In case of the Leaf, you really should think about the SOC in Gids. The SOC display in the car is based on gids. The low battery warnings in the car are based on Gids. For example Low Battery warning is at 50 GIDs. Very Low battery warning is at 25 GIDs. If you are looking at the leafspy logs and want to know what was the SOC displayed in the car, you have to find out what is the maximum Gids for that specific car. Unfortunately, that is not logged by, and probably not even known by leafspy. You can scan the logs and find the maximum value and use that as 100% charge, or you can use the following defaults: When new, a 30kwh leaf has about 365 Gids. The 24kwh has 281, and the 40kwh has about 505. (But the battery is a bit of a lottery. My 30kwh Leaf had 363 Gids when it was new, but my friend's which was manufactured a year later had 372 ) My 30kwh Leaf has a 5% degraded battery, which means that maximum gids is currently about 344. I just finished charging for todays trip, and it sits at 293 gids, which the car displays as 85%. (SOC as logged by leaf spy is currently displayed as 80%) Btw. the iOS version of leafspy will log to the server even if leafspy is running in the background. As long as it is not kicked out of the memory by the OS, it will continue logging.