APC BE425M battery teardown
- Battery
- Not user replaceable
- Max DC draw
- 25.9 A
- OEM cartridge
- None sold
- Cell size
- unverified
- In inches
- unverified
- Terminal
- unverified
- Rating
- 425 VA / 255 W
- Topology
- Standby
- Waveform
- Square Wave
- Transfer time
- 6ms typical : 10ms maximum
- OEM list price
- not published
- DC bus
- 12 V
- Last verified
- 2026-11-01
- LiFePO4 at full load
- RED
What battery does the BE425M actually use?
The BE425M has one internal 12 V lead-acid battery, and APC says it is not user replaceable. APC publishes no capacity or size, so the cube dimensions often quoted are unconfirmed. We link no replacement cell, and you should contact an authorized service center or replace the whole unit.
| Spec | Value | Source |
|---|---|---|
| VA and watts | 425 VA / 255 W | T1 se.com |
| Topology | Standby | T1 se.com |
| Waveform, in the OEM's words | Square wave | T1 se.com |
| Transfer time | 6ms typical : 10ms maximum | T1 se.com |
| Replacement | Not user replaceable | T1 APC manual |
APC says the battery is not user replaceable and publishes no size or capacity. The 90 x 70 x 101 mm cube and 4.5 to 5 Ah figures are unconfirmed.
How many DC amps does the BE425M pull?
At its 255 W rating, the BE425M pulls about 25.9 A from its 12 V bus, and about 29.6 A at 10.5 V cutoff, assuming 82% inverter efficiency. That is a high current for a small battery, which is why short runtime appears at full load.
| AC load | Nominal | At cutoff |
|---|---|---|
| 25 W | 2.5 A | 2.9 A |
| 60 W | 6.1 A | 7.0 A |
| 100 W | 10.2 A | 11.6 A |
| 128 W | 13.0 A | 14.9 A |
| 200 W | 20.3 A | 23.2 A |
| 255 W | 25.9 A | 29.6 A |
Is LiFePO4 safe in the BE425M?
We don't recommend LiFePO4 for the BE425M. APC says its battery is not user replaceable, so swapping chemistry means opening a sealed unit that was never designed for it. Even a 12 A BMS would limit it to about 118 W, under its 255 W rating. Buy a factory LiFePO4 UPS instead.
RED: BMS trip hazard
- DC draw now
- 13.0 A
- At 10.5 V cutoff
- 14.9 A
- Safe AC load
- 118 W
BE425M: 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.
| BMS continuous | Safe AC load | Share of 255 W |
|---|---|---|
| 10 A | 98 W | 39% |
| 12 A | 118 W | 46% |
| 15 A | 148 W | 58% |
| 20 A | 197 W | 77% |
APC says this battery is not user replaceable. So we show no drop-in link.
How long will the BE425M run on each battery?
APC publishes about 10.5 min at 128 W and 2.6 min at 255 W for the BE425M, and our lead-acid curve passes through both points. Since the battery can't be swapped, these figures only show what to expect from a healthy unit. Drag the slider for your own load.
| AC load | Stock 5 Ah | Upgraded cell | LiFePO4 10 Ah |
|---|---|---|---|
| 25 W | 72 min | none verified | no verified pack |
| 60 W | 26 min | none verified | no verified pack |
| 100 W | 14 min | none verified | no verified pack |
| 128 W | 10 min | none verified | no verified pack |
| 200 W | 4.2 min | none verified | no verified pack |
| 255 W | 2.6 min | none verified | no verified pack |
| Load | APC published | Raw Peukert | This site | Source |
|---|---|---|---|---|
| 128 W | 10.5 min | 11 min | 10.5 min | T1 se.com |
| 255 W | 2.6 min | 5.0 min | 2.6 min | T1 se.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 BE425M?
Only one of the three routes applies to the BE425M. Path A and Path B are withheld, because APC says this battery is not user replaceable. If it has failed out of warranty, Path C replaces the whole UPS, and you should check whether a service center is worth it first.
| Path | Best for | Load limit | Main risk |
|---|---|---|---|
| A: bare SLA swap | Lowest cost, any load | 255 W | Cell size unverified |
| 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 | 800 W | Slower transfer than this UPS |
Path A: the bare-cell SLA swap
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. Listings and reviews put Goldenmate's transfer at 8 to 20 ms, against this unit's 6ms typical : 10ms maximum, so check that your PC tolerates it.
How do you move the BE425M harness to bare cells?
You shouldn't move anything on the BE425M. APC says the battery is not user replaceable and points you to authorized service centers. Opening the case exposes live parts and may void your warranty, so this page gives no teardown steps. Contact support, or replace the whole unit if it is out of warranty.
How much would a replacement cost for the BE425M?
We can't state a saving for the BE425M, because there is no replacement part to price. APC says the battery is not user replaceable, and it publishes no cartridge or list price. Compare a service quote with the price of a new unit, since small units can cost less to replace.
| Item | Status |
|---|---|
| Internal battery list price | not published |
| Verified bare-cell reference | none |
What do the BE425M alarms and fault codes mean?
APC Back-UPS BE user guide lists 5 signals we track for the BE425M. Only 0 of them point to the battery, and 2 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.
These units have no numeric codes. The audible pattern depends on the alarm mode you set.
| Signal | Meaning | What to do | Battery swap? | Source |
|---|---|---|---|---|
| 4 beeps every 30 seconds, Full Alarm mode | On battery | Not a fault. Beeping stops when power returns. | Not a fault | T1 manual |
| Beep every half second | Low battery | Save work and shut down. | Not a fault | T1 manual |
| Power button flashes red, or alternates green and red, with a constant tone | Battery disconnected, or it needs charging or replacing | Check the connector and recharge. If it returns, replace the battery. | Check first, then decide | T1 manual |
| Constant tone, UPS shuts down on battery | Overload | Unplug something. A new battery won't help. | Do not buy batteries | T1 manual |
| Power button alternates green and amber | Short circuit or error detected | Unplug everything and contact support before buying cells. | Do not buy batteries | T1 manual |
How do you reach the battery in the BE425M?
We have no verified door procedure for the BE425M. APC says its battery is not user replaceable. Treat the unit as a service item, 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 | Not user replaceable | none |
| Cell orientation | Not stated in the manual we captured | none |
| Harness connector type | Not stated in the manual we captured | none |
| Cell layout | Sealed unit | inferred |