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

[maine50]

I did a west to east crossing (New England to azores) and return via Maderia, Antiqua (east to west) 2 yrs ago. I had 4 Trojan 105's (new) plus starting battery. I had 250 w of solar, 100 a alternator. I monitored my system daily,
mostly by voltage and amps being consumed. (not SOC). At 1 point it seamed I wasn't getting proper charging from solar and determined upon investigation 1 panel had suspect connection. Fixed and all was better. Electrical knowledge
is very important on crossing as everything except the sails depends on it.
I know someone who crossed this year and found that 800w of solar and lots of battery wasn't enough cause he had a freezer and it wasn't very sunny. Of course were all parts of his system working properly- who knows.

[john61ct]

3 in parallel is fine, 2 at higher Ah would be better, 2V cells come in big capacities *6 in series makes 12V, if needed parallel first then series, rather than prallelling strings.

Or 2*6V 4*3V, 3*4V etc can work to, but fewer paralleled the better.

Yes stick to sealed if under your bunk (!)

GEL can be made to last very long but more finicky about care protocol, lower volts and current, AGM is more mainstream.

You don't want to pay extra delivery fees

Call recommended good makers like Odyssey and ask for dealers local to where the boat is.

[skipmac]

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.

I have the same setup, 6 x 6V flooded lead acid batteries (FLAs) so a total of about 650 smp hours. With one 240W solar panel that was enough to run AP, fridge, lights, stereo and full electronics for four days before needing to run the engine.


Plain old FLA batteries are definitely the most bang for the buck and the least finicky and most tolerant of abuse.

[john61ct]

yes but he sleeps over the battery box

some may be fine with that, I'd give it a go, rig a fan if needed

but most not

[waterman46]

Originally Posted by ramblinrod

First, it is impossible to advise with any degree of certainty without knowing the system and user needs.

I understand you are crossing the Atlantic soon, but then what?

For example, how long will you own the boat? If a solution consideration has a long pay back, it may be a poor investment, if you sell the boat before it is realized. (Remember that average person owns their "this will be my forever boat" for about 6 years, and then they move up, move down, or move out of sailing.

If you plan to daysail from a marina, the answer is way different than if you plan to live-aboard on the hook.

Anyway, as a general rule of thumb without knowing details, the following should be decent...

Battery Technology:

A) If boat is most often on shore power, and batteries are located in ventilated, unoccupied space, choose standard lead acid batteries.

B) If boat is most often on shore power, and batteries are located in non-ventilated, occupied space, choose a sealed battery technology.

C) If boat is most often off-grid, and you are not sure how long you will own it before changing boats, go with a low purchase priced solution, of A or B.

D) If boat is most often off-grid, and you "know" you will own it at least 4 years, go with a premium-priced solution of A or B.

E) If boat is mostly off-grid, and you "know" you will own it for 7 years or more, consider LFP.

F) If money is no object, do whatever you wish.

Capacity:

Again this is best determined by needs and energy analysis of the particular case, but for a typical cruising boat your size, with the loads you have described, living aboard and rarely connected to shore power, I normally recommend...

For every 1 A-hr of anticipated daily consumption (at anchor)...

1. 3 to 4 A-hrs of house bank.
2. 3 to 4 Watts of alternative energy power generation.
3. 0.5 to 1A of alternator capacity.
4. 0.4 to 0.6 A of shore power charger.

Example: 40 ft boat, having a BD-35 compressor on a normally insulated ice box, with typical complement of vessel systems, instruments, and mobile charging needs.

Being reasonably energy conservative, at anchor, you will likely consume about 100 A-hrs/day.

Then I recommend:

1. 300 to 400 A-hrs of battery capacity (technology doesn't really matter).
2. 300 to 400 W of solar. You could choose all solar, if you hate noise and mechanical device maintenance/repair. If you do wish to have a wind generator, ensure at least 50% of the need is met by solar.
3. 50 to 100 A alternator.
4. 40 to 60 A shore power charger.

If you have higher than "typical" daily energy consumption needs, you will need to step up everything in ratio.

If your consumption is so high the battery capacity at this ratio becomes untenable, you will likely need a generator.

Actually the OP is more interested in capacity underway, not at anchor, for his Atlantic crossing. So we have to add generating capacity for the autopilot, probably 2A x 24H so another 48AH.

