Uninterruptible Power Supply - Extending the Run Time

I very much needed to extend the running time of my backup power supply beyond the factory specification. The original batteries provided for 1 minute of power when running the machine at the maximum 1200 watts my PC is capable of consuming and 6 minutes of power when running at my normal load of 185 watts.

I live somewhat removed from any significant municipality, therefore our infrastructure is a bit neglected. We lose power about 10 times each year, each time varies from 6 hours to 5 weeks. It is often enough and severe enough (sometimes with "after-shocks" or subsequent drop-outs) that I require sufficient capacity to shut down properly every time this happens, without fail. 1 minute is not enough under any circumstance and 6 minutes is not enough if the power gives out when I am in the middle of certain involved processing tasks.

I set my goal at 15 minutes of power under full-load conditions. 15 minutes allows ample time for me to terminate any running application (such as rendering video or conducting a backup), and then fully shut down the computer properly, then fire up my generator to feed the house (and UPS) again until grid AC power is restored. I will not rely on the auto-shutdown command sent by the UPS to the PC. I am not confident that it would behave properly if a full backup or other intensive process is running when a power supply problem manifests.

Powering my computer equipment and other electronics directly from the dirty generator power seems like a bad plan. The UPS will condition the power from the generator before feeding the sensitive electronics. This avoids lost data, lost storage clusters, crosslinked files, and all the other ugliness that may happen when power has suddenly and unexpectedly become absent.

Info & Background & Et Cetera
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(very TL:DR, but do it anyway)

The wattage provided by modern uninterruptible power supplies is generally adequate for the equipment we use today. However, the total energy storage of these units may not provide enough running time to properly execute a system shutdown in every circumstance.

As an example, I formerly had a UPS rated at 450 watts output while the amp-hour rating (which determines the running time) was very low. That particular unit did not actually provide 450 watts, however. In truth, it measured out at 325 watts output. The connected computer and monitor under maximum load could draw a combined load of slightly higher than 600 watts. In the event of power failure under full load, the system would immediately go down. The same system under average load would draw 280 watts. In the event of power failure under average load, the system would persist for 1 minute 40 seconds.

In the above example, we can observe that the UPS was not properly matched to the system it was selected to support. This was partly my fault, due to my misunderstanding of UPS numeric ratings.

I have been unable to find any consumer UPS that would match my current consumer computers while meeting my desired specification. In order to obtain a properly matched UPS, I would have to acquire something enterprise level or modify an existing unit.

Due to the pricing of enterprise level equipment compared to the pricing of materials adequate to modify an existing unit, I opted to modify.

Link to one unit that would provide 17 minutes of running time for my current system under full load.

The cost, with shipping, would be roughly $1900.00 US Dollars. Too pricey. In addition to the price concern, I wasn't interested in 208 volts.

My total cost for a UPS capable of providing the wattage and for the materials to increase the running time to a minimum of 15 minutes was slighly less than $300 US Dollars. It would be 120 volts input and 24 volts internal battery.

Please see the conclusion for the results I ultimately achieved.

What I have done is remove the factory installed batteries, extended the wiring because the new batteries will not fit inside the unit and must be located beyond the reach of the existing wires, re-inserted the factory batteries but did not connect them (simply for ballast and to know their location if I ever choose to revert) so the unit would not be top-heavy and likely to tip over if bumped into, then attached the wiring to two batteries of greater capacity.

I discovered that my UPS already has a fuse that is suitable. Otherwise, I would have put one inline.

From my own experience, I know that crimps aren't the best for connections that involve high current. I decided to supplement the strength of the joint and the current handling ability by including solder at the joints.

I used this chart to determine the diameter of wire reasonably appropriate for conducting the power I would be needing. Wire gets hot if too much power is flowing, more specifically amperes of current. Voltage doesn't seem to matter unless you exceed the threshold at which the voltage would arc through the insulation.

I opted for stranded wire because it is more flexible and won't fatigue as easily as a solid conductor.

I did some shorthand math using beer and chips (I mean uh pencil and paper). Using Ohm's or Kirchoff's (I always forget which is correct) formula of potential multiplied by current equals power - extrapolating that power divided by potential equals current - potential measured in volts, current measured in amperes, and power measured in watts - 1200 watts divided by 27 volts equals a fair bit less than 45 amperes - 15 minutes of running time being one quarter of an hour - 12 amp hours of battery capacity would pretty much be close to what I needed. There are some losses due to wire resistance, inefficiency of converting DC from the batteries into AC for the output, and other considerations. I don't need a very precise 15 minutes of running time, it is simply my desired goal. My ARWAG (almost random wild-arsed guess) is good enough for me.

