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APC SmartUPS 1400NET Expansion

I have had an old APC SmartUPS 1400NET for a number of years now.  Its something I salvaged from the trash heap, and in the end all it needed was a new set of batteries.  These old school APC UPSes are built like tanks, but they suffer from the problem that with a faulty battery you can't get them to power up, even plugged into the wall. 

Expanding the Battery Capacity

This project involves expanding the capacity of the SmartUPS 1400NET UPS.  By default, the UPS uses beefy 18AH 12V battery packs (Amazon has them for a reasonable price).

Although by default the capacity of the UPS is pretty spectacular, it can be made even better by adding more battery packs.

The Plan

Basically, you want to hook up another battery pack in parallel with the existing one.  You can split the existing connector on the UPS and solder on another connector for a battery pack, but I chose to just make a Y adapter I could just plug into the existing UPS battery connector.

What You Will Need

Making the Y-Adapter

The terminals slide into the grey housings and snap into place.  You can crimp the wires in, but I chose to solder them.  I put a bit of flux into each connector and slid it over the stripped 10ga wire.  I couldn't get it hot enough with my soldering iron (there is a lot of wire and terminal mass), so I just heated carefully with my propane torch until the flux started to sizzle a bit.  I fed solder in, and the result was a rock solid connection.

The end product, with a connector ready to hook up to a new battery pack:

The Anderson battery connectors I needed for my UPS expansion project arrived. I basically made a 2 way splitter for the existing battery connector so I can hook up a second battery pack in parallel with the existing one. Some wiring diagrams of the "officially expandable" version of this ups reveals that this is how the expansion packs wire up. When I connect to the ups serial terminal there are some "hidden" commands that let me add another battery pack.  I ended up soldering the 10ga wires into the battery connector terminals. I couldn't get the terminals hot enough for the solder to flow so I just used my propane torch. Worked great. To make the y-splice I initially tried butt splicing the 3 x 10ga wires together but quickly realized that was not fun. So I just used ring terminals and a small bolt to hold them together.  Next I'll build an acrylic box to house both battery packs under the ups. This way it'll be easier to disconnect them. The ups barely fits the battery pack as it is and I always worry im going to damage the exposed circuit board.

Programming the UPS

To program the UPS, connect it to a serial port on your computer using the serial cable.

I used minicom on linux to connect to the USB/Serial adapter serial port:
sudo minicom -D /dev/ttyUSB0 -b 2400

At this point I get the usual menu-based system for administering the UPS.
I chose the "logout" option.
Type '>' to display the number of configured external battery packs.  In my case 000.
Type '+' to add another external pack.
Then type '>' to show the new count.  In my case 001.
You can disconnect your terminal, and connect the new battery pack to the harness.

End Result

Here is the end product:

I chose to put the battery packs outside the UPS.  I found it hard to get in and out of the little panel on the front, and felt I risked breaking the thin ribbon cable hooking up the display.  I installed a grommet on the side of the UPS and just passed the wiring through the side.

In the future I plan on building an acrylic box to sit under the UPS where the batteries will be stored.