Even though the battery is relatively new (replaced last Winter), I was nearly stranded a few times late last year before replacement, and I've been vigilant ever since: Finally got myself a proper battery tender (installed in the basement last night), but also wanted something that would help me keep tabs on the battery's condition. Generally, in regard to modern Vespas, there have been two approaches: the cheap-but-not-too-convenient option was to buy a doohickey that connected to an SAE plug to measure battery output (or: install an SAE plug on the bike with a built-in color-coded indicator light performing the same function). Upside: it's cheap. Downside: Twofold: first, in either case, you need to install an SAE cable, attaching leads to the battery; and, you need to get on your knees in order to take a reading with either setup, whatever the weather.
The way-more-convenient-but-way-pricier option comes from Piaggio themselves: a two-piece module that installs in the bike, including a Bluetooth module that works with a smartphone via an app. The (obvious) upside here is convenience: just open the app, and you become privy to much of your ride's nervous system, including battery/charge status; no more hunkering-down to find out anything short of tire pressure. The (obvious) downside is price: some $300 for the hardware plus dealer installation (installation by the end-user is not recommended, but I know several folks here have DIY'd it anyway). Plus, a lot of the info this system offers on-screen isn't exactly critical (lean angle? Maybe if I was into doing track days, but…no).
But now, there's a nifty third way that splits the difference between the first two: Antigravity Batteries' Battery Tracker is a compact, Bluetooth-equipped box that connects to a bike's battery terminals, and communicates via an app (available for both Android and iOS). You can check voltage level, cranking power, and charging level (both at-idle and under load), to check on how well your alternator is really working.
Installation is…interesting. Connecting the unit is, as the Brits say, a doddle. But, here's the issue, at least if you're putting this thing in a Vespa GTS: once you attach the leads to the battery, you attach the unit to the side of the battery via the included velcro-pad set. Problem is, if you do this, you can't get the battery back into its perch - the entry-point is too narrow, as I discovered the hard way. There's plenty of room inside, however, so what I ended up doing was dangling the Tracker by its leads while dropping the battery back into the plastic basket sitting at the bottom of Melody's belly. This took a few tries, however, since I was jostling with both the regular leads to the bike's vitals plus the AES connector-leads my dealer retrofitted some months earlier. In the midst of this, I made the unfortunate choice of installing all this outdoors, late in the afternoon…with about 45 minutes of daylight left. The fact that I only lost one of four metal clips that help secure the top cover for the battery compartment was something of a miracle.
But, I got it properly installed, and yes, it works as advertised. The app works in a straightforward manner, presenting vital stats clearly and concisely. Plus, one cool trick I don't think even Piaggio's system offers: it will alert you if your battery's output dips below a level where things still start up. (You can preset two thresholds of voltage in the app.) I'd say this alone makes for a Killer App.
Bluetooth operating distance is listed at 30 feet; my tests confirm this.
Highly recommended. (Yes, you want this.)
The unit itself. (Photo: Antigravity Batteries.)
On the Phone: Pretty much everything you need to know, literally at your fingertips.
Screenshot: One of several parameters you can track (and be updated about at intervals of your choosing).