Never Jump

May 29, 2023

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It seems ridiculous, but even electric vehicles, plug-in hybrids, and hybrids that carry big powerful high-voltage batteries also require a 12-volt battery. And certain usage patterns can end up stressing these hard-working little batteries to the point that they can leave you stranded in need of a jump start. Global energy-storage solutions company Clarios has ways to help prevent this.

For over a half-century, 12-volt batteries were engineered and optimized to provide the cold cranking amps needed to start an internal combustion engine when it was cold, its oil was thick, and maybe its carburetor or fuel injection system needed several cranks to start sending a combustible mixture to the cylinders. Once started, the electrical system did its gol-dangdest to charge it back up to 100 percent all the time.

Flooded lead-acid batteries were the order of the day for a century or so. If these batteries spend too much time at 80 percent charge or below, sulfation can greatly diminish the battery's storage capacity. That's why flooded batteries so often fail in infrequently used vehicles with electronics that draw a small charge all the time. Absorbent glass-mat (AGM) batteries are better equipped to deal with this usage pattern, as they—like lithium-ion batteries—actually prefer to operate around 80 percent charge.

Hybrids typically draw on their high-voltage batteries to start and restart their engines and EVs never start an engine, so the cold-cranking amp capacity is far less important for their batteries. For decades, the industry standard operating voltage infotainment, lighting, and comfort features has been 12-volt electricity, which is supplied by the battery with support from the onboard electrical charging system. But during periods when that charging system's attention is focused on the high-voltage battery, all current may temporarily come from the 12-volt battery, resulting in periods of quite deep discharge. And recall that these batteries must be relied upon for safety critical functions to not only fail safe, but fail functional.

High-voltage batteries in EVs enjoy sophisticated cell- and pack-level monitoring, but monitoring 12-volt batteries has traditionally required pulling a cap off to see the "water" level and possibly adding some distilled water, or maybe looking for a green "hydrometer eye," or—as a last resort—pulling it out and letting your local parts retailer perform a load test. Today's most sophisticated electrical systems may actually monitor the battery capacity, but only as a whole, not at the cell level.

Clarios proposes integrating a battery monitoring system onto its 12-volt AGM battery, which can then monitor each of the battery's six 2-volt cells individually, communicating their state of health—individually and as a pack—to the vehicle via the CAN (or LIN) data bus. This will allow the vehicle charging system to make better choices about when and how to charge the 12-volt battery. It can even enable proactive replacement of this vital component. The Smart AGM battery thereby aims to reduce or eliminate internal failure modes, provide continued power supply operation with no leakage in the event of a crash, monitor battery performance over time, and end the need to ever jump start an electrified vehicle.

Clarios envisions OE and aftermarket applications for its Smart AGM technology, with the latter primarily communicating with an owner over Bluetooth, sharing battery health information and any recommendation to replace via smart-phone app or some other interface. The system is expected to become available by mid-decade, at a price that's "not double," but perhaps falls between today's dumb AGM and lithium-ion products.