I believe this 100AH consumption estimate, without autopilot, for some hypothetical boat would be if you don't have a freezer, only a reefer at about 5deg C. For a small freezer in the tropics, add another 60AH. Ours runs 28A for about 2 hours a day.

On passage we barely got by with 400AH battery, freezer and reefer, generator running 2H twice per day or engine several hours if not more, and autopilot full time. Got 2x75W solar panels, and I am not too interested in adding more as I don't get appreciable help from them. I added 400AH battery, now want to increase my 12V charging current from the AC generator as it is 100A max while the 800AH 50% discharged bank should take 200A for about the half hour anyway.

You can't have too much!

[seandepagnier]

how does autopilot use 2-7 amps? What kind of autopilot?

My autopilot consumes 0.1 to 0.5 amps most of the time on my boat and this is using a lead screw arrangement which is much less efficient than a ball screw.

My friend has a boat which is 22,000 pounds:
"... broad reach (150-160 degrees) with everything up in 13-15 kts true and the autopilot is steering well. currently averaging 13 watts."

This is 1 amp at 13 volts. This is using a hydraulic pump for the autopilot. The pump pulls 12 amps when running but most of the time it is not running. hydraulic pumps are about half as efficient as a mechanical ball screw arrangement.

In rougher conditions above 20 knots I would generally have switched to the wind vane especially if power is a concern.

[Mike Banks]

Carbon type lead acid.

Autopilots draw about 15 amps on full load, which in rough weather happens every few seconds for a second or two. In such a situation you need a wind generator to back them up. Under normal conditions, solar will be fine--but you may find that a wind vane would be OK too. I never had any trouble with my TMQ Autopilot, it was hydraulic, operated on GPS or its own fluxgate compass and was always able to function effectively without being overloaded regardless of weather--but in rough conditions it worked a lot and I sometimes started the engine to recharge my batteries because at the time I did not carry a small gen-set aboard, a situation I remedied shortly afterwards..

[conachair]

Originally Posted by sam_hawk

Yes the boat is currently in Portugal but started the trip in Norway. So we are looking for somewhere to order the chosen batteries that offers affordable delivery to Algarve.
]

One option is to buy from a uk supplier and have them delivered to Algarve express in the UK who run a truck down once a week then pick them up from just outside Faro. If you time it right you can get a hire car fron faro airport for next to nothing. Outside summer anyway.
https://www.algarveexpress.com/

[sebathon]

Originally Posted by boat_alexandra

how does autopilot use 2-7 amps? What kind of autopilot?

My autopilot consumes 0.1 to 0.5 amps most of the time on my boat and this is using a lead screw arrangement which is much less efficient than a ball screw.

My friend has a boat which is 22,000 pounds:
"... broad reach (150-160 degrees) with everything up in 13-15 kts true and the autopilot is steering well. currently averaging 13 watts."

This is 1 amp at 13 volts. This is using a hydraulic pump for the autopilot. The pump pulls 12 amps when running but most of the time it is not running. hydraulic pumps are about half as efficient as a mechanical ball screw arrangement.

In rougher conditions above 20 knots I would generally have switched to the wind vane especially if power is a concern.

That’s just what it uses mate.

Yeah on good days with no following swell it’s around 2amps when the rudders is under movement.

Depending on how the boats handling the amps go up with the more force required to turn the rudder. It makes sense to me.

It’s just a standard raymarine AP computer and a large hydraulic mechanism with pump unit.

I’ve never seen boats use much less but this may have to do with the hull shape and handling of this type of boat. Pretty heading sensitive during fast downwind days.

But that’s what I have and it’s no problem but the storage of batteries seems to be an issue.

[sebathon]

Originally Posted by TrentePieds

Sam Hawk:

Start with the easy bit first: AFAIK there are really only two BRANDS of batteries available in Norway: Exide and Odyssey. These days when goods from one manufacturer are sold under divers labels, there is no way for me to know who makes each of these brands. The place to go to find out is:

https://www.gylling.no/batterier.php?do=view&id=17

Your boat is in Portugal, you say. I dare say that the supply situation in Portugal is much the same as in Norway. I think you should be able to do your "homework" in Norway and defer the purchase of anything you may need until you get to Portugal.

