Adding Bluetooth battery monitoring

[Avalon]

Following on from the budget OBD2 reader I posted about, here’s another budget friendly way to add a little insight into alternator/battery condition without digging out a multimeter or laptop and VCI.

For about £17 (prices seem to fluctuate and are cheaper/slower direct from China vs UK sourced), you can buy what is marketed as a BM2 12v Battery monitor. I say marketed as because the iOS/Android app is known as BM2, the adapter itself doesn’t seem to have a brand name, but they’ve sold them for years and it’s been on my shopping list since they were circa £50. Installation is simple, 10mm spanner to loosen the Battery terminal nuts, connect the red to positive and black to negative, download the app and it syncs and will log Battery %, cranking voltage, alternator output testing and journey time to give you an idea how long the engine has been charging the battery. One thing I would suggest is charging the battery fully before you install this - it makes getting accurate charge levels a lot easier or it takes a while to calibrate itself. Better yet it’ll send push notifications when the battery is low, obviously being bluetooth, range is a claimed 10m and things like walls reduce this, if you are out of range, the push notification is queued until you are in range.

Having tested it back to back with the multimeter, the claimed accuracy of 0.02v is spot on as is the draw figure of 1mA. If I had this a few months back, I may have been aware that my alternator wasn’t charging the battery sufficiently before it died and left me in the outside lane of 3 at rush hour. For the relatively low price and ability to run multiple devices (cars, bikes etc.) and ability to move from one car to another if you change, it’s decent value. I have no link to any of the sellers on eBay/Amazon etc. selling them, but if anyone struggles to find one I can post a link.