My 2 cents here: there too many pitfalls when trying tell battery
capacity from voltage alone for these to be useful.  Also, some of
these try to pay attention to battery history, and will likely be even
less accurate if switched back and forth between two batteries.

Assuming you are the primary user of the van and don't need to keep it
simple for other users, I'd recommend getting a plain old 4 digit
voltmeter gauge (i.e."13.79V") instead.  No problem switching this
back and forth between batteries.  You'll quickly develop a feel for
what various voltage ranges mean, and can be smarter about it than a
gauge.  For instance 11.50V might indicate a low battery, but you know
you're running the microwave :), so it's just temporary sag, and the
battery likely has a good charge.

Alex

On Wed, Feb 27, 2019 at 10:08 AM Edward V Barger <edvbarger@mac.com> wrote:
>
> I am slowly making progress on the 87 Westy   Looking at this or something like it to monitor both my batteries
>
> Thought I could put in an A/B switch so could toggle between the two to check levels
>
>
> https://www.amazon.com/gp/product/B07759SLYP?ref=em_1p_1_ti&ref_=pe_3743280_396929690
>
>
>
> Edward V Barger
> edvbarger@mac.com
> 310 922 6251