ULTIMATE SPEED USBW 12 A1 4+

Firstly, it works fine to the point of displaying data from your battery (after realising you need to input the password on the back of the unit for it to connect via Bluetooth - tap top left of app on phone (icon looks like snapped phone) once done voila! But, there's always a but. It has a limited range. Our car is parked across from our house, ground floor with line of sight approx 4 cars away, if you had them end to end from our wall, but it cannot connect to our iPhone anymore. Unless your car is in a driveway or parked within approx 32ft (after reading up on Bluetooth...) and line of sight, it's probably going to be a hit or miss. Personally it should have a booster or at least tell you that on the box!!

It looks like the connection issues have been resolved with the latest update. Everything seems to work ok but the resolution on the voltage measurement is quite poor...it typically over-reads by around 250mV (against my lab cal’d dvm). If the developer could add a calibrate function in the app ot would get 5 stars!!!

The device doesn’t auto connect to Bluetooth for a good reason.... when connected it draws around 12mA from the battery, when not connected to Bluetooth this drops to around 2mA. So you don’t want it connected all the time like when you are in bed etc. Overall it is very good value for money, just a shame the accuracy is not a bit better.

Voltage measurement is accurate and simple to use. The software has a bug for temperature measurement as it increases every second (I think they have an error is their code ... probably the formula they are using to calculate the average of a number of readings received in 1s)