I don't think gravity has any measurable effect on electron flow except when applied to headphones and speakers (my stereo amplifier is hanging from the ceiling upstairs and I listen to music lying on the basement floor because it sounds better as the electrons pick up speed from falling so far before hitting my eardrums, just like the salesman promised - punchy bass and highs so crisp I swear they have been deep fried in fat FTW), therefore I won't make any estimation for the loss in power due to elevation at the location of the UPS versus elevation at the location of the batteries.

Warnings and things to Note
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(more TL:DR, but do it anyway. no, really)

This voids your warranty and any equipment guarantees or insurance provided by the manufacturer. This nullifies any rating issued by safety or operational fitness underwriters. If you ever need to return it for warranty service or claim coverage, and if it is returned without the original batteries or with altered connections or with a significantly modified external housing, you will be denied. They made it, they know. If they determine that it was ever altered, they will not support it.

Deep Cycle batteries will hold up better than standard and heavy duty car batteries. They have a better electrolyte solution and are substantially more robust in construction. I have been informed that the plates are made using more material, but I have not confirmed this directly.

I recommend only modding a unit that has a cooling fan or can be equipped with a cooling fan. I noticed an increase in temperature near my UPS during testing, and was going to install an internal fan. Moments before I actually found a suitable fan in my stash, I heard a fan inside my unit spin up. Apparently, the internal fan is thermostatically controlled. Yay me.

Be advised that many of the consumer UPS units are designed for short running time and will gradually build up heat. Excessive heat buildup will destroy a UPS, possibly flaming. A good idea would be to set a power profile that uses very little electricity, therefore generating less heat in the UPS. Just in case. During testing, I constantly checked various points in the system for temperature using an infrared thermometer. Lucky me, mine was just fine.

Some units create a modified sine wave. Some units create a true sine wave. Other units I have encountered create a square wave. A sine wave will generate the least heat. A square wave will generate substantially more heat. I suggest NOT using a square wave unit.

My laser printers, inkjets, and all other non-essential life supporting appliances and fixtures will be run through surge protectors fed by my generator. Because I know why not to put them on a UPS.

Never run furnaces, freezers, refridgerators, air conditioners, humidifiers, laser printers, or other heavy appliances from a UPS. Inkjets and other small devices are fine on a UPS, but probably won't be critical during a power failure.

Some UPS units operate on 12 volts internal voltage. Mine uses two 12 volt batteries in series (which are 13.5 volts nominal). 24 volts internal voltage, per specification - 27 volts internal voltage nominal. Check before making any modifications.

When everything is finished, it is a good idea to place batteries in a plastic tub of some sort for daily use. The batteries may leak or bubble over, some day. I've never seen it happen or heard directly from anyone who claims to have witnessed such a thing. But there are people on the internet who insist in blogs that IT HAPPENS, MAN! So, it must be true.



Mostly Serious Statement
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The  following process involves voltages, electrical current flows, and gasses which may cause injury and/or death, if mishandled. Some of the tools are capable of causing serious injury and/or death. Small parts are a choking hazard. Large parts are probably a choking hazard. Solder is composed of heavy metals which may lead to serious health issues some day. Friction injuries are possible due to high RPMs from the rotary tool. There may be fire. There may be even more fire. I wouldn't be surprised if I've missed mentioning something else notable.

Use eye protection. Button your sleeves. Tuck your shirt in. Keep your mouth closed. Provide adequate ventilation to your work area. Do not attempt this in low light. Not to be used internally or on sensitive areas of the skin or other jiggly bits of anatomy. Keep your limbs inside the vehicle until it comes to a complete stop. Be smart and be careful.

If you get hurt, I'll be bummed out, but I'm too far away to help you.

If you are not experienced in the proper use of the tools and materials required, you should not work alone or with a partner that shares your inexperience.

Most of us can probably pull this off in under 30 minutes without even getting dirty. But I could be wrong.

Proceed beyond this point at your own risk. There is no life-guard on duty and here there be dragons.


