White/clear battery icon while charging?

I've been seeing issues with my off-brand charger this week and just noticed my battery icon is different when I'm using it. The battery is white or clear (same color as menu bar) with black lightning bolt in it. Usually the battery is black with a white-outlined bolt in it. When I first plug it in it's black but after a second it goes clear.

The charger is a Chinese knock-off I bought off eBay years ago; it's a type-1 MagSafe that I'm using the 1>2 MagSafe converter on. This week I've noticed it hasn't been charging the laptop right away when I plug it in; battery has been draining to around 30% before I noticed it and jiggled the plug. Slowly recharging now. Is the clear battery an indicator of a slow or insufficient charge? I hadn't seen that before with this charger, perhaps it's a new El Capitan thing?

TIA,

L