stop charging

Hiya all. I have a problem with my zoe. I purchased a granny cable from Amazon and everyone online said it works fine with the zoe. But I can't get mine to stay charging. It starts happily but then cuts off after it gains a single percentage. I have to keep going into the app and restarting...

Quick question.. . Today I used EH at ferrybridge services, I started app successfully and went to grab a coffee. My phone battery died whilst I was getting coffee, no problem I could see unit was still charging upon my return. I only needed 25 mins of charge so wanted to stop charging before...