Jim Hawkins..............agree it takes 2 to make 12 volts........last batteries I installed weighed 124 lbs each and required 2 people. A 6v battery weighing 66 lb I can handle that myself.
Battery Sizing
- Thread starter sail sfbay
- Start date
Just to throw it out there our 12V group 31’s are 69 pounds each. So you could have 2 of those for about the same total aH and more redundancy than the 6V’s. 6V’s will probably do better and last longer in true deep cycle use, but for your 9 hour daysails you might not need that.
The other option is Lithium, in principle it is way better you can get by with 1/2 the ahr because you can discharge deeper without damage, they can sit in discharged condition without damage etc and so forth. The problem is to do it right is difficult and it looks like a lot of half baked solution are being sold hard.
With those plans, thinking of these batteries as transition batteries is a good approach. Two 6v GC batteries will give you about as much capacity as 2 Group 27s wired in parallel which should be more than adequate for the trip home. As transition batteries being cost effective would be a major consideration. Don't want to spend lots of money on something that is going to be replaced soon.
As for power consumption on the trip, one of the big draws was the AP, that can be controlled by doing some hand steering while sailing and when the AP is on, getting the sail trim right. The draw on the AP is mostly the motor, the less it runs the lower the energy consumption. Well trimmed sails will have a positive effect on energy conservation.
On an maiden voyage on a new boat, a BoatUS membership with unlimited towing might be a good investment.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,932
The 6v batteries in series gives you 12V power. The batteries are deep cycle.
You still only have 220 Ah. That means at 50% before you need recharge. So you have 110Ah to consume. The batteries weigh in at 60plus lbs.
[QUOTE="dlochner, post: 1664931, ......
On an maiden voyage on a new boat, a BoatUS membership with unlimited towing might be a good investment.
[/QUOTE]
Great advice!! I have BoatUS just for that purpose, if required. I also have a captain and a sailor friend with lots of experience driving a boat from the Stockton in the California delta to Emeryville in the San Francisco Bay.
On an maiden voyage on a new boat, a BoatUS membership with unlimited towing might be a good investment.
[/QUOTE]
Great advice!! I have BoatUS just for that purpose, if required. I also have a captain and a sailor friend with lots of experience driving a boat from the Stockton in the California delta to Emeryville in the San Francisco Bay.
Thank you for all the kind posts. Just purchased four (4) 6v Lifeline 220 Ah AGM batteries to replace the ten (10) 6v 6v lTrogan flooded batteries. Plan to install them before or no later than after the 100 nautical mile motoring trip next weekend from Stockton to Emeryville, California. Also plan to install a battery power consumption monitor and have my marine electrician inspect the system for adequacy. Hopefully, that the new batteries will be adequate for the power draw.
Step #1Install a battery monitor so you actually know what you are using.
Step #2 Choose a quality brand of AGM's but do not focus on 6V vs. 12V as that 6V cycle-life benefit is only in flooded batteries
Step #3 Ready your entire charging system for AGM batteries. This means all sources, solar, wind, alternator, charger or inverter charger are all temp compensated and at least one source can supply enough current to meet or come close to the minimum recommended charge rate.
Step #4 Read the May and August 2015 issues of Practical Sailor "Fighting Sulfation in AGM Batteries"
Considerations:
-The shallower you cycle your AGM batteries the longer the batteries will last.
- Because the Firefly AGM's can be cycled to 80% DoD, and resit sulfation quite well, you typically need one less battery so they are not at all as expensive as they may seem to be.
-If you choose Lifeline you will need to EQ more frequently than most assume. Good batteries but if you let them go too long between EQ cycles they won't last as you'd expect.
Step #2 Choose a quality brand of AGM's but do not focus on 6V vs. 12V as that 6V cycle-life benefit is only in flooded batteries
Step #3 Ready your entire charging system for AGM batteries. This means all sources, solar, wind, alternator, charger or inverter charger are all temp compensated and at least one source can supply enough current to meet or come close to the minimum recommended charge rate.
Step #4 Read the May and August 2015 issues of Practical Sailor "Fighting Sulfation in AGM Batteries"
Considerations:
-The shallower you cycle your AGM batteries the longer the batteries will last.
- Because the Firefly AGM's can be cycled to 80% DoD, and resit sulfation quite well, you typically need one less battery so they are not at all as expensive as they may seem to be.
-If you choose Lifeline you will need to EQ more frequently than most assume. Good batteries but if you let them go too long between EQ cycles they won't last as you'd expect.
There is no weight advantage to 6V batteries unless you are comparing to a 4D or 8D which is a form factor that is not necessary unless you have massive CAT, Cummins, Deere, MAN etc. engines. Lead acid batteries are best purchased by weight and design/cycle life.
For example:
Lifeline 4CT = 66 Pounds X 2 for 12V 220Ah = 132 Pounds
Usable Ah @ 50% DoD = 110Ah
110Ah / 132 Pounds = .83 Usable Ah Per Pound (Lifeline 8D = .82Ah per pound or just about identical to the two 4CT's)
Firefly G-31 = 74 Pounds X 2 for 12V 232Ah = 148 Pounds
Usable Ah @ 80% DoD = 185.6Ah
185.6Ah / 148 Pounds = 1.25Ah Per Pound (and more cycles than a Lifeline at 50% DoD)
Maine Sail..........OK........I just cancelled the order for 6v Lifelines and will take your advise under further consideration before I commit.