UPS for 30 watts for 1 day

If this is for use in your RV, you already have a massive UPS source. Your coach batteries. Just get an inverter if you don't already have one. A UPS is nothing but a battery and inverter in one package.

I use a battery jump pack and a small inverter.Runs what I need but can't kill my house battery and might be used some day to jump start something. Also gives me 110 power if I need to make a repair on the roadside.

Tom_M wrote:
... If this is for use in your RV, you already have a massive UPS source...

Right. I should have specified that this is for my house.

30*24=720 watt hours, adding 10% efficiency loss (cold be more) totals 792 watt hours
Keeping battery alive, means never discharging below 50%
You need battery capacity of 1600 watt hours , which is approx 140 amp hrs

You will have to find a UPS that has external battery connections
To attach a large deep cycle battery

If you can deal with the 100 millisecond flicker, then you can buy a standby UPS for about a C-note or two. The online versions (ones which always use the battery) are a lot more expensive.

If you want to DIY it, you can build a wooden box, toss in two 6 volt golf cart AGM batteries in series, add a three stage RV battery converter and a Morningstar SureSine 300 watt PSW inverter. Just as good as a $2000 online UPS for this amount of electrical load, and it would have definitely more than the 140 ampere-hours as calculated above. As an added bonus, if you wanted to add solar panels to your S&B house, it would be easy to wire up the panels to a charge controller and feed the batteries with the CC.

daamac wrote:
I'm looking for a backup power supply for a DSL modem, router, voip box and weather radio (just those devices, not a computer). According to my cheap clamp on amp meter, all of those devices combined draw less than 0.2 amps, somewhat less than 30 watts.

What sort of backup power supply could supply those 30 watts for at least 24 hours? I'd also prefer not to have to replace the batteries in the UPS very often. Suggestions as to type, brand, model etc.?

Everyone is overthinking this. Just buy one sized properly. Here is a manufacturer with a calculator on their website.

Tripp-Lite

APC

Nobody is over thinking
most UPS for residential use are designed to give ONLY a enough power to shut down your computer system to prevent disc corruption/file damage and file loss

he wants 24hr continuous use at 30 watts
using the links above
the 1000VA model is $1000+ the 1500VA model is $2063

unless i miss my guess, he doesn't want to spend that much to maintain his DSL modem signal and weather radio

maybe i'm wrong :h

MrWizard wrote:
1000VA model is $1000+ the 1500VA model is $2063

unless i miss my guess, he doesn't want to spend that much to maintain his Sat receiver signal lock

--- or VOIP connection.

I appreciate the thoughts and comments of all. However, Mr. Wiz, you are correct. I'll have to settle for less run time from the UPS which will still handle most of my outage problems. Besides, my Honda 2000i - which has seen as much use at home as it has in the RV - makes a dandy, if cumbersome backup power supply.

I would go with a UPS that is at least 3X th needs (100 watts or more) and a pair of Group 24 DEEP CYCLE batteries or a pair of GC-2 for power storage.

The group 24s are big enough, but price the GC-2's as they may be cheaper and .. Well,they weigh more and hold more power.

Avoid Optima.. They hold less power. (only 60% of the power of the same size other types) Source: Optima battery web sites.