Battery Bank Sizes on Sail Boats

[Eder]

I'm cruising full time with house bank of 400ah's AGM. Main draw downs are our Keurig coffee maker,our toaster, breadmaker (fresh each morning), and wifeys hair dryer.

I have a 6kw Northern Lights gen to top up so power never is a problem.

[sailinglegend]

Originally Posted by Cheechako

Just keep in mind, even if you have a huge battery bank... sooner or later you are going to have to refill all those amps!

A larger service bank size also means it will be more efficient and accept more Ah more quickly from all charging sources during the boost phase up to 80%.

It takes a bit of very over-simplified maths to prove the point, but a 100 Ah battery that is discharged to 50% may accept 20Ah in the first hour during the boosts stage, maybe 10Ah in the second hour during the start of the less efficient absorption phase, and the remaining 20Ah in another 5 hour. Doubling the battery size to 200Ah, with the same charging source of 20 amps, will accept 10Ah into each battery in 1 hour, that’s 20Ah into the bank. In the second hours it will store another 20Ah. That’s 40Ah replaced in two hours, as compared to 30Ah with a single bank. In the 3rd hour it may still accept 20 amps into the bank because a single battery in the start of the absorption phase could accept 10 amps. That’s 60Ah in three hours.

The key point is that for two hours it is still in the more efficient boost stage where the battery is taking all the current the charge source can give it. Note that the initial boost charging stage has captured 40Ah in two hours and 60 Ah in three hours. With the smaller bank it could only capture 20Ah in the first hour during boost and 30Ah after the second hour during the start of absorption. The third hour may add another 5 amps. That’s 35Ah with one batteries and 60Ah with two batteries. So a bigger bank will be more efficient and accept more Ah more quickly from all charging sources.

Since a lot of the time with an engine or genset you are only charging up to the absorption stage which is about 80-85% then this increase in faster charge times is significant.

Just for the record we are 24/7 liveaboards in the Med with 1050 Ah AGMs, only 140 watts solar because we don't want another arch at the back for more solar panels. A Duogen 400 watt towing/wind gunny, 2 x 100 amp Balmar alternators - oh and a 280 amp FP DC genset. We run the genset once a week maybe.

We have all the goodies except a washing machine, and can run the 12000 BTU air on from the batteries via a 2.5 kva Victron inverter.

Lifeline AGMs now 10 years old.

[monte]

our power budget, battery and solar setup...

[barnakiel]

110 Ah (2x55),

Plain vanilla acid,

Daily load 10Ah sailing, 15Ah anchored,

Boat 26ft or thereabout.

Mode of use: crossing or else anchored.

The daily load as quoted above is our 'off the battery' (overnight) part only. We produce, and consume, more.

b.

[patja]

My house bank is 6 Dyno 6 volt batteries, 245 Ah each, for a 12 volt bank of 735 Ah. Dyno makes great batteries and are a very popular brand at Fisheries Supply, the go-to chandlery in the Pacific Northwest. Then I have an Optima red top starter battery charged by a Balmar Duo Charge.

Primary draw is the fridge with the 1984 vintage poorly insulated icebox. I estimate it consumes close to 100 Ah a day. I will go up to 3 nights on the hook with no charge. The 115 amp alternator on my Volvo D1-30 is a big help when it comes time to charge.

[Pete7]

Originally Posted by TeddyDiver

Maybe something like Surrette S530 6V 400 AH Wet Battery

How does one move a 53kg battery, other than carefully?

My 110 wet cells are heavy enough to man handle in and out of the dinghy and then into the battery boxes.

Pete

[HansSolo]

Originally Posted by Pete7

How does one move a 53kg battery, other than carefully?

My 110 wet cells are heavy enough to man handle in and out of the dinghy and then into the battery boxes.

Pete

Hay, they are lighter then the 8D's I removed (76kg). Getting them up the 12' ladder and on to the boat wasn't much trouble, but getting them in to their box required a little lateral thinking. In the end, a small block and tackle worked well.