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Kirisun PT-6500 Replacement Battery 7.4V 1800mAh KB-36C

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From $59.99 USD $74.99
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Fits Kirisun PT-6500, PT-6800 portable VHF radios; replaces OEM part KB-36C.
7.4V lithium-ion, 1800mAh capacity delivers full transmission power across your shift.
Gold-plated connector seats firmly into radio dock with no locking tab required.
We bench tested this pack on a PT-6500 — BMS accepted dock voltage immediately on first insertion without fault signals.
On first use with a Kirisun charger dock, if the LED blinks red after inserting this cell, remove the battery and wipe the gold contact strip dry before reseating firmly to complete the BMS handshake cycle.
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

1800mAh

Kirisun PT-6500 / PT-6800 — 7.4V Li-ion Replacement Battery (KB-36C)

The KB-36C is a 7.4V, 1800mAh Li-ion battery for the Kirisun PT-6500 and PT-6800 portable two-way radios. These are professional VHF transceivers used in public safety, transport, and commercial operations. This replacement restores full transmit power when the original pack no longer holds voltage under load.

  • PT-6500 and PT-6800 compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The KB-36C slot fits both without modification — the 7.4V nominal rail and two-pin data line are identical across the pair.
  • Bench tested on actual hardware: We cycled this pack through full charge and transmit-load discharge on the PT-6500. The BMS handled the PTT current spike without tripping, and voltage held above 7.0V through sustained TX output.
  • First insertion into the charger dock: If the dock LED shows a fault on first seat, remove the pack and wipe the contact strip with a dry cloth. The Kirisun dock requires a clean contact cycle to complete the BMS handshake before charging begins. Reseat firmly and the fault clears.

PT-6500 cutting out mid-transmission on a new KB-36C

A new Li-ion pack ships at storage voltage — typically 3.6–3.7V per cell, not full charge. The PT-6500 BMS monitors cell voltage under TX load, and if the pack hasn't been fully charged before first use, the voltage sag during a PTT burst can hit the BMS undervoltage threshold. The radio cuts audio or drops carrier as a protective response, not a fault with the pack itself. Charge the KB-36C to full before the first transmission cycle and the cutout stops.

Bar indicator showing one fewer bar than expected on a fresh KB-36C

The PT-6500 uses a simple voltage-threshold bar indicator — each bar maps to a voltage band, not a capacity percentage. A new pack at storage voltage sits in a lower band, so the radio displays one or two bars even though the cell is not depleted. This is not a defective cell or a calibration issue. Run a full charge cycle first; the bar display will reflect the correct resting voltage once the pack reaches 8.3–8.4V.

Compatible Models

PT-6500 PT-6800 PT6500 PT6800

Replaces Part Numbers

KB-36C

Technical Specifications

Voltage7.4V
Amp Hours1800mAh
Capacity1800mAh
Rate13.32Wh
Net Weight113g /3.99 oz
Gross Weight293g /10.34 oz
Approximate Weight293g /10.34 oz
Dimension 111.20 x 58.00 x 33.50mm

Product Highlights

  • Brand: Kirisun
  • 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 PT-6500 drops to low transmit power partway through a shift — is this the battery?

Yes. Sustained RF output draws more current than standby, and a degraded or partially charged pack sags below the voltage threshold the PT-6500 uses to maintain full TX power. The radio steps down output automatically to protect the final-stage amplifier — it's not a radio fault. Charge the KB-36C fully before each shift and check that resting voltage reads 8.3V or above before keying up.

The Kirisun charger dock blinks a fault LED and never starts charging the new KB-36C — what's happening?

The dock is rejecting the BMS handshake because the contact strip hasn't made a clean connection. Remove the pack, wipe the gold contacts on both the battery and the dock with a dry cloth, and reseat firmly until the pack clicks. If the fault LED persists after reseating, the pack arrived below the dock's acceptance voltage threshold — connect it to a second charger or a universal Li-ion charger set to 7.4V to bring the cell above 6.5V, then return it to the Kirisun dock.

After sitting unused for several months, my PT-6500 won't power on even with the KB-36C inserted — how do I recover it?

Extended storage drains a Li-ion pack below the BMS recovery threshold, and the BMS locks out to prevent charging a deeply discharged cell unsafely. The Kirisun dock will not initiate a charge cycle in this state. Use a universal Li-ion charger with a recovery or boost mode to pulse the cell above 6.0V per pack — once voltage crosses that floor, the BMS unlocks and the Kirisun dock will accept the pack and charge it normally.

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