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Old 15-12-2016, 12:02   #1
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Are GC2s really better than Grp 27s?

I have seen a lot of posts and articles about various battery technologies, and I think a lot of people may be wasting a lot of money.

I service boats in Southern Ontario for a living.

My customer base ranges from "yacht club beer can racers" to "heading south full time cruisers", with "weekend warriors and vacation cruisers somewhere in the middle".

I see on forums so many folks talking about modified house bank solutions.

I have attended electrical seminars where speakers have suggested that everyone should switch from 12Vdc lead acid to 6Vdc lead acid, because they are so much better.

In my opinion, based on a lot of reading from various sources, combined with my own personal and professional experience, this is mostly BS.

I know there are design differences between GC2s and Grp 27s.

Do these differences really affect life expectancy? I think on the surface (thicker plates and deeper electrolyte reservoir) they look like they should, but do they really? I don't think they really do.

I suspect, as with many boat improvements, someone who has done some research and laid down a bunch of hard-earned cash will do everything they can to convince themselves, and others, it was all worth it.

I've heard lots of testimonials that one had grp 27s die in short order, and then installed GC2s and they lasted X years longer.

How much of this was because when they researched alternate battery technology, talked to some experts, laid out a bunch of cash to change out the wiring and boxes, that they also significantly increased their capacity, and learned how to treat their batteries a lot better so they would last longer?

I'd be really interested in hearing from someone who applied the same battery capacity, charging capacity and regime, discharge levels and partial state of charge practices to Grp 27s and GC2. I'll bet the differences are not so significant as many people believe.

I have seen no empirical evidence that switching from a 12Vdc grp 27 house bank, will make any significant difference in life expectancy in a real world application.

I have seen East Penn Grp 27 house banks fail in 2-6 years of use.

I have seen Trojan T105 house banks fail in 2-6 years of use.

So here are my beliefs, based on the credible information available to me, from various sources, and my own experience:

1. The most important choice one can make about their house bank, is to treat it well, whatever it is.

2. There are some very good reasons for sticking with 12 Vdc standard lead acid batteries rather than switching to GC2s.

3. Declarations that GC2's last significantly longer than 12 Vdc standard lead acid batteries in the real world, have yet to be proven.

4. Many manufacturers do not post life cycle data, some that did have stopped, and Rolls (who still do) show little difference between their GC2 and GRP 27, which difference is directly proportional to the difference in weight.

5. For any given manufacturer, in most cases, the w-hr, volume, and weight of their GC2's and Grp 27s are virtually identical.

And now for the standard lead acid vs Gel vs AGM vs LifePO4.

It is true that these other technologies have higher acceptance rates (to various degrees). And if one has dual high output alternators on a bank of 1000 A-hrs +, they may gain a benefit of faster charging that starts to justify the expense. Switching up to a 160 A-hr alternator for a bank of any type under 1000 A-hrs, really doesn't do anything for anyone.

And when I hear people justify it due to the wider charge cycle it makes me cringe.

First of all, the recommendation to size a standard lead acid house bank for 30% usable capacity (50% to 80% charge cycle) is based on ALTERNATOR CHARGING ONLY. As soon as one adds in a decent amount of solar and/or wind capacity, they can plan for 50% capacity (50% to 100% charge cycle).

With this, the slightly deeper discharge one may be able to get away with for AGM and GEL is pretty much negated by the lower A-hr rating for these technologies having same volume and weight as standard lead acid.

(Don't get me wrong, I recommend AGMs for every application where the only place to put batteries is in occupied space, especially under settees or berths that are poorly ventilated.)

So when comparing LifePO4 to standard lead acid, it is not a 80% vs 30% usable capacity discussion, as I hear so often. With alternate charging sources to just alternators or generators, (where run time is to be minimized for practical purposes) it is an 80% vs 50% discussion. Now this much more expensive technology is not nearly so attractive. And frankly, if one doesn't have one honking high current charging source, the higher acceptance rate does them absolutely no good. If you're solar and wind doesn't put out enough to exceed the acceptance of your standard lead acid batteries, nothing is going to change that charge rate when you switch to gels, AGMs, of L-Ions.

It's time to start spreading truth about battery technology.

If the boat is equipped with 12 Vdc standard lead acid technology batteries, and they are treated well, they will serve the boater well.

If the boater doesn't treat batteries well, switching to alternate technologies will likely end up being a big mistake.

If a boater switches to an alternate technology bank and at the same time, starts treating them a whole lot better, we can't attribute the improvement in longevity to the battery technology (at least solely).

