I've spent a very long time trying to work this out, but some websites seem to conflict the information - or I'm completely missing the point.

I have a rechargeable battery:
<li>2600mAh</li>
<li>4.2V max charge voltage</li>
<li>9.62Wh energy</li>

It is to charge from a vehicle 12V or 24V (battery runs through a circuit board...it's designed for vehicle tracking).

What I'm trying to work out is:
<li>The A - is it 2.6A? Is this the same as Ah? Meaning it will only last about the 2.5 hour mark before running out of juice.</li>
<li>The approximate charge time. I was using 12V but then read the max charge voltage on the side of the battery</li>

I have one of the batteries connected to a PSU, but the current needle flips up a few bars, then drops straight back down. The battery was flat, so I'm not really sure what's happening.
Appreciate any help understanding this.