after a year or two in this application.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 13, 2013, 08:26:55 pm
content: There's PicoUPS which might suit your requirements - seehttp://linitx.com/product/12438

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 13, 2013, 08:33:25 pm
content: Is it just me or does the output on that look unregulated? Or if it is regulated it certainly wouldn't meet spec; which states 10A load capability, I see no inductors which implys linear, and no heatsinks so......

author: madires
author_rank: Super Contributor
timestamp: April 13, 2013, 08:49:56 pm
content: If all the devices are DC powered, which cordless phones and DSL routers are, why don't you simply use a lead acid battery directly? Add DC/DC converters for the voltages you need, a charger circuit, some logic with a deep discharge protection and a central power supply to power your devices and to charge the battery. Plain simple :-)

author: madires
author_rank: Super Contributor
timestamp: April 13, 2013, 09:02:31 pm
content: Quote from: peter.mitchell on April 13, 2013, 08:33:25 pmYep, totaly unregulated. You have to add a fuse and a voltage regulator. The specs also don't mention any deep discharge protection for the battery.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 13, 2013, 09:03:50 pm
content: QuoteDunno - it's on my list of things I might acquire and look at since I need a UPS for much the same reason as kxenos but I haven't played with one as yet.Does it need to be regulated - most things that expect to be powered from a 12V wall wart would, presumably, have their own regulation.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 13, 2013, 09:04:41 pm
content: QuoteThatmightbe more of an issue.

author: kxenos
author_rank: Frequent Contributor
timestamp: April 13, 2013, 09:20:36 pm
content: Indeed, it has no discharge protection nor regulation. Regulation is not a big deal for my application though. But I think the guys that suggest a dc-dc for output are correct. Also, the PicoUPS might be a very good solution, thanks

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 13, 2013, 11:28:24 pm
content: The reason I said regulation is occasionally things run off silly voltages, like 15v instead of 12, and a SLA would need a boost converter for thatPicoUPS is very expensive for what it is IMHO, it seems like it could be accomplished with a LM317, a resistor or two and a relay.