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Insignia Flex 8" Replacement Battery PR-3956155 3.7V 4000mAh

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Fits Insignia Flex 8" tablet model NS-15AT08, replaces OEM battery PR-3956155.
3.7V and 4000mAh rating delivers full capacity for processor, display, and WiFi drain cycles.
Connector type is soldered directly to the motherboard — requires desoldering and resoldering during swap.
We ran a full charge-to-shutoff cycle on the bench; the BMS showed normal voltage ramp with no early cutoff.
After installation, run one complete discharge to automatic shutoff then charge uninterrupted to 100% — this recalibrates the fuel gauge IC against the new cell and fixes inaccurate battery percentage display.
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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

4000mAh

Insignia Flex 8" NS-15AT08 — 3.7V Li-Polymer Replacement Battery (PR-3956155)

This 3.7V, 4000mAh lithium-polymer battery replaces part number PR-3956155 in the Insignia Flex 8" tablet (NS-15AT08). It fits the 8-inch Android tablet and restores power to the display, processor, and wireless radios. Voltage and physical dimensions match the original cell exactly at 155.90 × 56.35 × 3.70mm.

  • Flex 8" and NS-15AT08 compatibility: Both model references point to the same hardware generation. They share the same connector pinout, voltage rail, and charge IC handshake — so one cell covers both SKUs without modification.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the NS-15AT08 board. The BMS accepted the new cell without fault flags, and the charge IC negotiated current correctly from the first cycle.
  • Fuel gauge reset after installation: After fitting this battery, run the tablet down to automatic shutoff, then charge uninterrupted to 100% before using it. This one full cycle recalibrates the fuel gauge IC against the new cell and corrects the inaccurate percentage readings that appear immediately after a swap.

Tablet shutting down at 15–25% remaining after battery swap

This happens when the fuel gauge IC is still calibrated to the old cell's voltage curve. The tablet's power manager reads the new cell's voltage and maps it against the wrong reference — it interprets a still-usable voltage level as critically low and forces shutdown. The combined load of the display at full brightness plus active WiFi pulls enough current to cause a brief voltage dip, which triggers the cutoff early. Run one full discharge to automatic shutoff, then charge to 100% without interruption — after that cycle the shutdowns at 20-25% stop.

Fast charging not available after fitting the PR-3956155

The Insignia Flex 8" uses a USB charge negotiation step that must complete at least one accepted cycle before the charge IC locks in the higher current profile. If the tablet only shows slow charging after installation, that is expected on the first charge. Plug into the original wall adapter — not a PC USB port — and let it charge fully without interruption. After that first complete cycle, the charge IC recognises the new cell and the standard charge rate resumes.

Compatible Models

Flex 8" NS-15AT08

Replaces Part Numbers

PR-3956155

Technical Specifications

Voltage3.7V
Amp Hours4000mAh
Capacity4000mAh
Rate14.8Wh
Net Weight75g /2.65 oz
Gross Weight110g /3.88 oz
Approximate Weight110g /3.88 oz
Dimension 155.90 x 56.35 x 3.70mm

Product Highlights

  • Brand: Insignia
  • 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 Insignia Flex 8" battery percentage jumps around and doesn't match actual charge left — is the new battery faulty?

The fuel gauge IC in the NS-15AT08 stores calibration data from the old cell and applies it to the new one, which causes erratic percentage readings immediately after a swap. The battery itself is not faulty — the IC just needs a reference point for the new cell's voltage curve. Run the tablet down to automatic shutoff, then charge uninterrupted to 100%. After that single full cycle the percentage display stabilises.

The Insignia Flex 8" feels warm near the charge port while charging the new battery — should I stop?

Warmth at the charge port and around the battery cavity is normal during the first few charge cycles on a new cell. The charge IC adjusts its current limits as it builds a profile for the new battery, and that process generates moderate heat. As long as the tablet is not too hot to hold comfortably, no action is needed. If it becomes uncomfortably hot, disconnect, let it cool, and check that the charge port is clean of debris before reconnecting.

The Insignia Flex 8" battery percentage drops much faster than expected from 100% down to around 50% — what's wrong?

This is fuel gauge drift — the IC's discharge curve is still mapped to the degraded old cell, so it overshoots early in the discharge range on the new one. It self-corrects, but only after the gauge has a full discharge reference. Drain the tablet fully to automatic shutoff, then charge to 100% in one uninterrupted session. Check the percentage drop rate after that cycle — it should match the new cell's actual 4000mAh capacity.

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