Reader Question: Hybrid recharging

Here’s the latest reader question, along with my reply!

Franks asks: Wow, I was always under the impression that the Hybrid passenger cars re-charged the batteries when the IC was being utilized. I guess that only happens in F1 race cars? Always glad to attend Eric University! Keep up the good work!

My reply: It depends on the hybrid – and to what extent. In the Volt – which is unique in this respect – the IC engine is basically a generator. It runs to make electricity, to power the motors which propel the car. But the key thing is that it doesn’t run until the battery discharges, which is how the car saves gas. The problem is that when the battery charge runs low, the gas engine runs more or less continuously to keep the electricity flowing, to keep the motors turning – to keep the car moving.

At this point, you’ll be averaging mid-high 30s. Until you can plug the car in and recharge.

In other plug-ins, the IC engine also cuts in when the battery charge runs low – and to provide supplementary power when maximum acceleration is wanted. As in the Volt,  when the battery charge is depleted to beyond a certain point,  the IC engine takes over – the difference vs. the Volt being it actually propels the car rather than serves as a generator for the electrical side of the hybrid system. In these hybrids, the electric motors/batteries revert to supplementary power, powering accessories when the car isn’t moving, etc. And during light load situations, such as coasting.

In both cases (the Volt and other plug-ins and hybrids generally) some recharging-as-you-drive occurs, as from recapturing the energy of deceleration (regenerative braking). But it’s not enough to put sufficient charge back into the batteries to allow any significant operation on just the batteries (i.e., all-electric drive).

You start out with a full charge and X range on just the batteries. It’s about 53 miles in the Volt and 20-25 in the others (for the most part). Once you travel that distance – or less – the battery pack is depleted and you’re now operating mostly on the gas engine.

And that’s the catch.

None of these can go far enough on just the batteries – without plugging in, without resorting to gas engine back-up. Unless most of your driving is abbreviated enough to keep the batteries perpetually charged up and the gas-burning engine perpetually asleep, your overall mileage will probably be very disappointing!

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Got a question about cars – or anything else? Click on the “ask Eric” link and send ’em in!