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

• • APC 9400024C serial cable (I bought it used on Amazon for $9) - to reprogram the UPS to recognize 2 battery packs.

  • 100amp fuse for the new battery pack - I used a LittelFuse 0498100.M 100amp fuse

  • Heavy gauge stranded wire - I used Turnigy 10 ga silicone wire from HobbyKing. It is cheap, and its EXTREMELY flexible despite how heavy it is.

  • Anderson Power Products SB50 battery connectors - manufacturer's part number 992-BK.

  • Power terminals for the SB50 battery connectors - for 10ga wire, use manufacturer's part # 5953-BK.

  • 10ga ring terminals - I tried a few times to splice together the 3 connectors by soldering the wires together, but try as I might I couldn't get a good solder joint. So, I crimped 10ga ring terminals and them hooked everything up with a couple bolts.

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:

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.