Every year, hundreds of people are killed by fumes from home generators.
While many more people sit in the dark when there is a line power failure.

A workable solution to both situations is a Battery Backup System.
Commonly called a UPS (Uninterruptable Power Supply) battery backup systems come in all shapes, sizes, capabilities and costs.

Most of us are familiar with the emergency lighting that we see on the walls of businesses, banks, etc.  Well, those are a type of UPS.  Then there are the small UPS's the we see in the electronics stores, that offer backup power to a home computer.  Those usually are only good for a few minutes of backup power, due to the very small batteries they use.

But what to do when you need backup power for a longer period of time?
Well, you can pay thousands of dollars for a factory made system or set about making your own.  Being basically a poor boy, I selected the latter.

I was given a 600w APC brand UPS, by one of my customers.  The batteries had failed in the UPS and had begun leaking out on their carpet.  They just wanted it OUT of the building.  I was glad to oblige.  

I was elated to find out that the UPS was still in working order.
Instead of buying another Gel-Cell battery for the UPS, I elected to go another route.  I bought two car batteries at Wal-Mart and put them in a plastic dish pan.  Then I wired them to the UPS with some extra wire I had laying around.  Some battery cables, also from Wal-Mart connected the two batteries in Parallel.  Then a 30A inline fuse from an electronics surplus store finished off the hookup.  Total cost....less than $100.
Here's the battery pack that I created for my 600w UPS:


The yellow wire is the POSITIVE lead going to the UPS, while the black wire is the negative lead.

I've found that the battery charger built into the UPS is sufficient for recharging the batteries after a use.  This UPS is set to turn on any time that the line voltage sags below 105vac.  I hear it click on for a few seconds several times a day.  
Where I live, line power is not the most reliable or consistent.  

So before you have to ask, "What do you do with this UPS?", I'll tell you.
I use it to back up my 25" TV, my Satellite TV Receiver, my DVD recorder, a small table light and a 10" personal fan.

For my computer, I have another "Cyber Power" UPS that will give me about 18 minutes to shut down programs and turn off the PC before the battery goes below operating range.  I have a similar UPS for my Satellite ISP Modem and wireless router.  I just bought another Cyber Power UPS for my service bench.  

So when there's a major power failure, I still have my TV and TV-Satellite Receiver, light and a fan.
But what to do when I get hungry?  None of my UPS's are powerful enough to power my 1000w Microwave oven, toaster, blender or electric can opener, or even my Mr Coffee.

So I came up with another power source that is heavy duty enough to power everything in my kitchen, except the Fridge. (but, not all at once)

This unorthodox looking setup is what I came up with.
It's a 1750watt Inverter that I picked up at the local truck stop and two Deep Cycle batteries....once again, from Wal-Mart.
I set the whole mess on a four wheeled movers dolly for portability.

This type of emergency power supply is ideal for apartment dwellers, campers or for and AC power is needed where line power is not available.  Total cost, about $450.

I keep a small trickle charger on these two big batteries to keep them fully charged.  
This setup is almost identical to what's used in large motor homes for emergency AC power.  Except, in a motor home, the inverter would be more like 3000w and the batteries would be four or more 8D batteries.

Inverters and UPS's for home use do not produce a sinusoidal wave form, required by some devices like induction and capacitor start motors, like the ones found in refrigerators and air conditioners.

For those devices that require an true AC Sine-wave, there are special, and more expensive, UPS's and inverters available.  Some can be seen here:
http://www.campsitevideos.com/xantrex.html

Well, that's my story!

Y'all have a great day now, Y'hear?
The Shadow  

Thanks for the write up.

TheShadow wrote on Oct 12^th, 2008 at 4:19pm:

I just wanted to comment really quick on the batteries you selected to replace the worn Gel-cell ones, since it may not be obvious to readers of this thread.  While these batteries may suite your purpose of weathering momentary sags in power, they would not be suitable for keeping equipment going during a full-scale outage.  Readers of this thread looking to build a power supply to keep the lights lit during an extended outage, should use deep-cycle batteries like you did in the kitchen.  Car batteries are designed to provide a lot of power for a short time, but their performance declines quickly.  Deep-cycle batteries are designed to power equipment over a longer time.

TheShadow wrote on Oct 12^th, 2008 at 9:09pm:

The point is that car batteries are not designed to be discharged more than a few amp/hours before being recharged.  Like I said, they probably work great for your purposes, but anyone building their own UPS should keep in mind that deep cycle batteries are more suited to being fully discharged.

TheShadow wrote on Oct 13^th, 2008 at 2:27pm:

Depends on your definition of 'discharged'.  10 Volts is fairly low for a car battery and will wear on the battery.

There's no argument.  Your method is fine and is obviously working for your purpose.  I was just clarifying a point for those interested in building their own.

Can you believe?  I completely answered your questions and right at the end of my post, the whole dang thing disappeared.  Then it took me about ten minutes to get back into the forum.  Stuff happens....I guess.

So let me see if I can give you the Readers Digest condensed version.

A UPS has no idea what battery it's connected to.  It only monitors the input voltage.  After an outtage, when the line power is restored, it will go back into recharge mode and yes it's only a "Trickle Charge".  So there's no problem with it overcharging the batteries or causing them to "outgas".

Inverters, like the one I showed in my original post, are designed for use in large trucks to run 110v appliances.  That use would usually be only temporary and not ALL-DAY. 

Since my big UPS is a 600watt rated unit and my power draw is only about 200 watts, it's only running at 1/3 of rated output.  It doesn't even get hot.  As long as there's enough voltage coming into it from the batteries, it will keep right on running as long as I need it to. 
So the run-time is only dependent on the amount of battery power available.  With a big enough battery, the UPS could theoretically run forever.

The little charger in the UPS is designed to recharge a Gel-Cell battery that should only be charged slowly to prevent 'Outgassing'.  So it also recharges the larger lead acid batteries 'slowly' and again, that slow charge prevents the batteries from 'Outgassing' and spewing out dangerous fumes.  I have no problem with these batteries sitting in my home.  It's completely safe, just like a stock UPS is completely safe.

Quote:


The internal structure and chemistry is quite different between batteries of different types.  Some can stand fast charges and some cannot.
Some, like a standard lead-acid battery, will charge at lower voltages and higher currents than a 'Maintenance Free' battery. 
Deep Cycle and Maintenance Free batteries want to be charged at higher voltages, but under limited current.

When I was doing the battery testing for the Caterpillar Tractor Co. in their research lab, we had to apply about 15 volts (current limited) to fully charge a maintenance free battery. 

Quote:


The standard UPS is only concerned about the load applied to it.
It has NO CLUE as to what battery is connected to it.
As long as that load does not exceed its rated wattage, it will continue to operate till the input voltage from the battery drops below its 'ShutDown' level.
Theoretically, if the input voltage never dropped below the shutdown level, the UPS could run indefinitely.

I hope that (sort of) answers you questions.

Let me post this before the forum goes away on me again and I loose everything.

The Shadow 

 TheShadow

Thanks for your answers--that cleared up some of my lack of knowledge!!!