CyberPower LX1500GU battery teardown

What battery does the LX1500GU actually use?

The LX1500GU uses RB1290X2, which holds two 12 V blocks in series rated 9 Ah on a 24 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.

CyberPower lists 150 x 66 x 99 mm. Full RB1290X2 teardown

How many DC amps does the LX1500GU pull?

At its full 900 W rating, the LX1500GU pulls about 45.7 A from its 24 V bus, and about 52.3 A as the battery sags to 21 V cutoff. Those figures assume 82% inverter efficiency, because CyberPower doesn't publish one for battery mode.

Is LiFePO4 safe in the LX1500GU?

A 12 A BMS limits the LX1500GU to about 236 W, well below its 900 W rating. At full load the verdict is RED. Packs in series can drift apart on the charger, so balance them first. Drag the slider below to test your own load.

Balance every pack first. Two independent BMS boards on one series charger can drift apart, and one can cut off early. Series drift and 0 V lockout explained.

How long will the LX1500GU run on each battery?

CyberPower publishes about 14 min at 450 W and 2 min at 900 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.

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 LX1500GU?

There are three routes for the LX1500GU. Path A swaps in two bare cells and reuses your harness. Path B adds LiFePO4 for loads under 394 W, by the listing's 20 A claim. Path C replaces the whole UPS, which makes most sense for units over six years old.

How do you move the LX1500GU 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 CyberPower's equipment guarantee.

How much do you save over the RB1290X2?

RB1290X2 lists at $117, and two bare cells cost about $69.88 at a non-Amazon single-unit price, saving roughly 40%. 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 LX1500GU alarms and fault codes mean?

CyberPower LX1500GU user manual lists 4 signals we track for the LX1500GU. Only 0 of them point to the battery, and 3 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.

This model uses F codes, not the E codes on CyberPower's PFC units.

How do you reach the battery in the LX1500GU?

On the LX1500GU, the manual says: screw panel: two retaining screws on the bottom. Inside there are two batteries of about 151 x 65 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.