Battery Sense ٤+

You can see the voltages nicely. However, there are two major downsides. Every time I open the app, it tried to force me to allow the app access to my location. I have to deny it every time. This is quite annoying.
When you are trying to monitor the battery voltage, you want to look at the past data. Unfortunately you cannot get a better resolution than a full day. To really understand battery charging etc, you would need to be able to zoom in. This is not possible though.
If both of these issues were resolved, if give 5 stars.

Bluetooth works while next to LNEX device. Security pin change works. Voltage page is clear. Flower shape design for main voltage display has different colors depending on voltage but nothing in manual/online about it. Short graph is clear but not very granular. Voltage detail page shows data for one day or custom but it has hidden data gaps, more in a moment. Latest data is plotted 1 hour later than actual. Selecting custom gives crowded/overlapping menu on smallest iPhone. Downloaded data reveals 5-6 large data gaps per day ranging from 20 to 55 minutes each! The detail voltage graph display doesn’t indicate any gaps, so smoothing overly compensated and down right deceiving. The cranking page is clear but the graph granularity is lacking especially when comparing between different starts. The charging page is clear. The trip page is clear but shows trips times 1 hour later than actual. Trips are missing due to gaps in data mentioned above, notwithstanding that the developers list numerous other reasons for inaccuracies. Overall 1 star but could be better if app is fixed. In contact with support … will update if any changes.

It works but really wanted to know temperature as it is important to battery health.