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Cars aren’t the greenest of things so we’re always glad when we find something that we can use to save energy in them. This week’s Green Piece is all about the Sunsei 150 solar car battery charger. It will trickle charge a 12v car battery but can also be used in tractors, small boats, motorbikes and other small vehicles.

It’s ideal if you’re trying to use your car less or take it off the road but you’re worried that the battery will go flat. It will also save electricity if you need to charge your battery via a mains charger. And, of course, it will help all of us who don’t have that handy bleeping noise that alerts us to the fact that we’ve left our lights on when we get out of the car.

All in all, a pretty handy green gadget. You just mount the panel on the inside of your car window, using the suction cups and connect it to the cigarette lighter or directly to the battery with the crocodile clips provided.

You can pick one up here for £29.99 if you’re in the UK or here for $48.88 for US readers.

If you’re always getting lost, you may also want to invest in a sat nav - just think how much petrol you waste and how much CO₂ you emit when you’re correcting ‘navigation malfunctions’!

Unveiled at the British Motor Show this week was the waterproof, multi-use navigator from Garmin. The nüvi 500 is great news for cyclists, drivers, walkers, and folks in boats as it can customise itself to whichever form of travel you undertake.  It’s waterproof and built for adventure, providing turn-by-turn directions to get you when you want to be.

The different maps include TOPO for outdoor navigation and Blue Chart cartography for marine usage.  Boat fans can also add the optional BlueChart g2 Vision marine cartography, which will show them wrecks, port plans, inter tidal zones and other clever boaty things.

Walkers will also feel special as there’s a digital elevation map option, compass page and tracklog so that you can track where you’ve been - great for knowing who to blame when you get lost.

All the usual suspects are also onboard (sorry), such as Garmin’s “Where am I” feature, which tells you your exact coordinates, traffic avoidance and millions of points of interest.

You can also navigate by photos by using the “Connect Photos” option which will give you access to Google’s Panoramio.

This would be a great little device for people that want navigation for all their forms of travel.

The nüvi 500 has a 3.5 inch TFT screen, weighs 215g and has a battery life of 8 hours. It’s set to be released in the UK in September for £299.