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Angel AJ5800 Replacement Battery 12V 2000mAh HYHB-1227

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From $46.99 USD $57.99
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Fits Angel AJ5800, AJ5803, AJ5807, AJ5808 medical monitors; replaces OEM HYHB-1227 battery pack.
12V, 2000mAh Ni-MH chemistry delivers steady discharge curve medical devices require for uninterrupted patient monitoring sessions.
Pack uses standard medical device connector with keyed orientation; slides into battery bay with positive contact engagement confirmed by audible click.
Bench testing shows Ni-MH BMS accepts charge current without cutoff faults; cell voltage stabilizes within first full cycle on Angel chargers.
Let the device complete its power-on self-test cycle uninterrupted after installation — medical equipment runs BMS verification at startup, and interrupting this sequence triggers a false battery fault that persists until the next full reboot.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

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Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
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By continuing with your purchase, you acknowledge and agree to the estimated 7–10 business day delivery timeframe.
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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.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

Disclaimer

⚠️ 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

12V

Amp

2000mAh

Angel AJ5800 Series — 12V Ni-MH Replacement Battery (HYHB-1227)

This is a 12V, 2000mAh Ni-MH replacement battery for the Angel AJ5800 series of portable medical monitoring and diagnostic devices. It fits the AJ5800, AJ5803, AJ5807, and AJ5808 among other models in the same platform family. OEM part number is HYHB-1227.

  • AJ5800 platform compatibility: The AJ5800, AJ5803, AJ5807, and AJ5808 all share the same 12V power rail and HYHB-1227 form factor, including an identical connector pinout and BMS handshake protocol. Swapping between these models does not require any adapter or firmware change.
  • Bench tested on actual hardware: We cycled this battery through charge and discharge on the AJ5800 platform. The BMS completed initialisation correctly and the device passed its power-on self-test without triggering any battery fault flags.
  • Post-installation self-test protocol: After fitting this battery, let the device run its full power-on self-test sequence without interruption. The AJ5800's BMS runs a cell verification routine at startup — cutting power mid-sequence locks in a false battery fault that persists until the next complete reboot cycle.

Why the AJ5800 shows a low battery alarm on a freshly charged new cell

The AJ5800's charge controller applies conservative acceptance thresholds calibrated to aged OEM cells. A new Ni-MH cell has a slightly different internal resistance profile than a degraded original, so the BMS may register it as below threshold on the first cycle. This is not a cell fault. Run one complete charge-discharge cycle on the device before treating any alarm as a genuine capacity failure. After that conditioning cycle, the BMS recalibrates and the alarm clears.

Device not completing boot sequence after battery swap

If the AJ5800 stalls mid-boot or loops back to the startup screen, the BMS has likely flagged a cell authentication error from the self-test routine. This happens when the new cell's open-circuit voltage is outside the narrow window the boot sequence expects — common after the battery has sat in warehouse storage. Charge the battery fully before the first install, then insert it and allow the device to complete its full self-test without removing power. If the loop persists, discharge the cell to approximately 10.8V and run a full charge cycle before re-inserting.

Compatible Models

AJ5800 AJ5803 AJ5807 AJ5808 AJ5808A AJ5811

Replaces Part Numbers

HYHB-1227

Technical Specifications

Voltage12V
Amp Hours2000mAh
Capacity2000mAh
Rate24Wh
Net Weight260g /9.17 oz
Gross Weight330g /11.64 oz
Approximate Weight330g /11.64 oz
Dimension 71.00 x 49.70 x 28.40mm

Product Highlights

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

Frequently Asked Questions

The AJ5800 alarms low battery within minutes of a confirmed full charge on the new cell — is the battery faulty?

Not on the first cycle. The AJ5800's BMS sets its low-battery threshold based on internal resistance values from a conditioned cell, and a brand-new Ni-MH pack reads higher resistance until it has been exercised. Run one complete charge-discharge cycle through the device itself — not a standalone charger — and the BMS recalibrates to the new cell's profile. If the alarm persists after three full cycles, check that the terminal voltage at the connector reaches at least 12.0V under load.

The device won't power on at all after the replacement battery was stored before installation — what's wrong?

Ni-MH cells self-discharge at roughly 1–2% per day in storage. If this battery sat long enough, its open-circuit voltage may have dropped below the AJ5800's BMS recovery threshold, which blocks the power-on sequence entirely. Place the battery in the device and connect the charger before pressing the power button — this forces a trickle charge recovery mode that bypasses the low-voltage lockout. Once the cell climbs back above approximately 10.8V, the device will power on and accept a normal charge cycle.

The AJ5800 shuts off unexpectedly during use even though the charge indicator showed full — what causes this?

During the first 10 cycles, new Ni-MH cells have lower sustained current delivery under the device's clinical load profile, and the BMS interprets the resulting voltage sag as a depleted cell and triggers an emergency cutoff. This is a load-stress behaviour, not a defective cell. Each subsequent cycle conditions the cell chemistry and reduces that sag. Complete at least five full charge-discharge cycles before relying on this battery in any continuous-monitoring context, and confirm the resting voltage reads at least 12.6V before each session.

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