I've had this problem before with my 2017 Macbook Pro. Try clearing the nvram and smc
GBAtemp.net - The Independent Video Game Community
The Catboy
reha
I've tried everything including those but no luck, it's 12 year old hardware this is pretty normal tbh. Thank you anyways 
Sono
Unplug battery, plug in charger. What happens?
Does the charger LED on the MagSafe connector light up at all?
Do any of the LEDs on the side light up?
Does the charger LED on the MagSafe connector light up at all?
Do any of the LEDs on the side light up?
reha
Well when I unplug the battery and plug the charger in, nothing changes (the battery indicators are flashing like 5 times when I press the indicator button I guess thats what you mean by LEDs on the side).
reha
The MagSafe charger LED is kinda blinking when it's plugged in. The weird thing is that it was working when the charger was plugged in, but it always shut down when I plugged out the charger so I decided to plug the battery out then plug it in to see if it will fix the issue but this time it doesn't even try to boot up at all...
Sono
Flashing LED means battery dead / rejected (must replace due to high cycle count).
You can force a power-on with battery unplugged by holding the Power button while plugging in the charger, and once you release it after holding it for 10s, it will turn on with fans spinning at max. Keep trying (up to 5 times), it's a bit unreliable for some reason.
You can force a power-on with battery unplugged by holding the Power button while plugging in the charger, and once you release it after holding it for 10s, it will turn on with fans spinning at max. Keep trying (up to 5 times), it's a bit unreliable for some reason.
reha
Yeah the battery cycle was around 1.5k 
It is unusable with the battery unplugged tbh the max fan speed really bothers me... I'll just wait a few weeks and hope that it will work again
It is unusable with the battery unplugged tbh the max fan speed really bothers me... I'll just wait a few weeks and hope that it will work again
Sono
But hey, at least you know it's not broken! Sounds like you actually got it to turn on?
reha
Sorry, it does not turn on with battery unplugged but even if it does, the fan speed will bother me, that's what I meant 
I assume that the battery was overcharged or something (I used the MacBook with charger plugged in most of the time), the cycle was around 1.5k but the health was still something around 75%
I assume that the battery was overcharged or something (I used the MacBook with charger plugged in most of the time), the cycle was around 1.5k but the health was still something around 75%
reha
Okay so I finally got it to turn on! I've basically unplugged the LED battery indicator's ribbon cable and plugged back in, it is now booting up!! At least I can use it this way for now!!!
reha
The status indicator light (the white light thats located on the left of the IR reciever) is blinking a few times whenever I turn the system on, it hangs on blank screen for a few seconds, then proceeds to boot up. The MacBook shuts off whenever I plug out the charger so I assume that I need to replace the battery.
Sono
It will eventually REFUSE to charge the battery, so you will have to replace it, as I did not find a workaround to trick it into re-enabling charging :<
reha
Okay so I've decided to dig this guy out of his grave and see if anything's changed. It still refuses to boot on battery but works fine (but it's slower for some reason? I assume that it underclocks the CPU to prevent damage) on charger with the same error (SIL blinking 5 times then booting up).
reha
The battery was at 100% last time but it's at 98% now, this probably means that the battery is still capable of holding charge, right? Why doesn't it want to boot up on battery then? The health is exactly on 74.7% 1.2k cycles (checked out with coconutbattery). My backup laptop (Macbook Air Early 2015)'s battery has like 50%ish health and 1.5k cycles but it is still running perfectly on battery.
reha
I know I could just get a replacement battery at this point but the seller that I'm currently contacting with isn't replying