Battery to Battery Trickle Charger - Bluetooth

AMT 12-2B Bluetooth Trickle Charger & Battery Maintainer – 12V/24V

Intelligent Starter Battery Maintenance | Bluetooth App Configuration | Solar & Mains Charging Compatible | Smart Alternator & Lithium Settings

The AMT 12-2B Bluetooth Trickle Charger and Battery Maintainer is designed to help keep your vehicle starter battery charged by intelligently transferring available energy from your leisure or auxiliary battery.

Ideal for motorhomes, campervans and other vehicles with dual-battery systems, the AMT 12-2B monitors both battery voltages and automatically supplies a maintenance charge to the starter battery when the programmed conditions are met.

When a solar panel system or mains battery charger is charging your leisure battery, the AMT 12-2B can use available energy to help maintain the vehicle battery, reducing the risk of it gradually losing charge during periods of inactivity.

With built-in Bluetooth connectivity, the charger can be configured and monitored using the Device Manager app, allowing you to view battery voltages, select battery and alternator settings, and adjust charging thresholds from a compatible smartphone.

The unit also supports automatic 12V/24V battery voltage detection, programmable lead-acid and lithium battery settings, and smart alternator applications.

Key Features and Benefits

• Bluetooth Connectivity: View and adjust settings using the free download Device Manager app for Android and iOS.
• Automatic Starter Battery Maintenance: Transfers available charge from the leisure battery to the vehicle starter battery when voltage conditions are met.
• Solar and Mains Charger Compatible: Designed for dual-battery systems where a solar or mains charger charges the leisure battery.
• 12V and 24V Operation: Automatically detects the connected battery system voltage.
• Smart Alternator Compatible: Includes settings for vehicles with smart alternators and regenerative braking.
• Lead-Acid and Lithium Settings: Configurable operating programmes for different leisure battery chemistries.
• Eight Operating Settings: Select charging behaviour according to alternator type, battery chemistry and parasitic drain.
• Up to 3A Maintenance Charging: Delivers controlled charging bursts according to the selected operating setting.
• Charge-Pooling Function: Helps share available energy between the batteries under specified voltage conditions.
• Low-Voltage Protection: Stops charging when the vehicle starter battery falls below 11.5V.
• LED Status Indicator: Provides visual information about charging, standby and low-voltage conditions.
• Manual Override: Allows temporary charging control through the app or an external override input.

What Is the AMT 12-2B?

The AMT 12-2B is a Bluetooth-enabled battery maintainer that helps prevent a vehicle starter battery from gradually losing charge while the leisure battery is being charged.

In a typical motorhome or campervan, solar panels may keep the leisure battery charged while the engine is switched off. However, the vehicle starter battery can still lose charge because of alarms, electronic systems and other standby electrical loads.

The AMT 12-2B helps address this by monitoring the voltage of both batteries and transferring a controlled maintenance charge when appropriate.

It is a battery maintenance charger, not a replacement for a main battery-to-battery (B2B) charger.

How Does the AMT 12-2B Work?

The charger continuously monitors the leisure battery and vehicle starter battery voltages.

Under normal operation, it supplies charging current when:

1. The leisure battery voltage exceeds its selected charging threshold.
2. The vehicle battery voltage is below its selected threshold but above the low-voltage cut-off.

The charger delivers current in short, controlled bursts rather than continuously.

Settings 1–4 are intended for most applications, while settings 5–8 provide higher-power operation for vehicles with greater parasitic battery drain.

This automatic operation helps maintain the starter battery without requiring regular manual intervention.

Built-In Bluetooth – Configure and Monitor from Your Phone

The AMT 12-2B includes Bluetooth connectivity for use with the Device Manager app, available for Android and iOS.

The app allows you to access the charger and manage its operating settings without manually changing internal hardware.

What Can You Do with the Device Manager App?

• View the current leisure battery voltage.
• View the current vehicle starter battery voltage.
• Select the appropriate battery type.
• Configure standard or smart alternator operation.
• View and adjust voltage thresholds.
• Access saved configuration profiles.
• Enable the override function when required.
• Save updated settings directly to the charger.

Keep Your Starter Battery Maintained with Bluetooth Control

The AMT 12-2B Bluetooth Trickle Charger and Battery Maintainer provides an intelligent way to maintain your vehicle starter battery using available energy from your leisure battery.

With automatic voltage monitoring, eight configurable operating settings, Bluetooth app access and compatibility with smart alternator systems, it is a practical addition to suitable motorhome and campervan electrical installations.

Choose the AMT 12-2B for convenient Bluetooth-enabled starter battery maintenance and intelligent dual-battery charging control.

Why Choose Sunshine Solar?

At Sunshine Solar, we have over 20 years of experience supplying solar charging equipment, batteries and renewable energy solutions throughout the UK.

Our knowledgeable team can help you select suitable equipment for motorhomes, campervans and other dual-battery installations.

We also offer friendly technical support over the phone to help with product selection and installation queries.

Sunshine Solar Technical Support: +44 (0)1508 488188

PRODUCT CODE: AMT12-2B

What does the AMT 12-2B do?

The AMT 12-2B helps maintain a vehicle starter battery by transferring available charge from the leisure battery when the programmed voltage conditions are met.

Can the AMT 12-2B maintain my starter battery using solar power?

Yes. When a solar charging system is charging the leisure battery, the AMT 12-2B can use available energy to maintain the starter battery, provided the required voltage conditions are satisfied.

Does the AMT 12-2B have Bluetooth?

