The GW 'kit' as designed is a poor excuse for an aux battery kit. Due to the
ridiculous current path it uses, the aux battery will never receive full
proper charge voltage. It can be modified but I would highly recommend a
Surepower 1314 or 1315 from www.ase-supply.com and wire the battery not only
better but with a much better quality relay. There are several batteries
that fit, the Odyssey 1750 I believe being the largest capacity. You'll need
to plan on an adjustable voltage regulator from davebarton.com also if you
want the battery to receive the proper voltage and last any reasonable
lifespan.