Relm RPU7500 Replacement Battery BL1703 7.4V 2100mAh
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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Relm RPU7500 Replacement Battery BL1703 7.4V 2100mAh - 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 2100mAh - is backordered and will ship as soon as it is back in stock.
Voltage
7.4V
Amp
2100mAh
Relm RPU7500 / RPV7500 — 7.4V Li-ion Replacement Battery (BL1703)
The BL1703 is a 7.4V, 2100mAh lithium-ion battery for the Relm RPU7500 and RPV7500 portable two-way radios. It replaces the original pack when capacity has faded or the radio no longer holds a charge between shifts. Voltage and connector match the OEM spec exactly.
- RPU7500 and RPV7500 platform fit: Both models run the same 7.4V power rail, share the BL1703 connector footprint, and use the same BMS handshake protocol — a single pack covers either radio without modification.
- Bench tested on actual hardware: We cycled this pack through full charge-discharge runs on the RPU7500 platform. The BMS held steady across transmit current spikes and reported no false cutoffs under sustained PTT load.
- First insertion into the charger dock: If the dock LED shows a fault on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat it firmly. The RPU7500 dock requires a clean contact cycle to complete the BMS handshake before charging begins.
RPU7500 cuts out mid-transmission on a new BL1703
A new lithium-ion pack ships at storage voltage — typically 3.6–3.7V per cell, not full charge. When you key up on a new battery straight out of the box, the transmit current spike can pull the cell voltage below the BMS undervoltage threshold, triggering an immediate cutoff. The radio cuts out not because the pack is faulty, but because the cells haven't been brought to operating charge yet. Charge the pack fully in the dock before the first transmission — the BMS will not trip once the cells are at 4.1–4.2V per cell.
Bar indicator shows one fewer bar than expected after inserting a new BL1703
The RPU7500 uses a voltage-threshold bar indicator — each bar corresponds to a voltage window, not a fuel gauge calculation. A new pack at storage voltage sits in a lower threshold window, so the display shows one or two bars even though the pack is not depleted. This is not a capacity fault. Place the pack in the dock, let it reach a full charge cycle, and the bar indicator will reflect the correct resting voltage — typically four bars at 8.2–8.4V across the pack.
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
The RPU7500 drops to reduced transmit power partway through a shift — is the new BL1703 pack the cause?
Reduced TX power mid-shift points to voltage sag under sustained RF output, not a faulty pack. When cell impedance is higher than the radio expects — common in the first few charge cycles on a new battery — the voltage drops under load and the radio steps down its output to protect the PA stage. Run two or three full charge-discharge cycles to condition the cells and lower internal impedance. If sag continues after conditioning, check that the dock contacts are clean and making full contact with the battery's gold strip.
The charger dock fault LED won't clear after inserting the new BL1703 — how do I fix it?
A persistent fault LED usually means the dock has not completed the BMS handshake, most often because of poor contact or because the pack voltage is below the dock's acceptance threshold from extended storage. Remove the pack, wipe the gold contact strip with a dry cloth, and reseat it with firm pressure. If the fault LED remains, leave the pack seated for 10–15 minutes — some dock controllers will retry the handshake once the pack's resting voltage stabilises above the minimum acceptance level of approximately 6.0V.
The RPU7500 radio powers on but shuts off the moment PTT is pressed on the new battery — what's happening?
This is a BMS overcurrent trip caused by the transmit current spike hitting the cutoff threshold on an uncharged pack. At storage voltage, the cells cannot supply the current peak that transmit demands, so the BMS opens the protection circuit and the radio dies instantly. The fix is straightforward: charge the pack to full before keying up for the first time. Once the cells are at 4.1–4.2V each, the BMS overcurrent threshold will not be breached by a normal PTT press.
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