A Tale of Two Batteries
When I bought my Bigfoot
, one of the features that appealed to me was that it came with two batteries, and both outside the cabin, so no storage space was sacrificed.
On the Bigfoot
they are 12 volt batteries and so wired in parallel.
But in many discussions on the forums, 6 volt batteries wired in series are strongly preferred.
At the time I questioned that preference, thinking 12 volt units made more sense. My reasoning was/is that when one of the batteries dies, you are in much better shape if the remaining one is 12 volt and still able to power all the dc circuits. On the other hand, a single 6 volt battery
is basically useless.
The counter arguments were that with only half the number of cells in the same volume, the 6 volt batteries will have heavier plates, provide more amp hours, and be more durable (last longer).
Certainly the second point makes sense.
Another argument was that in parallel, if one battery
died, it would kill the other one as well, from the excess draw.
Because that viewpoint seems almost universal I had about caved and was planning to switch sometime soon. I figured my current 12 volt units were due replacement anyway.
In the meantime, from my battery
monitor, I was not getting the charge life I would expect, but being inherently lazy, I didn't investigate whether that was true, or what the cause might be, since I was planning on new batteries anyway.
Then all of a sudden, after disconnecting shore power in preparation for a move, I had no 12 volt power at all. Ouch, what could that be? But I needed to get down the road and figured to investigate when I got to my next destination; my daughter's home. On the way I stopped at an Advance Auto and had the batteries tested. Sure enough, one read fine, at about 13v, but the other was essentially dead at about 0.6v. When i rewired for the one good battery, I've been good since, about three weeks now. At the time I was still in 6 volt thinking mode and asked if they carried any.They did not and didn't know where I could find them, another point in favor of a 12 volt choice when on the road.
With some more thought, the upshot of all this is that I'm now firmly back in the 12 volt battery mode. If I'd had 6 volt units and one failed, I'd have no easy way to continue. And it's clear that one dead 12v battery will not necessarily kill the other, at least not right away..
I'll still buy two new batteries soon, when I have time to decide which are the best available.
So the answer is that probably both arguments have some truth, but I now know which is best for me.