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Actual battery SOC vs. available SOC ranges

7778 Views 5 Replies 5 Participants Last post by  Sean_R
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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The 1st generation Volt started with using 65% of the battery with an upper state of charge of around 85-87% and a lower state at around 20-22%. The 2nd generation Volt uses about 76% of its capacity (14.0 kWh out of 18.4). Presumably better experience, battery design improvements, and the benefits of larger capacity (less likely to be fully discharged of usable capacity each charge cycle) lead to the increased state of charge usage. GM has claimed that battery aging studies project that the 2nd generation packs should last at least as long as the 1st generation packs and perhaps a bit longer.

If you believe that the Bolt EV's nominal capacity is not much more than the published 60 kWh then it appears to allow nearly all of the battery to be used. It may well charge as high as 97% and allow discharge down to near 2-3% at reduced speeds before finally rolling to a stop. Those numbers are just guesses because GM has not released actual numbers and some people suspect that the battery may be noticeably larger than its claimed size of 60 kWh thus allowing a bit more of a buffer zone at the top and bottom.
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