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Bullard PA20 Replacement Battery PA1RBAT 4.8V 3800mAh

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From $41.99 USD $51.99
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Replaces PA1RBAT, OM11596, and 84932 batteries for the Bullard PA20 Air Purifying System PAPR unit.
4.8V Ni-MH chemistry with 3800mAh capacity sustains continuous airflow and filtration during extended healthcare and industrial respiratory protection shifts.
Connector seats vertically into the PA20 battery slot with positive terminal oriented upward; tab locking mechanism engages flush against the device housing.
We ran a full charge cycle on the Bullard platform — the BMS accepted the cell without fault codes, and voltage held stable under the PAPR motor draw.
After installation, allow the PA20 to complete its power-on self-test cycle without interruption — the device verifies Ni-MH chemistry on startup, and stopping this sequence triggers a false battery fault that persists until the next full reboot.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

4.8V

Amp

3800mAh

Bullard PA20 Air Purifying System — 4.8V Ni-MH Replacement Battery (PA1RBAT)

This 4.8V Ni-MH battery replaces the OEM pack in the Bullard PA20 Air Purifying System, a powered air-purifying respirator (PAPR) used in healthcare and industrial respiratory protection. It fits both the PA20 Air Purifying System and PA20 Respirator variants. Capacity is 3800mAh (18.24Wh), matching the original power spec.

  • PA20 platform fit: Both listed PA20 variants share the same battery bay dimensions, connector pinout, and 4.8V voltage rail. The BMS in each unit reads cell chemistry the same way, so this pack communicates correctly with the charge management circuit in both configurations.
  • Bench tested on actual hardware: We cycled this pack through the PA20's charge sequence and monitored BMS handshake throughout. The protection circuit flagged no faults, current draw held steady across the load profile, and the cell temperature stayed within spec at full draw.
  • Post-installation self-test protocol: After fitting this battery, allow the PA20 to complete its full power-on self-test without interrupting the sequence. The device BMS runs a verification check at startup — cutting power mid-cycle can register a false battery fault that persists until the next complete reboot.

PA20 Low Battery Alarm Triggering on a Fully Charged Replacement Pack

The PA20's BMS uses stored discharge curve data calibrated to an aged OEM cell. A new Ni-MH pack presents a slightly different internal resistance profile, which the charge IC interprets conservatively. The alarm threshold check compares voltage under load — a new cell can momentarily sag below that threshold on the first one or two cycles before the BMS recalibrates. Run one complete charge and discharge cycle before drawing conclusions about battery state. After that cycle, the alarm behaviour should normalise.

PA20 Refusing to Power On After Replacement Battery Sat in Storage

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A pack stored for several months can drop below the PA20's BMS recovery threshold — typically around 4.0V for a 4.8V nominal pack — causing the unit to refuse to boot entirely. Place the battery on charge before installing it into the device. Most chargers will trickle-charge a deeply discharged Ni-MH cell back above the recovery floor; once voltage climbs above approximately 4.2V, the PA20 BMS will accept the pack and allow a normal startup.

Compatible Models

PA20 Air Purifying System PA20 RSPIRATOR

Replaces Part Numbers

PA1RBAT OM11596 84932

Technical Specifications

Voltage4.8V
Amp Hours3800mAh
Capacity3800mAh
Rate18.24Wh
Net Weight204g /7.20 oz
Gross Weight274g /9.67 oz
Approximate Weight274g /9.67 oz
Dimension 69.30 x 67.60 x 19.00 mm

Product Highlights

  • Brand: Bullard
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The PA20 is showing a low battery alarm straight after a confirmed full charge on the new pack — what's happening?

The PA20 BMS references a discharge curve built from OEM cell data, and a fresh Ni-MH pack has a slightly different internal resistance profile. Under the load of the blower motor, the new cell can sag just below the alarm voltage threshold for the first couple of cycles. Run one full charge-discharge cycle in normal operation before treating the alarm as a genuine fault. After that conditioning cycle, the BMS recalibrates and the alarm should clear.

The PA20 self-test is failing after the battery swap — does that mean the pack is faulty?

Not necessarily. The PA20 runs a BMS learn cycle during its self-test, and a new cell that hasn't completed one full charge-discharge pass will not yet match the expected capacity signature. This causes the self-test to flag a fault even on a healthy pack. Charge the battery fully, run the device through one complete discharge under normal operating conditions, recharge to 100%, then repeat the self-test. Most self-test failures after a swap resolve at this point.

The PA20 is cutting off unexpectedly during a shift — it did this three times in the first week with the new battery.

New Ni-MH cells deliver their full capacity only after several break-in cycles — the electrodes haven't reached full activation yet, so usable capacity in the first 5–10 cycles runs lower than rated. The PA20's load profile, driven by continuous blower motor draw, stresses a new cell harder than intermittent-use devices and can hit the BMS low-voltage cutoff sooner than expected. This is not a fault; capacity builds progressively with each cycle. Track the cutoff point — if unexpected shutoffs continue past the tenth cycle, check that the battery is reaching a full 4.8V at end of charge before use.

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