APC SMT1500RM2UC battery teardown

What battery does the SMT1500RM2UC actually use?

The SMT1500RM2UC uses APCRBC159, which holds four 12 V blocks, assumed to be two parallel pairs, rated 7 Ah on a 24 V DC bus. No source gives the cell size for this pack. This model has no serial-number split that we could find.

APC lists a 24 V module measuring 83 x 216 x 343 mm, and publishes no cell count, size or capacity. APC assigns APCRBC159, not APCRBC133, to the SMT1500RM2UC, and lists it at 24 V. The four-cell, 7 Ah layout comes from our starting research and no source confirms it. APC's published runtime suggests more capacity than that, so measure before buying. Full APCRBC159 teardown

How many DC amps does the SMT1500RM2UC pull?

At its full 1000 W rating, the SMT1500RM2UC pulls about 50.8 A from its 24 V bus, and about 58.1 A as the battery sags to 21 V cutoff. Those figures assume 82% inverter efficiency, because APC doesn't publish one for battery mode.

Is LiFePO4 safe in the SMT1500RM2UC?

A 12 A BMS limits the SMT1500RM2UC to about 472 W, well below its 1000 W rating. At full load the verdict is RED. We could not verify a LiFePO4 pack that fits this bay and harness, so we link none. APC doesn't support this swap. Drag the slider below to test your own load.

The cell layout is unverified, and four independent BMS boards in one pack multiply the balance risk. So we show no drop-in link.

How long will the SMT1500RM2UC run on each battery?

APC publishes about 25.9 min at 500 W and 7.2 min at 1000 W on the stock cells, and our curve passes through both points. We found no larger cell verified for this bay. Drag the slider for your own load.

Upgraded AGM scales from the anchored curve, with k = 1.18 standard and 1.12 high-rate. LiFePO4 uses a flat energy curve with inverter tare. Method.

Which replacement should you buy for the SMT1500RM2UC?

There are three routes for the SMT1500RM2UC. Path A is withheld, because this pack's cell size is unverified. Path B is withheld, because no verified pack fits. Path C replaces the whole UPS, which makes most sense for units over six years old.

How do you move the SMT1500RM2UC harness to bare cells?

You move the factory jumper and leads from the old blocks to the new ones, in the same polarity. Unplug the UPS first, and tape each lead as it comes off, because the battery stays live. Sealed sleds must be opened first. No soldering is needed.

1. Shut down the load, turn the UPS off and unplug it from the wall.
2. Take a photo of the wiring. Open the battery door or sled and slide the pack out.
3. Pull the red clip off the positive tab, and tape it straight away.
4. Remove the black lead and tape it. Then lift off the jumper between the cells, with its fuse if your harness has one.
5. Check the new cells have the right size and tabs, then add any adapters from the parts list.
6. Fit the jumper first, from the positive of one cell to the negative of the other. Fit the leads one at a time, matching your photo, and remove the tape only from the lead you are fitting.
7. Measure about 25 to 27 V across the two outer leads before you close the pack. Slide it back, plug in and charge for the time the manual gives before relying on it.
8. Recycle the old cells at a battery retailer. Never bin lead-acid.

Sixty seconds is the best case for a loose-cell unit. Sealed sleds need opening first, and opening them may affect your warranty and APC's equipment guarantee.

How much do you save over the APCRBC159?

We can't state a saving for APCRBC159, because we have no sourced price for a verified bare cell. Any figure here would be a guess, so this page leaves it out rather than estimating one for you. Compare the list price with your own quote.

What do the SMT1500RM2UC alarms and fault codes mean?

APC Smart-UPS SMT user guide lists 4 signals we track for the SMT1500RM2UC. Only 1 of them point to the battery, and 1 mean you should not buy batteries yet. Read your signal below first, because a new battery won't fix a charger, a relay or an overload.

The manual lists no separate Battery Disconnected or AVR Boost/Trim alarm in the text we captured.

How do you reach the battery in the SMT1500RM2UC?

On the SMT1500RM2UC, the manual says: front bezel comes off first. rack unit. Inside there are four batteries. Check the details below before you start, turn the unit off and unplug it first, and photograph the wiring so you can match it later.