I use the B&D VEC1093DBD 40AMP Smart Mode Charger here. Can run it with my 2KW Honda Generator anywhere I need it. The 40AMP DC Current available will allow me to recharge two 12VDC Batteries from the 50% charge state to the 90% charge state within a three hour generator run time.
Sometimes I have the problem that a battery is too low to get this unit started in smart mode. These batteries are toast already but I try to revive them anyway... A few times I have brought them back. I also carry a VEC 10AMP Battery maintainer to get the batteries to demand a few amps so that this 40AMP charger will start doing its business...
Has been my portable main Battery Charger since 2008.
Like said these are getting real hard to find now but are still available if you keep looking. I should have bought two of them back when they was so available...
Roy Ken