It sounds to me as if your existing batteries have come to the end of their anticipated service life. Quite apart from that, since I consider batteries "consumables", if I were setting out across the Atlantic I'd just bite the bullet and replace the existing batteries with new ones. Even for longish cruises I see no need for anything other than QUALITY flooded L/As which are still, I'm sure, the most cost effective, and the most easily handled. PROVIDED your physical battery installation is secure so the batteries cannot be flung about in a seaway, "floodeds" do not become a hazard due to the boats motion even in very heavy weather. Potential hazards emanate from shoddy electrics, but I'm sure you'll see to any such deficiencies before you set out.

You have not said what your destination is, but I assume that you intend to terminate somewhere in the Caribbean perhaps touching in the Azores and the Bahamas to re-provision. I mention that because you mentioned refrigeration. Why impose such a heavy draw on your necessarily limited battery capacity? I don't know that you are a Norseman, but if you are, you'll be perfectly aware that your forebears (and mine) undertook voyages of longer duration than the one you intend many centuries before refrigeration was invented. Careful attention to provisioning will permit you to cross the Pond with the refrigerator turned OFF for your batteries sake. Once you are in the Caribbean your can always turn it on again.

If your only draws while on passage are navigation and interior lights when required, and those lights are LED lights, you will, I believe, save yourself a lot of aggravation. Construct an "energy budget" defining both the energy consumed by your essential electrical devices, and the energy produced by your means of battery charging. Should you come up short on the charging side after having eliminated all "luxury" draws, you might consider a suitable "stand alone" generator rather than more "sophisticated" batteries, since a generator acknowledges that batteries are only a buffer, not a producer of juice. In a forty-footer you presumably have an engine of 35 or 40 horsepower, fitted with an alternator of 60 or 80 amps. Such an alternator is alright for replacing juice used to start the propulsion engine, but I would not rely on it to replace juice used in housekeeping because the engine is so grossly out of proportion the alternator, and you don't want to run the propulsion engine for hours and hours just to be able to read after dark, let alone to be able to keep your beer cold.

Anyway, you may find a look at the Gylling site and a chat with the Gylling people very beneficial.

Best regards

TrentePieds








.

Hey,


So destination is really NZ, going via the Carib and plan to continue along as far as we can.

Will be buying from Portugal and have now found a few places I. Spain that will deliver easily.

I’m really trying to a avoid FLA due to being under my bunk. So will 3 or 4 gel work?

Currently have a 40a changer but I don’t think it has options for Gel. With 440ah gel what charger options/sizes would be suitable ?

My alternator is 90amp and have 400wind 400solar

Thanks again

[Pete7]

The boat has a wind vane, so unlikely to need the auto pilot.

Batteries under the berth as they are now, is very common including ours. If a concern you could always drill some holes in the side.

Originally Posted by sam_hawk

Currently have a 40a charger but I don’t think it has options for Gel. With 440ah gel what charger options/sizes would be suitable ?

What make and model charger?, oh and is this the solar controller or mains driven charger? Does the Wind go through the solar controller or separate controller. They will all need to be adjusted.

What is the highest alternator voltage you see?



Pete

[john61ct]

The paralleling question already addressed, one string of paralleled 2V cells would be much better than 4 strings at 12V.

But yes, harder to find maybe more expensive, many owners just make do.

For 4-500Ah, a 60-80A shore charger with

user-custom adjustable setpoints, both voltage and Absorb hold time is best.

Ideally the stop-charge point (drop to Float) keyed off the current taper hitting an endAmps setpoint measured by a BM or shunt at the bank.

[NYSail]

Originally Posted by sam_hawk

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

6 V batteries like the Trojan T105 or T1 25 or true deep cell batteries. You will get your best performance from these

[GILow]

Not sure if it has been mentioned, but AGM's are not really great for this sort of serious off-grid work unless they can be regularly brought back up to 100% full charge.

I think, given the OP does not have a lot of time to get the charging setup perfect, that standard FLAs will be a safer bet, with a bit of time spent improving the ventilation under the bed.

