Fuel cell based rechargable power pack system and associated methods for controlling same

A rechargeable power pack comprising:

• a. a fuel cell stack;
• b. a DC-DC converter coupled to receive the output of said fuel cell;
• c. a first battery and associated battery protection circuit;
• d. a second battery and associated battery protection circuit;
• e. a system controller and balance of plant assembly configured to receive a signal indicative of a charge characteristic of each battery and to control operating characteristics of said fuel cell;
• and
• f. a switch network defining one or more power paths, such that in a first position, the switch network allows current to flow from the fuel cell to the first battery to charge the battery, and in a second position allows current to the second battery to charge the second battery.

A method of maintaining a desired charge on a set of isolated batteries the method comprising the steps of:

• providing a fuel cell as a power source;
• using a DC-DC converter to adjust the output of said fuel cell to the battery to be charged;
• providing two batteries in the power pack each with its own respective battery protection circuit;
• measuring an characteristic of each battery including current or voltage;
• selecting one of said batteries for recharging based upon a whether the measured characteristic exceeds a threshold value;
• and
• adjusting associated switches in a switch network in said power pack to allow current to flow to the battery to be charged.