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Fuel cell stacks and systems with thermal management systems to deliver a liquid heat exchange fluid into thermal communication with the stack and thereafter recycle the stream. In some embodiments, the system is adapted to selectively apportion the recycled liquid stream between a stream that, prio

Fuel cell stacks and systems with thermal management systems to deliver a liquid heat exchange fluid into thermal communication with the stack and thereafter recycle the stream. In some embodiments, the system is adapted to selectively apportion the recycled liquid stream between a stream that, prior to reuse as a heat exchange stream, is returned to a fluid reservoir and/or selectively cooled, and/or selectively returned to the reservoir and mixed with heat exchange fluid in the reservoir, and a stream that is returned into thermal communication with the stack without returning the stream to the reservoir and/or without heating or cooling and/or without being mixed with additional heat exchange fluid. In some embodiments, the system is adapted to automatically apportion the recycled stream responsive to its temperature. In some embodiments, the system includes a thermostatic valve and/or selectively apportions the recycled stream without requiring an electronic controller or manual input.

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1. A fuel cell system, comprising: a fuel cell stack;a thermal regulating assembly configured to selectively deliver a flow of a liquid heat exchange fluid having a temperature to the fuel cell stack, wherein the thermal regulating assembly comprises: a liquid reservoir, wherein the liquid reservoir

