Modification of an APC Smart-UPS 600 to accept the battery pack from a Smart-UPS 1000XL

Jesse Kovach

I recently came into possession of two battery expansion packs from an APC Smart-UPS 1000XL. Each pack contains four 17 amphour 12 volt sealed lead-acid batteries. Each set of two batteries is connected in series to make a 24-volt unit, and then the two units are connected together in parallel for a total capacity of 34 amphours at 24 volts. The battery packs plug into a connector on the back of the Smart-UPS 1000XL to extend the runtime of the unit. Up to ten battery packs can be daisy-chained to a 1000XL. Not having a Smart-UPS 1000XL, I set about modifying my Smart-UPS 600 to add a connection for one of the battery packs. If this modification holds up, I plan to hack the other battery pack onto my Smart-UPS 700. The Smart-UPS 700 is still under warranty, so I was hesitant to experiment on it...

Yeah right.

"Before" picture of battery pack guts coming soon.

APC wasn't taking any chances when they specced out this wire that connects the battery pack to the UPS.

The inside of the battery pack after the daisy-chaining connector was removed. The daisy-chain connector will be added to the Smart-UPS to allow for the connection of the battery pack. Of course, this means you can't daisy chain the batteries, but I don't know if the charging circuit in the 600 could take it if you did...

Note the 100 amp fusible link that was connected between the daisy chain connector and the batteries. Learning from my experiences with the Evil Wind Turbine of Doom, I decided to do the safe thing and rearrange the wiring so the fuse is inline with the connection to the UPS in case something goes wrong.

New arrangement of wiring for the inside of the battery pack. The fusible link is held in position with double-stick foam tape because of a lack of a suitable place to screw it in. Some of the connection cable has been fed out the back of the UPS to accomodate the new arrangement.

The batteries from the inside of the battery pack. Each of those guys is actually 2 12-volt lead acid batteries connected in series and attached to one of those connectors. Heavy as hell.

Note the two connection cables are now uneven lengths due to the new wiring arrangement. Oh well.

Now that the battery pack has been rewired, we move on to the UPS itself. First we solder the connector taken off the battery pack to wires of a more manageable size.

I never claimed I knew how to solder.

That's Maryland Kwality. Kwality with a Kapital K. Kwality in the great tradition of Jayson Blair.

Now we solder the connector to the battery inputs of the UPS, leaving a second set of wires to connect to the UPS' internal batteries.

Did I mention I failed soldering school with an "E" for Effort?

The finished arrangement within the UPS. The two wires going to the battery inputs of the UPS circuit board now lead both to the connector on the back of the UPS and to the two yellow connectors for the internal batteries.

Duct tape. Not only does it hold your shoes together and protect you from the chemical weapons of the evil terrorists, it also is great for holding your battery wires in place when you feed them out the back of the Smart-UPS. Duct tape (quack quack). It's what keeps America together.

(Bonus points if you get the reference. Using Google is cheating.)

This is the inside of the Smart-UPS with the wiring completed and the internal batteries installed. These are two 12-volt 7 amphour batteries connected in series. Total capacity of the internal batteries combined with the external batteries is 41 amphours.

No kidding. Those big heatsinks on the power transistors you can see in the other pictures aren't grounded, they're connected to a voltage source through one of the big capacitors. I found this out the hard way when my screwdriver touched a heatsink and the case of the unit and threw a nice big spark. Thankfully, there was no damage.

Note the battery connector now protruding from the back of the UPS.

Lead is heavy.

The finished product, connected together. I tested the runtime of this thing by pulling the plug out from the wall. After 90 minutes of waiting for the batteries to die and not receiving so much as a low battery warning, I got bored and plugged it back in. I think that "over 90 minutes" is plenty of runtime... some day I'll let it run down all the way and see how long that takes.