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<blockquote data-quote="helotaxi" data-source="post: 4963416" data-attributes="member: 550915">Works OK for A/B amps except that you&#039;re really making assumptions that aren&#039;t accurate.&nbsp; You method assumes 50% efficiency at full power which is really bad.&nbsp; If we&#039;re looking for worst case, then OK, but if we&#039;re talking real world, apply reality all the way &#039;round.&nbsp; Figure in crest factor which will greatly reduce real world current consumption from the max.&nbsp; When figuring how much fusing you need, just go with what the manufacturer specifies.&nbsp; If you&#039;re blowing fuses, you have other problems.&nbsp; Wouldn&#039;t it be easier to teach them something hat is universally applicable and more correct?&nbsp; It&#039;s pretty basic to just tell them divide the output power by the normal car voltage and then divide that by amp efficiency.&nbsp; From there just tell them to assume that Class A/B amps are going to be around 60% efficient at full power on test tones (not that that&#039;s real world but we&#039;re figuring max draw here) and that Class D amps will be around 75% efficient.By dumbing it down you&#039;re not helping anyone to really learn anything; you know the whole give a man a fish, teach him to fish thing.My real question is, &quot;why does any of this really matter in the real world?&quot;&nbsp; The current draw is going to vary wildly with every install and user even if we&#039;re talking the same amp wired into the same load.&nbsp; If the point is to ensure that the charging system is up to snuff, in most cases, assuming worst case current draw would lead to a lot of electrical upgrades that would be a waste of the customer&#039;s money.&nbsp; If electrical upgrades are more targeted to the use that the system will actually see from the owner, their budget can be more wisely applied to increase their enjoyment of their system.For example, the system that I&#039;m working on right now would require some serious electrical attention if we looked at worst case.&nbsp; 4 amplifiers and 1400+ watts on paper.&nbsp; However, since I know my listening habits, both music type and volume level, I know that I will be fine with some basic efficiency upgrades to the factory charging system and I&#039;m adding a small secondary battery as a little insurance against light dimming for the rare occasions when I turn it up a bit.That kind of instruction is what I think most shops could benefit from.&nbsp; Yes, that&#039;s difficult to get across if they don&#039;t understand basics, but giving them a crutch rather than teaching the basics (which they should darn well know anyway) isn&#039;t going to get them to the next level.</blockquote>

[QUOTE="helotaxi, post: 4963416, member: 550915"] Works OK for A/B amps except that you're really making assumptions that aren't accurate. You method assumes 50% efficiency at full power which is really bad. If we're looking for worst case, then OK, but if we're talking real world, apply reality all the way 'round. Figure in crest factor which will greatly reduce real world current consumption from the max. When figuring how much fusing you need, just go with what the manufacturer specifies. If you're blowing fuses, you have other problems. Wouldn't it be easier to teach them something hat is universally applicable and more correct? It's pretty basic to just tell them divide the output power by the normal car voltage and then divide that by amp efficiency. From there just tell them to assume that Class A/B amps are going to be around 60% efficient at full power on test tones (not that that's real world but we're figuring max draw here) and that Class D amps will be around 75% efficient. By dumbing it down you're not helping anyone to really learn anything; you know the whole give a man a fish, teach him to fish thing. My real question is, "why does any of this really matter in the real world?" The current draw is going to vary wildly with every install and user even if we're talking the same amp wired into the same load. If the point is to ensure that the charging system is up to snuff, in most cases, assuming worst case current draw would lead to a lot of electrical upgrades that would be a waste of the customer's money. If electrical upgrades are more targeted to the use that the system will actually see from the owner, their budget can be more wisely applied to increase their enjoyment of their system. For example, the system that I'm working on right now would require some serious electrical attention if we looked at worst case. 4 amplifiers and 1400+ watts on paper. However, since I know my listening habits, both music type and volume level, I know that I will be fine with some basic efficiency upgrades to the factory charging system and I'm adding a small secondary battery as a little insurance against light dimming for the rare occasions when I turn it up a bit. That kind of instruction is what I think most shops could benefit from. Yes, that's difficult to get across if they don't understand basics, but giving them a crutch rather than teaching the basics (which they should darn well know anyway) isn't going to get them to the next level. [/QUOTE]

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