Popular as NiMh batteries, Nickle-metal hydride batteries are secondary (electrochemical cells) in nature and similar to the nickel-cadmium cells. However, for the negative electrode, these NiMh batteries carry a hydrogen-absorbing alloy instead of cadmium. That is why NiMh batteries are better and more efficient companions than nickel-cadmium cells of equivalent sizes. If we compare lithium-ion cells with NiMh batteries then the volumetric energy density in NiMh batteries will be lower and self discharge capacity will be higher.
NiMh Battery Disection
With common AA cells, these NiMh batteries offer nominal charge capacities at a discharge rate of 0.2xC per hour but at a rate of 1xC, there is no significant difference though. In contrast, if we talk about the specific energy density then NiMh batteries are value for money products but not superior than Li-ion batteries.
Users who are desperate to replace their non-rechargeable batteries and fervently hunting for a replacement can certainly consider these NiMh batteries as a good alternative. Being a safer product, these NiMh batteries are apt for the personal use as they comprise hydrogen absorbing alloys in place of electrodes.
Pricing
Usually, alkaline batteries are heavy on the wallet and can run out quickly if used in a digital camera or so. If you wander around the market, you will get to know that the digital camera batteries are not pocket friendly at all and can easily affect your overall budget. That is why connoisseurs recommend NiMh batteries instead of their costly counterparts. However, the price of NiMh batteries also vary from model to model and some models could also be expensive in nature.
Recharging Capacity
Categorized in three distinct groups, the recharging rate of NiMh batteries could be slow, brisk and fast. A slow recharging battery would normally take around 14 to 16 hours whereas quickly rechargeable batteries merely need 3 to 6 hours. A fast rechargeable product need less than one hour only. Truthfully, the rate of charge is also affected by the current passing into your switch board.
Discharge Rate
Well, discharge rate attribute towards the duration in which a battery loses its energy when left unused. However, the discharge time of NiMh batteries is not desirable. It’s not intended to retain its power for a longer extent and loses the same fairy fast. For instance, if you keep your battery as it is it will discharge around 40% of its power at the end of the month. To reduce its discharging capacity, users can simply keep these NiMh batteries in a cooler place.
Disassembled Ni-Mh AA cell ---- 1: positive terminal 2: outer metal casing (also negative terminal) 3: positive electrode 4: negative electrode with current collector (metal grid, connected to metal casing) 5: separator (between electrodes) - Taken from WikiPedia.com
Environment Friendly
In the absence of toxic cadmium, NiMh batteries are not hazardous to the environment at all. However, the batteries comprising electrodes are posing environmental impacts. That is why NiMh batteries are recommended to the users and as their improper disposal also will not affect our surroundings.