I'm concerned it's only starting well from the initial charge. Until you can monitor voltage white running for an extended periods you can't tell. You can buy a plug in tester that goes in the cig lighter socket. That could also answer the problem with usb charger.

You need a DMM to work on a car. Get a non-shitty one. Gently used fluke from eBay is a good way to go. I've seen decent new Klein models under $50 don't buy a no-name model.

Here's a big duh: did you say you have the wifi obd dongle? Use dash command app to monitor voltage.

If the voltage is not reliable the abs will likely disable as well as the trans. Car can still drive with trans in limp home mode just only uses 4th gear so be gentle off the line it will feel like you have some mates outside pushing vs engine. It's called fail *safe*. I drove mine at least 10 miles through 2/3 red lights before I found a place to pull in and Google how to reset the transmission.

Having dash command is a life saver I have twice had a sporotic misfired cylinder that tripped an engine limp home mode and it feels like 3/6 cylinders are shut off when that happens. I was able to clear the code and life was back to normal without even stopping the car! That was wild having the engine instantly start working properly while I was still driving!

I suspect I might have a weak spark coil as it was the same cylinder but it's only happened twice in 25,000 miles so I have not been able to track down that exact source.

Back to your issue: you need to confirm the charging system is working properly before you destroy the new battery. Also confirm no parasitic drain which will require a DMM.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)