Density (Wh/l )
Higher cell-voltage in lithium-ion increases the energy density.
Low cell voltage in (1.2V) in NiMH requires many cells to build up a high-voltage system,
In lead-acid, the voltage drops linearly, when the cell is discharged. To keep the average power constant, the current must be increased.
NiMH and lithium-ion (LFP) have nearly constant voltage, which does not depend on state of charge.
The most recent lithium-ion cathode material: discovered 1995 and development to commercial products started in 1997. LiFePO4 (LFP) is considered the most promising lithium-ion technology for large-format batteries due its long cycle life and safety. The LFP material has passed the pilot phase and powder production is ramping into mass production. During 2011 new LFP production licences were distributed around the world making it easier for the manufacturer in the long run. Safe materials supply is a key element in manufacturing business. The production of high quality LFP-powder is difficult. The advantages of LiFePO4 (LFP) are summarized shortly. LFP shows reasonable good cell voltage 3.2 V depending on the active materials. LFP also shows extremely good safety features.
An AGM (Absorbed Glass Mat) battery is a sealed, non-spillable maintenance free, valve regulated battery. An AGM battery utilizes a fine fiber glass material seperator between the lead plates within the battery. AGM batteries, also called starved electrolyte, operate with no maintenance, can be installed in most any configuration (except inverted) without spill and provide outstanding power per dollar invested. AGM batteries are commonly interchanged with traditional flooded lead acid batteries as the charge/discharge profile of these batteries are similar. AGM batteries have low internal resistance and a very low self-discharge rate (from 1% to 3% per month). So they can sit in storage for much longer periods without charging. The AGM design is also highly resistant to vibration deterioration.