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Standard Horizon HX400IS Replacement Battery 7.4V 2550mAh

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From $53.99 USD $66.99
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Fits Standard Horizon HX400IS and HX400 handheld radios, replaces SBR-29LIIS, FNB-115LIIS, SBR-45LIIS, SBR-45LI packs.
7.4V and 2550mAh capacity delivers full RF output on sustained maritime transmissions without voltage sag.
Connector slides straight down into the radio slot with a single locking tab that seats flush.
We tested the BMS on a bench charger — accepts full charge cycle without dock fault codes or cutoff.
On first insertion into the HX400IS dock, if the charger LED blinks, remove the battery and wipe both gold contact strips with a dry cloth, then reseat firmly to clear the BMS handshake fault.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
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By continuing with your purchase, you acknowledge and agree to the estimated 7–10 business day delivery timeframe.
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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

2550mAh

Standard Horizon HX400IS / HX400 — 7.4V Li-ion Replacement Battery (SBR-29LIIS)

This 7.4V, 2550mAh Li-ion battery replaces the Standard Horizon SBR-29LIIS in the HX400IS and HX400 handheld marine VHF radios. It also cross-references OEM part numbers FNB-115LIIS, SBR-45LIIS, and SBR-45LI. Voltage and capacity match factory spec exactly.

  • HX400IS and HX400 fit: Both models share the same battery bay geometry, contact layout, and BMS handshake protocol — one pack covers both. The SBR-29LIIS form factor was carried across the HX400 line without revision to the connector or locking tab.
  • Bench tested on actual hardware: We ran this pack through a full charge cycle and PTT transmit load test. The BMS held voltage stable through repeated transmit bursts and returned clean cutoff behaviour at low-cell threshold — no false trips under normal TX current draw.
  • Marine environment contact care: Salt air and moisture accelerate oxidation on the gold contact strip. Before first use, wipe the contacts with a dry cloth and seat the pack firmly into the dock — the HX400 platform requires a clean contact cycle to initiate the BMS handshake and begin charging.

Why the HX400IS drops to reduced TX power mid-call on a new battery

The HX400IS transmits at 5W on full power, which pulls a significant current spike from the pack. If the replacement cell shipped at storage voltage (typically around 3.7V per cell), the BMS may sag under that load and throttle output before a full charge cycle has been completed. This is not a faulty pack — it is a storage-voltage limitation. Run one full charge cycle before using the radio on full TX power and the behaviour stops.

Bar indicator showing one fewer bar than expected after a fresh charge

The HX400IS uses a simple voltage-threshold bar indicator — each bar corresponds to a voltage band, not a percentage. A new cell fresh from storage sits slightly below the top threshold band even after the dock shows a full charge LED. The fix is straightforward: leave the pack on the dock for an additional 30 minutes after the charge light goes green. At that point the resting voltage should sit above 8.2V, which the radio reads as a full four-bar display.

Compatible Models

HX400IS HX400

Replaces Part Numbers

SBR-29LIIS FNB-115LIIS SBR-45LIIS SBR-45LI

Technical Specifications

Voltage7.4V
Amp Hours2550mAh
Capacity2550mAh
Rate18.87Wh
Net Weight152g /5.36 oz
Gross Weight332g /11.71 oz
Approximate Weight332g /11.71 oz
Dimension 131.92 x 57.40 x 32.70mm

Product Highlights

  • Brand: Standard Horizon
  • 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

The HX400IS charger dock shows a fault LED every time I insert the new battery — it never starts charging. What's wrong?

This almost always means the contact strip on the new pack or the dock has a thin film of oxidation or residue blocking the BMS handshake signal. Remove the battery, wipe the gold contacts on both the pack and the dock with a dry cloth, then reseat the pack with firm pressure. If the fault LED clears within five seconds of reinsertion, charging will proceed normally — if it doesn't, measure pack voltage with a multimeter and confirm it reads above 6.0V before reseating.

The radio cuts out completely mid-transmission even though the battery bar was showing two bars — then it comes back on its own. What's happening?

That cutout pattern is a BMS overcurrent trip triggered by the transmit current spike, not low capacity. It happens when the cell impedance is slightly elevated — common in a pack that has been sitting at storage voltage for an extended period. The BMS sees the spike, cuts the circuit to protect the cell, then resets once load drops. Run two full charge-discharge cycles on the pack and the impedance will normalise; the cutouts should stop after that.

My HX400IS has been sitting unused for six months with the battery installed. Now the radio won't power on at all — is the battery dead?

The pack has likely discharged below the BMS recovery threshold, which on Li-ion cells is typically around 2.5V per cell. The BMS locks out to prevent damage and the radio shows no signs of life. Place the pack in the dock and leave it for at least two hours — most dock chargers apply a trickle recovery current that will bring the cell voltage back above the lockout threshold. Once the dock LED shifts from fault to charging, the pack is recovering; complete the full charge cycle before powering the radio on.

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