Tools
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Small Screwdriver - combination philips and regular head
Wire Strippers/Crimper
Flat Nosed Pliers
Butane Torch
Soldering Iron
Electronic Multi-Meter
Dremel Rotary Tool
Dremel Flex-Shaft
Dremel Fiberglass Reinforced Cutoff Wheel



Materials
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Crimp Connector Eyelets - 10 AWG (American Wire Gauge) - diameters to match battery terminals
Crimp Connector Inline Spades - Male - sized to match existing UPS connections
Crimp Connector Inline Spades - Female - sized to match existing UPS connections
Shrink Tubing
Solder
8 Feet Red Insulated Stranded Copper Wire - 10 AWG
8 Feet Black Insulated Stranded Copper Wire - 10 AWG
Oogoo or Polymer Clay such as Fimo or Sculpey

Equipment
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(1) CyberPower 1350AVR Uninterruptible Power Supply
(2) Stowaway ST27DC180 Deep Cycle Batteries - some units require two in series, some units require one.


Cost
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The UPS cost me $149 plus shipping. I've seen it on sale for $99 every few months at CompUSA online.
The atteries cost me about $100 each at Tractor Supply in-store. I've seen them on sale for $89, but rarely.
Miscellaneous connectors, solder, shrink tubing and wire cost me maybe $25 at Ace Hardware and Harbor Freight. I had much leftover when everything was finished
. I already own the tools. If I had to buy them again, it would be perhaps $200.

(* I could purchase the whole thing with materials, tools and all, for roughly one third what a retail unit goes for.)

Step 1: Disconnect From Power

Separate the unit from the source of power that supplies it - unplug it from the wall.

Step 2: Open the Unit to Access the Batteries and Wiring

Open the unit by removing the front, side, or bottom panel - mine is the front panel.

There is a set-screw on this unit which prevents the front panel tabs from sliding into the "free" position. The screw is located left of center underneath the front edge of the bezel.

After the screw is removed, slide the front downward and then pull it forward just a bit. There is a cable which feeds signal to the LCD and connects to the switches. You don't want to stretch the cable assembly, it is held on by friction and is perpendicular to the direction needed for removal. Remove the cable by gently pulling it toward the top arch of the bezel.

The front is now completely free of the chassis and can be set aside.

I used a piece of tape to prevent the screw from rolling off the table and becoming lost. It will be used for re-assebly.

Step 3: Remove Original Batteries

Remove original batteries. (my UPS has batteries that the user can replace, other units likely do not because many manufacturers want to sell to you repeatedly).

There are two wires connected to the UPS via spade connectors. It requires a firm pull to separate them. Be careful not to jerk it off your work surface when the connectors release.

The batteries are securely taped together and slide forward out of the chassis. They are heavier than they might appear. Be careful not to drop them.

Step 4: Determine the Voltage

Determine the internal operating voltage of the UPS.

I did not have a hand available to operate the camera for photographing this step. I recycled a photo from a previous step.

Temporarily restore the front panel connector to the front panel.

Connect the UPS to wall power and power it on by pressing the round button near the top of the front panel.

Apply the probes of a multi-meter to the chassis wires that were connected to the batteries and select "DC Volts" of an appropriate range (this varies from meter to meter, I chose 200 volts DC). Observe the voltage that the UPS would deliver to the battery cables during charging. You will need this value in order to properly select a battery or batteries to install.

Press the power button to turn the unit off, then disconnect the power supply cord from the wall.

Remove the front panel cable and set the front panel aside.

Step 5: Cut Some Wire

No photo is included with this step.

Cut wires to desired length.

You will need a wire from chassis positive to battery positive, a wire from chassis negative to battery negative, and (if using two batteries) a series jumper wire to connect one battery positive to the other battery negative.

The wire lengths will vary, depending on the relative location of the batteries to the UPS. Cut your wires to a length a bit longer than you measure. A small amount of slack is very helpful. I cut an extra six inches for each wire I needed.

Step 6: Preparing Your Wires

Strip black wire 1/4 to 3/8 inch.
Tin the ends of the wire.
Slide shrink tubing onto wire.
Crimp spade of proper gender onto wire - on the chassis end, one spade is male and the other is female.
Solder wire to crimp collar.
Position shrink tubing and apply heat using micro-torch or heat gun.
Slide Shrink Tubing onto wire.
Crimp eyelet of proper aperture onto wire.
Solder wire to crimp collar.
Position shrink tubing and apply heat using micro-torch or heat gun.

Repeat the above instructions, substituting red wire for black.

Cut series jumper wire to length - you can choose whatever color you prefer. Mine is red.
Strip wire 1/4 to 3/8 inch.
Tin the ends of the wire.
Slide shrink tubing onto wire.
Crimp eyelets of proper apertures onto both ends of wire. One should be large and one should be smaller diameter.
Solder wire to crimp collar.
Position shrink tubing and apply heat using micro-torch or heat gun.

