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Relm RPU7500 Replacement Battery BL1703 7.4V 3350mAh

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From $64.99 USD $80.99
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Fits Relm RPU7500 and RPV7500 radios; replaces OEM battery part number BL1703.
7.4V and 3350mAh capacity sustains full transmit power across a shift without voltage sag mid-RF output.
Connector seats into the radio's battery slot with a positive tab lock; orientation marked on housing.
We ran this cell on the RPU7500 transmit cycle — BMS accepted the charge handshake on first dock insertion with no fault LED.
On first use with the RPU7500 charger dock, if the fault light appears after seating, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly — the platform needs a clean contact cycle to accept the new BMS before charging begins.
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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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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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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🔹 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.

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

Voltage

7.4V

Amp

3350mAh

Relm RPU7500 / RPV7500 — 7.4V Li-ion Replacement Battery (BL1703)

This 7.4V 3350mAh Li-ion battery replaces the BL1703 pack on the Relm RPU7500 and RPV7500 handheld transceivers. Both radios share the same battery bay geometry, contact layout, and BMS handshake protocol, so one part number covers both models. Capacity is rated at 24.79Wh.

  • RPU7500 and RPV7500 platform fit: Both models run the same 7.4V nominal voltage rail, use the same multi-pin connector footprint, and expect the same BMS communication signal from the pack. One replacement covers both without any modification.
  • Bench tested on actual hardware: We cycled this pack through charge and full transmit-load discharge on the RPU7500 chassis. The BMS held voltage under sustained PTT draw and tripped correctly at the low-voltage cutoff threshold — no premature shutoff and no overcurrent fault flagged.
  • First-insertion contact cycle on the RPU7500 dock: If the charger dock shows a fault LED on the first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The RPU7500 charging dock requires a clean contact seating before it accepts the new BMS handshake and begins the charge cycle.

Why the RPU7500 cuts out mid-transmission on a new BL1703

A new Li-ion pack ships at storage voltage — typically 3.6V to 3.7V per cell, not full charge. When you key up and transmit, the RPU7500 draws a sharp current spike that the BMS reads as a low-voltage condition and responds with an immediate cutoff. This is not a faulty battery. Charge the pack fully before the first transmit cycle and the cutoff will not recur. A fully charged BL1703 sits at 8.4V across both cells before any load is applied.

Bar indicator showing one fewer bar than expected after inserting the BL1703

The RPU7500 uses a voltage-threshold bar indicator — each bar maps to a specific resting voltage band. A new pack at storage voltage reads in the lower threshold band and displays one or two bars even though the cell capacity is intact. This is not a capacity defect. Charge the battery fully, let it rest off the charger for five minutes, then reinsert — the indicator will read the correct resting voltage of approximately 8.2–8.4V and display full bars.

Compatible Models

RPU7500 RPV7500

Replaces Part Numbers

BL1703

Technical Specifications

Voltage7.4V
Amp Hours3350mAh
Capacity3350mAh
Rate24.79Wh
Net Weight135g /4.76 oz
Gross Weight285g /10.05 oz
Approximate Weight285g /10.05 oz
Dimension 110.00 x 56.30 x 23.50mm

Product Highlights

  • Brand: Relm
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My RPU7500 drops to low transmit power partway through a shift — could this be a voltage sag problem?

Yes. Under sustained RF output, the BL1703 cells experience voltage sag as internal resistance builds across the discharge curve. When the pack voltage dips below the RPU7500's reduced-power threshold, the radio automatically backs off TX output to protect the final amplifier stage. This is not a faulty battery — it is normal behaviour on a partially discharged cell. Start each shift with a fully charged pack sitting at 8.4V before load.

The charger dock fault LED never clears after inserting the new BL1703 — the dock just blinks continuously.

A continuous fault blink on the RPU7500 dock usually means the pack voltage is below the dock's acceptance threshold, which is typically around 6.0V. A pack stored for several months can drop below this level, and the dock refuses to engage the charge cycle. Remove the pack, check that the gold contacts are clean and seated flat, then use a compatible bench charger or a second dock to apply a slow trickle charge until the pack reaches at least 6.5V — at that point the dock will accept it and switch to normal charge mode.

The BL1703 pack feels fully charged but the RPU7500 won't power on at all — what's happening?

This points to a BMS lockout triggered by deep discharge during extended storage. The protection circuit has shut the pack output off entirely and will not pass voltage to the radio until it receives a recovery charge pulse. Seat the pack in the dock and leave it undisturbed for 20–30 minutes — most docks apply a low-current wake pulse before ramping to full charge current. If the dock fault LED clears and charging begins, let the cycle run to completion before powering the radio on.

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