Here's the first photos of our ScoreSure Golf Pro device (yes, still in development!) running off a 400mAh 3.7v li-polymer rechargeable battery. We think it looks the business! And of course, using a rechargeable battery (whether eventually a li-po or a li-ion) means lots more possibilities for the enclosure, since we no longer have to worry about battery flaps and making the inside accessible.

Following a discussion on the RobotBrighton Forum, Robot Steve suggested that li-ions are better/safer than li-po batteries. Despite a recent post here extolling the virtues of li-pos, I think he might be onto something: but perhaps not for the reasons he outlined...

After much reading up on li-ion batteries and their variants, it seems that such batteries have a limited shelf-life. Not just a "hanging-around-waiting-to-be-sold" shelf-life (remember, if the battery discharges too much it can become damaged so they need to be used/charged every few months) but also a "use-by" date: typically 18 months - 5 years.
In fact, due to the heavy charge/discharge cycle that laptop batteries go through, many suppliers treat them as consumables now, and I'm thinking along similar lines for the ScoreSure range of devices. So the batteries need to be removeable at some point, not soldered to the PCB via short wires (as was the idea using li-pos).
Because mobile phones are so commonplace, it shouldn't be difficult to get hold of stocks of 3.7v batteries, quite cheaply, in future - and most of these are li-ion, hard-cased batteries, not the lightweight flexible li-pos discussed in recent posts.

When it comes to recharging li-on batteries, eBay is awash with USB phone chargers, for a couple of quid each (less if you buy in bulk) similar to this one.

So while it's going to be interesting to see what turns up in the post over the next few days, there is still plenty of research ongoing, into li-ions as an alternative.

Watch this space....

That's what's needed - by switching to a lipo battery, the entire device footprint can be almost halved! First thoughts were of a 7.4v lipo (double-cell battery) but the Nokia shield has already proved that a simple dc-to-dc step up converter can do the job where supply voltage is lower than the required voltage.

Charging requirements for lipo (or li-ion polymer) batteries are very specific and charging more than one cell can be quite tricky - particularly because of the need to stay within safety limits during charging.

It would probably be much easier/safer to stick to a single 3.7v battery with integrated USB charging circuit, and use this to power the Score Sure range of devices.
From initial investigations, a single battery would be much simpler to work with.
In fact, a recent email from NuElectronics confirms that they are working on developing this very idea themselves, to allow roboteers to power Arduino boards (which require 5v) from a single 3.7v lipo cell.

Charging circuits for single cells are freely available on the net and use relatively simple and inexpensive components.
At the heart of most chargers is the MCP73861 by Microchip.

More details (and schematics) will be posted here as they become available....