V is for Voltage electric vehicle forum - Power Density
https://visforvoltage.org/topics/power-density
enEnergy Density, Power Density, and tradeoff's in vehicle size
https://visforvoltage.org/book/ev-batteries/13235
<div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>It is with batteries that the electrons are stored that make the vehicle move. Roughly speaking, the number of electrons you can store in the vehicle determines how far it will go. The angst of batteries in electric vehicles is the speed and range characteristics you can get in the vehicle using the battery technology available. The common battery technology, lead-acid batteries, have been in use for nearly 200 years and have changed relatively little in that time. By contrast think of the changes and improvements the internal combustion engine has seen in that time. In the late 1800's, in the infancy of the automobile, internal combustion engines were so unreliable that the most popular cars were electric, due to their ultra reliability. Fortunately lithium ion batteries are becoming popular enough to displace lead acid, but both are far less energy dense than gasoline and that is a core factor of the relative attractiveness.</p>
<p>When I said "the number of electrons you can store" what that meant is the number of kilowatt-hours.</p>
<p>For a given vehicle, it can safely carry a given cargo, and that cargo must be split between battery weight, vehicle weight, and passenger weight. Hence each vehicle has a given budget of weight it can carry, and it's up to the vehicle designer to choose the tradeoff's of weight to driving/riding range and speed.</p>
<p>We went over what energy density is:- <a href="http://visforvoltage.org/book/ev-batteries/13233">Energy Density and Power Density in Batteries and Electric Vehicles</a></p>
<p>That page discussed energy and power density two ways: Weight and Volume.</p>
<p>The "budget" in designing a vehicle is actually two budgets: Weight and Volume.</p>
<p>The battery pack must be within a given weight AND a given size. For example a battery might have great energy density (e.g. 1000 kilowatt-hours/kilogram would be a fantabulous energy density today) but be made of stuff that is very large for the weight (that is, kilograms/liter). A concrete example is hydrogen storage for a fuel cell, where hydrogen has a great energy density per kilogram but is the least dense element in the universe hence has a low volumetric energy density. As a result fuel cell vehicles have to consider some way to compress hydrogen e.g. at 10,000 psi.</p>
</div></div></div><div class="field field-name-taxonomy-vocabulary-2 field-type-taxonomy-term-reference field-label-above"><div class="field-label">Topics: </div><div class="field-items"><div class="field-item even"><a href="/topics/energy-density">Energy Density</a></div><div class="field-item odd"><a href="/topics/power-density">Power Density</a></div></div></div>Tue, 30 Oct 2012 06:52:57 +0000reikiman13235 at https://visforvoltage.orghttps://visforvoltage.org/book/ev-batteries/13235#commentsEnergy Density and Power Density in Batteries and Electric Vehicles
https://visforvoltage.org/book/ev-batteries/13233
<div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Power density is the core measure controlling the speed and range you can get with a given vehicle. Power density controls the quantity of electricity you can store within a given space, and is measured two ways: (For more about these units see <a href="http://visforvoltage.org/book/ev-batteries/13232">http://visforvoltage.org/book/ev-batteries/13232</a>)</p>
<p></p><blockquote><div class="quote_start"><div></div></div><div class="quote_end"><div></div></div><br />
volume = the size of the area for batteries<br />
weight = the carrying capacity of the vehicle<br /></blockquote>
<p>These are usually measured as</p>
<p></p><blockquote><div class="quote_start"><div></div></div><div class="quote_end"><div></div></div><br />
volume energy density = kilowatt-hours / liter = kwh / l<br />
weight energy density = kilowatt-hours / kilogram = kwh / kg<br />
volume power density = kilowatt-hours / liter = kw / l<br />
weight power density = kilowatt-hours / kilogram = kw / kg<br /></blockquote>
<p>Remember that</p>
<p></p><blockquote><div class="quote_start"><div></div></div><div class="quote_end"><div></div></div><br />
1 kilowatt-hour = 1 kilowatt used over 1 hour = kwh<br />
1 kilowatt = 1,000 watts<br /></blockquote>
