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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 08-02-2004
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house batteries

has anyone ever used 2 6 volt golf cart like batteries for their house battery set up some one told me they will be better than just having a big 12 volt deep cell . if you have any info please help
rob& paul
"kinship"
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Old 08-02-2004
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house batteries

hey are better? Well they are differnt! 6 volt batteries are normally wet cell and there fore need maintanance as well and the most upright place you can place them. They don''t do will if tip too far and the plates MUST remain flooded. You can get 12 volt batteries that don''t have these draw backs. Then again two 6 volt batteries will have more reserve power than the average 12 volt. If you install 6 volt put them there you can service them at least monthly. Make sure they stay upright and you never heal too far over. I am installing them on my boat because I need the deeper reserve. Good luck on your decision. Six volters aren''t for everyone on every applacation.
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Old 08-02-2004
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house batteries

Also wet cells ideally should be located in compartment that is sealed from the interior of the boat but vented to the exterior as charging produces hydrogen gas.

Jeff
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Old 08-15-2004
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house batteries

Jeff speaks the truth. I replaced 6 golf cart batteries with 2 AGM bateries. The Golf cart batteries were in a settee and that settee housed the A/C Unit. The hygrogen was eating the aluminum air intake.

Golf carts are a great economical solution but venting is more important than you think and you do have to maintain them. Skipping the venting is not an option. The damage it does can be expensive not to mention the danger of hydrogen and acid spills.

12 volt AGM batteries do cost more up front but they take less energy to recharge and they have zero maint. costs and nothing to spill. I like the group 4 Concorde Lifelines for the budget, but a Rolls is not without merit.
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Old 08-16-2004
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house batteries

Isn''t there something tricky about recharging the AGM batteries? I think I heard you need some kind of special alternator or regulator. Any thoughts on that?
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Old 08-17-2004
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house batteries

The charging voltages for Absorbed Glass Matt (AGM) Batteries are generally the same as for any standard battery** - BUT CHECK with your SPECIFIC Manufacturer’s Charging Instructions. Since their internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents.

The AGM battery has an extremely low internal electrical resistance. This, combined with faster acid migration, allows the AGM batteries to deliver and absorb higher rates of amperage than any other sealed batteries during discharging and charging.

For flooded wet batteries, internal resistance can be as high as 26%, which is the charging current lost to gassing, or breaking up of water. Gel acid batteries are better at approximately 16% internal resistance and require only roughly 116% of rated capacity to be fully charged. Advanced AGM has the lowest internal resistance of any battery manufactured - only 2 percent.

Most flooded batteries should be charged at no more than the "C/8" rate for any sustained period. "C/8" is the battery capacity at the 20-hour rate divided by 8. For a 220 AH battery, this would equal 26 Amps.
Gelled cells should be charged at no more than the C/20 rate, or 5% of their amp-hour capacity.
The Concorde AGM batteries are a special case - the can be charged at up the the Cx4 rate, or 400% of the capacity for the bulk charge cycle. For a 220 AH battery, this would (theoretically) equal 880 Amps - much higher than your wiring could accommodate!

**Charging at 15.5 volts will give you a 100% charge on Lead-Acid batteries. Many authorities suggest 14.0 volts (2.25 - 2.33 volts per cell) as the maximum charge voltage for AGM’s. Refer to specific your AGM Battery manufacturer’s Charging Instructions, and compare to your Alternator & Charger output characteristics (With engine running AND lights or other loads on, voltage reading on Alternator/cCharger output should read between 13.0 and 15.0 volts).

“Concorde” AGM VRLA-AGM Batteries:
Initial charge or recharge - 14.22 to 14.4 volts at 250C (770F)
Float charge - 13.38 volts at 250C (770F)
Equalize charge - 14.4 volts at 250C (770F)

“MK” Initial charge charge 14.6 - 14.6 v
“Optima” Initial charge below 15 v - float charge 13.8 v (1 Amp)

AGM batteries will not gas under normal operating conditions, however, under severe overcharge conditions gassing is probable (to some degree).
AGM batteries can be equalized, but only under controlled constant current conditions. Always follow manufacturer’s recommendations for the correct charging voltage profile.

