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Guide: Adding Extra Run-Time to Your UPS - Build the Battery Pack
Written by Gizmo   
Monday, 30 January 2006 00:00
Article Index
Guide: Adding Extra Run-Time to Your UPS
The Operation
The Operation - Removing the Face-Plate
The Operation - Removing the Battery
The Operation - Opening It Up
The Operation - Exposed Wiring
The Operation - Changing Connectors
The Operation - Splicing
First Smoke Test
Build the Battery Pack
Build the Battery Pack - The Wiring Harness
Second Smoke Test
Reassembly and Final Configuration
Reassembly and Final Configuration - Calibration
Reassembly and Final Configuration - All Done
All Pages

Build the Battery Pack

Next, we have to build the battery pack. Smaller UPSes like this SU1400NET tend to use 24v battery packs. Larger ones, like the SU3000NET that I have at my office, use 48v battery packs. With APC, the easy way to tell what size pack you need is by simply looking in the PowerChute software; it will indicate what the nominal battery voltage is. If all else fails, simply open the thing up and look at the battery pack. If it appears to consist of two 12v batteries, then it is a 24v system. If it has two packs of two batteries each, or (more rarely) one pack of 4 batteries, then it is a 48v system. In our case, we are building a 24v battery pack, so we need two 12v batteries. Ideally, we want to use batteries of the same rating, or an even multiple of the rating that is already used in the UPS. APC always uses 18 Ampere-Hour (AH) batteries in their Smart-Ups systems that are larger than 1000VA, to the best of my knowlege. These can be purchased for about $40 each. If you want to go with a larger battery size, then the next step up that you should use will be 36 AH batteries. The reason for sticking to even multiples of the already in-use rating is because the Smart-Ups internal battery management software wigs out if the capacities are too far off what it is expecting.

To build the battery pack, we will need to take the two batteries and mate them together as a single unit. That's where the double-sided foam tape comes into play; take one of your batteries and apply three strips of tape, like so:


Carefully line up the batteries so that they are side-by-side, and the positive ('+') terminal of each battery is next to the negative ('-') terminal of the other battery, and push them together so that the foam tape adheres them together (note: hot-melt glue can also be used for this, though it is more difficult to get the batteries together before the glue cools, and hot-melt can have a rather abrupt tendency to lose its adhesion). If you have done this correctly, you will have a pair of positive and negative terminals next to each other at each end of the battery pack. At this point, take your 100A car fuse and attach it across on of the terminal pairs. Set this assembly aside for a moment.

Take your black and red wire and attach the pins for your connector to the wire, one pin to each wire. If you have connectors for attaching the wire to the battery, go ahead and attach them to the other end of the wire now, as well. Now, insert the pins into the connector housing, taking care to ensure that the black wire goes into the side of the housing marked with the '-' symbol, and the red wire goes into the side of the housing marked with the '+' symbol.

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