1. A fuel cell system, comprising: a fuel cell stack;a thermal regulating assembly configured to selectively deliver a flow of a liquid heat exchange fluid having a temperature to the fuel cell stack, wherein the thermal regulating assembly comprises: a liquid reservoir, wherein the liquid reservoir is configured to containa volume of the liquid heat exchange fluid during use of the thermal regulating assembly;a fluid circuit fluidly interconnecting the fuel cell stack and the liquid reservoir and including a plurality of fluid conduits, wherein the plurality of fluid conduits includes a delivery conduit through which the liquid heat exchange fluid may flow from the liquid reservoir to the fuel cell stack and a return conduit through which a return stream of the liquid heat exchange fluid may flow from the fuel cell stack, and further wherein the plurality of fluid conduits further includes a bypass conduit fluidly interconnecting the return conduit and the delivery conduit and configured to provide a flow conduit through which the liquid heat exchange fluid may flow from the return conduit to the delivery conduit without flowing to the liquid reservoir;a pump assembly configured to selectively propel a flow of the liquid heat exchange fluid within the fluid circuit; anda thermostatic distribution assembly configured to automatically apportion the flow of the return stream between a bypass stream that flows to the bypass conduit and a recycle stream that flows to the liquid reservoir, wherein the apportioning is directly responsive to a temperature of the return stream, and further wherein the apportioning is not directly responsive to a temperature of the liquid heat exchange fluid that is supplied to the fuel cell stack in the delivery conduit. 2. The fuel cell system of claim 1, wherein the thermostatic distribution assembly is configured to automatically increase a percentage of the return stream that forms the recycle stream as the temperature of the return stream increases. 3. The fuel cell system of claim 1, wherein the thermostatic distribution assembly is configured to automatically decrease a percentage of the return stream that forms the recycle stream as the temperature of the return stream decreases. 4. The fuel cell system of claim 1, wherein the thermostatic distribution assembly is configured to automatically increase a percentage of the return stream that is diverted to the bypass conduit when the temperature of the return stream is less than a minimum operating temperature for the fuel cell stack. 5. The fuel cell system of claim 1, wherein the thermostatic distribution assembly includes a thermostatic valve assembly that is configured to automatically apportion the flow of the return stream between the recycle stream and the bypass stream. 6. The fuel cell system of claim 1, wherein the thermostatic distribution assembly is configured to selectively apportion the flow of the return stream between the recycle stream and the bypass stream responsive at least in part to at least one thermostatic flow-regulating device. 7. The fuel cell system of claim 1, wherein the thermostatic distribution assembly is not electrically powered. 8. The fuel cell system of claim 1, wherein the thermal regulating assembly is configured to maintain the fuel cell stack at an operating temperature of less than 80° C. 9. The fuel cell system of claim 1, wherein the fuel cell stack is configured to receive an oxidant stream and a hydrogen stream, and further wherein the fuel cell system includes a source of hydrogen gas from which the hydrogen stream is delivered to the fuel cell stack. 10. The fuel cell system of claim 1, wherein the thermal regulating assembly further includes a heat exchange assembly that is configured to selectively heat or cool the liquid heat exchange fluid in the liquid reservoir. 11. The fuel cell system of claim 1, in combination with at least one energy-consuming device configured to apply a load to the fuel cell system. 12. The fuel cell system of claim 1, wherein the thermal regulating assembly is configured to maintain the fuel cell stack at an operating temperature of greater than 40° C. 13. The fuel cell system of claim 1, wherein the thermal regulating assembly is configured to maintain the fuel cell stack at an operating temperature of greater than 40° C. and less than 80° C. 14. The fuel cell system of claim 1, wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion at least a portion of the return stream to the bypass conduit. 15. The fuel cell system of claim 14, wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion all of the return stream to the bypass conduit. 16. The fuel cell system of claim 14, wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion all of the return stream to the bypass conduit if the temperature of the fuel cell stack is less than a minimum threshold operating temperature of the fuel cell stack. 17. The fuel cell system of claim 16, wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion all of the return stream to the bypass conduit if the temperature of the fuel cell stack is less than the minimum threshold operating temperature of the fuel cell stack and if the temperature of the liquid heat exchange fluid in the liquid reservoir is also less than the minimum threshold operating temperature of the fuel cell stack. 18. The fuel cell system of claim 1, wherein the thermostatic distribution assembly is configured to receive the return stream and to selectively produce the bypass stream and the recycle stream therefrom. 19. A fuel cell system, comprising: a fuel cell stack;a thermal regulating assembly configured to selectively deliver a flow of a liquid heat exchange fluid having a temperature to the fuel cell stack, wherein the thermal regulating assembly comprises: a liquid reservoir, wherein the liquid reservoir is configured to contain a volume of the liquid heat exchange fluid during use of the thermal regulating assembly;a fluid circuit fluidly interconnecting the fuel cell stack and the liquid reservoir and including a plurality of fluid conduits, wherein the plurality of fluid conduits includes a delivery conduit through which the liquid heat exchange fluid may flow from the liquid reservoir to the fuel cell stack and a return conduit through which a return stream of the liquid heat exchange fluid may flow from the fuel cell stack, and further wherein the plurality of fluid conduits further includes a bypass conduit fluidly interconnecting the return conduit and the delivery conduit and configured to provide a flow conduit through which the liquid heat exchange fluid may flow from the return conduit to the delivery conduit without flowing to the liquid reservoir;a pump assembly configured to selectively propel a flow of the liquid heat exchange fluid within the fluid circuit; anda thermostatic distribution assembly configured to automatically apportion the flow of the return stream between a bypass stream that flows to the bypass conduit and a recycle stream that flows to the liquid reservoir, wherein the apportioning is responsive to a temperature of the return stream, wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion at least a portion of the return stream to the bypass conduit, and further wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion all of the return stream to the bypass conduit if the temperature of the fuel cell stack is less than a minimum threshold operating temperature of the fuel cell stack. 20. The fuel cell system of claim 19, wherein the thermostatic distribution assembly is configured to automatically increase a percentage of the return stream that forms the recycle stream as the temperature of the return stream increases. 21. The fuel cell system of claim 19, wherein the thermostatic distribution assembly is configured to automatically decrease a percentage of the return stream that forms the recycle stream as the temperature of the return stream decreases. 22. The fuel cell system of claim 19, wherein the thermostatic distribution assembly is configured to automatically increase a percentage of the return stream that is diverted to the bypass conduit when the temperature of the return stream is less than a minimum operating temperature for the fuel cell stack. 23. The fuel cell system of claim 19, wherein the thermostatic distribution assembly includes a thermostatic valve assembly that is configured to automatically apportion the flow of the return stream between the recycle stream and the bypass stream. 24. The fuel cell system of claim 19, wherein the thermostatic distribution assembly is configured to selectively apportion the flow of the return stream between the recycle stream and the bypass stream responsive at least in part to at least one thermostatic flow-regulating device. 25. The fuel cell system of claim 19, wherein the thermostatic distribution assembly is not electrically powered. 26. The fuel cell system of claim 19, wherein the thermal regulating assembly is configured to maintain the fuel cell stack at an operating temperature of less than 80° C. 27. The fuel cell system of claim 19, wherein the fuel cell stack is configured to receive an oxidant stream and a hydrogen stream, and further wherein the fuel cell system includes a source of hydrogen gas from which the hydrogen stream is delivered to the fuel cell stack. 28. The fuel cell system of claim 19, wherein the thermal regulating assembly further includes a heat exchange assembly that is configured to selectively heat or cool the liquid heat exchange fluid in the liquid reservoir. 29. The fuel cell system of claim 19, in combination with at least one energy-consuming device configured to apply a load to the fuel cell system. 30. The fuel cell system of claim 19, wherein the thermal regulating assembly is configured to maintain the fuel cell stack at an operating temperature of greater than 40° C. 31. The fuel cell system of claim 19, wherein the thermal regulating assembly is configured to maintain the fuel cell stack at an operating temperature of greater than 40° C. and less than 80° C. 32. The fuel cell system of claim 19, wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion all of the return stream to the bypass conduit. 33. The fuel cell system of claim 19, wherein the thermal regulating assembly is configured to, during startup of the fuel cell stack, automatically apportion all of the return stream to the bypass conduit if the temperature of the fuel cell stack is less than the minimum threshold operating temperature of the fuel cell stack and if the temperature of the liquid heat exchange fluid in the liquid reservoir is also less than the minimum threshold operating temperature of the fuel cell stack. 34. The fuel cell system of claim 19, wherein the thermostatic distribution assembly is configured to receive the return stream and to selectively produce the bypass stream and the recycle stream therefrom. 35. The fuel cell system of claim 19, wherein the apportioning is directly responsive to the temperature of the return stream. 36. The fuel cell system of claim 19, wherein the apportioning is not directly responsive to a temperature of the liquid heat exchange fluid that is supplied to the fuel cell stack in the delivery conduit.