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Midtronics OP-5500 Compatible Battery 3.6V 2000mAh Ni-MH

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Fits Midtronics OP-5500 battery analyzer; replaces OEM part numbers 59873353, BP-55, and HHR-15F3G1.
3.6V 2000mAh Ni-MH pack delivers 7.2Wh — sufficient for full measurement cycles in field diagnostic sessions without mid-test shutdowns.
Connector slides into the battery slot with positive contact first; locking tab seats flush against the instrument chassis.
We bench-tested this cell in the OP-5500 load tester circuit; BMS accepted the pack on first insertion with no fault delay or contact cycling needed.
After installation, run the full self-calibration routine from the instrument menu before field deployment — the OP-5500 maps battery state during calibration, and skipping this step causes false low-battery warnings on first measurement session.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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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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🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

3.6V

Amp

2000mAh

Midtronics OP-5500 — 3.6V Ni-MH Replacement Battery (59873353)

This is a 3.6V 2000mAh Ni-MH replacement battery for the Midtronics OP-5500 battery analyzer and load tester. It fits the OP-5500 directly, using OEM part references 59873353, BP-55, and HHR-15F3G1. Capacity is sourced from the product specification — 2000mAh (7.2Wh).

  • OP-5500 platform fit: The OP-5500 draws from a single 3.6V NiMH cell block with a fixed connector and a BMS that handshakes on pack recognition at power-up. All three OEM part numbers — 59873353, BP-55, and HHR-15F3G1 — reference the same cell format, voltage rail, and connector footprint used across this analyzer generation.
  • Bench tested on actual hardware: We cycled this pack through the OP-5500's standard power-on sequence and load test routine. The BMS accepted the pack without triggering a fault code, and the cell voltage held within the expected window through a full diagnostic cycle.
  • First-use calibration cycle: After installing this pack, run a full calibration sequence through the OP-5500's instrument menu before taking it into the shop. The analyzer maps battery state during calibration — skipping this step causes premature low-battery warnings during the first live testing session, even with a fully charged pack.

BMS lockout after the OP-5500 sat unused in a carry case for months

Ni-MH cells self-discharge during storage, and if the pack drops below approximately 0.9V per cell, the BMS enters a protection state and refuses a standard charge cycle. The OP-5500 will either show no response or a battery fault at power-up. To recover, apply a slow trickle charge at low current — most smart chargers have a recovery or reconditioning mode that brings the cell voltage back above the 1.0V threshold before switching to normal charge. Once the pack reads above 3.2V total, a standard charge cycle completes normally.

OP-5500 shuts down the moment a load test sequence initiates

The OP-5500 draws a short current spike when it energises the load test circuit at the start of a test sequence. A degraded or partially discharged pack can't sustain that spike, and the BMS trips into cutoff to protect the cells — the analyzer goes dark mid-operation. This is different from a low-battery warning during idle use. Charge the pack fully to 3.6V before running load tests, and confirm the charger completed a full cycle rather than stopping early on a timed cut-off.

Compatible Models

OP-5500

Replaces Part Numbers

59873353 BP-55 HHR-15F3G1

Technical Specifications

Voltage3.6V
Amp Hours2000mAh
Capacity2000mAh
Rate7.2Wh
Gross Weight180g /6.35 oz
Approximate Weight180g /6.35 oz
Dimension 52.80 x 42.80 x 15.00mm

Product Highlights

  • Brand: Midtronics
  • 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 OP-5500 powers on fine but shuts off the moment I start a load test — is the new battery faulty?

It's not a fault in the cell itself. The load test circuit pulls a brief current spike when it initialises, and if the pack isn't at a full state of charge, the BMS trips into cutoff before the test completes. Charge the pack fully and confirm the charger reached end-of-charge rather than terminating early. Run the load test again once the pack measures at or above 3.6V.

After the OP-5500 sat in the carry case all winter, the new pack won't charge — the charger just sits idle.

Ni-MH cells drop below the BMS recovery threshold after extended storage, and the charger won't initiate a normal cycle on a pack it reads as dead. Most smart chargers include a reconditioning or recovery mode that applies a low-current trickle until the pack climbs above 1.0V per cell. Once total pack voltage exceeds 3.2V, switch to a standard charge cycle and let it complete fully before using the analyzer.

The OP-5500 is showing low-battery warnings within minutes of a full charge — readings are cutting out during logging.

This happens when the instrument's battery state map is still calibrated to the old, degraded pack. The OP-5500 sets its low-voltage threshold reference during the calibration sequence, and a new pack installed without running that cycle will trigger early warnings against the wrong baseline. Go into the instrument menu and run a full calibration cycle — the analyzer resets its internal reference to the new pack's actual voltage curve, and the false low-battery warnings stop.

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