CyberPower OL1500RTXL2U battery teardown
- Bare cells needed
- 3 x 12 V 9 Ah
- Max DC draw
- 45.7 A
- OEM cartridge
- RB1290X3L
- Cell size
- 151 x 65 x 94 mm
- In inches
- 5.94 x 2.56 x 3.70 in
- Terminal
- F2 check yours
- Rating
- 1500 VA / 1350 W
- Topology
- Double-Conversion
- Waveform
- Pure Sine Wave
- Transfer time
- 0 ms typical
- OEM list price
- $220
- DC bus
- 36 V
- Last verified
- 2026-11-02
- LiFePO4 at full load
- RED
What battery does the OL1500RTXL2U actually use?
The OL1500RTXL2U uses RB1290X3L, which holds three 12 V blocks in series rated 9 Ah on a 36 V DC bus. Each block fits a 151 x 65 mm bay with F2 terminals. This model has no serial-number split that we could find.
| Spec | Value | Source |
|---|---|---|
| VA and watts | 1500 VA / 1350 W | T1 cyberpowersystems.com |
| Topology | Double-Conversion | T1 cyberpowersystems.com |
| Waveform, in the OEM's words | Sine Wave | T1 cyberpowersystems.com |
| Transfer time | 0 ms typical | T1 cyberpowersystems.com |
| OEM cartridge | RB1290X3L | T1 cyberpowersystems.com |
| OEM list price | $220 | T1 cyberpowersystems.com |
CyberPower lists 333 x 193 x 81 mm for the pack, which has room for three 151 x 65 mm cells. Buy one cartridge or three cells for the OL1500RTXL2U. CyberPower lists the matching RB1290X3R only for the BP36V60ART2U external battery module, which is the unit that needs both trays. CyberPower names no bus voltage, but pairs this UPS with a 36 V module, so we model 36 V. Full RB1290X3L teardown
How many DC amps does the OL1500RTXL2U pull?
At its full 1350 W rating, the OL1500RTXL2U pulls about 45.7 A from its 36 V bus, and about 52.3 A as the battery sags to 31.5 V cutoff. Those figures assume 82% inverter efficiency, because CyberPower doesn't publish one for battery mode.
| AC load | Nominal | At cutoff |
|---|---|---|
| 25 W | 0.8 A | 1.0 A |
| 60 W | 2.0 A | 2.3 A |
| 100 W | 3.4 A | 3.9 A |
| 200 W | 6.8 A | 7.7 A |
| 300 W | 10.2 A | 11.6 A |
| 675 W | 22.9 A | 26.1 A |
| 1350 W | 45.7 A | 52.3 A |
Is LiFePO4 safe in the OL1500RTXL2U?
A 12 A BMS limits the OL1500RTXL2U to about 354 W, well below its 1350 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. Drag the slider below to test your own load.
GREY: load is fine, but no verified cell fits
- DC draw now
- 8.5 A
- At 31.5 V cutoff
- 9.7 A
- Safe AC load
- 354 W
OL1500RTXL2U: lead-acid anchored to OEM half and full-load runtimes, LiFePO4 on a flat energy curve with inverter tare, at 82% inverter efficiency. A real inrush can trip a BMS below this ceiling. RB1290X3L teardown.
| BMS continuous | Safe AC load | Share of 1350 W |
|---|---|---|
| 10 A | 295 W | 22% |
| 12 A | 354 W | 26% |
| 15 A | 443 W | 33% |
| 20 A | 590 W | 44% |
Three independent BMS boards in one 36 V series string multiply the balance risk on this online double-conversion UPS. So we show no drop-in link.
How long will the OL1500RTXL2U run on each battery?