<p>And remember that, as an electric vehicle moves down the road, it consumes electricity. Say the vehicle has a 120 volt electrical system, and uses 30 amps to cruise, therefore the vehicle cruises at 3.6 kilowatts. If the vehicle is run for an hour, it consumes 3.6 kilowatt hours of electricity.</p>
<p>The main measurement controlling the range capability of a given battery pack in a given vehicle is, how many kilowatt-hours can you carry in the vehicle. Hence, the power density of the chosen battery pack directly determines the kilowatt-hours in the vehicle. Obviously the batteries have to fit within the physical dimensions of the vehicle, hence the "<i>volume power density</i>" measure given above. Another consideration is how much weight the vehicle can carry on its frame, tires, and suspension system, maybe you have lots of room for batteries but you'd overload the car if you filled it to capacity. Hence the "<i>weight power density</i>" measure given above.</p>
</div></div></div><div class="field field-name-taxonomy-vocabulary-2 field-type-taxonomy-term-reference field-label-above"><div class="field-label">Topics: </div><div class="field-items"><div class="field-item even"><a href="/topics/battery-packs">Battery Packs</a></div><div class="field-item odd"><a href="/topics/energy-density">Energy Density</a></div><div class="field-item even"><a href="/topics/power-density">Power Density</a></div></div></div>Mon, 29 Oct 2012 21:49:07 +0000reikiman13233 at https://visforvoltage.orghttps://visforvoltage.org/book/ev-batteries/13233#commentsBattery pack power density and energy density
https://visforvoltage.org/book/ev-electrical-circuits-basics/7685
<div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Energy Density and Power Density are two ways to measure the speed and range you can get with a given vehicle. Each vehicle has a maximum weight it can carry, and a maximum volume or size it can carry. Together those form a budget into which you fit the people, cargo, drive train, electronics, and battery pack. </p>
<p></p><blockquote><div class="quote_start"><div></div></div><div class="quote_end"><div></div></div><br />
volume = the size of the area for batteries (in liters)<br />
weight = the carrying capacity of the vehicle (in kilograms)<br /></blockquote>
<p>Energy density is the kilowatt-hours stored by volume or by weight. Power density is the energy (in watts) that can be delivered by volume or by weight. </p>
<p></p><blockquote><div class="quote_start"><div></div></div><div class="quote_end"><div></div></div><br />
power-density = max-watts / liter or kilogram<br />
energy-density = kilowatt-hours / liter or kilogram<br /></blockquote>
<p>These are usually measured as</p>
<p></p><blockquote><div class="quote_start"><div></div></div><div class="quote_end"><div></div></div><br />
volume energy density = kilowatt-hours / liter = kwh / l<br />
weight energy density = kilowatt-hours / kilogram = kwh / kg<br /></blockquote>
<p>Remember that</p>
<p></p><blockquote><div class="quote_start"><div></div></div><div class="quote_end"><div></div></div><br />
1 kilowatt-hour = 1 kilowatt used over 1 hour = kwh<br />
1 kilowatt = 1,000 watts<br /></blockquote>
<p>And remember that, as an electric vehicle moves down the road, it consumes electricity. Say the vehicle has a 120 volt electrical system, and uses 30 amps to cruise, therefore the vehicle cruises at 3.6 kilowatts. If the vehicle is run for an hour, it consumes 3.6 kilowatt hours of electricity.</p>
<p>The main measurement controlling the range capability of a given battery pack in a given vehicle is, how many kilowatt-hours can you carry in the vehicle. Each vehicle has a designed carrying capacity in both volume and weight. Based on the energy density of a given battery pack determines how many kilowatt-hours can be fit into the vehicle. Obviously the batteries have to fit within the physical dimensions and carrying capacity of the vehicle. </p>
<p>Adapted from: <a href="http://www.7gen.com/book/batteries-electric-vehicles/power-density-batteries-and-electric-vehicles/656">Power Density in Batteries and Electric Vehicles</a></p>
</div></div></div><div class="field field-name-taxonomy-vocabulary-2 field-type-taxonomy-term-reference field-label-above"><div class="field-label">Topics: </div><div class="field-items"><div class="field-item even"><a href="/topics/battery-packs">Battery Packs</a></div><div class="field-item odd"><a href="/topics/energy-density">Energy Density</a></div><div class="field-item even"><a href="/topics/power-density">Power Density</a></div></div></div>Mon, 12 Oct 2009 17:50:58 +0000reikiman7685 at https://visforvoltage.orghttps://visforvoltage.org/book/ev-electrical-circuits-basics/7685#comments