I sell and install batteries (as well as many other boat products and services), and I can't count the number of times I've talked a customer down from spending a whole lot of money on alternate tech. batteries they didn't need, but instead, taught them how to treat their batteries better. In most cases, they come back years later wishing they had talked to me much sooner.

It's easy to get all caught up in the geek speak, media, advertising, and what not, but for most weekend warriors and even full-time cruisers, 12 Vdc standard lead acid is the best way to go.

And if a customer absolutely insists on alternate tech. batteries I don't feel they need, after a pros and cons discussion, if they still feel that way, I reluctantly sell and install what they want and take their money.

Reluctantly, because 2 or 3 years down the road, when they've killed their very expensive batteries, they will likely go elsewhere to avoid the "I told you so" embarrassment. Or if they did learn to treat their batteries right, and they last longer than there old standard lead acid did (treated poorly) they go elsewhere because obviously I didn't know what I was talking about.

It would be easier (and better for business) for me to promote alternate technology batteries like gang busters (like most other marine retailers); it just wouldn't be right, because for most, they are not likely to be the best solution for their needs.
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Old 15-12-2016, 13:12   #2
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Re: Are GC2s really better than Grp 27s?

If you use the follow the money of what is best you would to accept the GC2 golf cart type battery is best. The millions of golf cart batteries being used makes the boat market a waste of effort. if the 12v batteries were better the golf courses would know it.
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Old 15-12-2016, 13:17   #3
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Re: Are GC2s really better than Grp 27s?

Show me an amp hour that is cheaper than a Sams Club or Costco golf cart battery, even if they don't last longer, they are cheaper to buy
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Old 15-12-2016, 13:28   #4
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Re: Are GC2s really better than Grp 27s?

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Originally Posted by a64pilot View Post
Show me an amp hour that is cheaper than a Sams Club or Costco golf cart battery, even if they don't last longer, they are cheaper to buy
Paid $470 for 6 GC2's yesterday at a golf cart dealer in Ormand Beach, FL. Deka GC10 same as Sam's Club. The golf cart guys always have good prices and they will deliver.
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Old 15-12-2016, 13:33   #5
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Re: Are GC2s really better than Grp 27s?

Quote:
2. There are some very good reasons for sticking with 12 Vdc standard lead acid batteries rather than switching to GC2s.
Rod, I'm in agreement with much of your post, but the quoted statement above puzzles me. What are those very good reasons for sticking with 12V?

Jim
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Old 15-12-2016, 13:44   #6
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Re: Are GC2s really better than Grp 27s?

Rod, if you haven't already, you might review posts by MaineSail here... and on his own Compass Marine website.

I suspect actual users present a significant difficulty in apples-to-apples -- but anecdotal -- comparisons. Mr. Perfect may have treated his 12V batteries... ummm... perfectly... for his application, whereas Bozo The Clown my have completely mis-used his 6V GCs. And even that depends on whether the right batteries were selected for the right application (12V starting, 6V deep cycle for house, 12V dual-purpose when appropriate, etc.).

And then there's that whole system thing going on. Charging regime, bank sizes versus charger capability, whether there's solar and wind augmentation involved, and that pesky user again: routinely drawing to no more than 80% SOC? Or down to 50%? Or even down to 20%? And so forth.

And almost finally (from me, anyway), there's that brand thing. Might be that Brand X of some AGMs or FLAs or whatever just aren't as good as Brand Y of the same type of product.

Which in turn leads back to how Mr. Perfect and Bozo The Clown used their specific batteries. Mr. Perfect may have bought crap and nursed them all pretty well, and Bozo may have bought gold and killed 'em.

Et cetera.

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Old 15-12-2016, 14:28   #7
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Re: Are GC2s really better than Grp 27s?

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Originally Posted by ranger42c View Post
Which in turn leads back to how Mr. Perfect and Bozo The Clown used their specific batteries. Mr. Perfect may have bought crap and nursed them all pretty well, and Bozo may have bought gold and killed 'em.

Et cetera. -Chris
Also at what point do they swop out the batteries? does Bozo keep going with knackered batteries until one day he goes down the boat and finds they are sat at 6v and won't even power a light bulb, or does Mr Perfect notice that they don't seem to hold the charge for the lights and fridge overnight as they used to, checks the label on the battery when he bought them and decides its time to change before there is a failure.

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Old 15-12-2016, 14:42   #8
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Re: Are GC2s really better than Grp 27s?

Sailorboy, a64, etc.. got this completely correct, with ranger picking up the slack as to why we as boaters will never really know from an absolute scientific standpoint.