Yes. The AMT 12-2B features Bluetooth connectivity and can be configured using the free to download Device Manager app on compatible Android and iOS devices.

What is the difference between the AMT 12-2 and AMT 12-2B?

The AMT 12-2B is the Bluetooth-enabled version, allowing compatible settings and battery readings to be accessed through the Device Manager app.

Can I use the AMT 12-2B with lithium batteries?

Yes. The charger includes dedicated lithium leisure battery settings. Select the appropriate programme for your battery chemistry and alternator type.

Is the AMT 12-2B compatible with smart alternators?

Yes. The charger includes operating settings for smart alternator vehicles, including those with regenerative braking.

Does the AMT 12-2B work with 24V batteries?

Yes. According to the supplied installation manual, the charger automatically detects battery system voltage and supports 12V and 24V operation.

How much charging current does the AMT 12-2B provide?

Settings 1–4 provide up to 2A, while settings 5–8 provide up to 3A. Charging is delivered in controlled bursts according to the selected programme.

Will the AMT 12-2B charge a completely flat starter battery?

No. The unit stops charging when the vehicle battery voltage falls below 11.5V. It is designed to maintain batteries rather than recover deeply discharged batteries.

What is the factory default setting?

The AMT 12-2B is supplied with Setting 4 selected, intended for smart alternator vehicles with a lead-acid leisure battery.

Can I manually activate charging?

Yes. The charger includes an override function that can be activated through the app or the external override input. Battery voltages should be monitored during override operation.

Is the AMT 12-2B a replacement for a B2B charger?

No. The AMT 12-2B is a battery maintainer designed to provide a small maintenance charge to the starter battery. It does not replace a main B2B charger used to charge a leisure battery from the vehicle electrical system.

How to Connect the AMT 12-2B to Bluetooth

1. Download the Device Manager app from Google Play or the Apple App Store.
2. Open the app and navigate to Settings → Device Connections.
3. Select Re-scan to search for nearby devices.
4. Find your charger in the device list. Its identification may appear similar to ABB07-000XXX.
5. Tap the green + icon to connect.
6. The app will retrieve the settings stored on the charger.
7. Navigate to Device Settings to make any required changes.
8. Select the Update icon to save and transfer the new settings.

The Home screen provides an overview of battery voltages and access to the override function.

Eight Configurable Operating Settings

The AMT 12-2B features eight operating programmes to suit different alternator types and leisure battery chemistries.

Factory Default: Setting 4

The charger is supplied configured for a smart alternator vehicle with regenerative braking and a lead-acid leisure battery.

If your installation uses a lithium leisure battery or a standard alternator, the operating setting should be adjusted accordingly.

Settings 5–8 use the same voltage thresholds as settings 1–4 but provide higher charging current and longer charging bursts.

Smart Alternator and Regenerative Braking Compatibility

Many modern vehicles use smart alternators to manage charging more efficiently and reduce engine load.

These systems can operate at different voltage levels compared with traditional alternators.

The AMT 12-2B includes dedicated smart alternator settings, allowing it to be configured for vehicles using this technology.

This makes it suitable for appropriately configured modern motorhome and campervan electrical systems.

Charge-Pooling Function

The AMT 12-2B incorporates a charge-pooling feature designed to help retain charge across the leisure and starter batteries.

According to the manufacturer instructions, charge pooling can operate when:

• The leisure battery voltage is at least 0.3V higher than the vehicle battery voltage.
• For lithium battery configurations, the leisure battery must be at least 1.0V higher.
• The vehicle starter battery voltage is below 12.1V.

This function helps make use of available battery energy under the specified conditions.

Vehicle Battery Low-Voltage Protection

To avoid attempting to charge a deeply discharged starter battery, the AMT 12-2B stops supplying charging current when the vehicle battery voltage falls below 11.5V.

When the leisure battery is above its selected threshold and the vehicle battery is below 11.5V, the LED flashes red to indicate the low-voltage condition.

Important: The AMT 12-2B is designed for battery maintenance. It is not intended to recover a deeply discharged or faulty starter battery.

LED Charging Status Indicators

The built-in LED provides a quick visual indication of the charger's operating state.

These indicators make it easier to check the charger's operating condition without opening the Bluetooth app.

Manual Override Function

The AMT 12-2B includes an override function that allows temporary manual control of charging.

When activated through the override input, the charger operates in a repeating cycle of approximately:

• 9 seconds ON
• 1 second OFF

The override function can be used for manual charging or control through compatible external equipment.

The LED illuminates amber while override mode is active.

Important: Override operation may discharge either the leisure battery or the vehicle battery. Battery voltages should be monitored while this function is being used.

Technical Specifications

Installation Information

The AMT 12-2B is designed to connect to the leisure and vehicle starter battery circuits within a suitable dual-battery installation.

The installation diagram in the supplied manual shows the unit used alongside a B2B charger or MPPT solar charging system.

Important Installation Requirements

• Connect the positive and negative battery inputs for both the leisure and vehicle batteries.
• Confirm correct polarity before programming the charger.
• Use a minimum cable cross-section of 1.5mm² for the connections specified in the installation guide.
• Follow the manufacturer's wiring diagram and connection sequence.
• Ensure the main vehicle input supply and battery output cables connect to the B2B charger, not directly to the AMT 12-2B.
• Select the appropriate operating programme for the alternator and leisure battery chemistry.
• Verify the selected settings after programming.

Installation should be carried out by a competent person familiar with vehicle electrical systems.