I really should not stick my neck out when it comes to rechargeable batteries and charging them, as I have had so many failures, including so-called smart chargers.
The main problem with them, is that when they do not do the job whether due to the battery or the charger, they are so smart they keep all the knowledge inside them, and so a fault can remain a mystery.
But, others may swear by them.
Of all the methods I use, by far the most reliable and easy to diagnose, is to combine a solar panel and charge controller.
Moncrystalline panels are by far the best in my opinion but a little dear; but shopping around (e-bay) bargains can be found.
A 20w (nearly 2amp) 12v (actually about 20v when not under load) can be got for thirty quid.
Charge controllers come in all shapes and sizes.
A 10amp (about the smallest but adequate here) with leds to show what is going on can be found for under a tenner.
Wiring up is a doddle and you can put a volt meter across the panel or the output to the battery easily for actual readings.
I actually have that combo sitting on top of the dash of the 5008 at his moment, as the bus gets little use.
We have loads of solar panels for different things, which is not surprising given the sunshine we have, but monocrystalline still give a good voltage on totally overcast days, so fully functional in the UK.
Hope that helps. :beer:
Stewart
Incidentally, only our ageing Mondeo Estate has an auxiliary socket "on" all the time for easy connection for charging; all others I have to resort to croc clips as sockets only live with "ignition on". Bloody infuriating! :x