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Motorola NTN4594 Astro Saber Replacement Battery 7.2V 2800mAh

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From $61.99 USD $76.99
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Fits Motorola Astro Saber, MX1000, and MX2000 portable radios; replaces OEM part numbers NTN4594, NTN4593, NTN4595, NTN4538, and NTN4592.
7.2V Ni-MH pack delivers 2800mAh capacity for sustained RF output across full shift without mid-transmission voltage sag.
Slides into vertical belt clip slot with keyed connector; locking tab seats flush against radio frame to prevent accidental ejection during field work.
We bench-tested this cell on an Astro Saber transmit cycle; BMS accepted charge handshake on first dock insertion with no fault delays.
On initial deployment, insert the pack and allow one complete charge cycle before sustained transmission — Ni-MH chemistry requires formation on first energize to reach rated output.
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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

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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

7.2V

Amp

2800mAh

Motorola Astro Saber / MX Series — 7.2V Ni-MH 2800mAh Replacement Battery (NTN4594)

This is a 7.2V Ni-MH battery rated at 2800mAh, built to replace OEM packs NTN4594, NTN4593, NTN4595, and related variants. It fits the Motorola Astro Saber, MX1000, MX2000, and MX3000 portable two-way radios. The physical dimensions are 102.01 × 74.23 × 30.01mm — confirming fitment before purchase avoids compatibility issues on older chassis variants.

  • Astro Saber and MX platform compatibility: The Astro Saber and MX1000/2000/3000 share the same battery bay format, contact rail, and 7.2V BMS handshake threshold. That common architecture is why a single pack covers all four platforms without modification.
  • Bench tested on actual hardware: We ran this pack through full charge and transmit-load cycles on an Astro Saber chassis. The BMS held steady through repeated PTT keying without triggering overcurrent cutoff, and the charger dock accepted the pack cleanly on first insertion.
  • Contact rail prep on first fit: If the radio was sitting with a degraded or absent pack for an extended period, oxidation can build on the chassis contact rail. Wipe the battery's gold contacts with a dry cloth before first insertion — the Astro Saber's BMS handshake requires clean contact continuity to register the pack and begin charging.

Why the Astro Saber cuts out mid-transmission on a new pack

The Astro Saber draws a sharp current spike the instant PTT is pressed — RF output stage startup pulls significantly more current than standby. If the new Ni-MH pack is still at storage voltage (typically around 7.0V open circuit), that spike can trip the BMS overcurrent threshold before the cells have warmed into normal operating impedance. The fix is a full conditioning charge before field use. After one complete charge cycle, cell impedance drops and the BMS handles transmit spikes without interruption.

Bar indicator showing one fewer bar than expected after fitting a new pack

The Astro Saber uses voltage-threshold bar indicators — each bar corresponds to a specific voltage window, not a percentage calculated by a chip. A new Ni-MH pack at factory storage voltage sits below the threshold for a full bar reading, so the display can show one bar short even on a fresh battery. This is not a capacity fault. Charge the pack fully until the dock indicator goes solid green, then power on — the bar reading will reflect the correct rested voltage above 7.8V.

Compatible Models

Astro Saber MX1000 MX2000 MX3000 MX3010 Saber I Saber I R Saber II Saber II R Saber III Saber 1 Saber 2 Saber 3 T2000

Replaces Part Numbers

NTN4594 NTN4593 NTN4593DR NTN4595 NTN4595A NTN4595B NTN4595DR NTN4595M NTN8251AR NTN4538 NTN4592 NTN4595N

Technical Specifications

Voltage7.2V
Amp Hours2800mAh
Capacity2800mAh
Rate20.16Wh
Net Weight349g /12.31 oz
Gross Weight419g /14.78 oz
Approximate Weight419g /14.78 oz
Dimension 102.01 x 74.23 x 30.01mm

Product Highlights

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

Frequently Asked Questions

My Astro Saber loses TX power partway through a shift — is the new pack failing?

This is voltage sag, not a dead pack. Ni-MH cells under sustained RF output drop voltage progressively as internal temperature rises across a shift. The radio's power control circuit reads that lower voltage and steps down TX output to stay within operating limits. A full charge before each shift and avoiding prolonged back-to-back transmissions keeps voltage above the sag threshold — check rested open-circuit voltage after the shift; anything above 7.6V confirms the cells are healthy.

The charger dock flashes a fault LED and never clears after I insert the new battery — what's wrong?

The Motorola dock checks pack voltage on insertion before it will begin a charge cycle. If the pack has been in storage and the cell voltage has dropped below the dock's acceptance threshold (typically around 6.0V for a 7.2V Ni-MH pack), the dock reads it as a fault rather than a dischargeable pack. Remove the battery, wipe the gold contact strip with a dry cloth, reseat firmly, and try a different dock port if one is available — a clean contact cycle is often enough for the dock to re-read voltage correctly and begin charging.

The radio sat unused for several months with this pack inside — now it won't power on at all. Is the battery dead?

Extended storage inside the radio allows the radio's standby drain to pull the pack into deep discharge, which can push Ni-MH cells below BMS recovery voltage. The dock may refuse to charge it using the standard cycle. Try a known-good universal Ni-MH charger that supports recovery mode — most will apply a low-current pre-charge to bring cells back above 1.0V per cell (6.0V total) before switching to a full charge. If the pack recovers to above 7.8V rested after that cycle, it is usable.

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