Shoppers naturally assume that a 1.5 volt disposable alkaline must outperform a 1.2 volt rechargeable nickel-metal hydride cell. In the high-drain devices that consume most household batteries - digital cameras, flash units, motorised toys, controllers and personal-care motors - the opposite is routinely true. This paper explains why the nominal-voltage comparison is misleading, how internal resistance and the shape of the discharge curve decide real runtime, and why a NiMH cell can be delivering more useful energy minutes into a heavy load even though its nameplate voltage is lower. Understanding this is the foundation for matching chemistry to device across the whole consumer range.
An alkaline cell starts near 1.5-1.6 V open-circuit but its voltage slopes downward continuously under load, like a ski hill, from the first minute toward the device cut-off near 0.9-1.0 V. A NiMH cell sits on a flat plateau close to 1.2 V for the great majority of its capacity and falls sharply only at the end. Independent discharge comparisons at a few hundred milliamperes show the curves crossing: after the early minutes the NiMH terminal voltage is actually higher than the alkaline's because the alkaline has sagged while the NiMH holds its plateau. For a device that needs a stable supply, the area under the curve above its cut-off - not the open-circuit starting voltage - is the energy it can actually use.
The alkaline slope steepens dramatically with current because its internal resistance is comparatively high and rises as the cell discharges; under a heavy pulse the terminal voltage is the open-circuit voltage minus the drop across that resistance, so a high-resistance cell appears to 'die' the moment a motor or flash draws current, then partially recover when the load stops. NiMH has much lower internal resistance and can sustain high current with a small voltage drop. This is why a camera that reports 'low battery' with alkalines after a handful of flash shots keeps shooting on NiMH: the NiMH holds above the camera's cut-off through the pulse that the alkaline cannot survive.
The large mAh figures printed on alkaline cells are measured at very low current and shrink sharply as discharge current rises; a cell that looks capacious in a remote control can deliver a fraction of that energy in a camera. NiMH capacity is far less sensitive to current, so its advantage widens with drain. The animated trace below overlays the two chemistries at a high pulse load and marks a typical device cut-off line, making visible the usable-energy region that each chemistry occupies above that line. The lesson for sourcing is to compare chemistries at the device's actual pulse and average currents, never at the datasheet's gentlest test.
Whether 1.2 V is 'enough' is set by the device's low-voltage cut-off, chosen by its designer for the chemistry originally intended. Well-engineered high-drain electronics set the cut-off low enough - around 0.9-1.0 V per cell - to use a NiMH plateau fully; a few devices, designed around a steep alkaline curve, cut off higher and waste part of the NiMH capacity. This is a design and specification point, not a fundamental NiMH weakness, and it is why a manufacturer advising an OEM can recommend a cut-off that releases the full plateau. In most cameras, toys and motors the existing cut-off already favours NiMH strongly.
Motors and xenon or LED flash represent the two harshest household loads: a motor draws a high starting inrush then a sustained current, while a flash charges a capacitor in repeated high-current pulses. Both punish internal resistance - the alkaline sags on every pulse and recovers between them, delivering weak motor torque and long flash recycle times, while NiMH supplies the pulse with little sag for strong torque and fast recycle. The qualitative comparison in the second animation ranks chemistries across inrush handling, sustained current, voltage stability and delivered energy for a motorised device, showing where NiMH dominates and where primary lithium reserves a niche.
The commercial power of this analysis is that it converts a perceived disadvantage - lower nominal voltage - into a demonstrable superiority in the devices where battery spend is highest. A credible consumer article or sales sheet pairs the curve explanation with a simple at-home test the buyer can repeat: run the same camera or toy on alkalines and on LSD NiMH and compare shots or runtime. Paper B maps specific device categories to the right cell, and Paper C shows how to test high-drain performance rigorously so the marketing claim rests on measured pulse behaviour rather than assertion.
Weijiang Power supplies low-internal-resistance LSD NiMH AA cells engineered for high-drain cameras, flashes, motorised toys and personal-care devices, with flat-plateau discharge data at real pulse currents. Send your device current profile and cut-off voltage and we will specify a cell that maximises usable runtime above cut-off.
