I believe it's time to replace my house batteries and as usually it's difficult to choose.
I currently have two GC2 6volts installed in series, however I think it may be an overkill. I say that because I keep the boat on a mooring and use the engine about 10mins each sail about 3 days a week. I mainly race the boat in local regattas, but this weekend I plan on cruising. Thus my interest in replacing these damaged batteries.
My concerns are:
1. I don't have any charging source other than my 10min alternator run each time I sail.
2. I live in Miami and am aware that the high temperatures are deadly.
Are my concerns valid? Should I re-buy these big batteries once again considering the conditions?
As of now I'm leaning to re buy them again because the trays are all ready for them. So I would like to know what are the recommendations, which model/brand and where to buy?
Any Help is much appreciated.
You have a few things to think about or that are issues:
Where you boat is a problem just due to the high temps. Anything over 80F and batteries begin to lose life. Heat also leads to significantly faster "self discharge" so even if you got back to 80% SOC with the alternator the heat chewing into capacity at a significantly faster rate then batteries that remains in the 60's & 70's...
Unfortunately you can't do much about the heat, it is just a fact of life for where you live. AGM's would self discharge more slowly but then bring on a whole hose of other issues such as even shorter life, in your situation, and much more added cost come replacement time.
#2 Poor Charging:
Lack of "full" chargers lead to sulfation of the battery plates. Sulfation becomes considerably more aggressive at anything other than 100% SOC +/- a few %. Sulfation is like battery cancer. Once it starts it only compounds until the battery dies. You can do periodic equalization charges but would need shore power. Equalizations are like Chemotherapy. It helps, but also degrades the battery via plate erosion... Best way to fight off battery cancer, on a mooring, is to keep the batteries full via solar.
Heat only speeds and compounds the sulfation issue and 20 min is doing very, very little to even replace what you used in Ah capacity. Even if you ran the motor for 2-3 hours you're still barely getting above 85% state of charge due to acceptance issues. This side of the equation you can change and you can add solar to deal with this and help minimize sulfation.
There are a few options here. Spend some money on a small solar array (30W+) and leave it connected when you are not there. Depending on the array size in 2-5 days the batteries will eventually get from 80% to full. Once a week "full" for batteries helps tremendously. This can easily double the useful life of the batteries and also give you more reliable batteries that you can depend on.
The other option is to just accept the short life and live with it., many do. If that is the case the "big" 6V batteries are still going to be your least expensive option and may last two years+...
6V golf cart batteries deal with "abusive" situation better than their 12V cousins and as such last longer in the same abusive environment. They are also the least expensive battery to buy on a $$ to / Ah / longevity calculation. Heck they are usually the cheapest battery you can buy anyway. You can buy a pair of 6V batteries for $160.00 if you shop around. Having more Ah capacity is NEVER a bad thing especially when the batteries receive less than optimal charging..
Stick with the 6V batteries and buy the new ones from a major golf course supplier, Sam's Club or Costco. Expect to pay $80.00 or less ea for a 6V GC2 battery, especially in Florida, the land of inexpensive 6V batteries.......