APC XS 1300 UPS Using 2 AGM Batteries

My trusty APC XS 1300 UPS’s battery died and wouldn’t keep a charge anymore. I really like this UPS, so I wasn’t ready to give up on it yet.

Original Battery

I first set out to buy a replacement battery, APCRBC109, but at $109.00, it was almost as expensive as a whole new unit. The APCRBC109 is 2 SLA 12v 9Ah batteries, which means its 2 sealed lead acid 12 volt 9 amp hour batteries that are wired in series to product 24 volts.

An amp-hour in its basic idea would be you can get 1 amp for 9 hours or 9 amps for 1 hour at 12 volts each.

So, if we were to use the UPS at full power we can estimate how long the battery on the UPS would last. This would give a estimate to compare other batteries with. You can get the total rating from the specs, 780 watts. To figure out how many amps it will draw from the battery, use the watts formula:

Watts is voltage x amperage, w = v x a. Re-arrange it so a = w / v
780w / 24v = 32.5 amps

In a perfect condition (ignoring UPS electronics loss, heat, etc)

9ah / 32.5a = 0.277 hours

Or about 16 minutes run time at full power. Pretty good to protect against short power outages, but we can do better if we want.

Replacement Battery

I bought 2 AGM 12v 55ah batteries.

If I apply the same formula as above, I can calculate theoretical run-time.

55ah / 32.5a = 1.69 hours

Or about 101 minutes! That makes sense because our new batteries hold about 6.11 times more power (55ah / 9ah) then the old ones.

The batteries need to be hooked up in a series, or positive to negative, circuit to create 24 volts (voltage is added in series) in the same way the original batteries do.  The batteries wont fit into the UPS, so I picked up 2 battery cases from Amazon and a resettable fuse.  The fuse was tied in series with the batteries just in case too much power is being drawn.


You can run standard AGM batteries to increase run time.

Backyard Theater

I became interested in a backyard theater while camping. There was a guy there who had just a white sheet, DVD player and a projector. It was awesome, they (him and his family) sat by the campfire and watched movies all night. It reminded me of the old drive-ins, just watching movies in the night air.

After getting home, I set out to build a system of my own. I had a few basic ideas and must-haves.

  • Cheap – Get used or make parts
  • Portable – In case I want to take it camping or a friends house
  • Bright – I want it easy to see, even in the moonlight of a full moon
  • Simple – Easy to setup/take down

After spending about 5 seconds looking at prices of new projectors, it was clear that Ebay was the way to go. There were some great deals that could be had on Ebay, but like anything else, you need to do your research. With projectors, there are so many specs on them that it can make your head spin. I’ll go over the major ones to look at:

  • Brighness / Color Light Output – Rated in lumens, this is the amount of light coming from the projector. The bigger the better, but get at least 2000, anything less will seem dark and not work very well with other light, such as moonlight.
  • Resolution – This is the number of pixels that can be displayed. The higher the better, but I recommend at least 1024×768.

I found a Epson 3LCD LCD Projector PowerLite 85 H295A but it was listed as Non-Working/Parts and didn’t have a bulb in it, so I checked Ebay again to find out how much bulbs were and since they we cheap, I bought the unit.  After installing the new bulb, the unit ran perfect.

Next thing on my list was to create a video source for it since I didn’t want to lug around my DVD player everywhere I went.  My solution for this was to load up XBMC on the RaspberryPi and run my videos from there.  The only issue was the projector had a PC VGA input, so I picked up a 1080p Hdmi Male Input to VGA +Audio Output Cable Converter Adapter on Amazon.

For audio I needed something loud, so I used an old pair of computer speakers that had a amp and subwoofer built in.  It worked out perfect, the HDMI adapter had a 3.5 mm plug that plugged right in.

Last, but not least, I needed a screen.  I found Ron-Loc Budget Blackout Lining at Joann Fabric.  This heavy cloth reflects light well and prevents light from going through.  If you’re on a budget, a white sheet works well too.

Overall, I spent less then $200 on the system for those hot summer nights to watch our favorite movies outside.

Cisco CP-7912 IP Phone

Cisco CP7912
I acquired a couple of Cisco CP-7912 IP Phones to take apart and see how they work, because around here, we love old, broken hardware to learn from and experiment with.

The Cisco 7912 usually runs SCCP (Skinny Call Control Protocol) and is not very useful for our purposes because we run Asterisk with SIP based hardware.

After googling for a bit, I found SIP firmware for this model phone, CP7912080001SIP060412A.ZIP on Cisco’s site, but you need an account with them to download the file. If you don’t have an account, try googling the file name.

