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Teardown & Rebuild of a MuscleGrid LiFePO4 Server Rack Battery
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<blockquote data-quote="rsaeon" data-source="post: 2506539" data-attributes="member: 76792"><p>Looks like the only way to get a larger DC load at these voltages is to get a second one and connect in parallel. Maybe later, when I'm building more of these.</p><p></p><p></p><p></p><p></p><p>I feel like I could write a thousand words eviscerating this company's ineptitude — they have the golden opportunity to make a name for themselves in the market as a price conscious lithium battery manufacturer but they're drowning in their own ignorance.</p><p></p><p>I finished one of the capacity tests, the first cell. To recap, it was shipped at 74.5% SoC while the highest SoC of any cell was was 89%. It's now been tested at 104.689Ah or 99.7% SoH with a 19.99A CC load.</p><p></p><p>There's just no excuse — these are decent cells. They're not A+ but they're not terrible in anyway. But the people assembling this pack have no idea what they're doing and they're putting together mismatched cells, not top balancing in any way and relying on an outdated BMS to fix things in the long run. It'll take months if not years to rely on a BMS to average out a pack that is this unbalanced.</p><p></p><p>Updated table with SoC calculations:</p><p></p><table style='width: 100%'><tr><td><p style="text-align: right"><strong>Cell</strong></p> </td><td><p style="text-align: right"><strong>Vpc as received</strong></p> </td><td><p style="text-align: right"><strong>+Ah for 3.650Vpc</strong></p> </td><td><p style="text-align: right"><strong>SoC as received</strong></p> </td></tr><tr><td><p style="text-align: right"><strong>1</strong></p> </td><td><p style="text-align: right">3.328</p> </td><td><p style="text-align: right">26.8</p> </td><td><p style="text-align: right">74.5%</p> </td></tr><tr><td><p style="text-align: right"><strong>2</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">13.9</p> </td><td><p style="text-align: right">86.8%</p> </td></tr><tr><td><p style="text-align: right"><strong>3</strong></p> </td><td><p style="text-align: right">3.328</p> </td><td><p style="text-align: right">17.7</p> </td><td><p style="text-align: right">83.1%</p> </td></tr><tr><td><p style="text-align: right"><strong>4</strong></p> </td><td><p style="text-align: right">3.330</p> </td><td><p style="text-align: right">11.8</p> </td><td><p style="text-align: right">88.8%</p> </td></tr><tr><td><p style="text-align: right"><strong>5</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">11.8</p> </td><td><p style="text-align: right">88.8%</p> </td></tr><tr><td><p style="text-align: right"><strong>6</strong></p> </td><td><p style="text-align: right">3.330</p> </td><td><p style="text-align: right">13.5</p> </td><td><p style="text-align: right">87.1%</p> </td></tr><tr><td><p style="text-align: right"><strong>7</strong></p> </td><td><p style="text-align: right">3.328</p> </td><td><p style="text-align: right">29.3</p> </td><td><p style="text-align: right">72.1%</p> </td></tr><tr><td><p style="text-align: right"><strong>8</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">13.0</p> </td><td><p style="text-align: right">87.6%</p> </td></tr><tr><td><p style="text-align: right"><strong>9</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">11.5</p> </td><td><p style="text-align: right">89%</p> </td></tr><tr><td><p style="text-align: right"><strong>10</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">12.7</p> </td><td><p style="text-align: right">87.9%</p> </td></tr><tr><td><p style="text-align: right"><strong>11</strong></p> </td><td><p style="text-align: right">3.330</p> </td><td><p style="text-align: right">14.4</p> </td><td><p style="text-align: right">86.3%</p> </td></tr><tr><td><p style="text-align: right"><strong>12</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">14.2</p> </td><td><p style="text-align: right">86.5%</p> </td></tr><tr><td><p style="text-align: right"><strong>13</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">13.6</p> </td><td><p style="text-align: right">87%</p> </td></tr><tr><td><p style="text-align: right"><strong>14</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">13.4</p> </td><td><p style="text-align: right">87.2%</p> </td></tr><tr><td><p style="text-align: right"><strong>15</strong></p> </td><td><p style="text-align: right">3.331</p> </td><td><p style="text-align: right">13.6</p> </td><td><p style="text-align: right">87%</p> </td></tr></table><p></p><p>I've two questions for anyone who can answer them:</p><ol> <li data-xf-list-type="ol">SoH, state of health, does this mean how much of the original capacity is left? Like, are my calculations correct? If a 105Ah cell tested at 104.689Ah, then is it correct to say it is at (104.689/105) x 100 = 99.7% State of Health?</li> <li data-xf-list-type="ol">SoC, state of charge, would this be calculated at rated capacity of 105Ah or tested capacity of 104.689Ah?</li> </ol></blockquote><p></p>
