Improving my Toyota Prius - part two

Converting my Toyota Prius into something even more fuel efficient was a first for me (in general I like cars to remain standard), but turned out to be a hugely interesting experience.

I am very lucky to know a person like Antony English that has the know-how and expertise to make this Prius project work. He also has the benefit of dealing with people at Evert Energy Systems in the USA that have built and provided the control unit for the battery pack.

So, what is it like driving the first plug-in hybrid in the country? Well, first off, you notice that it is heavier. Adding about 160 kg behind the rear axle is not insignificant, and required some beefing up of the suspension by adding airbags - an operation which in itself turned out to be hassle-free and effective. It is possible to adjust the suspension by using compressed air at any filling station.

Secondly, the car makes use of the petrol engine less, which is the whole idea. The principle of this conversion is to keep the car’s own (0.5 kWh) NiMH battery at almost full charge by “topping it up” when it reaches about 75 – 80 percent full, with the new (10 kWh) Lithium Iron Phosphate battery. Suddenly I am cruising on the highways at 115 km/h on battery power alone, which was not possible before.

The fuel consumption I get depends very much on the average speeds and driving style. Driving at lower speeds (due to heavy traffic for example) means that I only use battery power, but when I need to push on, the petrol engine comes more into play.

Best case scenario was a trip to a customer at 0.8 l/100 km (or 125 km/l) which is significant. My trip home last week (which included some steep hills) and which is about 29.5 km, used only 340 ml of petrol – there is a real risk that the fuel will evaporate before being used!

I now charge the battery at home and at work, which makes a big difference. My last fill-up required 36.6 litres. The range on a tank is 1 518.4 km’s and cost R524.37. This is my best case scenario so far, but I have no doubt that I can improve on this by being more patient and not running out of battery power (which happens a few times on every tank).

Driving mostly on electric power gives me a range of about 80 km’s, but luckily, there is no range anxiety being a hybrid. The increase in cost of my electricity bill at home and at work is almost negligible - I suspect that I will be able to offset it with a solar heater.

Has this conversion been worth it? From a pure interest point-of-view, absolutely! It has achieved exactly what I was hoping. Is it cost effective? Probably not. The conversion cost me R115 000 and if I reduce my fills from two tanks a month to one (which is about the case at the moment), my saving equates to about R550 per month (at current prices) which means I will have to drive 17 years to get my investment back. The conversion also needs some refinement, like adding a charge level meter and so on. I do however realize that this is pioneering stuff and a first in this country at least, which is a huge reward in itself!