Battery group 24? 27? deep cell?

[Matt19020]

I have a 2007 "M" with a 70 HP and I will be putting new batteries in come spring time.
My typical sail is about 6 hours with the following always on:
radio (AM/FM)
GPS
wind knotmeter
Transducer/Depthmeter
VHF

There is typically no motoring once I clear the marina until the 6 Hour mark....
The last 2 times out I found myself needing to go to the battery switch and switch over to my starting battery to kick the motor on...
Normally I could just do the six hours and it will still start on the #2 battery but as I can see this battery is getting tired
secondly I want to match the batteries ....either 2 deep cells or 2 conventional

To the members with more expierience then myself what do you reccomend? Deep? Conventional? Group 24? or Group 27?

[tangentair]

24 if you are going to mount it next to the current battery under the stairs, 27 if you are going to put it under the sink, a deep cell weather it matches the current battery or not, add a shore side marine battery charger with two seperate charging cords, with a long enough extension cord to reach a power source at home or at the pier, charge both after each extended use with the battery switch to off. Easy, relatively cheap, and simple - for more complex solutions e=search the archives - this has been hashed and rehashed many times.

[Hardcrab]

What tangentair said plus:
If money is no object, the the blue top or yellow top Optima batteries have alot going for them. They are expensive in the short term, but their long life can make the price come down over time. I especially like the "mount in any position" feature due to it's AGM construction. They wIll not leak acid even if mounted upside down.

WalMart has some good deals on normal wet cell marine "dual use" batteries if a tighter budget is required.

I would offer that the batteries can be charged in the "Both" position. Not a problem if one battery is more discharged than the other. Once the switch has been placed to "Both", the higher battery will just bring up the lower battery until they are equal voltage. The charger will simply see a twelve cell series-parallel load, and will proceed as normal.

As for your 2007 battery being "tired" already, that sounds somewhat early, IMHO.
Have you pulled and checked terminal connections for corrosion and tightness?
Water levels?
A good bout with a higher quality recharger?
The better chargers have a "equalization" feature that really gets wet cell batteries up to snuff by raising the voltage during the charge cycle. Usually done once a month for best results.

Any of these things could be the source of the weak performance you have seen before it's time.

[March]

Hold on. In my book, the Optima batteries have become highly suspect. I got myself two yellow tops last year, based on the same rationale Hardcrab is quoting above> It seemed like a good idea at the time but now I am beginning to reconsider.

After only one summer, my electrical system that used to be pretty well balanced, is out of kilter. I am debugging it step by step--so I cannot present a full report yet. However: some preliminary findigs suggest that Optima/Gel batteries tend to create "pockets" of gas that compromise their ability to hold electrical current. It also seems like they need to be constantly trickle-charged at less than 1 Amp) very slowly (meaning, both during the day AND during the nigh, which obviates the use of a solar panel tha works only half the time) or else they will lose the above-mentioned ability. That doesn't make any sense to me, since the Optimas are advertised as "deep cycles" A deep cycle battery must be recharged as quickly as possible after it gets completrely drained, I would say.

Apparently, that is not the case.

My system was MUCH more stable with a regular engine battery from WalMart and a deep cycle, bigger house battery, than with two yellow topped Optimas that cost 3 times as much.

I'll keep you updated and report the findings. For the time being, the Optima battery is at the dealer's who is trying to top it off--since it no longer retains its full charge. I am curious how he will test its capability to be recharged fully, OTHER than by slow, continuous trickle-charge

[c130king]

Matt,

It is normally recommended to do a search. If you search on "battery" you come up with 879 threads...so then I typed in "wet cell" and the list was narrowed to 38 threads...a number that is easier to manage.

Two that stand out as answering some of your questions:

Battery Choices (House vs. Start)

and

Change Both Batteries or Only One?

Personally, I am going to get 2 x Group 24 Wet Cell Deep Cycles [approx 75ah] (both the same)...unless I can determine for sure that 2 x Group 27 will fit in the battery box without any modification. Wet cells are cheaper...and I am cheap. And then I will use the alternating day theory similar to what some (FrankC comes to mind) recommend. I agree that we don't really need a dedicated start battery.

But of course I carry a jump-start battery every time I go out. My power useage is very similar to what you describe so I really don't need any more than this.

Lots of info.

Good Luck,
Jim

[Frank C]

The above story about the failed Optima has one interesting aspect ... that battery was used constantly while it's brother was reserved solely for the engine. The Engine battery never gets much exercise, while the House battery gets repeatedly consumed, and finally just worn out.

The real reason for switching to identical batteries (if possible) is to better manage their life-cycles by alternating them.
Each battery can be drawn down, then recharged and rested. Batteries also like to be drawn down by at least one-third before recharging. So, you can leave yesterday's battery recharging on alternator or Honda genset ... while intentionally pulling today's House battery down by 20 to 40 percent.

