Choosing deep-cycle (house) batteries

[Davie J.]

What is the difference between golf cart batteries and "marine" batteries? It seems to me that both do the same thing. Am I wrong?

[john61ct]

Originally Posted by Davie J.

What is the difference between golf cart batteries and "marine" batteries? It seems to me that both do the same thing. Am I wrong?

The word marine has no objective reference pertaining to batteries, just a meaningless marketing label.

Batteries are designed and built for specific uses. Quality varies very widely as to whether they actually perform well or not.

The desired quality here is the ability to last many cycles being repeatedly drawn down by 40-60% DoD, maybe occasionally more in a crisis.

A cranking Starter batt like you find in big box and automotive retail is very different from UPS/standby batteries, which are both different from deep cycling ones.

Those used to power golf cars are at least intended to perform well deep cycling. Same with those for forklifts, industrial floor polishers, etc

https://marinehowto.com/what-is-a-deep-cycle-battery/

[Adelie]

Originally Posted by Davie J.

What is the difference between golf cart batteries and "marine" batteries? It seems to me that both do the same thing. Am I wrong?

“Marine” batteries are really hybrid Starting/Deep-cycle batteries which will have a bit better cycle life than starting batteries when used for house loads but not really that good.

Batteries labeled “Golf cart” by any major manufacturer are likely a real Deep-cycle battery that will provide a lot more cycles to 50%.

For off brand batteries, my assumption is they are a battery battery at best regardless of the label.

[MJH]

Originally Posted by suiramor

What factors should I consider when looking for new house batteries for my Benetau 46 (I currently have 2x NG-4D, 9 yrs old! - I think 500AH)? At this time I am mainly doing coastal sailing, day trips, sometimes on anchor but usually on marina power in cooler (Pacific NW) climes.

Because of your current limited use I don't see any reason to change total battery Ah SIZE. Should your cruising style involve more anchoring
or you increase the electrical need you should consider moving to greater Ah capacity.

You don't say how religious you are caring for your current FLA batteries or where they are located on your boat (but you got 9 years out of them anyway) and you don't report any adverse affects from the FLA gassing that they are known to do. Should those factors change you should consider moving to sealed batteries.

A change to larger Ah capacity and different chemistry is more involved than just buying the batteries. Get educated on a system wide electrical approach before making the upgrade as proper implementation will give you overall greater capacity, a longer life for your battery investment, and elimination of the gassing.

I replaced my 2x8D GEL batteries this year with new ones and they were 15 years old.

~ ~ _/) ~ ~ MJH

[ranger58sb]

Originally Posted by suiramor

The current ones are flooded. What would be the reason to change to sealed?

Less physical maintenance, lower off-gassing, mountable in odd positions (except upside down), relatively high bulk charge acceptance.

At extra co$$t. Or co$$$t, for the better ones.

-Chris

[a64pilot]

See, I would even tell you that “dual purpose” is yet another marketing lie.
Makes people think this must be the best battery it can be used for both.
The difference in a Dual purpose battery and the starter battery is the label I bet.

However unless you have truly large engines, a house bank of a decent size has way more cranking amps than needed to start most any engine.

[Frankly]

14 years ago I decided to try a sightly different approach in revamping a new to me IP32. 6 GC2 batteries for a house bank and starting. 4 midships and 2 in the fwd bilge. Each pair can be switched in/out of the one 12 V DC system. I test each pair (starting at the bow) a couple of times a year in starting the 3GM Yanmar. Front pair is not quite as quick out of the box, but will always start the Yanmar. Normally they all just stay connected as one 600 AH bank. Typically replace all 6 every 5 or 6 years (Sams Club).


After 14 years I wouldn't consider any other way. But some still like Vanilla ice cream, I am a Butter Pecan sort of guy.


Frankly

[roland stockham]

Originally Posted by a64pilot

See, I would even tell you that “dual purpose” is yet another marketing lie.
Makes people think this must be the best battery it can be used for both.
The difference in a Dual purpose battery and the starter battery is the label I bet.

However unless you have truly large engines, a house bank of a decent size has way more cranking amps than needed to start most any engine.