[TrentePieds]

Sam Hawk:

Let me compliment you on your neat and tidy installation :-)* The space you have is indeed very little — really no more than I have in a 30 footer devoted to local, coastwise cruising — so I am confirmed in my opinion that you need to lay a strict energy budget, eliminating all consumption that is not absolutely essential for the actual ocean crossing. That may mean eliminating the AP in favour of a vane :-)!

John61ct in #34 above sez he'd be okay with having FLAs under his berth. So would I. And here is why: EXCEPT for the possibility of “gassing” endangering you while you are in the berth, there is NO reason FLAs shouldn't be there as distinct from any other place in the boat.

So consider gassing: AGM and “gels” are S'POSED not to gas. But is it really true? Well, “sort of”, I think, but this advantage is achieved at the cost of a trickier charging regime, and in the case of “gels” the possibility of a “thermal runaway”. J61ct knows far more about that than I do, so let him chime in :-)

But if you stick with FLAs there are, as I understand it, three things to consider: 1) Spillage arising from the boats motion. 2) Hydrogen “gassing” arising from ANY charging at all, at any time, due to electrolysis of the water that dilutes the sulfuric acid electrolyte. 3) Hydrogen Sulfide (H2S) gassing arising from charging at too high a voltage. Considering each in turn:

1) I wouldn't think that spillage would be much of a danger at all, because the caps on modern FLAs are really very secure, and even in heavy weather you are not likely to be rolling enuff to cause spillage through the caps.* I also think there is benefit in having access to the electrolyte for monitoring and maintenamce of the batteries. ABYC guidelines say that the battery enclosure has to be lined with a material impervious to battery acid.* I do not see in your picture that such a lining is in place. It can be made by simply lining the compartment with fiberglass. Unless my eyes deceive me, there are no mechanical “hold-downs” for your batteries. Solid mechanical hold-downs are an absolute essential for every kind of battery aboard a boat. Having batteries sit loose in a box is asking for trouble. Loose batteries make BIG effective hammers!

2) Due to the inevitable electrolysis of the water in the electrolyte that is always the consequence of charging a FLA battery, hydrogen is developed and WILL escape from the box. Hydrogen gas is flammable, explosive, and lighter than air. It is therefore good practice to provide venting to take it overboard, although often that detail is neglected.* As hydrogen is lighter than air it WILL rise out of a compartment such as yours and settle under the deckhead unless a dedicated vent is provided. One of our experienced people suggested drilling vent holes in the box to ensure precisely this :-)! Normal ventilation practices will keep the amount of hydrogen below the critical concentration at which, in combination with atmospheric air, it becomes flamable/explosive.* While I'm not denying that a hydrogen explosion is possible, I have never heard of one occurring. Even so, a vent through which it can rise and go overboard is good practice even if that vent is only the companionway hatch.

3) Hydrogen sulphide smells like rotten eggs and it is heavier than air. If it escapes your battery box it will settle in the bilge and lie in wait to give you a nasty surprise. It is poisonous, flammable and explosive. “Off gassing” of this majorly dangerous gas occurs when a FLA batt is charged at too high a voltage, i.e. if it is “done in a hurry” by attempting to “force the pace” to recover from heavier use than the installation can support. The probability that new/well maintained batteries will generate H2O is very, very low PROVIDED the charging rate is kept within bounds. The normal “sniffer vigilance” one maintains aboard will warn you if there is any H2S about.

So all-in-all I see no need for anything more “scientific” than FLAs used on the basis of a sensible power budget. I think also that AGM and Gel type batteries were halfway houses with very little merit in a well maintained boat. The new style ion chemistry has its own problems, and at this time I consider the use of these sorts of batteries a “hobby within a hobby”. Nothing wrong with that at all, but as I understand your plans, and as others have said, I would think you wouldn't do yourself any favours by trying to get up to speed on monitoring and maintenance of these sorts of batteries. I gather that their maintenance is both finicky and exacting. You probably have more important things to do in preparation for your Atlantic crossing. Such as reducing your power usage to the barest of minimums :-)!

In respect of the power budget, I would think that depending on the conditions obtaining, and therefore on how hard it has to work, an AP might require anywhere from 20 to 100 A-hrs in 24 hours, so consider that carefully! And while you are at it, give careful consideration to what Ramblingrod had to say in #19 above.

Once again, all the best,

TrentePieds