GM executives said while the changes came following a federal probe into three fires in Volt battery packs after crash tests, they had seen no complaints from customers, no reports from Volts on the road and no sign of fire in its own crash testing.
The recall — which GM calls a "customer service campaign" — will involve adding steel plates around the battery pack, add a sensor to watch coolant levels for the battery's temperature controls and a new cap to prevent coolant overfilling. The fixes will take about two hours at a dealership.
"We have tested the Volt's battery system for more than 285,000 hours, or 25 years, of operation," said Mary Barra, GM senior vice president of Global Product Development. "We're as confident as ever that the cell design is among the safest on the market."
GM execs also said only 250 Volt customers requested either a loaner or for GM to buy back their Volt following the federal probe. For their part, federal officials said the probe was still open, but that their testing of GM's fixes also showed no signs of fire.
Since the repair offered by GM does not qualify as an official federal safety recall, it can continue selling Volts while it makes the parts for the repair, which it expects to have by late February.
In November, the National Highway Traffic Safety Administration revealed that a Volt battery pack had smoked and caught fire more than three weeks after a side-impact test where the car had been smashed into a pole at 20 mph. At the time, GM had said the agency had not followed the automaker's procedures for discharging the battery following a crash, and had it done so, there would have been no fire.
NHTSA later said it had recorded two more fires after simulated crash tests on three of the Volt's 390-lb.lithium-ion battery packs, rupturing their coolant lines and damaging their outer compartments.
NHTSA says the tests were meant to show how the Volt might respond to real-world impacts side-on into narrow objects such as poles or trees. The Volt's battery packs hold 32 kWh of electricity when fully charged, or about what a typical American household uses in two days; it can travel about 40 miles on a full charge before the gas engine kicks in to provide an additional 340 miles of travel. Many Volt owners so far report averaging more than 100 miles traveled for every gallon of gas they've pumped.
GM has also faced questions about the Volt's 120-volt charging cord, after several customers reported the cords had overheated or even melted while charging. GM has said the cords were safe, but has been replacing them for free if owners complain.
NHTSA said in a statement that while its probe was still open, GM's changes had addressed its concerns about what might happen in a crash if the battery pack was punctured and coolant leaked. The agency crash-tested a Volt battery pack with the changes on Dec. 22, and saw no signs of fire.