Friday, 21 August 2015

Battery Life

A lithium-ion battery, sometimes referred to as Li-ion battery or LIB, is a member of a family of rechargeable battery types. The lithium-ion (Li-ion) batteries are used in many tablets, smartphones and portable PCs. However they require very different care and feeding regime than their predecessors the nickel-cadmium (Ni-Cd) and nickel-metal-hydride (Ni-MH) batteries.

For example, lithium-ion batteries are becoming a common replacement for the lead acid batteries that have been used historically for golf carts and other vehicles. Instead of heavy lead plates and acid electrolyte, the trend is to use lightweight lithium-ion battery packs that can provide the same voltage as lead-acid batteries, so no modification to the vehicle is required. I expect that in time they will become common place in boats once the costs of production are reduced.

Chemistry, performance, cost and safety characteristics vary across LIB types. Hand held electronics mostly use LIBs based on lithium cobalt oxide (LiCoO2), which offers high energy density, but presents safety risks, especially when damaged. 
Lithium iron phosphate (LiFePO4), lithium manganese oxide (LMO) and lithium nickel manganese cobalt oxide (NMC) offer lower energy density, but longer lives and inherent safety. Such batteries are widely used for electric tools, medical equipment and other roles. NMC in particular is a leading contender for automotive applications. 
Lithium nickel cobalt aluminium oxide (NCA) and lithium titanate (LTO) are special designs aimed at particular niche roles. The new lithium sulphur batteries promise the highest performance to weight ratio.

Meanwhile, back at the Li-ion battery. I have a Lenovo laptop which has an option that allows me to charge the battery pack to  60% capacity. As the laptop is permanently plugged into the boats 12v supply. This level is maintained and the capacity of the battery is also maintained. Proper care of a Li-ion battery can result in a much longer service life than with an improperly cared-for battery. 

Keep your lithium batteries cool:
I was surprised to learn that heat is the number-one enemy of Li-ion batteries. Heat caused by heavy usage and the speed and duration of battery charging and discharging. 

Li-ion batteries perform best at about normal room temperature. If the device warms to 86F/30C, its ability to hold a charge reduces by about 20 percent. If the battery is used at 113F/45C battery capacity can be reduced by half.

Unplug the charger to save the battery:

Overcharging, leaving a battery connected for too long can reduce a Li-ion battery's ability to hold a charge. Li-ion batteries have a very low rate of self-discharge. Its not necessary to leave a Li-ion device on charge. Unplug the charger when the device shows a full charge.

Do not deep-discharge your battery:

Like the battery on your boat not all discharge cycles exact the same toll on a battery. Long and heavy usage generates more heat, putting more stress on the battery. While smaller, more frequent discharges extend the overall life of lithium batteries.

Slow charge and discharge is best:

One source of low-output charging is the USB port on a standard PC. The low amperages offered by USB ports will usually provide cool, safe charging of almost any Li-ion device.

Use a spare battery:

When the in-use battery approaches 15–20 percent charge, simply swap out the drained battery for a fresh, cool one you get instant full power, with no heat worries. Having two batteries should also eliminate any need to use fast chargers — you can charge the spare at a safe, slow rate while the other is in use.

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