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Question about Lithium battery vs AGM
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<blockquote data-quote="Original wis" data-source="post: 8786725" data-attributes="member: 685344"><p>Lithium battery vs AGM</p><p></p><p>So amp hours are amp hours no matter which medium you choose right? Or is there some conversion factor from AGM to lithium?</p><p></p><p>I'm hearing people say that they're running an 8k all day with only 45ah battery. But according to basic math, I'm supposed to run 400ah at minimum (3,900 watts/12.8 volts)=304 amps. 304 amps/.75 amp efficiency = 406 amps. 200 amp alternator at resting cuts that to 206 amps roughly.</p><p></p><p>This is what I think though:</p><p></p><p>One amp has a 150 amp fuse (Smart 3k), one has 50 amps (440 x 4), one has 40 amps (400 x 4). So they should never need more than 240 amps or a fuse should blow. Which means that if the alternator makes 200 amps at idle I could probably cut that to 100ah and worse case scenario, be able to run the system off battery for 20 minutes more or less being conservative. The math is closer to 25 minutes actually. Which is fine since I'm not building a demo vehicle.</p><p></p><p>So my plan is to put a group 35 (60ah) under the hood and a 100ah in the trunk which should be easy overkill.</p><p></p><p>But just in case I'm missing something, can anyone help?</p><p></p><p>Lewis King</p></blockquote><p></p>
[QUOTE="Original wis, post: 8786725, member: 685344"] Lithium battery vs AGM So amp hours are amp hours no matter which medium you choose right? Or is there some conversion factor from AGM to lithium? I'm hearing people say that they're running an 8k all day with only 45ah battery. But according to basic math, I'm supposed to run 400ah at minimum (3,900 watts/12.8 volts)=304 amps. 304 amps/.75 amp efficiency = 406 amps. 200 amp alternator at resting cuts that to 206 amps roughly. This is what I think though: One amp has a 150 amp fuse (Smart 3k), one has 50 amps (440 x 4), one has 40 amps (400 x 4). So they should never need more than 240 amps or a fuse should blow. Which means that if the alternator makes 200 amps at idle I could probably cut that to 100ah and worse case scenario, be able to run the system off battery for 20 minutes more or less being conservative. The math is closer to 25 minutes actually. Which is fine since I'm not building a demo vehicle. So my plan is to put a group 35 (60ah) under the hood and a 100ah in the trunk which should be easy overkill. But just in case I'm missing something, can anyone help? Lewis King [/QUOTE]
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