APC BK500 Uninterruptible Power Supply Teardown

Hello all!

Sorry for the long delay, exams happened and now I am just getting settled in at my Co-op position at Dairy Cheq (Electronics R&D)!

I have some projects planned for the near future, stay tuned!

In the meantime, I acquired quite a chunky piece of office kit that is nearly functional, a APC brand UPS!

From what I can tell, everything in it works a treat, except the battery is shot (sitting at 7 mV of voltage right now). I will be looking for a used UPS battery, but I decided to take a look inside at all the heavy goodies!

Front of the unit. Unfortunately, it was way too easy to open to include more disassembly pictures (2 screws and a tug).

Here is the back end, with all the protected and backed up mains connections.

Here is how the inputs are laid out in the back, quite an interesting setup to distribute that power around. Also a side shot of the ethernet and phone line protection circuitry.

Look at all of those heavy duty connectors! And the heat sink with the high current transistors! That’s one big chunky relay for the battery pack (I think)!


Now that’s an inductor. This is definitely a quarter of the units weight, after the battery (probably half of the weight).

Warning! High voltage! Keep yer fingies out!

Right around here I noticed the lack of board gunk for all of the tall components, the big filter cap had nearly wiggled off!

Otherwise, damn this is a nice looking board.

The culprit to the problem. The battery is shot, and I’ll have to snag a replacement somewhere. Checked its voltage, 7 mV! Hah! It is a 12 V, 7.2 Ah lead battery by CSB.

Pretty! Look at those mystery components! And a 10 mOhm trace resistor? I wonder what that is for.

The one (ST Micro) chip I could not read, but I assume it is some sort of main microcontroller because:

Tadaa! A Cypress Semi USB controller for the data aquisition/control! Quite nifty!

Everything else on board was kind of boring, lots of passives and voltage control circuitry. Would it ever be a blast to design this piece of kit though!

Here are some more pictures.

How cool was that? Tearing stuff apart always leads to a good time, look forward to more of it from me in the future!

Questions? Comments? The section is below!



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