Quite true but unfortunatly irrelevant. What the starter needs is volts and a battery cabable of maintaining them for 30sec at cranking amps. My engine manual specifies a batt rated to 660cca so able to supply 660 amps. Although my house bank is 400a/hrs its max recomended discharge rate is 86a so no comparison. Starting your engine with a house bank is like trying to tow the boat with a Farrari, on paper it may have the power but it wont like it, it's a speed machine and so is a start batt. Your house bank is the equivelent of a tow truck, no speed but will pull forever.

[john61ct]

Originally Posted by a64pilot

See, I would even tell you that “dual purpose” is yet another marketing lie.
…
The difference in a Dual purpose battery and the starter battery is the label I bet.

Yes, when used by companies other than those that can be trusted absolutely true.

Just like being 12V and automotive sizing, or seeing a CCA rating, or sold in a big box retail outlet,

99.9999% of the time a clear indicator of inappropriate for deep cycling usage.

But, as an example, if you needed true deep cycling AGM for a sideways install, or their high C-rate capacity, and were willing to pay more per Ah per year, then

Odyssey's PC-2150 would be an excellent choice. Go to the data sheet, and not only see they are 12V and G-31s, but tagged "dual use".

[john61ct]

Originally Posted by roland stockham

Quite true but unfortunatly irrelevant. What the starter needs is volts and a battery cabable of maintaining them for 30sec at cranking amps. My engine manual specifies a batt rated to 660cca so able to supply 660 amps. Although my house bank is 400a/hrs its max recomended discharge rate is 86a so no comparison. Starting your engine with a house bank is like trying to tow the boat with a Farrari, on paper it may have the power but it wont like it, it's a speed machine and so is a start batt. Your house bank is the equivelent of a tow truck, no speed but will pull forever.

If House is of a much larger Ah capacity, it will be 100% fine for cranking, in fact better than a smaller battery designed for cranking.

[a64pilot]

Originally Posted by roland stockham

Quite true but unfortunatly irrelevant. What the starter needs is volts and a battery cabable of maintaining them for 30sec at cranking amps. My engine manual specifies a batt rated to 660cca so able to supply 660 amps. Although my house bank is 400a/hrs its max recomended discharge rate is 86a so no comparison. Starting your engine with a house bank is like trying to tow the boat with a Farrari, on paper it may have the power but it wont like it, it's a speed machine and so is a start batt. Your house bank is the equivelent of a tow truck, no speed but will pull forever.

Your 86 amps is a continuous rating, it can do that until it’s discharged without overheating.
Cranking is a short time rating which is usually not given in a deep cycle battery as CCA isn’t given.
But that doesn’t mean they aren’t capable, this 200 AH Gel battery is unusual, it doesn’t give you a CCA rating, but does tell you that you can draw 2,000 amps for 5 sec, 2,000 amps for each battery is a whole lot, even a bank of only three of them gives 6,000 amps available for starting
https://www.renogy.com/deep-cycle-pu...12-volt-200ah/

[Frankly]

Blue Sea Systems published some info a few years back on avaliable fault current of different types of LA batteries. A single pair of 6 V GC batteries in series comes in at about 5,000 Amps (50 amps/ lb). Not a condition you would intentionally subject your bank to (the reason we have fuses), but certainly capable of starting most sailboat auxiliary diesels. When I test start with my fwd bank the start current is traveling through approx 30 ft of #4 AWG wire in adition to the normal 12 ft of #1/0 from the main 12V bus.


Frankly

[geoff3nebel]

Two Rolls S12 185 in parallel will give you 410Ah and three years warranty. Not cheap; heavy too - 135lbs each, but with that amount of lead they’ll outlast any comparable battery. They also have enough grunt to crank your engine.

[john61ct]

Yes, any bank built up from Rolls/Surette cells would be top notch, if money is not an issue.

The 2V cells last very very long, give lots of flexibility in bank design and are easiest to wrestle with especially for large banks.

[zengirl]

I have 4 -50ah each LiFepo4 on one bank and was thinking of buying Interstate agm next. Any feedback on that would be welcomed.