Teardown & Rebuild of a MuscleGrid LiFePO4 Server Rack Battery

So 48v 160ah lifepo4 will have 15 cells right and we can re-arrange it to 24v and higher AH, will that give longer run time if running 1kw plus load.
 
rsaeon said:
  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?
  2. SoC, state of charge, would this be calculated at rated capacity of 105Ah or tested capacity of 104.689Ah?
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1. Yes, SoH is the measure of the capacity left in the battery.
2. SoC will be calculated for the available capacity (in your case-104.68 ah)
 
nithishsabapathi said:
1. Yes, SoH is the measure of the capacity left in the battery.
2. SoC will be calculated for the available capacity (in your case-104.68 ah)
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Thanks! I needed to know for when I make my own BMS and do some kind of coloumb counting to get SoC numbers for the whole pack.

I'm guessing the SoH for the entire pack would be updated only when it is discharged enough to have one of the cells reach 2.5V.

rockyo27 said:
So 48v 160ah lifepo4 will have 15 cells right and we can re-arrange it to 24v and higher AH, will that give longer run time if running 1kw plus load.
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Actually, that pack may be 16S, there's a repair video of a smaller 86Ah pack on YouTube and I think I counted 16 cells. Also the specifications on the side say it's a 51.2V pack, which implies 16S (3.2 x 16 is 51.2)

So you could rewire it as a 8S2P pack for 24V at 320Ah for a 24V inverter, using a quality BMS.
 
OT- Are there any cheap battery capacity testers for 60v battery packs?
I want to check the capacity of my e-scooter battery, getting really bad range these days.
 
nithishsabapathi said:
OT- Are there any cheap battery capacity testers for 60v battery packs?
I want to check the capacity of my e-scooter battery, getting really bad range these days.
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Cheapest way is to connect 5 identical new headlight bulbs together for a 60v load and connect that to your battery pack after a full charge.

Then time it to see how long it takes until the BMS cuts power.

If you're using 90w bulbs, then that's 90 / 12 = 7.5 amps, and if the pack lasts for 5 hours, then that's a 7.5 x 5 = 37.5Ah.

Have a voltmeter or a multimeter to check voltages every half hour or so to make sure it's not discharging lower than the safe limit. For a 60v/20S LifePO4, that's 50V. I don't know what it is for Lithium Ion.
 
rsaeon said:
Have a voltmeter or a multimeter to check voltages every half hour or so to make sure it's not discharging lower than the safe limit. For a 60v/20S LifePO4, that's 50V. I don't know what it is for Lithium Ion.
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Thanks for the suggestion, for the lower voltage protection, the BMS will cut off the pack at the set low voltage right?

Won't the battery tester work for this purpose since i saw it rated for 120v??
 
nithishsabapathi said:
Thanks for the suggestion, for the lower voltage protection, the BMS will cut off the pack at the set low voltage right?

Won't the battery tester work for this purpose since i saw it rated for 120v??
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Yes, the BMS should have a low voltage cutoff. I'm not familiar with EV packs but any Lithium chemistry should not degrade noticeably within three years of daily charging and discharging, so in your case it could be a wonky BMS.

Also yes, the battery tester linked above would work fine for this and it'll be quicker with a 20A discharge but it's 3500. If you go this route and don't want to keep it after you're done, I'd be interested in buying it — I need another one of these.
 
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