Actual battery SOC vs. available SOC ranges

7781 Views 5 Replies 5 Participants Last post by Sean_R, Nov 21, 2016

Sean_R

Discussion Starter · Nov 18, 2016

My understanding is that the Volt's battery is never fully charged to 100% or discharged to 0%, but is kept in a range of state of charge in-between.

Has anyone determined what the state of charge (SOC) range is that the onboard charging system maintains as hard minimums and maximums, and how this corresponds to the displayed charge level on the driver's display panel?

On a related note, I've read elsewhere on this forum that maintaining a SOC on the battery centered around the 50% level, with small deviation from this level, will significantly prolong battery life due to not fully exercising the limited number of charge cycles. I'm wondering if a charging strategy of keeping the SOC between 45 and 55% would accomplish extending the battery life.

While reviewing specs on the earlier Gen 1 Volts, the 2015 Volt, and now the newest Gen 2 model, the battery capacity has only increased a small amount (<10%), yet the Gen 2 models jumped in EV-only range from 35 to 53 miles (50%). Aerodynamics aside, this might imply that GM has opened up the available amount of capacity on the battery for driving use, while eating into the cycle life of the battery.

If this is so, perhaps it's because GM's had 5 years of history with Gen. 1 battery life to get more comfortable with meeting the battery life warranty requirements. But this claimed increased range might then come at a reduction in battery life, of which customers would be unaware. There would be nothing wrong with this per se, but it would be nice to know the approaches that owners could take to keep the battery best-cared for to promote maximum longevity. Any thoughts on this?

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canehdian

· #5 · Nov 18, 2016

These are fuzzy numbers, which can vary a little because of mismatches of charging levels, resting SOC levels, and computer estimation algorithms.
e.g. you could charge a hot battery to 83.5% ("Full"), which then cooled off overnight, resulting in a lower SOC (82%?) by the time you drive off. Conversely you could charge a cold battery to 83.5% and it warm up during the day and technically be "overcharged"
to 85%.
The computer will also recalculate SOC periodically while driving, and after being parked for about 1-2h. In-use estimates aren't as accurate as standby estimates.

Gen1.0:
87%-22%
Gen1.5:
83.5%-18.5%

Hard floor of 15% - propulsion power reduced if you hit this level

Gen2.0:
I don't have data. Someone's probably posted it here, somewhere. But the window has widened, as mentioned.
10% more battery is being used every charge, thus the larger jump in range.

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