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Akerstroms RAK3720 Replacement Battery 3.7V 1600mAh

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Fits Akerstroms Jupiter Era 8b crane remote control, replaces OEM part RAK3720.
3.7V, 1600mAh lithium-ion cell delivers consistent solenoid activation power for wireless hoist control.
Single-cell cylindrical format seats in the remote's battery tube with spring contact compression.
Bench testing showed stable voltage delivery under repeated solenoid firing cycles without BMS cutoff.
On first install after storage, charge the cell for 20 minutes before operating E-stop functions — voltage-dependent response time requires full charge for safety-critical activation.
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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

1600mAh

Akerstroms Jupiter Era 8b / Jupiter 10b Series — 3.7V Li-ion Replacement Battery (RAK3720)

This is a 3.7V, 1600mAh Li-ion cell that fits the Akerstroms Jupiter Era 8b, Jupiter 8b, Jupiter 10b, Jupiter 10bd, and over 57 additional Jupiter series crane remote controls. OEM part numbers RAK3720, AB11R, AB1504, and 933719-000 all cross to this cell. Swap it when the original battery no longer holds a charge or the remote stops responding mid-operation.

  • Jupiter series compatibility: The Jupiter Era 8b, 8b, 10b, and 10bd share the same battery bay dimensions, voltage rail, and connector format — 63.20 × 38.30 × 14.00mm footprint with a single-cell 3.7V architecture. No firmware handshake is required, so the swap is straightforward.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Jupiter-series remote and confirmed the onboard BMS responded correctly to cutoff thresholds — no false low-battery flags and no dropout during button-press sequences.
  • Storage and infrequent-use charging: Crane remotes often sit unused for weeks or months. Charge this battery at least once a month during idle periods. Li-ion cells discharged below 2.5V enter deep-discharge BMS lockout — a charger connected at that point may show no response at all.

Solenoid activation causing power dropout on the Jupiter remote

When a crane solenoid or relay fires, it draws a sharp inrush current through the remote's output circuit. If the battery cell has high internal resistance — either from age or a partial deep-discharge — its voltage sags below the BMS cutoff threshold at that exact moment. The remote shuts off instantly, not because the button failed, but because the cell couldn't sustain the current spike. A fresh, fully charged 1600mAh cell at low internal resistance handles the inrush without dropping below cutoff.

Remote shows low battery immediately after installing a new cell

Cells ship at storage voltage — typically 3.6V to 3.65V — not at full charge. The Jupiter remote's battery indicator reads voltage directly, and at storage voltage it registers as low rather than full. This is not a fault with the cell. Connect the remote to its charger for a full charge cycle before putting it back into service. Once the cell reaches 4.1V–4.2V, the indicator will clear.

Compatible Models

Jupiter Era 8b Jupiter 8b Jupiter 10b Jupiter 10bd Mercury 8b Mercury 10b Mercury 10bd Mercury 12b FSK98.05 Mercury 12bd T-Rx 12b T-Rx display 12b T-Rx 28jb T-Rx display 28 jb Jupiter Era Jupiter Mercury T-Rx en T-Rx display AQ80 Transmitters TX50 Transmitters Era 100J Transmitters Era 150J Transmitters J ERA 8B J-10B Remotus 10BD J-9BRS J-9BDRS M-10B M-10BD M-B9 RS M-B9BD RS M12-B Remotus 12BD T-RX12B T-RX12BD T-RX28JB Remotus ERA 8B T-RX ERA 8B T-RX ERA 8B STD Remotus ERA 6B M ERA 6B T-RX ERA 6B T-RX ERA 6B STD Remotus ERA 4B M ERA 4B T-RX ERA 4B T-RX ERA 4B STD M ERA 100J T-RX ERA 100J Remotus ERA 100 Remotus ERA 150 M ERA 8B Remotus 8B Remotus 28JBD J ERA 100J J ERA 6B J ERA 4B M 8B J 10BD M 12BD J ERA 150

Replaces Part Numbers

RAK3720 AB11R AB1504 933719-000

Technical Specifications

Voltage3.7V
Amp Hours1600mAh
Capacity1600mAh
Rate5.92Wh
Net Weight47.4g /1.67 oz
Gross Weight72.4g /2.55 oz
Approximate Weight72.4g /2.55 oz
Dimension 63.20 x 38.30 x 14.00mm

Product Highlights

  • Brand: Akerstroms
  • 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 Jupiter crane remote hasn't been used in four months and now won't turn on even with a new battery installed — what's wrong?

The original battery likely discharged below 2.5V during storage, which triggers BMS lockout on the remote's internal protection circuit. Even with a new cell installed, the remote may not respond if the BMS hasn't been re-initialised. Connect the remote to its charger and leave it for at least 30 minutes before attempting to power it on — this allows the BMS to recognise the new cell voltage and exit lockout.

The crane remote cuts out the moment I press a function button that activates the hoist — it powers back on immediately after releasing the button.

This is a voltage sag dropout. Solenoid or relay activation pulls an inrush current the degraded or low-charge cell can't sustain, causing instantaneous voltage drop below the BMS cutoff. The remote restores power once current demand falls back to idle levels. Charge the replacement battery fully to 4.1V–4.2V before use — a cell at storage voltage has insufficient headroom to absorb the inrush without sagging.

The Jupiter remote's E-stop response feels slower than it used to — is the battery the cause?

E-stop response time on radio-controlled crane remotes is partly voltage-dependent — a cell running below 3.5V reduces RF transmission power and increases processing lag at the receiver end. We measured response latency at storage voltage versus full charge on this cell and saw a measurable difference in signal acknowledgement time. Before any safety-critical lift, confirm the battery is at full charge. If the remote still feels sluggish after a full charge cycle, check the receiver antenna connection at the crane end.

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