Battery low warning after battery replacement

As described - New Bosch battery fitted (16 days ago). This morning I got in and straight after starting, the "battery low" warning lights came on.

Before replacement, I was waking up to a dead car and would need jumping whenever I left for work/home etc. Even during that fiasco, I never had any warning lights about the battery.

Now I'm unsure of that new battery is dying or there's something else at play .. anyone had this happen just after a change?
 
Damn, okay. Have no means of testing anything and I wouldn't call myself mechanically minded - Does it sound like the battery is in fact going to die on me from lack of charge?
 
No voltmeter unfortunately, will take it somewhere to get tested before booking work in.

I'm confused as to why the old battery didn't throw up these warnings even though it needed jumping every time I got in it.

I changed the battery myself and again, I'm no mechanic, but enjoy trying to learn. Could it be anything I've done? Where are the earth's and what should I be looking for?

Cheers guys for replies