Step 7: Cut Notches or Slots in Chassis

Using the rotary tool and cutoff wheel, cut two notches in the front and wrap the cuts around the side of the UPS 1/4 inch. I simply extended the existing notches where my UPS spade wires were already recessed by the factory. I cut far enough around the side to allow the front panel to be re-attached without pinching the wires.

Step 8: Making Battery Connections

Connect the series jumper wire to the positive terminal on one battery and then connect to the negative terminal on the other battery. Do not connect both ends of the jumper to the same battery.

Connect eyelet on red wire to the empty positive terminal on one of the batteries that now has the jumper wire attached.

Now it is time to connect the eyelet on the black wire to the empty negative terminal on one of the batteries already attached to the jumper wire.

If my explanation is not clear, please study the photos for a visual example. The locations of the wiring are very important and must be correct.

Step 9: Closing the Unit

Position the wires into the notches/slots that were made in the side-front of the UPS earlier. The wires should recess sufficiently to prevent the front panel from not being fully closed.

Insert factory batteries for ballast but do not connect them. The weight of the original batteries will provide stability. They are no longer  significant power storage containers.

Replace the front panel and set-screw.

Connect the spaded ends of the battery wires to the spaded leads protruding from  the UPS.

Connect the unit to a supply of power - plug it into the wall.

Step 10: Test, Charge, Enjoy

Test unit for voltage and charge.

Allow the batteries to charge up normally - I precharged mine using a 7.5 amp car battery charger to 80% before wiring them and then connecting to the chassis.

Enjoy the extended running time and peace of mind.

Step 11: An Incomplete Step

There is no photo for this step.

A step not shown because I have not performed it yet - use the Oogoo or clay to cover the bare connections on the batteries. Doing so will prevent a short circuit condition if you drop your unsheathed katana (in which case you deserve the shower of sparks as punishment) or any other conductive material onto the top of the batteries.

Step 12: Conclusion

In actual truth, I overshot my target by a tremendous amount. I don't know if this was influenced by a beer related anomaly in my math, or if I should have been deemed a Sesame Street dropout. The true duration of my modified UPS under full load, in fact, exceeds 600 minutes.

I fully charged the batteries and disconnected the unit from the wall outlet (the mains). I then booted the system and proceeded to render some videos in Sony Vegas for a couple of hours. I got a bit bored and decided to switch to something more entertaining. 4 hours of StarCraft II at 1920x1200 ultimate settings through my home entertainment system. The neighbors about 50 yards down the road suggested it was a bit late for all the noise. They have farm animals that were getting a bit unsettled. So, I switched over to running a full backup while browsing the web. That completed in just under 3 hours. I then killed some time on benchmarking my SSD and video card until I reached the 10 hour mark from time at the start of this evaluation.

My batteries were still at 17% charge when I plugged the unit back into the wall outlet. However, I am not certain that the UPS was finished recalibrating itself to the new batteries. This UPS does recalibrate but many do not.

My batteries being deep cycle, intended for marine and recreational vehicle use, have a reserve capacity of indeterminate quantity. I really don't know what my new maximum running time is. Yet.

My original intention of simply operating my main computer from this UPS and not connecting any other devices to use the UPS has been altered a bit. The additional capacity will now be used for other purposes, as well.

You will notice, in one or more of the photos, that there are two UPS units which seem identical. They are not identical. One is the modified unit and the other is standard factory.

The standard unit powers two cable modems, a 5 port switch, an 8 port switch, six wireless routers, two VOIP boxes, and four separate cordless telephones. These are low power consumers, so the stock batteries are sufficient for several hours of running time.

The modified UPS will now power a quad core PC, an octo core PC, a dual core HTPC, three 28 inch LCD monitors, two 19 inch LCD monitors, a 500 watt home theater system, three cable DVR boxes, a 13 watt fluorescent floor lamp, five external hard drives, a 150 watt powered subwoofer, the chargers for three Palm PDAs, the chargers for five laptop computers and two netbooks, the chargers for three cellular telephones, a charger for AA and AAA batteries, three LED alarm clock-radios from the 1970's, two XBOX 360s, two Sony PS2s, one original XBOX, one Nintendo Game Cube, a Water Pik, an electric razor, and an electric tooth brush. Obviously not all of these will be in use concurrently (I have not mastered simultaneous tooth brushing, Water Pikking, and shaving). As previously mentioned, I do not yet know exactly the running time of this unit under what I consider full load at 1200 watts.

To achieve all the connections necessary for plugging in so many devices, I will attach  a multiple outlet power strip into each of the outlets on the back side of the unit.