Partial State-of-Charge Duty: A Challenge but Not a Show-Stopper for Lead-Acid Batteries!

Abstract

The mechanism by which conventional lead-acid batteries (both flooded and valve-regulated designs) fail when subjected to highrate partial-state-of-charge (HRPSoC) operation in hybrid electric vehicles is manifested as poor dynamic charge acceptance at the negative plate. This parameter is defined as the amount of charge that is actually delivered to the battery during regenerative braking phases of a driving cycle, divided by the amount of charge that

Experimental analysis of Dynamic Charge Acceptance test conditions for lead-acid and lithium iron phosphate cells

“…In traditional internal-combustion (IC) engined vehicles the battery is used exclusively as an auxiliary energy store for when the engine is switched off, once running the engine provides all power for the vehicle, both mechanical via the drive-train and electrical via the alternator. In this configuration the battery is subject to infrequent, short discharges at high currents (around 16 times the 1-hour rate, C 1 ) when starting the engine, followed by modest recharging to full state-ofcharge (SoC) at around 1 C 1 from the alternator [1]. The use of automotive batteries for starting, lighting and ignition (SLI) and their failure modes under these conditions is well understood.…”

“…The charging profile is similarly modified, the batteries are no longer steadily charged back to full SoC, instead operation is often at partial SoC. Charging from the engine is controlled to a modest rate, but is interspersed with large charge spikes due the regenerative braking system; these spikes can reach up to 30 C 1 under heavy braking [1]. The operation of batteries under these conditions of high-rate partial-state-of-charge (HRPSoC) is becoming increasingly common as the number of HEV's increases.…”

An analysis of the influence of high-frequency ripple currents on dynamic charge acceptance in lead-acid batteries

“…A key area of interest stemming from this change has been the study of Dynamic Charge Acceptance (DCA) in batteries. This is important because the nature of the operating environment for HEV batteries means they are often subjected to very high rates of charge, up to 30 times the 1-hour rate (C 1 ), during regenerative braking [3]. Overall battery effectiveness under these conditions is determined to a large extent by how well they are able to accept the energy available from these high-current pulses.…”

An Experimental Analysis of the Effect of Cell Degradation on Dynamic Charge Acceptance in Lead-Acid Cells

“…This eliminates the need to plug the vehicle in to rechargealthough plug-in hybrids (PHEV) retain the ability to do so -and means the user can operate it in the same way as they would a conventional IC-engined vehicle. The duty imposed on a HEV battery is much less predictable than that of an EV and dominated by short, high-power pulses of either discharge during acceleration or charge when braking [3]. The ability to perform reliably under these conditions becomes a crucial factor for HEV batteries, other aspects such as capacity and cycle-life assume a lesser priority.…”