So, I've covered a good 200 miles with my Jimmy pack
I should say it arrived well packaged, on time and with a full discharge chart at 10a load
"I would like to explain that the test was carried out with a constant 10A of current draw from the battery. This is a fairly high value for the full duration of the discharge period and for a battery to return almost all of its quoted capacity is an excellent result.
Manufacturers use 0.2C (in this case 3.2A current drain) to achieve higher capacity figures which we don't think is realistic." Said Jimmy
It is always on(so the button is redundant) as advised and expected.
In both my crank gsm mtb and my bpm hub powered hybrid bike it has performed very well. Clearly it is 16ah (or near enough) ,implied by the mileage I get and charging time after my standard commute.
No voltage sag that is perceptible. And I'm convinced that the 250w 18a gsm actually pulls loads more if de restricted
All in all very happy.
I'll report again in a year or so !