Tomorrow, let the alternator recharge it, while the reserve battery services the House loads. It obviously means you want to be using some recharging capability every day, but my weekend jaunts fill that need without a problem. With the Gp-29s, either battery can serve my House needs for two days. I always carry a power-pack battery too.

See more discussion on the subject of Alternating Batteries...

search terms: Alternate, odd even

[Hardcrab]

March,
thanks for the info. Many, many more in service do not show that issue.
Perhaps a lemon?
I'll stay tuned.

c130king,
I went to the link you provided about charging batteries in single or dual fashion.
Batteries and chargers are presented as having much more human-like intelligence than possible.

A higher charged battery placed in parallel with a lower charged battery can not and will not remain as two seperate batteries with indivdual preferences.
It now becomes one battery, just mechanically located in two cases.
They will equalize.
The low takes from the high until they are equal.
The majority of this transfer can happen pretty fast. The rest takes longer.

Many, many boat systems use multiple batteries in parallel to keep voltage constant, but to add amperage.
Bigger boats can use mulitple 8 battery banks.
All of those batteries have become one big battery located in many small boxes.
They are all equalized to each other.
These systems do not charge the batteries indivdually, but all at once.

The "Both" position in a two battery set-up is very much the same.

Chargers can not and do not determine how much current the battery "wants".
It can only limit it to a specific amount no matter what the battery wants.
(eg., 2A trickle charger is current limited to a max of 2A )
The battery tells the charger how much current it is going to take,if it's available.(one battery or more)

It does this by seeing the voltage level of the charger.

The higher the voltage at the charger, as compared to the voltage level of the battery, the more current the battery "takes" (one battery or more)
As the voltage of the battery come closer to the voltage of the charger, the current it "takes" decreases. (one battery or more)
This continues until the charger and battery have equalized at the same voltage. (one battery or more)
At this time the battery is fully charged.(one battery or more)

Lead Acid Batteries are recharged with a constant voltage, variable current charging "model". (one battery or more)

(Nicads use a constant current, variable voltage model, not that this matters for this discussion.)

[Matt19020]

More details on my battery and set up:

Battery location is under stairs

The batteries were actually late 2006 even though the boat is a 2007 I picked up 11/06 (this still may not explain the weak battery but may help in diagnosis)

They are on a switch as follows:
_______OFF
_____ 1------2
______ Both

The charger I have is http://www.marinco.com/product/20-amp-d ... ng-charger Guest dual charger 20 Amp

Battery 1 is the factory wet cell

Battery 2 is a gel cell smaller then the factory battery (I do not recall size) maybe 100 amp hrs?? or not...

no other battery monitoring other then a paneltronics battery test guage

1 shore power hookup to the charger


Tangentair- I have the 2 cord setup as suggested

Hardcrab- My charger is wired directly to the batteries not the switch and they are corrosion free....I would prabably opt to replace batteries every 2-3 years instead of the Optima batteries you suggest mainly because I believe the newer the better (this may not make sense but it makes me sleep better at night)

Jim- I believe in a Start battery ....Again.....it makes me sleep better at night! but I think I am on the same page as you ....
{going to get 2 x Group 24 Wet Cell Deep Cycles [approx 75ah] (both the same)...unless I can determine for sure that 2 x Group 27 will fit in the battery box without any modification}

Frank- I really never thought about rotating the battery from start to charge on different outings .... when I make the upgrade that seems like a common sense approach to the potetial problem

Thanks all for the guidence....

[Hamin' X]

After only one summer, my electrical system that used to be pretty well balanced, is out of kilter. I am debugging it step by step--so I cannot present a full report yet. However: some preliminary findigs suggest that Optima/Gel batteries tend to create "pockets" of gas that compromise their ability to hold electrical current. It also seems like they need to be constantly trickle-charged at less than 1 Amp) very slowly (meaning, both during the day AND during the nigh, which obviates the use of a solar panel tha works only half the time) or else they will lose the above-mentioned ability. That doesn't make any sense to me, since the Optimas are advertised as "deep cycles" A deep cycle battery must be recharged as quickly as possible after it gets completrely drained, I would say.

I believe that you are confusing Optima batteries for some other, March. Optima's are AGM batteries and are not gel cells. While gel cells are susceptible to the pocketing that your refer to, AGM's are not. So google searches for "starved electrolyte", or "absorbed glass mat". Both are terms used for AGM.

Again, AGM batteries are not Gel cells.

~Rich

[March]

Thank you for the information, Hamin' X. I followed the link that you provided in a different thread and got all sorts of interesting facts from a FAQ page that did not answer the questions I had in the least--evidently, because the question I had are not frequently asked. I assummed (erroneously) that you sent me to that page because that page mentioned shortcomings of gel batteries and mine are Optima. If the Optima batteries are AGM, then again according to the page you provided, they have none of the disadvantages the gel batteries have--including the gas pockets--so the link doesn't really answer my questions, though it is very informative.

