Its an SAE connector I believe.
According to "wiki"
"The SAE connector is a hermaphrodite two-conductor, DC connector commonly used for automotive applications (also motorcycles). It is so named for the Society of Automotive Engineers who created its specifications.
This connector is typically used for applying a maintenance charge to a vehicle battery. The polarity of the connector, when installed in a vehicle and attached to a battery, is always such that no short circuit will occur if the exposed terminal were to touch the vehicle chassis. In most vehicles, this means that the exposed terminal connects to the negative terminal of the battery. Conversely, the positive terminal on a battery charger is exposed, to mate with the concealed one on the vehicle side.
Although there is a risk of short-circuiting a battery charger, the risk is minimal and often mitigated by the circuitry of the battery charger itself. On the other hand, the short circuit current of the lead-acid batteries installed in vehicles is sufficiently great, that a short circuit could result in a fire or explosion. The priority is therefore given to avoiding short circuits of the vehicle battery, rather than of the charger."
http://upload.wikimedia.org/wikipedia/commons/3/3d/SAE_Connector.png
try
http://www.twistedthrottle.com/trade/productview/5228/621/
or
http://www.powerlet.com/product/powerlet-basic-plug-to-sae-garage-duty-cables/315
for more info lots of adapter options which is the good news
