APC SMT1500C battery teardown

What battery does the SMT1500C actually use?

The SMT1500C uses RBC7, which holds two 12 V blocks in series rated 17 Ah on a 24 V DC bus. Each block fits a 181 x 76 mm bay with NB terminals. This model has no serial-number split that we could find.

Sized from the CSB GP12170NB 17 Ah nut-and-bolt block. Schneider lists 24V 17Ah and a reseller lists 12V 18 Ah blocks, so the pack is taken as two blocks in series. The 181 x 77 x 167 mm size often quoted is within 1 mm of the 181 x 76 x 167 mm block used here. Full RBC7 teardown

A 151 x 65 mm F2 cell doesn't suit this bay and harness: terminal nb mismatch.

How many DC amps does the SMT1500C pull?

At its full 1000 W rating, the SMT1500C 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 SMT1500C?

A 12 A BMS limits the SMT1500C to about 236 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.

This pack uses nut-and-bolt terminals, and the LiFePO4 pack we checked has F1 tabs. So we show no drop-in link.

How long will the SMT1500C run on each battery?

APC publishes about 23.1 min at 500 W and 6.5 min at 1000 W on the stock cells, and our curve passes through both points. The 12V 18 Ah AGM nut and bolt option adds runtime in the same case. Drag the slider for your own load.

Same footprint, 5.9% more rated capacity. 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 SMT1500C?

There are three routes for the SMT1500C. Path A swaps in two bare cells and reuses your harness. 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 SMT1500C 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. This pack uses bolted terminals, so it needs a wrench. 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. Undo the bolted lead on the positive post first, and tape it straight away. Keep your wrench away from the other post.
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 RBC7?

RBC7 lists at $392, and two bare cells cost about $120.94 at a non-Amazon single-unit price, saving roughly 69%. That reference is a premium CSB block from one store, so cheaper brands may save more. Check Amazon for its current price.

What do the SMT1500C alarms and fault codes mean?

APC Smart-UPS SMT user guide lists 4 signals we track for the SMT1500C. 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 SMT1500C?

On the SMT1500C, the manual says: front bezel unclips, with no tools named. Inside there are two batteries of about 181 x 76 mm. 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.