Okay, so Optimas are not gel batteries. One of them still failed me for whatever reason. Might be a lemon, as Frank suggested. If it's not the gas pockets, it's something else

I doubt that googling the term "starved electrolyte" will solve my problem though

[DaveB]

I have had Gel,agm and Marine deep cycle wet cells and unless you have deep pockets I would go with the Walmart Marine deep cycle Group 27, 125 amp hr batteries for $75 each. I put two of them in parrel up forward against vberth partion and went from center to starboard and fit nice in the Mac. X . These are house batteries and putting the weight up forward were I needed it. My starter battery is still original location and completely seperate from house tho my 10 amp charger charges both banks seperatly .
My Honda outboard 10 amp charger only charges the Starter battery, as the twin 125 amp hr can keep me going for a week or more useing 2 fans, depth,lights,sterio,vhf,TV with DVD,chargeing cell phones, and aaa batteries and battery goes down to about 12.25 volts. One time I forgot to put back wire from charger to house battery because I was working on something and didn't remember it until I came back from a 4 day trip and cked voltage and was at 11.8 volts . thats doing 3 trips without chargeing.
Batteries sulfate after awhile and loose full voltage potential and for that reason alone I like to change out every 3 yrs and for $150 I get full voltage, longer running time.
I figuare usage as 75 amp hr per battery for 50 % compacity so 150 amp hr is a lot of juice for small items.
I have two 15-LED bulbs I need to change out in my cabin lights, but have to switch wires first.
Dave

[Hamin' X]

Thank you for the information, Hamin' X. I followed the link that you provided in a different thread and got all sorts of interesting facts from a FAQ page that did not answer the questions I had in the least--evidently, because the question I had are not frequently asked. I assummed (erroneously) that you sent me to that page because that page mentioned shortcomings of gel batteries and mine are Optima. If the Optima batteries are AGM, then again according to the page you provided, they have none of the disadvantages the gel batteries have--including the gas pockets--so the link doesn't really answer my questions, though it is very informative.

Okay, so Optimas are not gel batteries. One of them still failed me for whatever reason. Might be a lemon, as Frank suggested. If it's not the gas pockets, it's something else

I doubt that googling the term "starved electrolyte" will solve my problem though

I am not sure why you were misled in my referral to This Battery FAQ's site, March. It is certainly not specific to Gel-Cell batteries, but rather to Lead-Acid chemistry batteries and IIRC, I stated that I believed that your problem was related to a faulty charge controller that was causing chronic under charging of your batteries. I apologize if I somehow led anyone to believe that Optima batteries were Gel-Cell and not AGM.

~Rich

PS: Just to clarify, "starved electrolyte" is another term for AGM, as is "Absorbed Glass Mat".

[John Christian]

Matt, I also have a 2007 M with a DF70. My electrical use is similar although I do not use a knotmeter. As others have already noted the group 27's won't fit in the M battery location and even your DF70 won't require a starting battery. I went with 2 identical GRp 24 AGM batteries. Deka 79 ahrs each.

When purchasing the boat I made many concessions to cost. But not with the batteries. I did a lot of research and ended up going with the "best" I could buy. After almost 2 seasons they still charge and perform like new. If they continue to perfom for another 3 -4 years I'd be happy. Less than that and I'd have to re-think the decision.

Since I made a significant investment in the batteries ,I purchased a duplicate combiner Blu Seaand charger ProMarinerfor winter storage. They are connected just as they would be on the boat and I turn the charger on every 4 - 6 weeks.

The AGM's will easily cost you double what the wall mart equivalent wet cell will cost. Do your own research and weigh your options.

JC

[noahvale]

I agree with DaveB. Spending a lot of money on batteries is a waste. I have a 20 watt solar panel with a charge controller maintaining the one lead/acid battery in my Mac25. I took that battery out of an RV I had. It's about five years old. When I was an electrical apprentice at Newport News Shipbuilding, we studied battery construction and maintenance. Keeping them at full charge as much as possible and always using only distilled water in them is necessary. Any contaminates, even minerals in the water will greatly reduce the life of a battery. At NNS, there was a large battery bank that was used for starting the shore power generators. The batteries in that bank were installed in the 40's and where still working fine in the 70's when I was there. The phone companies use large banks of batteries for the 48 volts that the phone lines run on. Those banks last decades. Even cheap consumer batteries should last five years or more with proper care.

[March]

Took the Optima battery to the dealer. Just as I suspected, the battery would not hold charge. It was labelled as "bad". A lemon? Bad luck? They insisted that the Optimas need to be trickle-charged--which they were, via the colar panel. So that ain't it.
Got a deep cycle regular battery and I will mount it today--see how the system behaves.I will keepo the other Optima battery as an engine battery. It seems to be doing fine.
The odd thing is, the batter was less than 2 years old, and it did have a 24 month warranty--yet they didn't give me all the money back--only about half of it. Not sure how that works--they took into account the "core" and did some other calculations that were beyond me.
I was hoping on a one against one exchange, but I wouldn't have taken another Optima anyways