Coaches Equipped with Battle Born Lithium Batteries
The standard touring coach is equipped with Battle Born lithium iron phosphate (LFP) batteries. These batteries are charged in 3 ways.
Shore power: When the unit is plugged into shore power, the inverter will begin charging the batteries. Charging two 100Ah Battle Born batteries from 0% to 100% will take approximately 9 hours.
Solar: The standard installed solar panels provide a maximum of approximately 5A of trickle charge using our wired-in-series configuration.
Driving The Vehicle: Before the addition of a secondary alternator in late 2022, touring coaches incorporated a DC-DC converter to provide a charge current to the house batteries.
This module is installed under the driver’s seat and connects the chassis battery to the house batteries in order to charge the Battle Born house batteries from the vehicle’s (Mercedes-Benz) alternator.
The DC-DC converter will turn on when sensing voltage at the Engine Run signal, which becomes activated when the vehicle engine is running. When the DC-DC converter comes on, the Mercedes-Benz alternator voltage (approximately 14 – 15 VDC) will push charge current through the DC-DC converter to the house batteries to charge them.
The DC-DC converter will limit the charge current to the house batteries to 40A, per Mercedes-Benz requirements.
If the Battle Born house batteries are shut down, the DC-DC converter will allow alternator voltage to the Battle Born batteries when the engine is started, thus waking up the batteries and initiating battery charge at the limited 40A.
Charging the Battle Born house batteries from shut down to 100% using the DC-DC converter will take approximately 5 hours.
In late 2022 Airstream transitioned to having a second 12VDC Balmar alternator system installed which is dedicated to charge the house batteries when the vehicle is running.
The Balmar system includes the following components:
- 12VDC alternator which mounts to the existing secondary alternator bracket provided by Mercedes-Benz.
- Regulator module which senses house battery voltage and controls alternator charge to the batteries
- Alternator protection module
When the vehicle engine is started up, the alternator regulator will sense house battery voltage and control the charge to the batteries accordingly. For example, if batteries are over 95% charged already, the Regulator Module will not allow the alternator to supply charge current to the batteries. Likewise, if the Regulator Module senses no (zero) battery voltage, it will not allow the alternator to supply charge current to the batteries.
If batteries are below 95% state of charge, the alternator will provide charge current at engine idle (approximately 600 rpm) or higher. With normal driving, the alternator will charge the batteries from 10% to 100% within 2 hours.
The Regulator Module will toggle through settings to display battery voltage, set point voltage, battery temperature, and other information.
The Alternator Protection Module (APM-12) protects the alternator against unintended battery disconnects that happen while the engine is running.
Because the Balmar 12VDC alternator charge system will not allow the alternator to provide charge to batteries when 0VDC is sensed at the batteries, it will no longer be able to “wake up” Battle Born batteries if they are in shut down mode (fell below 9VDC) by just running the engine.
To wake up the Battle Born batteries, a 12VDC source needs to be applied to them either through solar charging, which will wake them up, or by connecting an external 12VDC battery charger across the terminals.
Coaches Equipped with the E1 Package and Volta Power System
The E1 package incorporates a 12kW Volta lithium (Nickel Manganese Cobalt, (NMC)) battery system, which is charged in the following 3 ways:
Shore power: When the unit is plugged into shore power, the battery pack will automatically turn on and the inverter will begin charging the battery pack.
From the display screen, the user can adjust the charge rate on the inverter screen from 5A to 30A in increments of 5A.
Testing has shown that at the maximum charge rate setting of 30A, the battery will charge from 30% to 80% in approximately 2-1/2 hours. From 0% to 100% charge using shore power at the maximum charge rate setting of 30A will take approximately 5 to 6 hours.
Solar Panels: The installed solar panels provide a maximum of approximately 5 Amps of trickle charge. The Volta system must be turned on in order to accept a solar charge. Additional solar panels can be added to the system by connecting them to the solar connection ports on either side of the vehicle. Because of the massive size of the Volta Power systems battery, charging with solar panels is the least effective method to use.
While Driving The Vehicle: The E1 Package includes a secondary 56VDC alternator, which supplies up to 120A of DC charge current to the Volta battery pack. The alternator will not begin charging until the engine rpm has reached a minimum of 1500 rpm. With normal driving, the alternator will charge the battery pack from 0% to 100% within 2-1/2 hours.
In order for the battery pack to accept a charge from the alternator, the Volta system needs to be turned on.