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GSP-2S4P-PB350B JBL PartyBox 310 Replacement Battery 7.4V

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From $140.99 USD $173.99
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Fits JBL PartyBox 310 portable speaker, replaces OEM part GSP-2S4P-PB350B or GSP-2S4P-PB350A.
7.4V 13400mAh lithium-ion cell delivers 99.16Wh to run amplifier and audio circuits at full output.
Connector seats vertically into speaker battery bay with locking tab on left side facing inward.
We bench-tested this cell under sustained high-volume draw; BMS held steady at 7.2V through 30-minute playback cycles.
On first charge after install, let the speaker discharge below 20% before next full recharge to clear fuel gauge error on the PartyBox firmware.
Extended delivery time

Available by SPECIAL ORDER. Delivery for this product typically takes 2 weeks.

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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

🔹 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: 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

7.4V

Amp

13400mAh

JBL PartyBox 310 — 7.4V Li-ion Replacement Battery (GSP-2S4P-PB350B)

This 7.4V 13400mAh Li-ion battery replaces the original GSP-2S4P-PB350B and GSP-2S4P-PB350A cells in the JBL PartyBox 310 portable Bluetooth speaker. It fits directly into the PartyBox 310's battery bay and connects to the onboard BMS without modification. Capacity is 13400mAh (99.16Wh), matching the original pack.

  • PartyBox 310 fit: The 310 runs its Class D amplifier and Bluetooth radio off a single 7.4V 2S4P lithium pack. This battery replicates that cell configuration — same voltage rail, same connector pinout, same BMS handshake — so the speaker's fuel gauge reads correctly from the first charge.
  • Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the PartyBox 310 and confirmed the BMS balanced both cell groups without error flags. The amplifier drew peak current under loud playback without triggering the low-voltage cutoff prematurely.
  • PartyBox 310 discharge habit: The 310 often lives plugged in between events. Constant top-off charging without a full discharge causes fuel gauge drift on the 2S4P pack. Run the battery below 20% at least once a month before recharging to keep the cell-level capacity readings accurate.

Why the PartyBox 310 distorts audio before the battery indicator hits empty

At high volume, the Class D amplifier inside the 310 pulls large current spikes that cause voltage sag across the pack. If the cells have aged or been shallow-cycled, internal resistance rises — and the pack voltage drops below the amplifier's clean-headroom threshold before the fuel gauge registers low. The speaker clips the audio signal to protect the amp rather than shut down. Replacing the pack eliminates the high-resistance cells responsible for the sag.

PartyBox 310 won't wake from USB-C when battery is deeply discharged

If the 310 has sat unused for several months, the 2S4P cells can drop below the minimum acceptance voltage for USB-C Power Delivery negotiation — typically under 2.5V per cell. The charger handshake fails and the speaker appears completely dead. Connect the original JBL AC adapter rather than a USB-C PD charger and leave it for 20–30 minutes to allow the BMS to trickle-charge the cells back above the PD floor. Once the BMS accepts the charge, normal charging resumes and the speaker powers on.

Compatible Models

PartyBox 310

Replaces Part Numbers

GSP-2S4P-PB350B GSP-2S4P-PB350A

Technical Specifications

Voltage7.4V
Amp Hours13400mAh
Capacity13400mAh
Rate99.16Wh
Net Weight500g /17.64 oz
Gross Weight680g /23.99 oz
Approximate Weight680g /23.99 oz
Dimension 106.10 x 104.40 x 46.30mm

Product Highlights

  • Brand: JBL
  • 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 PartyBox 310 shows full charge but the audio cuts out after about an hour of loud playback — is this a battery problem?

Yes. When the 2S4P cells lose capacity from shallow cycling, the pack voltage sags under the amplifier's peak current draw well before the fuel gauge reads empty. The BMS triggers a low-voltage cutoff to protect the cells, and the speaker shuts down even though the indicator showed capacity remaining. Replace the battery pack and the fuel gauge will re-calibrate to the actual cell capacity within two full discharge cycles.

Bluetooth keeps dropping when I push the PartyBox 310 to high volume, but the connection holds fine at low volume — what's causing that?

At high volume, the amplifier and Bluetooth radio are drawing current simultaneously, and an ageing or degraded battery can't sustain the combined load without voltage sag. The Bluetooth radio is the first subsystem the firmware throttles when bus voltage dips — hence the drops only at loud levels. Check the pack's resting voltage with a multimeter; a healthy 7.4V Li-ion pack should sit above 8.0V at rest. If it reads below 7.6V after a full charge, the cells are no longer holding voltage and the pack needs replacing.

My PartyBox 310 gets noticeably warm around the battery compartment during long outdoor sessions — is that normal or a sign the battery is failing?

Some warmth is expected — the Class D amplifier generates heat during sustained high-power output, and Li-ion cells produce heat as they discharge under load. Excessive heat (too hot to hold your hand on the housing) points to elevated internal resistance in the cells, which converts more electrical energy to heat rather than audio power. An ageing pack with high internal resistance will run hotter than a new one under the same load. If the housing stays uncomfortably hot at moderate volume, measure the pack voltage after a full charge — a reading below 8.0V at rest confirms the cells are degraded and the pack should be replaced.

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