Updates to the 2015 Chevy Volt include minor things like interior and exterior color choices, WiFi connectivity, and … an unannounced upgrade to the propulsion battery to 17.1 kilowatt-hours – up from 16.5.

The extended-range electric Volt was launched December 2010 as a 2011 model with a 16.0-kwh pack rated at 35 miles electric range, 94 MPGe. For model year 2013 GM gave it an increase to 16.5-kwh, 38-miles range, 98 MPGe.

The 2015 – still considered first generation albeit refreshed – went into production in June with the larger battery. Perhaps tellingly, the 2015 has not been re-certified with the EPA to account for the kilowatt-hour increase that was larger than the last one, but the change is otherwise official.

According to GM’s Kevin M. Kelly, manager, Electrification Technology Communications, the battery upgrade was an incremental one done in the interest of improving where possible.

“We did make an engineering change to the cells for the 2015 Chevrolet Volt which resulted in an increase in energy capacity to 17.1 kilowatt-hours,” said Kelly. “This was done as part of our continuing improvement efforts, to make the product better, to respond to the demands of our customers, and what they expect from the product as we go along. So it’s likely that some customers may experience an improvement in range over prevous model years.”

Right – this last statement is something 2015 Volt owners may wish to look for if they were not told by their dealers.

When asked further questions, Kelly said he could not answer anything that would give away where the Volt is in its product life cycle.

Kelly’s deflection was customary for automakers to avoid hints tipping their hand for future product plans, but the Volt’s next generation is otherwise only a somewhat kept secret.

It’s been generally leaked and reported that GM is at work on a second-generation Volt, and it maybe a 2016 model, though this has not been confirmed by GM.

As for the present 2015 Volt, despite an upgrade that could have made public relations hay, it was not re-certified for the EPA, thus the 2014 EPA numbers must carry forward.

When asked why, Kelly said GM did make a few other changes to the 2013, and this time GM did not think it wanted to make as much of the 2015 upgrades.

This decision stands in contrast to how a relatively big deal was made of the 0.5-kwh increase for 2013, including press release and follow-up interviews for news that hit every publication that writes about cars.

The increase for the 2015 is actually slightly more than last time – 0.6-kwh versus 0.5-kwh – but Chevrolet only quietly advertised it on its consumer site as part of the car’s specification.

One might surmise this is another indicator that the Volt is indeed due to be replaced.

When the 2013 was updated, GM at the time said its engineers also expanded the state-of-charge window to use 10.8 kwh of the total battery energy – up from 10.3 kwh used in 2011-2012 models.

Kelly did not know whether this specification had been again changed for 2015, but did concede the Cadillac ELR – which uses a Volt’s T-pack – already has less of a buffer, and uses proportionally more on-board juice.

This indicates the first-gen Volt was conservatively set up for long life, and GM – still conservative – feels confident using more of the ELR’s battery capacity, and yet warranting this premium product for customers who likely have higher expectations.

Noteworthy also is the present Cadillac ELR still has the 16.5-kwh battery specification, and we have even fewer indications what future plans are for it.

And as for the Volt, it would appear it may have enough electric range capacity that if it were re-certified, the EPA could say it is a 40-mile car.

This is double the Ford Energi products rated at 19 each, and nearly half a Nissan Leaf albeit with no range anxiety – and the Leaf is known to lose capacity faster than the Volt, if anecdotes and other reported indications are correct.

So what’s next for the Volt? Lots of speculation out there, but you can see GM won’t even confirm whether the 40-mile 2015 is the Volt’s last hurrah before generation two.

GM’s former CEO Dan Akerson was quoted as saying the next Volt ought to have significantly more range.

Rumors have also been that the Volt might get a small three-cylinder range extender, among other improvements to cut production cost, and increase efficiencty.

We noted to Kelly that if GM wanted to do nothing else, it could simply – and safely – use more of the Volt’s battery as per ELR practice.

At this, Kelly only laughed, without further commenting on this speculative (and obvious) observation.