Charge or use a T:slim X2 with an external cell phone USB battery pack

[Tim35]

All the time.

T-slim charging

400 watts is a lot to pull from your vehicle cigarette lighter. If you do connect enough devices, you could blow a fuse depending on your vehicle. I do like the vehicle power inverters for their convenience for some devices but really not necessary in this case. In any event, just be careful how much power you pull through it. When considering switching to the Tandem t:slim X2, I was initially of the opinion of @rgcainmd and thinking replaceable batteries would be better for a pump. That is…