The firmware will be loaded from a TFTP server when it boots, so you will need to extract the zip file and place the 3 files from the zip file into the TFTP root folder. The files you need are:


Then you will need to set the TFTP servers IP address in the phone. There are 2 ways to do this, 1) set option 66 in the DHCP server, 2) set in phones network configuration menu.

To set the TFTP server IP address via the phones menu, go to Settings and then Network Configuration. Go down to TFTP Address and press **# to bring up the hidden edit menu.

The main problem I had with this phone was it was password protected, but I didn’t know the password. I tried the default password of 1234 but that didn’t work, so I had to factory reset it. While in the settings menu press **2 on the phones key pad (not all together, but one at a time).

After saving the TFTP IP Address, the phone will reboot. If you watch the TFTP servers log, you should see the phone downloading the files.


It’s a nice 1 line, super easy phone. My biggest complaint is there is no speaker phone and SIP options are very limited. The phone does have keyhole openings in the back of the phone to make mounting on a wall real easy.

XBOX 360 Heatgun RROD Fix

I’ve been doing electronics for a long time and when a friend gave me a broke Xbox 360 with the RROD (Red Ring of Death), I jumped at the chance to try and fix it.

I googled the issue and found out it has to do with the use of Lead Free solder where the CPU/GPU/RAM/Bridge can develop broken connections. These chips are BGA chips, which mean they have the balls of solder under the chip itself so there is no way to visually inspect them. By searching, there seemed to be 2 ways to fix this, 1 was to replace the X-Clamps with screws and the other was to reflow the chips with a heat gun.

Replacing the X-Clamps

This way involves replacing the X-Clamp with bolts and washers so tight to warp the board/chip to make the connection. In no way do I recommend this to fix the RROD because by clamping the heatsink so tight, you can actually damage the chip. However, I do recommend replacing the X-Clamps with screws because trying to get these on and off can be a chore and one small slip with a screw driver, you can scratch a trace and damage the board. I used allen key (hex key) head screws, #10 x 32″ .

Heat Gun Reflow

DO NOT DO THIS! I will say this one more time, DO NOT DO THIS! We can, and do, learn a lot from the internet and I research things every day, but this is a bad popular myth. I do electronics all the time and design my own circuits, and this just does not make sense, but I figured why not try it anyway to see what happens. It failed, and failed bad. The traces bubbled and the chips fried even before I got the solder to melt. Lead free solder, on average, starts melting around 230C but a cheap heat gun runs at 300C (572F) on low (which is OK) and 600C (1112F) on high (which is just way too hot!). The bigger issue is applying that much heat to just the top of the chip will fry the chip. That big of a board really needs to have a preheater to heat the bottom of the board to around 170C and to just heat the chip itself to above 230C (until solder melts) from the top, so you’re only applying about 60C extra to just the top of chip. Also, you really need to monitor the board/chip temp with a thermocouple to make sure you’re at the right temp.


Pay someone to do a proper reflow or DIY it yourself with proper equipment. Make sure they use a thermocouple to monitor temps, a board preheater and a temperature controlled hot air reflow station. If I come across another RROD Xbox, I’ll try it on my reflow station.

Arduino Mega 2560

I picked up an Arduino Mega 2560 R3 clone on Ebay for $27.50 and it is definitely worth the money.  I was a little concerned that the construction might not be that great because of the price, but it has surprised me, construction is good and soldering is very professional (no cold solder joints that I can see).

My primary development machine is a Ubuntu 12.04 LTS box.  Installing the Arduino IDE was easy, I just followed Mark Loiseau’s instructions on his blog.  I have been playing with basic sketches and they compile and run great.

Overall, I am very happy with the product.

Teensy USB Development Board

I started working with the Teensy USB Development Board from www.pjrc.com and I have to say it is nothing short of amazing.

The Teensy is an AVR microcontroller board and comes in 2 flavors, the Teensy 2.0 and the Teensy++ 2.0.  The Teensy has 25 I/O, 12 analog and 7 PWM whereas the Teensy++ has Teensy has 46 I/O, 8 analog and 9 PWM, but on both boards they have shared pins, so an I/O may also be an analog pin.

It’s almost like a Arduino, but smaller, runs full USB, and you can solder directly to it.  They both have their pros and makes a great addition to a makers toolbox.

Code is easy to create for the Teensy using the library’s or you can even put it in Arduino dev environment.

So for the $16, it’s worth a try.  Shipping was fast and the developer at PJRC seems like good person.