increasing current from a 12v 12w solar charger.

Your 12 watt charger is determined by the capacity of the solar cells. You can not exceed this by changing the wire size. One amp is all the charging current your going to get.

At 1 amp, the resistive losses in the wire and connectors is negligible.
You don't need to worry about wire sizes too much until you are over 10amps.
Del

If the solar charger is only rated at 12 watts then thats the max you can get. The max you can get at 12 volts is 1 amp. If you want more, double the solar panel and you will get 2 amps.

Those who have commented that electrical tinkering will not produce an increase in output are of course right. But you could try using mirrors to direct more sunlight onto the cells. It depends on your latitude and the prevailing weather - as long as you do not overheat the cells you may get a useful improvement.

You can increase the power delivered to the battery if you use the right type of charger. Most solar chargers only extract about 70% of the available power (watts) from the solar panel. Most 12v solar panels have a maximum power point of about 17.5 volts, 12w/17.5= 0.678 amps. Assuming you are charging the battery at 13.6 volts yields 13.6*0.678= 9.22 watts. There are chargers available that regulate the panel voltage at the maximim power point thus extracting the maximum power, and deliver it to the battery in the form of increased current. The solar industry uses the term MPPT (maximum power point tracking) technology to describe this type of charger. I use one on a motor home that is capable of handling about 350 watts of panel power with a loss (operating current) of only 70ma. Two companies that I am aware of are Outback and Blue Sky Energy Inc. I'm not that familar with Outback but the one I got from Blue Sky works as promissed.

Hope this helps.