> ...using a bridge rectifier might be cheaper than
> a series diode in some cases.

    That is, "using four diodes might be cheaper
    than [using] one diode".

    Well, to paraphrase 'twelve angry men'...

    ...I suppose.  ;)

> However, I'm worried that using a bridge would result
> in strange potentials relative to vehicle ground, but
> I haven't thought about it yet.

    Oh, these batteries aren't (usually) used while
    in a vehicle.  They're just a convenient, portable,
    robust, and easily recharged power source.  Bung
    a couple in the back of the 'ute and you're set.

___Bob