Hey Eric,
Thanks for doing the math. I already did it. I also consider the fact that 50% of the T105 is dead weight, also for my application, as anyone with a MH knows you can't fill all the storage space without going over weight. I regularly weigh my RV on the scales and have the weight capacity for 100Ah of NiFe. The heat battery will take more space than the NiFe battery.
The cost of going NiFe has already been spent on Lead in the past, and I am close to the cross roads that determine my next course of action. I personally know the folly of lead acid investment.
Cruising on the boat that was dry, with serious weather the bilge pump had to run more often. Electronics failed under these conditions. I wonder about lithium batteries on a cruising boat, but that is only my opinion, (Well, OK, backed up by an engineer friend that designs lithium backup supplies for consumer electronics). Now it is easy for the week ender to avoid times when waves are crashing over the decks, but 15 or more days on the pond can't be predicted. We are lucky when the weather predictions are good for 5 days let alone 15 or more, if you could find such a prediction.
As I have stated with my specs there are more things to consider than weight and space. I understand the need to stay light with multi hulls, and a multi hull can make a passage much shorter than with a mono. Maybe enough to stay within the weather prediction window, but cruisers typically find weight less important than convenience over time. The water line keeps raising with every year they spend on their boats. Soon the multi hull dream of go fast, gives way to a better life, at close to mono hull speeds.
This may be the reason experience gives way to desiring a mono hull rather than a multi. The desire for space gives way to trollers rather than multi hulls. All that said if I were to build or buy a gunk holer it would likely be a multi. If I were to build or buy a seasonal boat it may likely be a multi hull. If I were to go back to cruising, it would likely be a mono with hybrid power. It would be without sail but not a troller. If it were a power boat however, here is no way it would be any other kind of of boat but a troller. Mono hull Sail boat modified to be a power vessel would likely be my pick.
Kevin Pemberton
On 11/16/2010 01:47 AM, Eric wrote:
Kevin,
I did the math with the data on the link that you provided. One 100Ah 1.2V cell weighs 4.9Kg (dry weight?), so 10 dry cells would weigh 49Kg which is 107.8 pounds. That battery would be rated for 1200Wh which is 11.1 Wh/lb. But the page says that you need to add distilled water to make them work, and of course the link doesn't say how much. If a 100Ah cell takes only 2 cups of water, then one cell is close to 12 pounds and we're back to 10Wh/lb. Looking at the 200Ah cells, they are 26.4 pounds dry or 264 pounds for a dry 200Ah 12V (2400kWh) battery. Add water and you're probably past 280 pounds or 8.5Wh/lb.
Alternatively, a T-105 weighs 62 pounds (according to Trojan) and is rated for 225Ah @ 6V or 1350Wh. That works out to 21.8 Wh/lb. Take two in series and you've got a 225Ah 12V battery that weighs 124 pounds.
Are you really sure that size doesn't matter? Lets compare the 200Ah 12V NiFe to the 225Ah 12V T-105s
2400Wh NiFe = 13.2" x 32" x 13.6" = 5745 cu. inches, 280 pounds
2700Wh T-105 = 10.4" x 14.3" x 10.7" = 1591 cu. inches, 124 pounds
The NiFe battery is more than 3 times the volume of the two T-105s for 10% less rated capacity.
I'm not passing any judgement, just doing the math so that people can decide for themselves.
Fair winds,
Eric
Marina del Rey, CA
-- Ubuntu10.04, Acer AspireOne, Virgin Mobile 3G Broadband2go. Doesn't get any better than this!
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