Hi, I have been looking at Lithium batteries since they are lighter and give more power but not sure I can afford them. They are quite high priced.
One guy at work said to use two 6V batteries instead of 12 volt batteries. But if you hook two 6V batteries in parallel to make 12V the capacity is the same as one battery. If you hook up two 12V batteries in series the voltage remains the same 12V but the capacity doubles. So isn't the 2 - 12V batteries better ?
I would also like to hook up a couple of solar panels on the roof and have them charge two batteries. But I need to learn a lot more about what equipment to use.
Any help would be appreciated.
Sorry I am coming in late but our Christmas season has been hectic.
To answer your question regarding 6V or 12V batteries, here goes...
Batteries are rated in terms of Amp-Hour capacity at a certain current drain. For example a 12V wet cell, maintenance free battery might be rated at 45 Amp-Hours at a discharge rate of 5 Amps. That means that in theory if you started with the battery at 100% capacity that it would be totally drained after 9 hours, BUT discharging to 0% would seriously damage the battery! Wet cell batteries should not be discharged beyond 50% without damaging them. AGM batteries have much greater Amp-Hour capacities (80-100 Amp-Hours) AND you can discharge them further without damaging them. Typically you can discharge an AGM to 20-25%. Each brand can be different in the Amp-Hour and how far it can be discharged. For RV use an AGM battery often is the most financially effective as you have more capacity AND you can discharge it further without damage.
A 6V battery (as used in golf carts) packs in more Amp-Hours as there are only 3 cells in the battery as opposed to 6 in the 12V battery. The lead plate size (surface area) can be larger (perhaps over twice) in a 6V battery with the same outside dimensions as a 12V battery. Hence the Amp-Hour capacity will be greater (over twice) in the 6V battery. If you choose to use 6V batteries and want 12V then you will need to connect two of them in SERIES.
If you connect two 12V batteries in PARALLEL then you will receive twice the Amp-Hour capacity of just one.
So from the above two conditions you should start to see that two 6V batteries will produce slightly higher Amp-Hours than two 12V batteries, but my guess the increase in density is only worth about 10% gain in Amp-Hours.
In conclusion I encourage you to go back to the mfr ratings. Assuming you decide to get AGM batteries look at the cost of two 6V AGM batteries and the resulting Amp Hours compared to two 12V AGM batteries. To me it is all about the performance that you get per dollar. I think if you do the same analysis on Lithium batteries you will spend much more $$$ and only gain in the wieght and size of the batteries. That's my 2¢.
PS. I will ad that one of my beefs is that the WFCO converter in my FF did a lousy job of charging even a normal 12V wet cell and would not have gone to a high enough voltage to properly charge an AGM battery. Any the WFCO is not programmable for other battery chemistries, including lithium. Solar chargers often have switches to set charging different battery types. My solution was to add a Renogy 12V-12V charger to my system in the FF. The output of the WFCO powers the Renogy and the batteries now properly charge. You can find my write-up elsewhere on this website.