What size and type batteries do I need for a crossing.

[sebathon]

Hi,

Just in the process of upgrading electrics onboard a 40’ cruiser for a planned Atlantic crossing this year and not really sure on the total capacity or type needed for this.Currently have 280Ah ( 2x 140) lead acid cells and it’s never really capable of running the AP for anything longer then an hour or so.

My usage is mainly autopilot between 2 and 8 amps depending on weather, fridge usually 7amps and some basic instruments and lights and device charging.

Have installed silentwind 400w and 440w solar which has helped a little but I’m concerned to total Ah storage is not sufficient.

If anyone’s does a similar trip and knows what’s works well or doesn’t, advice would be much appreciated.

[Nelsons]

I would add some batteries. Keep in mind that you can use on 50 % max of you batteries and 140 Ah seems not to be really comfortable.

[Nelsons]

...pushed sent button too quick :-)

I had 640 Ah AGM, Generator and Solar on my Atlantic crossing

[Auspicious]

You're going to get a lot of opinions. Here is mine.

I still like wet lead acid golf cart batteries (6V) in series-parallel for Ah/$/year of service life. 675 Ah is a good capacity for general cruising. 900 Ah is nicer yet.

[Pete7]

Originally Posted by sam_hawk

Currently have 280Ah ( 2x 140) lead acid cells and it’s never really capable of running the AP for anything longer then an hour or so.

My usage is mainly autopilot between 2 and 8 amps depending on weather, fridge usually 7amps and some basic instruments and lights and device charging.

How old are the existing batteries? because this doesn't sound good.

Pete

[sebathon]

Originally Posted by Auspicious

You're going to get a lot of opinions. Here is mine.

I still like wet lead acid golf cart batteries (6V) in series-parallel for Ah/$/year of service life. 675 Ah is a good capacity for general cruising. 900 Ah is nicer yet.

So a lot of small ones hooked up series-parallel. Is there other Benefit to this other then cost?

[sebathon]

Originally Posted by Pete7

How old are the existing batteries? because this doesn't sound good.



Pete

They are 2.5 years old living onboard in Norway. Probably been mistreated on few occasions through some learning processes.

[sebathon]

Originally Posted by Nelsons

...pushed sent button too quick :-)

I had 640 Ah AGM, Generator and Solar on my Atlantic crossing

Ok would you say AGM is a good move compared to my lead acid? I can only have room for 2 x 220 Ah AGM if I took that option. Would this be suitable?

[cal40john]

Originally Posted by sam_hawk

Hi,

Just in the process of upgrading electrics onboard a 40’ cruiser for a planned Atlantic crossing this year and not really sure on the total capacity or type needed for this.Currently have 280Ah ( 2x 140) lead acid cells and it’s never really capable of running the AP for anything longer then an hour or so.

My usage is mainly autopilot between 2 and 8 amps depending on weather, fridge usually 7amps and some basic instruments and lights and device charging.

Have installed silentwind 400w and 440w solar which has helped a little but I’m concerned to total Ah storage is not sufficient.

If anyone’s does a similar trip and knows what’s works well or doesn’t, advice would be much appreciated.

You're saying you have 15 amps of load, let's bump to 20 amps times 2 hours is 40 amp-hrs. Drawing down the batteries to 50% you theoretically have 140 amp-hrs usable, and close to double that before things stop working. Either you are using a lot more electricity than you think or your batteries are significantly damaged.

Also to make sure, are your two batteries 6 volt in series? If so then you actually only have 140 amp-hrs total.

[Auspicious]

Originally Posted by sam_hawk

So a lot of small ones hooked up series-parallel. Is there other Benefit to this other then cost?

Cost - lots of Ah (usually 225 each) for the money.
Service life - with good care you can get eight years out of a set.
Weight - a human being can shift them around without hurting yourself.


Also more options for physical arrangement. More options to respond to failures.



If you are really weight sensitive lithiums are attractive. That choice ripples through your charging system. If you have to mount batteries on their side lithium or AGM become attractive. Both are fussy in other ways.

[Pete7]

Recent survey of CF members gives some idea of what the most popular batteries are:

http://www.cruisersforum.com/forums/...-a-221512.html

[Flod]

I Would go for lifepo4. They are a game changer in my mind. Look at this for example: https://www.ev-power.eu/Winston-12V-...ing.html?cur=1

I installed this in June and couldn’t be happier. There are also several knowledgeable Norwegian companies in the rv market that build “drop ins”

[john61ct]

Originally Posted by sam_hawk

Ok would you say AGM is a good move compared to my lead acid?

Good quality FLA will be better value, last longer than AGM.

Either way need to learn how to care for them to get good longevity.

6V GC type - T-105 Trojans are the classic, Rolls / Surrette better but pricey.

LFP is much more so, require precise infrastrucure and knowledge to care for, but can fit lots more Ah in a given space.

IMO better to expand the space available as needed.

[sebathon]

Thanks for the info all.

As I’m after sealed and something I can have sent to the boat in Europe I’m looking at either 2 x Mastervolt AGM 225ah or 2 x Varta AGM 210ah.

Is there any issues with either? Or has anyone had experience with there for house banks?

[Pete7]

Originally Posted by Flod

I Would go for lifepo4. They are a game changer in my mind. Look at this for example: https://www.ev-power.eu/Winston-12V-...ing.html?cur=1

I installed this in June and couldn’t be happier. There are also several knowledgeable Norwegian companies in the rv market that build “drop ins”

Really? are you sure given the information above like "crossing the Atlantic this year" and "probably been mistreated on few occasions"

Wouldn't it be safer to recommend another battery chemistry rather than risk a major failure in 2 months time, mid Atlantic with no power for the auto pilot?

Pete