Replacement battery suggestions?

[Oldrig]

After determining that my batteries are indeed dead as door nails (see my earlier thread), I've now got to buy a new pair of batteries.

When I bought Creme Brulee, she had a pair of sealed "maintenance-free" batteries. I don't remember the brand, but they held up for two seasons. Then, when a winter storm surge flooded the battery-storage shed at my boatyard, the yard replaced them with Exide Nautilus Gold G-24s.

Now that I have killed the Exides, I'm looking for suggestions on which type of deep-cycle batteries to buy.

Being more than a little lazy, I like the idea of "maintenance-free," but I'm always interested in what some of the really knowledgeable folks at SailFar have to say. I know there are lead-acid, gel and AGM batteries out there.

So, please, bombard me with suggestions.

And I promise never to hook my new batteries up to no-name trickle chargers that came from someplace in the mysterious Far East. :(

Thanks, guys,

--Joe

[Captain Smollett]

Type - Flooded, Gel or AGM - is going to be personal preference to a point.

When I replaced my two Flooded Group 27's, I went with two flooded 6 V batteries (in series).  Got more amp-hours per weight (about 30% more) for no additional room.

The Gel batts are more expensive but give the benefit of lower self-discharge rate and lower chance of a big mess in a knock-down, but have more stringent charging requirements.  I chose the cheaper option.

[Marc]

Go with TROJANS 6V wired in series, they may be spendy but worth every penny.

[marujo_sortudo]

I guess a consideration would be whether your on-board charging system is Gel or AGM friendly (AFAIK, all are Flooded friendly.)  A battery that plays well with your charging system is definitely preferable.  Fully charged AGM's are pretty happy to go all winter without any attention, as I understand it, though, I have been spending a good bit of time recharging mine after this last Maine winter, so who knows.  They seem to be taking the charge quite happily.

[tomwatt]

According to my local battery guy, Trojan also makes a large, gel battery.
Both my Jeeps have Optima gel batteries... one of them is over 5 years old and still going strong, including long periods of sitting unused for months at a time while maintaining its charge. Might be worth looking into.

[s/v Faith]

According to my local battery guy, Trojan also makes a large, gel battery.
Both my Jeeps have Optima gel batteries... one of them is over 5 years old and still going strong, including long periods of sitting unused for months at a time while maintaining its charge. Might be worth looking into.

Gel is good for a car, I am not sure that they translate so well to boat use.

They do self discharge at a lower rate, but you pay for that.

Solar panels like to make higher voltage then gel cells like (some charge controllers have a setting for Gel)...

Gel cells prefer their own charger, and charge controller... might keep that in mind.

Some folks have found a shorter life with gel cells aboard, but that is likely the result of the wrong charge voltage.

[Oldrig]

I guess a consideration would be whether your on-board charging system is Gel or AGM friendly.

My answer will display my ignorance of matters electrical.

Right now my "onboard charging system" consists of the original equipment: the engine's alternator and a three-way battery switch.

When I bought the boat, the PO, who was a boatyard employee and scrounger of old stuff, told me that he just kept the battery switch on "both" when he ran the engine or the batteries. I'm a bit more sophisticated, trying to use one battery only for starting and the other as a house battery--alternating daily.

It seemed to work: My batteries were always well balanced, according to to the built-in battery meter on the original-equipment electrical panel.

I don't know if the PO's batteries were gel or AGM--only that they were sealed.

--Joe

[Captain Smollett]

Right now my "onboard charging system" consists of the original equipment: the engine's alternator and a three-way battery switch.

The question to answer is the voltages of the charging steps your alternator is putting out.

It's my understanding that deep cycle batteries (as opposed to starting batteries like in a car) "prefer" a 3 step charge cycle; automobile alternators and a bunch of voltage regulators use a 2 step cycle.

More importantly, though, are the voltages delivered at each step of the cycle.  This is where gel batts have a different requirement than flooded batteries.

Perhaps you can use google to find out what your model alternator/voltage regulator is doing.  That will answer your present charging characteristics.

But, even if you know this, it only applies when your engine is running since that's the only charging you presently have...sorry to state the obvious, but it's important stuff to keep in mind if you add charging later in the form of solar panels (even ones just to maintain the batts while the boat is not in use like you mentioned in the other thread), a wind gen or other.

The voltage regulation during charging is important for battery longevity.  To my mind, this is another reason to go with the simpler, cheaper flooded batteries - they are more forgiving (at least they seem so to me).  Higher end charge controllers and chargers allow you to set the. voltage set points (or have them pre-programmed for various battery types and use types).

Nigel Calder's book is a good read; perhaps you can find it at the library if you don't have a copy.  Lots of good stuff there to help design an electrical system and make the components last.

[phil416]

      Plenty of good advice here.  One additional thought for those headed off shore.  Away from the major yachting centers ( America, Canada England) exotic batteries (agm gel) can be astronomically expensive to replace.  As for myself the 6v golf cart batteries are the only way to go.   Phil

[Oldrig]

Update:

I replaced my dead batteries with a pair of Group 24 Lead Acid batteries made by US Battery. When I switched 'em out, they looked identical to the so-called marine batteries that the yard had given me five years earlier.

I took this route because the batteries were much cheaper than more exotic types, and because I got five good years out of the previous batteries. It's my understanding that keeping lead-acid batteries fully charged can be a challenge, but I plan to buy a reputable "smart" charger and take them off the boat every year. Presumably that will keep them running well.

