smkettner said:
I am thinking Nissan wants to avoid the high temperatures seen in a space heater.
The liquid heat system may well be lower cost due to space constraints.
Anyone know the BTU of the heating element vs. BTU of the air conditioner?
It's not lower cost it is more complex, add up the many parts. The temperatures are not an issue, the ones I use mount directly to plastic with no problem. Water based EV heaters use:
Hoses
Fittings
Water tank
Overflow
Electric water pump
Submersible heat coil
Radiator
Valves
Coolant
Here is a description of one:
Offered EV heater is liquid heater type designed to be a heat source for existing heating system instead of an ICE. All vehicle's heat controls are retained and work the same way and apparent operation is the same. No under dash modification or taking the dash panel out is needed. The heater simply connects to the same heater core fittings at the firewall former engine hoses use to connect to, and on-off control switch is installed on the dash. The switch can be a regular toggle automotive type operated by hand, or linked to existing heat dial or lever.
The water (or regular antifreeze ethylene glycol solution for cold climates) temperature in the heater's tank is maintained at 70°C±2°C (158°F±3.6°F). Electric circuit consists of resistive element immersed in liquid and controlled by a FET switch, in turn controlled by a PIC micro controller. The firmware is sophisticated enough to provide safety check and emergency shutdown if any parameters exceed specified limits or electrical connections become loose. In case of emergency the heater is able to discharge vehicle controller input capacitors. Open collector output allows to monitor status of the heater. All inputs/outputs are galvanically isolated from the high voltage (traction battery) circuit.
Two models are offered: RM3 without water pump and RM4 with integrated pump. Each model has two versions with different working voltages: 100 VDC...250 VDC and 200 VDC...450 VDC, and both versions are made with 2 kW, 3 kW or 4 kW heater power. All versions still has the same set point temperature (70°C standard), and once it's reached, will consume THE SAME amount of power nesessary to maintain the temperature. It is only initial ramp up is quicker for 4kW model compared to 3kW or 2kW units.
16.5 mm, 18 mm or 20 mm diameter inlet and outlet fittings can be ordered. Standard size is 20mm. Manufactured by MES-DEA in Switzerland, one year warranty.