Three-Step “Smart” Charging”
The first step is bulk charging where up to 80% of the battery energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger. When the battery voltage reaches 14.4 volts this begins the absorption charge step. This is where the voltage is held at a constant 14.4 volts and the current (amps) declines until the battery is 98% charged. Next comes the Float Step. This is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries but will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. Some gel cell and AGM batteries may require special settings or chargers.

Temperature Compensation is important for all battery types, but AGM and gel cell (valve-regulated type batteries) are more sensitive to temperature. For maximum life, temperature compensation is essential when the operating temperature is outside the range of 68 to 77̊F (20 to 25̊C).

AGM''s may cost 2 to 3 times as much as flooded batteries of the same capacity. AGM batteries main advantages are no maintenance, lower self-discharge, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs (or can afford) these features. Brand names, such as Concord, Lifeline, Odyssey & Optima, are all excellent batteries, but beware of AGM batteries coming out of China.

HTH
Gord
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Old 08-18-2004
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house batteries

Great, detailed answer Gord, but you''ve convinced me to stay away from AGMs. Sounds like I''d need to buy a new engine to avoid destroying them!
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Old 08-19-2004
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house batteries

HHJ:
I’m sorry, if my posting seemed ambiguous - I don’t like to give specific recommendations based upon less than complete familiarity with the application. Hence my “cautions”.

My intent, however, was NOT to disparage AGM batteries, in any way. I think they’re great - their principal disadvantage being cost.

Given the time (of which I’m short), I could offer is “caution list” on “Flooded” (or any other) batteries that would cause wonder why anyone could possibly contemplate their use.

I’ve installed 6V Flooded “Traction” Batteries (Trojan T-105 / T-125) on all of my previous boats; but will likely use AGM’s on my next boat.

There is no escaping the cost, though - especially if you’re looking at a new Charger and Alternator regulator (which do have value, even with flooded batteries, on their own merits).

FWIW,
Gord
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Old 08-19-2004
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house batteries

When I switched from 6 volt Trojan T105''s (still a great bargain for a flood cell) to AGM''s I didn''t redo my charging system one bit other than to make a few adjustmkents on the charger itself.

It already was a good 3 stage charger. They are just a flat out good idea period - no matter what battery system you use. They charge faster, safer, and yield longer battery life. They save you money by giving you more hours! The batteries go dead eventually - all of them.

I also suggest you not get suckered into exceptionally high rate alternators. They generally have a poor payoff. They only run real high for a VERY short time before a smart regualtor will knock the voltage down. You can''t throw huge amp loads at a battery all at one time for a long time. When you start running the numbers you find a high output alternator shaves only a few minutes off your recharge time. they also eat belts faster and cost a whole lot more.

Charging systems first, then batteries would be my order of preference.

I just added a Xantrex Link10 battery monitor. That is one slick device for telling you about how you use power and how much you really have at any point in time. If you shop you can find them for about $125. It can be added to any single bank system. After a few trips with it you''ll know more about your personal battery consupmtion to resize it perfectly.

You want all the power you need, but you only want to pay for all the capacity you''ll really use.
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Old 08-23-2004
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house batteries

The reason golf cart batteries are ''better'' is because have very thick plates and are designed for hours of heavy discharge each day, followed by a fast recharge in only a few hours each night (think about how golf carts are used). Thus golf cart batteries are a good choice for the type of use the ''house bank'' sees, only in reverse (i.e., heavy usage at night, and charging during the day).

That''s why you wouldn''t want to use a plain ol car battery for the house bank. It has thinner plates which is better for a heavy discharge lasting a few seconds, followed by a long period of slow re-charge.

In addition, golf cart batteries have a better ''bang for the buck'' when comparing $$$ per amp/hr with deep cycle marine batteries. The downside is you also have more weight and space requirements to contend with.

Whatever battery type you use proper charging is absolutely the key to extended battery life. As PaulB says, investing in a good quality multistage charger is more important than what type (wet, gel, AGM, etc.) of battery you use.
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