Relm RPU7500 Replacement Battery BL1703 7.4V 1600mAh
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Relm RPU7500 Replacement Battery BL1703 7.4V 1600mAh - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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
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
⚠️ 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.
Relm RPU7500 Replacement Battery BL1703 7.4V 1600mAh - is backordered and will ship as soon as it is back in stock.
Voltage
7.4V
Amp
1600mAh
Relm RPU7500 / RPV7500 — 7.4V Li-ion Replacement Battery (BL1703)
This is a 7.4V, 1600mAh Li-ion replacement for the Relm BL1703 battery pack. It fits the RPU7500 and RPV7500 portable transceivers used in public safety, security, and commercial communications. Voltage and capacity match the OEM spec exactly.
- RPU7500 and RPV7500 platform fit: Both radios share the same battery bay dimensions, contact arrangement, and BMS handshake protocol — one pack covers both. The 7.4V nominal rail matches the TX power stage on each unit without triggering undervoltage shutdown on key-up.
- Bench tested on actual hardware: We cycled this pack through repeated PTT key-up events to confirm the BMS handles the transmit current spike without tripping into protection mode. Voltage held stable across the RF output stage throughout each test.
- First insertion into the charger dock: If the dock LED flashes a fault pattern on initial seating, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The RPU7500 dock requires a clean contact cycle to complete the BMS handshake and begin the charge sequence.
Why the RPU7500 cuts out mid-transmission on a new BL1703
New Li-ion cells ship at storage voltage — typically around 3.6–3.7V per cell, not full charge. When you key up at that voltage, the transmit current draw pulls the pack voltage below the BMS protection threshold momentarily, and the radio drops the TX stage. This is not a faulty pack. Fully charge the battery before first use and the cutout stops.
Bar indicator showing one fewer bar than expected after full charge
The RPU7500 uses a simple voltage-threshold bar indicator — it reads pack voltage and maps it to a bar count. A new cell's internal impedance is slightly higher before its first few cycles, which causes a small voltage drop under load and shifts the reading down by one bar. This is not a calibration fault. Run two or three full charge and discharge cycles and the bar reading aligns with actual capacity.
Compatible Models
Replaces Part Numbers
Technical Specifications
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-power TX mid-shift even though the battery was fully charged — what's happening?
Sustained RF output draws continuous current, and if cell impedance rises after several hours of use, pack voltage sags enough for the radio to reduce transmit power to protect the output stage. This is a voltage-sag response, not a BMS trip. Check the pack resting voltage after the shift — if it reads above 7.0V and the behaviour still occurs, the cells are fatiguing and the pack needs replacing. A healthy BL1703 at rest should sit between 7.4V and 8.2V after a full charge.
The charger dock LED never stops blinking after I insert the new BL1703 — it won't accept the pack at all.
A persistent fault blink usually means the dock is reading the pack voltage as below its acceptance threshold, which happens when a new cell has been in storage long enough to drop below the BMS recovery floor. Remove the pack, wipe the gold contacts with a dry cloth, and reseat firmly — dirty contacts cause the same symptom. If the fault clears within 30 seconds of reseating, the dock has accepted the BMS handshake and charging has started. If it doesn't clear, measure pack voltage across the contacts — it needs to read at least 6.0V for the dock to initiate a charge cycle.
The RPU7500 powers on fine but the battery bar drops suddenly from three bars to one after pressing PTT a few times — is the pack defective?
This is a PTT transmit-spike response, not a defective pack. Each key-up pulls a short burst of current that momentarily drops pack voltage, and the radio's voltage-threshold bar indicator reads that dip as a lower state of charge. After you release PTT and voltage recovers, the bar count should jump back up within a few seconds. If the bars do not recover after releasing the key, measure resting voltage — a healthy BL1703 after partial use should read above 7.2V at rest.
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