today my mac didnt turn on, i plugged în and turned on then i saw 0% battery. Why? At only 350 cycles and 2 years.enter image description here

  • Just charge it! The design capacity looks ok. – lhf Jun 4 at 0:43
  • @lhf the design capacity is what the label says, not what current degradation state is – John Keates Jun 4 at 8:24

The battery status of Poor indicates that something isn’t lining up in how the measurement circuit sees the voltage profile change.

The mAh are all estimates / derived / statistical numbers and the only thing the system can really measure directly are voltage - current in - current out and estimated wattage of the CPU. When those 4 values are not aligned or our of what the “model” predicts - you get a Poor / Check Battery / Replace Battery status.

If I didn’t see the “poor” I would say you probably are fine. Also, if you get no charge when there should be charge - examine the pins and cords and cables that are external and then seek service. Make sure you have a great backup in case you can’t turn on the Mac again. Also, once you’re backed up, you might reset the SMC one time (or once every 3 months) if you haven’t recently. The SMC measures and integrates the voltage / time measurements to derive the mAh so it can get stuck and need a restart on occasion or when you see something amiss like you see now.

If none of these work, there's a hardware failure that could be a cable disconnected or a part or two that need to be swapped.

  • I have no charge and i reseted The SMC – Andrei Penică Jun 4 at 10:56
  • @AndreiPenică That leaves hardware repair - reconnecting things internally I'm afraid. I've added that as the last step in my triage for this issue. – bmike Jun 4 at 11:41

There is probably a dead cell / pack that disables the battery. Since it’s a balanced setup you are going to have to replace it. Be sure to check the case for swelling

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