Thursday, January 5, 2017

Can't we get some agreement, gentlemen?

Science... data... standards... You'd think those applied to something like the state of charge of a 12 Volt deep cycle battery. Because it's not subjective, like politics, fashion or the world's best recipe for chicken fried steak.

A 100% charge is ________.

A 50% charge (which one should avoid going below) is ________.


But here's what you get when you search the interwebs. About the only thing they agree upon is that green is good and red is bad.

Maybe the exacting science is out there, somewhere, and the problem is with those making and disseminating the charts.

The last chart seems most credible to me, because it accounts for temperature. It at least offers up, "It depends," to the question of full and half charge. Serious, accurate science is big on qualifiers. Other qualifiers might be the type of battery and the length of time without a load being applied. However, that might give us charts beyond the comprehension of mere mortals.

The second chart uses the term leisure batteries. I first encountered that yesterday, on a nomad forum. What? Batteries for relaxing? Batteries for non-work purposes? Batteries for which accurate data is unimportant?

"Hey, don't sweat it, pal. They're just leisure batteries. Come here, take a load off your feet, loosen your tie, have some of the world's best chicken fried steak."

Oh, they mean batteries that power the systems in your leisure vehicle, as opposed to the battery that starts and runs the engine.

I could be wrong, but leisure battery has sort of an old midwestern feel about it, like calling a casserole a hot dish, or a water fountain a bubbler.

In the name of caution and long battery life, I'll avoid anything lower than 12.4 Volts. Even if it means I can't reheat hot dish leftovers.


  1. I've always liked the term "leisure batteries" as well. I guess it makes sense, since it's used in the UK where they go "on holiday." It all sounds so festive, doesn't it? :)

    I don't know that there can be one chart. The one that's posted most often (the pretty green/red/yellow one can be somewhat unfortunate if one has, say, Lifeline AGMs, because 12.73 (full on that chart) is nowhere near full on a Lifeline (12.8 or greater is full, 12.7 is something like 85-90%. 12.5 (80% on the pretty chart) is only 75% for a Lifeline. I think maybe the common charts are for flooded batteriesLifeline does publish their own battery manual with all the data (gee, now I sound like a stockholder, but no, I just like that they give you an actual manual that tells you all the specs and how to care for them).

    The thing that "got" me when I first started learning the intricacies is ... wait... 12.0 volts isn't fully charged on a 12 volt battery? Wha?? And then to find out that tenths of a volt are HUGE. Whoda thunk.

    Anyway.... leisure battery! Yay, let's go on holiday! :D

  2. Yes. Here's the manual for my Sun Xtender AGM batteries.

    It gives the absorption voltage (14.2 - 14.4V) and float voltage (13.2 - 13.4) but not what they consider full or half voltage. Oh well.