The depth of the average discharge is a huge factor in what solar wattage/capacity ratio will be acceptable to the battery.
I have 198 watts and 90AH of AGM battery, more than 2 watts to one AH, and while it is enough to get my battery to absorption voltage ( 14.46v) and hold it there until amps taper to 0.4a(0.5% of capacity) most days, performance degrades without that occasional higher amp recharge when most depleted.
When the batteries are not discharged much below 80% then the high amp recharge on the AGM is much less necessary.
200 watts on 232AH of 6v GC-2 battery will only be enough if you never drop much below 75%. If you deplete to 50%, then there is no chance of 200 watts being able to restore 115AH in one day.
Any solar is better than no solar, but there is a sweet spot zone in the wattage/capacity ratio, and how deep one discharges, the battery type, and how much sunlight one can expect all play huge parts in ultimate battery longevity, and system reliability.
The availability of and employment of other charging sources also plays a huge part in what solar wattage/battery capacity ratio will be acceptable to the battery.
Consider that Trojan recommends a 10 to 13% charge rate, assuming one has a plug in charger and 8 to 12 hours to complete the recharge.
200 watts flat on the roof will yield about 13 amps max in summer, about 10 amp max in winter at 32 north.
10 amps on 200Ah of capacity is a 5% rate, and half of what Trojan 'recommends'
Rolls Surrette make the uncontested premier deep cycle flooded battery.
Their recommendation is even higher regarding the solar/capacity ratio.
The Rolls Surrette user manual is an excellent read BTW, especially for those that think they already know everything:
http://rollsbattery.com/uploads/pdfs/documents/user_manuals/Rolls_Battery_Manual.pdf
Regarding their solar wattage to battery capacity ratio, scroll to page 27
On page 29:
Batteries which are discharged should be recharged as promptly as possible. A
Renewable Energy PV system should be designed to provide a charge current that is
capable of recharging the batteries quickly, efficiently and within the window of time
when the system is generating peak power (peak sun). The charge current should be
within 10-20% of the 20 Hr AH rate (C20) rate of the battery bank
Of course you can get away with less, the unknown variable is how long you can get away with it, and will premature failure grind your gears? After a possible and 'likely' premature battery failure, will you bother seeking to upgrade in a hope to extend battery longevity the next time? If so, why not do it now, the first time? More expensive up front, much cheaper in the long run.
Having too much solar means batteries that are that much longer lived. Some people find having huge battery capacity as a buffer to be soothing. I'd find more solar for the same capacity more soothing, as charge rate is important.
My previous flooded battery I had downgraded to 130Ah of house capacity from 230, and got a better cycle/dollar ratio. When that 130Ah battery achieved ~ 470 deep cycles it was worn out, and I have never bothered to replace it cycling my AGM 'engine ' battery.
Well , the 130 Ah flooded battery is not quite done. I've put another 100+ cycles on it on it in my workshop with relatively shallow discharges, and for this duty, it is 'just fine'. Some others might even claim it is not only just fine, but still going strong too, perhaps breaking their arms trying to pat themselves on the back.
But the fact is it is severely capacity compromised and just waiting to short a cell. But it is still capable of being 100% recharged, it is just that when new it might have had 130Ah of capacity, now it only has 50 to 60Ah total and takes twice as long to get from 95% to 100%.
As long as I draw no more than 40Ah from it, it is 'just fine'
But in reality it could fail at any time with a shorted cell, and is anything but just fine, but ignorance is bliss, and enjoys company.
