What’s the diff, scientist???
Mike,
Is there an advantage to having two 6-volt batteries vs two 12-volt batteries given the same available amperage? Cost, weight, charge time?
Also, I have read that some RV owners have a system with two 12 volt batteries, but only draw from one at a time – using the second as a backup. Any good reason to consider this option? – Sharon M.
Dear Sharon,
The key thing to know is that 6-volt FLA (Flooded Lead Acid) batteries are always “Deep-Cycle” batteries rated for a 20-hour discharge rate, while many of 12-volt FLA and AGM (Absorbent Glass Mat) batteries you get for your RV will be “dual-purpose” that are also rated with Cold Cranking Amps (CCA). This allows dual-purpose batteries to supply the hundreds of amps of current needed by a starting motor on a gas or diesel engine, but they’re not optimized for deep discharge cycles day after day.
Compared to a dual-purpose battery, a deep-cycle battery can get discharged and recharged many more times without any significant wear and tear. The thicker plates inside of a deep-cycle battery are tougher and can withstand more charge/discharge cycles than your typical dual-purpose battery.
What about weight?
And deep-cycle batteries tend a lot heavier that dual-purpose batteries since they have much thicker plates. And that’s what allows them to be discharged to lower levels without damage compared to dual-purpose batteries.
But deep-cycle FLA batteries do need to have water added at regular intervals, which could be once a month. And you do have to contend with potential sulphuric acid damage to clothing and body parts.
What about adding a switch to 12-volt batteries
There’s really no advantage to using a switch for a pair of 12-volt batteries to pick battery A or battery B except that you can mix batteries of different capacities and ages.
More info…
For a great article from Abyss Battery on the differences between Deep-Cycle and Dual-Purpose batteries please click HERE.
But the real winner of charge/discharge cycles are Lithium batteries. I’ll soon do a full comparison article on cost per cycle for all battery technologies. But for now, at least, the clear winner is Lithium Iron-Phosphate technology for RV house batteries. Just be prepared to pay extra for that technology.
Let’s play safe out there… Mike
