Battery stuff

You might begin here, this is where you will find most of the information we have, regarding the Prius which is the most converted. http://www.eaa-phev.org/wiki/Prius_PHEV
This section also has some more generic information on some of the principals that we use to do our conversions. http://www.eaa-phev.org/wiki/Template:Terms
Also check out the wikipedia article. http://en.wikipedia.org/wiki/Plug-in_hybrid_electric_vehicle

There are some folks who claim to improve mileage by charging the 12v battery with PV or by plugging in. Which may in fact reduce the amount of power that the DC-DC converter "alternator" needs to provide, but I really have my doubts about how much this could help. The 12v battery holds just a fraction of what the stock HV traction battery does...

The OEM NiMH traction battery has a nameplate rating of about 1kWh 6.5Ah @ 201.6v nominal. But the car only uses approximately half of this capacity, it operates in a range from 40% to 80% SOC. The Prius consumes roughly the same as a pure electric vehicle which is in the ball park of 3 miles per kWh. So the OEM battery is good for about 1, maybe 2 miles worth of range. The Prius tries to keep it's battery at about 65% SOC at all times, so if you assume that you will park the car at that level you would only be able to safely add 15% more charge to fill it up. This would amount to 0.15 kWh of energy, good for perhaps a half a mile, and you would need to be very careful while charging to keep from overcharging and damaging the battery.

What we do is add an additional battery with 3kWh or more worth of energy. I use PbA, others use higher capacity and lighter weight but more expensive Lithium batteries. My 3kWh battery gives my Prius about 10 miles of electric only range. On the freeway when the ICE must run, because of the cars software, the added battery can inject about 6kW of power for 20 miles. Since the normal 50mpg represents consumption at about 12kW this means that I use half the fuel and get twice the normal mileage for those 20 miles of "blended mode" driving. After the battery has been depleted the car reverts back to it's normal mode of operation. Then of course we recharge the extra battery from the grid at home or work.

As I mentioned, all of the principals and methods we use in the Prius should work in other hybrids with similar powertrains. But noone has done so in cars other than the Prius, and the Ford Escape seems to be the next vehicle on everyones list...

 

Toyota itself is coming out with the 2008 lithium battery prius. Testing in the UK listed on EVworld shows is can get 94 mpg. The batteries are lighter and can use more of the stored energy. NiMH are great but only get to use 30-35% of their energy so they last longer. The new lithium can use 70% and last longer.

I feel Toyota will have another 2-3 year backlog of orders when they release the lithium batteries. In a few years when they catchup a plugin option with more batteries will follow.