[QUOTE="rsaeon, post: 2506539, member: 76792"] Looks like the only way to get a larger DC load at these voltages is to get a second one and connect in parallel. Maybe later, when I'm building more of these. I feel like I could write a thousand words eviscerating this company's ineptitude — they have the golden opportunity to make a name for themselves in the market as a price conscious lithium battery manufacturer but they're drowning in their own ignorance. I finished one of the capacity tests, the first cell. To recap, it was shipped at 74.5% SoC while the highest SoC of any cell was was 89%. It's now been tested at 104.689Ah or 99.7% SoH with a 19.99A CC load. There's just no excuse — these are decent cells. They're not A+ but they're not terrible in anyway. But the people assembling this pack have no idea what they're doing and they're putting together mismatched cells, not top balancing in any way and relying on an outdated BMS to fix things in the long run. It'll take months if not years to rely on a BMS to average out a pack that is this unbalanced. Updated table with SoC calculations: [TABLE] [TR] [TD][RIGHT][B]Cell[/B][/RIGHT][/TD] [TD][RIGHT][B]Vpc as received[/B][/RIGHT][/TD] [TD][RIGHT][B]+Ah for 3.650Vpc[/B][/RIGHT][/TD] [TD][RIGHT][B]SoC as received[/B][/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]1[/B][/RIGHT][/TD] [TD][RIGHT]3.328[/RIGHT][/TD] [TD][RIGHT]26.8[/RIGHT][/TD] [TD][RIGHT]74.5%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]2[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]13.9[/RIGHT][/TD] [TD][RIGHT]86.8%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]3[/B][/RIGHT][/TD] [TD][RIGHT]3.328[/RIGHT][/TD] [TD][RIGHT]17.7[/RIGHT][/TD] [TD][RIGHT]83.1%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]4[/B][/RIGHT][/TD] [TD][RIGHT]3.330[/RIGHT][/TD] [TD][RIGHT]11.8[/RIGHT][/TD] [TD][RIGHT]88.8%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]5[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]11.8[/RIGHT][/TD] [TD][RIGHT]88.8%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]6[/B][/RIGHT][/TD] [TD][RIGHT]3.330[/RIGHT][/TD] [TD][RIGHT]13.5[/RIGHT][/TD] [TD][RIGHT]87.1%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]7[/B][/RIGHT][/TD] [TD][RIGHT]3.328[/RIGHT][/TD] [TD][RIGHT]29.3[/RIGHT][/TD] [TD][RIGHT]72.1%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]8[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]13.0[/RIGHT][/TD] [TD][RIGHT]87.6%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]9[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]11.5[/RIGHT][/TD] [TD][RIGHT]89%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]10[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]12.7[/RIGHT][/TD] [TD][RIGHT]87.9%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]11[/B][/RIGHT][/TD] [TD][RIGHT]3.330[/RIGHT][/TD] [TD][RIGHT]14.4[/RIGHT][/TD] [TD][RIGHT]86.3%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]12[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]14.2[/RIGHT][/TD] [TD][RIGHT]86.5%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]13[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]13.6[/RIGHT][/TD] [TD][RIGHT]87%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]14[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]13.4[/RIGHT][/TD] [TD][RIGHT]87.2%[/RIGHT][/TD] [/TR] [TR] [TD][RIGHT][B]15[/B][/RIGHT][/TD] [TD][RIGHT]3.331[/RIGHT][/TD] [TD][RIGHT]13.6[/RIGHT][/TD] [TD][RIGHT]87%[/RIGHT][/TD] [/TR] [/TABLE] I've two questions for anyone who can answer them: [LIST=1] [*]SoH, state of health, does this mean how much of the original capacity is left? Like, are my calculations correct? If a 105Ah cell tested at 104.689Ah, then is it correct to say it is at (104.689/105) x 100 = 99.7% State of Health? [*]SoC, state of charge, would this be calculated at rated capacity of 105Ah or tested capacity of 104.689Ah? [/LIST] [/QUOTE]
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