I looked into the amount of current available from a USB charger when investigating how to charge multiple iPhones / iPads simultaneously. Below is something I learnt that might be relevant.
There are several different ways that a charger can "tell" an iPod how much current it can provide - the iPod can't determine this directly. If the charger is a computer, it will communicate this through a data transfer (similar to transferring MP3 file data).
But a simple charger won't use this method. Instead, there are various standards (some proprietary, I believe!) which specify how much current can be provided, by providing certain voltages at the data lines. USB has four pins: one ground, one power, and two data. For example, apparently 2.8V on one of the data pins and 2.0V on another means "you can draw up to 1 amp". See this link for some detail, although I think some of that is out-dated.
I'd guess that the LG adaptor doesn't provide the signalling that the iPod expects. I don't know a way to resolve this, other than to try a different adaptor - sorry.