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Q & A: Plug-in Hybrid Vehicles: Do you really have to plug it in?

Question: Do I need to plug in my hybrid vehicle to charge the high voltage battery, or will the engine charge the high voltage battery like a normal hybrid vehicle will?

Answer: Yes, and here's why..

No matter the chemical make up of a battery, small or large, high voltage or low, almost all operate between 20 - 80% (even though your battery gauge reads 0 - 100%) capacity simply to prevent undercharge and overcharge. Lithium based battery packs operate under far stricter voltage tolerances to keep the cells balanced and in good health, preventing thermal runaway. In a plug-in hybrid powertrain platform, the lithium-ion battery is designed to be wall charged while not in use. Operating your vehicle on a constantly low state of charge increases the likelihood of weaker cells dropping below manufacturer thresholds, preventing the car from starting or driving all together. This had become more and more common in vehicles such as the first generation Chevrolet Volt where customers will continue to drive on an old and degraded lithium-ion battery pack without plugging in the vehicle overnight, or while at work. Once the high voltage battery pack unbalances, there is no safe and comprehensive way to bring it back into a balanced state without potentially damaging the rest of the battery, unlike a NiMh battery found in most non plug-in hybrids. Beyond that, you're not getting the full EV range coupled with increased fuel economy while driving with a fully charge hybrid battery.

Pictured: A standard SAE J1772 style plug used to charge the high voltage lithium battery

To Summarize:

You must charge your plug-in hybrid according to the manufacturer's owner's manual in order to prevent premature damage to the high voltage lithium-ion pack, and extend it's usable life as much as possible.

If you're unsure whether or not your high voltage battery is in good shape, or if you're planning on buying a used plug-in hybrid vehicle, Evergreen will perform a series of comprehensive hybrid diagnostic load and stress tests, ensuring all the critical high voltage components are operating as designed. Call or message us today!


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