--Joe

[CharlieJ]

Laura and I went back to a single Grp 27 100 amp bat. Marine deep cycle. Our 32'watt panel gives us all the juice we need.

Of course, we are MUCH more frugal with electricity than most.  ;D

[Captain Smollett]

they looked identical to the so-called marine batteries that the yard had given me five years earlier.

Hmmm.  Just because the LOOKED identical, does not mean they ARE identical.  It's the internals that matter, not the case or packaging.

A better metric is the weight.  Within a given form factor, heavier batteries are better for deep cycle use.  If both old and new are Group 24 and the new ones are significantly lighter than the old ones, I'd be weary.  YMMV.

It's my understanding that keeping lead-acid batteries fully charged can be a challenge,

Not really a 'challenge.' Just don't leave them 'alone' for extended periods...always on a charger with proper voltages.  The problem with flooded cell batteries is self discharge rate, so if they are left completely disconnected, they discharge.

With ANY lead acid battery, depth of discharge lessens life.  If you discharge to 'parade rest,' you may only get a few discharge/charge cycles.  If you keep topped off (say always 90-ish% or more), they'll last a LONG time...or can.

Another thing often overlooked is discharge RATE.  Even if you are just pulling down to say 70%, but are doing that with BIG loads for short periods, that application is better served by a starting battery.  Different jobs, different tools.

What is overlooked about this is the so-called Peukert Effect...the available capacity is dependent on discharge rate.  A 100 amp-hr battery does not have 100 amp-hours available if the load is "too high." "Too high" is defined as "higher than the test load."  Most test loads are 5 amps, but I understand this can vary.

Soooooo, if you are consistently drawing greater than about 5 amps off your battery, you will NOT get 100 amp-hours out of it.  This factors into your "how much am I discharging" parameter.  Say you set up your charging system to keep your batts at or above 50%...based on PUBLISHED capacity.  If your continuous load is over the test amperage (for that manufacturer), you may really be drawing down to 40% or 30% or even worse.  Capacity decreases as the discharge current to the 1.3 power, so it's a bit worse that "inversely proportional."  The farther you get from the test current, the more dramatic the Peukert Effect is going to be.

What this means for 'cheaper' batteries is that they can easily fudge the capacity number on the label by lowering the test load.  It's not standard, and it's not stated like "100 amp hours at 5 amps."  USUALLY, it's 5 amps; not always.

Another wrench in the works is temperature...increase the temp, lower the capacity.  How much wiggle room on temperature do you have if that battery is a hot engine compartment, for example?

It's easy for a cheaper battery to appear "just as good" from the label by fudging with the test conditions just a bit.

Probably most folks just buy a 'whatever,' stick in the slot, wire it up and go with it.  And probably most don't really ever have any trouble.  But then again, most boats seem to never leave the dock, too, huh?  Quality is measured differently at the marina than 1000 miles from 'home.'  Sorry if that sounds preachy...

Understanding this stuff is important if longevity and reliability is important.  Not all batteries are created equal, and not all are best suited for a particular application.  I sorta cringe when I see some of the batteries that go on boats here...but then again, they are the ones generally NOT leaving the dock.  And, they seem to be the same boats with external structures made of AB plywood and pine 2x4's from Lowes.  Oh well.

Not saying that's you or the batts you bought...just making a general statement/observation.

Presumably that will keep them running well.

--Joe

Should do.  Keep 'em charged whether on the boat or off and they will last a WHOLE HEAP longer than if allowed to discharge.  While in use, recharge as often as is practicable...again, keeping them "up" as close to full charge as possible, and limit discharge rates when you can.  That's what makes good batteries last and worth the investment.

My two cents.

[Mario G]

When we installed the new soler panel I figured a new set of house batteries were in order also, so we bought 2 type 31 Deka gel's. Power has not been a problem and we have yet to hook to shore power since.

[JWalker]

another +1 for two 6 volt golf cart batteries
8)

[maxiSwede]

That's a very good post re. battieries Cap'n Smollett!

[Oldrig]

That's a very good post re. battieries Cap'n Smollett!

It certainly is.

I think that one improvement I should make is to replace the almost useless battery "meter" that is original equipment on my electrical panel (circa 1982) with a real battery monitor. Either that, or I'll have to make it a routine to crawl into the depths of the battery compartment with my trusty multimeter, so I know what's really going on with the batteries.

Somebody, either Smollett or somebody on the Cape Dory board, warned me that using the alternator to charge my batteries will never get them back to full charge.

So, at the very least, I will have to get a good quality, "smart" charger to keep up the batteries when they're off the boat. (I don't have shore power access.)

Anyway, that's the plan.

--Joe

[Auspicious]

Most test loads are 5 amps, but I understand this can vary.

Are you sure? I thought it was usually 20A. I did some Googling and I see 100, 20, and 8 amp ratings but mostly 20.

Either that, or I'll have to make it a routine to crawl into the depths of the battery compartment with my trusty multimeter, so I know what's really going on with the batteries.

... and a hydrometer. Log your numbers.

[Captain Smollett]

Usually, it is the current the batt can deliver for 20 hours. That's what I've been told and what I have read. For my example of 100 amp hr, that would be 5 amps. Lots of group 27's I spec'd when buying batts were only around 70 amp hr...or test current less than 4 amps if the 20 hour thing is the test.

Pretty sure most consumer grade group 24 and 27's are gonna fry pretty quick at consistent 20 amp draws.

Bottom line...ya get what ya pay sometimes applies. I think it does with batteries.

[Auspicious]