Chosen Solution
My MacBook doesn’t start and shows permanent the red bad battery sign like on an iPhone when there is no power. This battery sign doesn’t let me through any system. No BootDeviceManager, no Reinstall menu, no maintenance menu, No SMC reset, no NVRAM reset,… Its just turning off after showing the red battery sign. I would like to know, if I could bridge the battery contacts. So I could use it as a desktop PC and know if the logic board is broken or the battery. Can someone tell me where I have to connect which kind of power? What i found out: The big middle contacts seems to be the output pins with 8,59V.The Label on the Battery is telling me that it has 7,56V, which is the battery output? I would assume that I could bridge the 8,59V pins to the pins on the right side next to the output, but I don’t know if this is a good idea and if yes, which contact is plus and which is minus. And what is the single left pin for? Would be cool if i can start this thing without the battery.
@yuna this model will flash the battery symbol briefly, then boot once the charger is plugged in, even with the battery disconnected. If this is not booting with the battery disconnected, you have a logic board issue. If it is not booting with the battery connected (but is fine while disconnected) and you are using a genuine charger and have left it on charge for at least a couple of hours, you have a battery issue.
Before you go down this path lets see if we can get your system going. I find it hard to believe your battery has died this soon. I’m assuming you can get the system to run with the power adapter plugged in if that is the case you should see a charging symbol. If not you either have a bad charger, USB-C cord or the outlet on your system has failed. You’ll need to start with testing with new (good known) units. If the outlet is bad here is the IFIXIT guide to replace it: Retina MacBook 2015 USB-C Port Replacement. Apple won’t admit it but having only one USB-C port on this model was a bad idea. I’ve seen three systems with bad ports now. Lets say you can get the system to run then we need to first check the battery to see what it is telling us. Download this gem of an app: CoconutBattery paste a screenshot of the full main screen so we can see what it tells us. In the meantime lets see if giving the system a SMC reset helps things. Here is the Apple T/N on how to do it: Reset the System Management Controller (SMC) on your Mac. Sometimes the simplest solutions are the better! As to your questions on rigging your systems power system. Not so simple! Apple uses a feedback circuit which is what the small three contacts are for. You can’t plug in a different power source internally. You’re stuck in using an Apple battery here. Update (10/07/2017) At this point I think you’ll need to visit an Apple Store or authorized Apple service center to see if they can help you isolate the problem. They will have a good working charger and cord. At worse the system may need a new battery as sitting unused for such a long duration could explain why the battery is dead.