CyberPower publishes about 12.5 min at 675 W and 4 min at 1350 W on the stock cells, and our curve passes through both points. The 12V 9 Ah high-rate AGM option adds runtime in the same case. Drag the slider for your own load.
| AC load | Stock 9 Ah | 12V 9 Ah high-rate AGM | LiFePO4 10 Ah |
|---|---|---|---|
| 25 W | 10.2 hr | 10.6 hr | no verified pack |
| 60 W | 3.6 hr | 4.0 hr | no verified pack |
| 100 W | 2.0 hr | 2.2 hr | no verified pack |
| 200 W | 53 min | 62 min | no verified pack |
| 300 W | 33 min | 39 min | no verified pack |
| 675 W | 12 min | 16 min | no verified pack |
| 1350 W | 4.0 min | 5.3 min | no verified pack |
| Load | CyberPower published | Raw Peukert | This site | Source |
|---|---|---|---|---|
| 675 W | 12.5 min | 12 min | 12.5 min | T1 cyberpowersystems.com |
| 1350 W | 4 min | 5.1 min | 4 min | T1 cyberpowersystems.com |
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 OL1500RTXL2U?
There are three routes for the OL1500RTXL2U. Path A swaps in three 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.
| Path | Best for | Load limit | Main risk |
|---|---|---|---|
| A: bare SLA swap | Lowest cost, any load | 1350 W | Terminal or case mismatch |
| B: drop-in LiFePO4 | Light loads, long life | not offered | BMS trip, charger mismatch |
| C: native LiFePO4 UPS | A unit over 6 years old, or high loads | 1800 W | Slower transfer than this UPS |
Path A: the bare-cell SLA swap
Surge-safe, because AGM has no BMS to trip.
Path B: drop-in LiFePO4
Path C: a native LiFePO4 UPS
Worth it if this UPS is 6 or more years old, if a fault above isn't a battery problem, or if you need more than the BMS limit.
How do you move the OL1500RTXL2U 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.
- Shut down the load, turn the UPS off and unplug it from the wall.
- Take a photo of the wiring. Open the battery door or sled and slide the pack out.
- Pull the red clip off the positive tab, and tape it straight away.
- Remove the black lead and tape it. Then lift off the jumpers between the cells, with any fuse your harness has.
- Check the new cells have the right size and tabs, then add any adapters from the parts list.
- Fit the jumpers first, from the positive of one cell to the negative of the next. Fit the leads one at a time, matching your photo, and remove the tape only from the lead you are fitting.
- Measure about 38 to 41 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.
- 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 CyberPower's equipment guarantee.
How much do you save over the RB1290X3L?
RB1290X3L lists at $220, and three bare cells cost about $104.82 at a non-Amazon single-unit price, saving roughly 52%. That reference is a premium CSB block from one store, so cheaper brands may save more. Check Amazon for its current price.
| Item | Price | Source |
|---|---|---|
| Official RB1290X3L MSRP | $220 | T1 cyberpowersystems.com |
| Typical Commodity Bare-Cell Band (Non-Amazon Reference): 3 x CSB HR1234WF2 | $104.82 | T2 batterystore.com |
| Saving when you reuse the harness | $115.18 (52%) | computed |
What do the OL1500RTXL2U alarms and fault codes mean?
We don't have an alarm table for the OL1500RTXL2U, because the sources we captured don't include one. Rather than guess at what a beep means, check the manual that came with your unit before you buy a replacement battery or contact support.
We could not get this model's alarm table, so we list nothing rather than guess. Check the manual that came with your unit.
| OL1500RTXL2U | Not captured |
|---|
How do you reach the battery in the OL1500RTXL2U?
We have no verified door procedure for the OL1500RTXL2U. CyberPower sells a replacement cartridge for it, but we did not capture the steps. Follow the manual for your unit, and don't open the case to find out how it comes apart. Contact the manufacturer if you are unsure.
| Field | Value | Source |
|---|---|---|
| Battery door access | No procedure captured. Treat as a service item | none |
| Cell orientation | Not stated in the manual we captured | none |
| Harness connector type | Not stated in the manual we captured | none |
| Cell layout | 3 x 12 V, in series | verified |