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Arlo Ultra Compatible Battery A-4a 3.85V 4800mAh

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Fits Arlo Ultra, Ultra 4K UHD, and VMS5140 cameras; replaces OEM part A-4a and 308-10069-01.
3.85V, 4800mAh cell delivers 18.48Wh — sufficient for continuous video and motion detection on wireless Ultra models.
Connector slides straight in with a single locking tab; orientation marked on the camera battery slot itself.
We bench-tested the BMS against Arlo's firmware handshake; the cell accepted registration within one app power cycle without fault codes.
On first install, power cycle the camera through the Arlo app — firmware must register the new cell before motion recording logs correctly to cloud.
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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

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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

3.85V

Amp

4800mAh

Arlo Ultra / Ultra 4K UHD — 3.85V Li-ion Replacement Battery (A-4a)

This is a 3.85V, 4800mAh Li-ion cell built to replace the original A-4a battery in the Arlo Ultra and Ultra 4K UHD wireless security cameras. It fits VMS5140 and VMA5400-10000S units along with four additional models in the same Ultra lineup. Voltage and capacity match OEM spec exactly — no adapter, no modification needed.

  • Ultra series compatibility: Every model in this group runs the same 3.85V power rail, uses the same magnetic charge contacts, and communicates with the same BMS handshake sequence. Swapping the cell does not require re-pairing the camera hub — the hardware recognises the same voltage profile on contact.
  • Bench tested on actual hardware: We cycled this cell through the Ultra's BMS under motion-triggered recording loads, including back-to-back IR LED activations. The protection circuit held within spec on both overcurrent and low-voltage cutoff thresholds throughout testing.
  • First-install power cycle: After fitting the battery, trigger a full power cycle through the Arlo app — remove the camera from the base station view, reinsert it, and let firmware re-register the cell. Without this step, the motion recording scheduler can fail to log clips correctly to cloud storage.

Camera going offline in the app after a battery swap

The Arlo Ultra stores a session token tied to active power state. Pulling the battery clears that token, and the base station marks the camera as offline rather than waiting for re-authentication. This is a firmware behaviour, not a battery fault. Open the Arlo app, go to Device Settings, and use the Sync button to force a fresh handshake — the camera should come back online within 60 seconds at a clean 3.85V resting charge.

App showing 0% or wrong battery percentage after install

The Arlo Ultra uses a voltage-threshold indicator, not a fuel gauge IC. It maps percentage to discrete voltage steps, so a freshly installed cell at partial charge can read 0% or jump erratically until the firmware calibrates. Run one full charge cycle through the magnetic base — charge to 100%, let the camera operate through at least one full discharge — and the percentage readout will track the actual voltage curve correctly from that point forward.

Compatible Models

Ultra Ultra 4K UHD VMS5140 VMA5400-10000S Ultra + VMC5040 Pro 4 VMC4040P

Replaces Part Numbers

A-4a 308-10069-01

Technical Specifications

Voltage3.85V
Amp Hours4800mAh
Capacity4800mAh
Rate18.48Wh
Net Weight87g /3.07 oz
Gross Weight157g /5.54 oz
Approximate Weight157g /5.54 oz
Dimension 47.63 x 39.44 x 30.00mm

Product Highlights

  • Brand: Arlo
  • Manufacturer: CS
  • Series: Standard
  • Color: White
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Arlo Ultra stops recording mid-clip and I keep finding incomplete videos in the app — what's causing it?

A WiFi reconnect event during recording draws a current spike that can trip the BMS overcurrent threshold, cutting power to the processor mid-clip. This happens most often when the camera is at the edge of your WiFi range and the signal drops briefly during an active recording session. Move the camera closer to the router or add a range extender to reduce reconnect frequency. If the cutoffs continue, check that the resting voltage reads above 3.7V after a full charge cycle — cells below that threshold sag under combined WiFi and processor load.

Night vision cuts out after dark and the camera appears to go to sleep — is the battery the problem?

Sustained IR LED draw is one of the highest continuous loads the Ultra places on the cell. If the battery has degraded below usable capacity, the BMS will hit its low-voltage cutoff during a prolonged night-vision session and shut the camera down to protect the cell. A fresh 4800mAh cell at full charge should carry continuous IR operation without triggering cutoff. After fitting this replacement, run a full charge to 100% before the first overnight session and confirm the app shows a stable percentage above 80% at dusk.

My Arlo Ultra is solar-panel mounted but the battery keeps depleting and never recovers — why won't the solar panel charge it back up?

The Arlo solar panel outputs around 1W at peak sun, which is enough to maintain a healthy cell but not enough to recover one that has dropped below the BMS re-entry voltage — typically around 3.0V. Once the cell falls into deep discharge, the BMS blocks incoming charge as a protection measure and the solar panel cannot push past that gate. Remove the battery, charge it directly via the magnetic charging cable until it reads at least 3.4V, then reinstall it — at that point the solar panel can resume normal top-up charging.

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