Finding The Best Hybrid Mix

Finding The Best  Hybrid Mix
What the Hell is that stuff?
I will be discussing things here that are potentially dangerous and could kill you and damage your car. This blog is my journey towards making the Insight all it can be.


Electric motors produce torque at any rpm. Gas engines produce little power, at lower than 1000 rpm, and only put out full torque when at much higher rpm. Mix the two in the correct proportions, and you have the best hybrid mix for any given situation. The torque is limited by how many amps and volts you can provide to the motor, and the ability of the motor to dissipate the waste heat. More amps and volts equals more power. Electric cars will rule some day, but for now we have the mix.

The battery needs to provide that power, and is one of the more expensive components in the hybrid system, but is much less expensive than what is needed to run on pure electric, so the full electric is battery cost limited. The Insight has a 1liter gas engine and a 13hp 144v electric motor. The 144v battery pack is composed of 120 "D" size NiMH batteries in a series string. The cells are only 6.5Ah, and are not allowed to fully cycle, so as to extend their life, thus the useable capacity is more like 4Ah.

The development of MIMA and the combined experiences of the users, has led to our realizing, that more aggressive use of the electric motor, while boosting the MPG of the car by a large amount, depletes the charge quickly. The gas/electric mix that Honda decided on when specifying how the control software would use the electric, seems to be largely a factor of how much they were willing to pay for batteries. A pack of 2 to 4 times the capacity, would allow more aggressive use of the electric for many 20-40 mile per day commuters, and a subsequent large increase in MPG. The additional cost would have raised Hondas' cost for the car, and they would have lost even more money, as Toyota had set the competitive price point for the hybrid market.


When you are fooling with a battery pack over 24v, you need to be concerned with safety. With 144v at >100a, it is a matter of life and death that you do. Adding a second NiMH pack, adds to the complexity of safely charging and discharging the two packs as well as thermal monitoring and cell reversal monitoring requirement. I will go down that road soon, but for now we have added a 48v, 85-100Ah booster battery pack. The booster pack will power 11 efficient dc/dc converters. Each can output 16.5v at 16.5a., with the inputs driven in parallel, and the outputs in series. The 16.5a constant current charge will be applied to the 144v pack, to provide a constant but low rate replenishment of charge without the need to rob energy from the gas engine. Regenerative braking still can provide charge as well, for quicker charging. The 144v pack becomes a buffer between the relatively low current constant booster charge, and the motors 100a peak amperage.

MIMA allows full control of the system, and is able to turn the boost charge on or off as needed. If a long period of non electric driving occurs, the booster will automatically shut off when the pack is fully charged. With the addition of a 144v to 48v dc/dc, we would be able to recharge the booster pack once the main pack is charged via the regenerative braking while under a long down hill charge. The 48v boost system can be grid or solar charged.

The large batteries need air springs to hold them up.
The air springs need compressed air.
The spare tire is the air tank.

Since we will then have a larger battery on board, and an air supply, we may as well use it for some more electric goodies.

An Etek powered 5th wheel that will drop down when stopped at a light. This 48v motor will accelerate the car from a stop to nearly 30 mph, using only electric, therefore further saving gas, and allowing pure EV mode, like the Prius.

This blog is the story of the development, and it starts at the bottom of the page.