Has anyone thought about adding a mains charger (110/230V) for the regular (non-plugin) Prius? The NiMH battery pack holds 1.3 kWh of energy, of which roughly half (650 Wh) is available for use (SOC 40%...80%). Gasoline has energy density of 9,700 Wh/l. Assuming that the engine-generator-converter chain works with 30% efficiency, it takes about 0.2 litres of gasoline to recharge the traction battery. Again assuming that you always arrive with near-empty battery pack (easily happens if your trip ends up with few km of slow speed driving), and you commute for 258 days per year, making 2 * 258 trips, you will burn ~100 litres of fuel yearly just for battery recharging (= 165 € here in Finland). So there is a significant saving potential, if you could plug in the car twice per day to recharge the deflated battery. Anyone aware of such charging systems? (diy or commercial) (Here up in the north, parking areas typically have mains power available for block heaters, so if you hook up the charger with block heater wires, there are no extra steps required for charging, as you would anyway plug in the car.)
There's no charger that will automatically stop charging at 80% SOC. It will keep going til 100%. By the time, you've already shorten the battery life. While it may be true about what you said about fuel use to charge, however, the Prius doesn't charge the battery to 80% SOC with ICE. It only charges from 2 bars to 3 bars then the ICE turns off. You can charge faster and use less gas just by accelerating to 60mph and regen brake to 20mph a couple of times. If you're dead set on using a charger I found a couple of chargers that meet the Prius traction battery voltage Quick Charge Variable Multi Voltage 36V-240V 6A - Free Shipping: BatteryMart.com DC Power Supply - Switching Power Supply - VOLTEQ High Voltage Variable DC Power Supply HY30005EX 300V 5A (Powered by CubeCart) The Mastech charger can also be adjusted to charge the 12V battery.
You're looking at the potential savings wrong. The Prius doesn't start with a dead battery and charge it by the time you reach your destination, it can start and end each trip at any SOC. Not all of the charging is done with gas, regen can do quite a bit depending on the driving conditions. Given that 4kw+ plug-in kits only increase mileage to 70-80ish (seems like the average for most conversions I've seen), I wouldn't expect much or any gains from charging the existing battery.
In a closed hybrid system all charging is done with gas in the end, because there is simply no other energy input source than the gas. It does not matter whether you regen, run the engine stationary or charge during normal driving. The point of mains charger is to add another (cleaner) external source of energy, although very limited, but not totally insignificant (as my calculation above proves). It's true that SOC can be anything in the end of trip after random driving, but if you had the mains charger available, in many cases you could take the advantage of it by emptying the battery during the last miles (and thus saving the equivalent amount of gas). The charger having to be able to stop charging at 80% SOC is good point though.
While this method may be faster, it would definitely use more energy than letting the system to charge during normal driving, because there is extra conversion step to kinetic energy (but when traffic conditions require braking, regen is of course superior to brake pads). Just to be clear, I'm not saying the driver should care about the efficiency of charging methods, just drive normally and let the computer optimize for you.
It would be a pain setting up the system, but I'm inclined to give it a go out of interest. There probably are minor savings in gas but I would say not enough to recoup the costs. I'll report back when I have some figures.
Here's a charger. It might be able to be modified to only charge to about 80%, to save the battery (charging to 100% occasionally is good, doing it daily would probably kill it fairly fast). Traction Battery Preventative Maintenance - Hybrid Automotive Chargers | PriusChat
