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Hacking an APC Matrix 3000 UPS to Improve Backup Time

I got tired of Malaysia's electric power utility monopoly TNB frequent blackouts. Several times a year, blackouts exceed 30 minutes, with one lasting 8 hours. At least once a year we have to throw out all our frozen food. It does not help that we are at the very end of our mains feeder line, and that the neighbour operates a sawmill-sized lumber saw in his spare time. Add being on top of a hill where frequent lightning strikes cause power trips ... you get the idea.

Picked up an old APC Matrix 3000 at a garage sale some time ago. This bad boy put out sine-wave AC at 3KVA! Distortion is 5%. It seems ideal for my freezer and refrigerator.

Note that it is far cheaper and easier to use a petrol/diesel generator for mains backup. But if you are an electronics guy, a lot of problems seem to have electronic solutions.

APC did not publish the battery Ampere-hours in their specifications, but the maximum run-time in backup mode for a single XR Battery Pack is 3 hours at a load of 1KVA.

Four NS60SL car batteries, each at 12V 47Ah can just about fit in an XR battery pack casing if you remove the middle horizontal plate.

Click to enlarge

Note: car batteries are built for a few seconds of very high current output and do not like the way a UPS may require a sustained discharge over many minutes or hours. They do not last as long as a UPS battery which tend to be of the "deep-cycle" variety. Still, a wet lead-acid car battery is cheap and cheerful, and rather than buying a new battery for your UPS, you might want to use your old/spare car batteries ...

Warning! UPS contain dangerous voltages even when disconnected from the mains. Do not mess with them unless you are a qualified technician. The APC Matrix 3000 packs a 3KVA wallop disconnected: that is the same as a mains connection!

When connecting the battery pack to the UPS, first plug in the battery cable. Next hold down the reset button(I use a cocktail stick) and connect the battery communications cable to the UPS. Finally release the reset button. The front panel LED should flash on and then go off. You now have a UPS battery upgrade!

Warning! Wet (not sealed, or not "maintenance-free") car batteries will produce hydrogen gas when charging. Hydrogen is explosive in confined spaces. Install in a well-ventilated area

Click to enlarge

My preliminary results are : 8 hours continous backup time while connected to a 2-door domestic refrigerator, one freezer, 2 PCs, 1 router, 1 ADSL modem, 1 WiFi router and a couple of energy-saving bulbs.

Unfortunately, the batteries produced too much heat while charging, or the XR Battery pack was not sufficiently well-ventilated. My ambient in-door temperature is 32 degrees Celsius, and the battery pack temperature hovers around 40. This greatly reduced the service life of the NS60SL. I had to replace them after 18 months. Running with the front and back panels removed eliminated this problem. The main UPS module is cooled by 3 hunky fans and does not have this problem. I suspect the UPS is meant to operate in an air-conditioned room.

A related problem is the XR Battery Pack microprocessor-based controller failing. It was mounted right at the top where the heat tends to collect, and browns very badly during re-charging. Again, removing the front and back panels solved this.

Warning! This upgrade will result in the XR Battery Pack overheating while charging. Do not install the front and rear panels!

My preliminary results are : 8 hours continous backup time while connected to a 2-door domestic refrigerator, one freezer, 2 PCs, 1 router, 1 ADSL modem, 1 WiFi router and a couple of energy-saving bulbs.

 

Software

Use apcupsd to control the APC Matrix 3000

Here is a screenshot

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