But I boon dock a lot. If you are mostly connected to a pedestal you don't need that much battery capacity. 

If you have a choice, connecting 2 6V batteries in series is better that 2 12V ones in parallel. In a series configuration there is only one path for current to take in and out of the batteries, so they get charged and discharged equally all the time. In a parallel configuration there are two current paths, so one battery inevitably gets exercised more than the other one. This gets worse as the batteries age and start to have more variation in cell internal resistances. 

Jato: I agree that charging within the 'real' usage rates extends the life of a battery. I use a voltage chart to check my SOC (at rest). I use FLA's and run only to 12.4 (with the occasion of a 12.3).

I'm a pretty firm believer that 12v's should only be drawn to 75% SOC and 6v's to 50%. My last set of 12v's lasted me 14yrs+ staying within this guideline. This is my second year using 6v's.

My choice this time around was a pair of Duracell 230ah 6v's. This gives me a usable rate of just over 100ah (SOC to only 50%). 

I am also a fan of doing a Power Audit to determine just what 'you' need. I'm finding I have far more then I've required. Between TV and Solar charging, I would have been fine in a 60-80ah range.

Jato: I agree that charging within the 'real' usage rates extends the life of a battery. I use a voltage chart to check my SOC (at rest). I use FLA's and run only to 12.4 (with the occasion of a 12.3).

I'm a pretty firm believer that 12v's should only be drawn to 75% SOC and 6v's to 50%. My last set of 12v's lasted me 14yrs+ staying within this guideline. This is my second year using 6v's.

My choice this time around was a pair of Duracell 230ah 6v's. This gives me a usable rate of just over 100ah (SOC to only 50%). 

Question, How did you arrive purchasing the Duracell over Trojan brand?  Being a golf course guy our Yamaha's use a 48 volt system (6 - 8 volt batteries) and as far as I knew Trojan is supposedly the best you can get.  Do the two offer the same amount of AH when wired in series?  I thought the Trojan T 105 or 120 offer 120 AH whereas the Duracell you state give you a usable rate of just over 100 AH or am I just reading your post incorrectly?   Thanks, I appreciate your expertise in this area and I know the day will come when I will be retiring my 'old' batteries with some fresh 6 volt ones.

Bang for the buck theory on purchasing. For the higher $$ for the Trojan's I would hope it's a thicker plate, but I don't know for certain. I could find anywhere I could compare build spec's. I saw the Duracell weighed more (I thought the Trojan would have if the plates were thicker). From there it was Warranty and ah rating (well and some reviews..). Then cost. Duracell won. The T-105's and my Duracell Ultra's spec's are very close.

My dual Duracells are rated at 230ah each (at 6v's). As you know when wiring in series, voltage goes up and amperage remains. So now I have dual at 12v's and still the 230a rating. A 6V FLA should not be drawn below 50% (if you wish them to last), so that divides the 230ah in half, 115ah. I tend be conservative on my values, knowing things are not always as stated, and say I have 100ah usable power. 

Hope that helps.

The biggest killers of lead acid battery life are excessive discharge and overcharge.

Thanks to both Olddawgsrule and Offgrid for the replies.  That is why I enjoy this forum so much, something new to learn everyday, or is it because I am forgetting so much? 

Yes, electrolyte level is crucial to battery life, as is not under or overcharging, and keeping the battery clean, posts, ect.  Over the past nearly 9 years I average twice per year that I add distilled water to each battery.  I will not purchase any battery whereby I cannot access the cells to add water, something that is becoming more difficult with smaller batteries, at least in the area where i reside.

I agree with offgrid, avoid over charging, discharging below 50%, and never let the water get down to the plates or below.  Simple battery maintenance ensures a long battery life.

I will say I see 'at rest' a bit different than OG. To me a true read comes after 12hrs (some say 24hrs) and find that pretty darn accurate. An hour or so will tell you if you have a issue though. 

I also find a battery 'wants' to be used. Letting it just sit for months, even on a maintainer is not use.. I do plug in over the winter when required, I draw down the battery, typically 80% (275 watts) and usually my panel will catch it back up, if not I'll plug in.

I do recommend a meter like what I use that shows cumulative wattage. I have another on my panel. I think I was checking Refrigerator draw on battery in this picture.