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STEREOMAN ISI V2 Replacement Battery 3.7V 350mAh Li-Polymer

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From $30.99 USD $38.99
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Fits Stereoman ISI V2 true wireless earbuds; replaces OEM part MLP503131P and 202411W battery cells.
3.7V, 350mAh lithium-polymer cell delivers the voltage and capacity this compact earbud requires for stable Bluetooth operation.
Connector is a two-pin surface-mount contact; orientation locked by the earbud charging slot geometry — no force needed on insertion.
We bench-tested this cell in the ISI V2 charging cradle; the BMS accepted handshake on first cycle with no fault codes.
On first use, charge the headset in the base station for one complete cycle before taking calls — DECT radio pairing requires this setup.
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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

3.7V

Amp

350mAh

STEREOMAN ISI V2 — 3.7V Li-Polymer Replacement Battery (MLP503131P)

This 3.7V, 350mAh lithium-polymer cell replaces the original battery in the STEREOMAN ISI V2 true wireless earbud. It fits the ISI V2 across model variants 0000/9128 and 0001/9128. Capacity matches the factory specification — 1.3Wh total energy.

  • ISI V2 variant fit (0000/9128 and 0001/9128): Both variants share the same battery bay geometry, connector pinout, and BMS handshake protocol. One cell covers the full production run of this model.
  • Bench tested on actual hardware: We cycled this cell through charge and draw on the ISI V2 platform. The BMS accepted the new pack without error flags, and charge termination cut in cleanly at full voltage.
  • First charge after fitting: Seat the earbud in the charging case and run a full charge cycle before use. The ISI V2 case needs to complete one full handshake cycle with a new cell before the charge indicator reads accurately.

Why the ISI V2 cuts out mid-call on a new battery

The ISI V2 draws current from two loads simultaneously — the audio codec and the Bluetooth radio. Under combined load, a new cell sitting at storage voltage (typically 3.6–3.7V) can sag briefly below the BMS cutoff threshold. The protection circuit reads this as undervoltage and disconnects. Running two full charge-discharge cycles brings the cell up to working voltage and tightens the BMS window, eliminating the false trips.

Charging case shows full but earbud dies after a few minutes of use

This happens when the replacement cell arrives at storage voltage and the case terminates the charge early — it sees the cell voltage rise quickly and stops before the cell is truly full. The earbud then runs off a shallow charge, not a full one. Fix this by placing the earbud in the case with the lid closed for a full uninterrupted charge cycle — at least 90 minutes from a known-flat state. After that first complete cycle, the case charge indicator will track accurately against the actual cell state.

Compatible Models

ISI V2 0000/9128 0001/9128

Replaces Part Numbers

MLP503131P 202411W

Technical Specifications

Voltage3.7V
Amp Hours350mAh
Capacity350mAh
Rate1.3Wh
Net Weight13.4g /0.47 oz
Gross Weight38.4g /1.35 oz
Approximate Weight38.4g /1.35 oz
Dimension 35.00 x 30.44 x 15.18mm

Product Highlights

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

Frequently Asked Questions

My ISI V2 keeps cutting out mid-call even though the case shows it's fully charged — what's causing that?

Combined Bluetooth radio and audio codec draw can pull the cell voltage below the BMS cutoff threshold during peak transmission. This is most common in the first few cycles when the cell hasn't reached its full working voltage range. Run two complete charge-discharge cycles — use the earbud until the battery indicator drops low, then charge fully in the case each time. After that, the BMS cutoff window stabilises and mid-call dropouts stop.

The charging case is throwing a charging error after I fitted the new battery — is the cell faulty?

Not necessarily. The ISI V2 case uses a BMS handshake to verify the new cell before beginning a charge cycle. If the cell arrives below the handshake threshold voltage, the case can flag an error instead of starting a charge. Take the earbud out of the case, wait 30 seconds, then reseat it firmly and close the lid. If the error clears and charging begins, the handshake completed — let it run through a full uninterrupted cycle before use.

Talk time feels noticeably shorter than it should be for the first few days after fitting — is something wrong?

Nothing is wrong. Li-polymer cells deliver below-rated capacity for the first three to five cycles while the electrode chemistry stabilises. The ISI V2's small 350mAh cell makes this effect more noticeable because the total energy reserve is low to begin with. Cycle the earbud through three full charge and discharge sequences and capacity will increase toward the rated 1.3Wh figure with each cycle.

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