Google tells me that there are 15,372 golf courses in the US. I'll bet something north of 95% of those that use electric carts use flooded GC batteries. (Some may be 8V or 12V tho, but I'd also guess that most are 6V. )

That's a metric shipload of batteries being used every year. If there was something better you absolutely know that golf courses would switch to them. In this case 'better' means most AH for the buck AND needs replacement as infrequently as possible. I'd also say that golf courses beat the livin crap out of their batteries WRT deep discharges so GC batteries are also likely better there. Golf courses do, however, charge to a 100% SOC every single day.

Ranger points out that the boating market likely doesn't have enough data with enough variables held constant to make for anything but an anecdotal analysis. I know Mainesail has tested various other technologies, but don't think a GC6 vs G27 test was ever done.

But anecdotally, many boaters (and RVers, which is a similar problem space) will testify as to how the GC batteries are better. I replaced 2 G27s with 2 GC6s. They've lasted longer. They hold more electrons. They'll run my fridge for a coupla days and still start the motor. I have the same shorepower charger, but added solar. They are definitely 'better'. That's my anecdote, it's not scientific data.

I replaced 2 G27s on my motorhome with 2GC6s. I run a 10cf 110v household fridge on them off of an inverter. The G27s couldn't even start the fridge (yes, they were old so the comparison is really invalid). Going on the 5th year or so with them, and they do get used quite a bit keeping the fridge going. 400w of solar to pop em back up.
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Old 15-12-2016, 16:45   #9
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Re: Are GC2s really better than Grp 27s?

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Rod, I'm in agreement with much of your post, but the quoted statement above puzzles me. What are those very good reasons for sticking with 12V?

Jim
Reasons for sticking with Grp 27s instead of GC2s

1. Availability. 12 Vdc Grp 27s are available everywhere. GC2s, not so much.

2. Usable voltage. Small (or independent) systems: If a single 100 A-hr Grp 27 is plenty for the intended app (say bow thruster), for GC2s it would take two batteries to make the necessary 12 Vdc.

3. Loss of capacity on failure. If a house bank consists of 2 x GC2's and one develops a shorted cell, 100% of capacity is lost, whereas 2 x Grp 27s, you can run on one and only loose 50%. For 4 x GC2s if one goes down 50% of capacity is lost as two have to be taken off the bank, whereas for 4 x Grp 27s, only 1 battery (25%) capacity is lost.
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Old 15-12-2016, 16:54   #10
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Re: Are GC2s really better than Grp 27s?

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Originally Posted by ranger42c View Post
Rod, if you haven't already, you might review posts by MaineSail here... and on his own Compass Marine website.

I suspect actual users present a significant difficulty in apples-to-apples -- but anecdotal -- comparisons. Mr. Perfect may have treated his 12V batteries... ummm... perfectly... for his application, whereas Bozo The Clown my have completely mis-used his 6V GCs. And even that depends on whether the right batteries were selected for the right application (12V starting, 6V deep cycle for house, 12V dual-purpose when appropriate, etc.).

And then there's that whole system thing going on. Charging regime, bank sizes versus charger capability, whether there's solar and wind augmentation involved, and that pesky user again: routinely drawing to no more than 80% SOC? Or down to 50%? Or even down to 20%? And so forth.

And almost finally (from me, anyway), there's that brand thing. Might be that Brand X of some AGMs or FLAs or whatever just aren't as good as Brand Y of the same type of product.

Which in turn leads back to how Mr. Perfect and Bozo The Clown used their specific batteries. Mr. Perfect may have bought crap and nursed them all pretty well, and Bozo may have bought gold and killed 'em.

Et cetera.

-Chris
Yes, I am very familiar with Rod (nice name BTW ;-) and the Compass Marine article.

I have a lot of respect for Compass marine and the investigation and reporting they do regarding matters of importance to boaters.

But I do question the validity of some of the arguments. My issue with it, is on one hand it suggests one can't count on the stated lab cycles, and on the other hand it draws conclusions on effectiveness based on lab cycles.

The evidence of GC2s actually lasting longer than Grps 27s in a real world application is a battery manufacturing engineer stating, "Yeah I think so".

Trojan stopped publishing lab cycles. Why?

Rolls still publishes a cycle chart. Their GC2s a spec'd to tolerate 30% cycles more than their Grp 27s. Then again, their GC2 are 30% heavier and 30% more expensive than their Grp 27s.

The balance of your questions is exactly my point. Is anyone really getting the best value for money by changing out from grp 27s to GC2s?

I have seen no concrete evidence that is trustworthy.
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Old 15-12-2016, 17:01   #11
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Re: Are GC2s really better than Grp 27s?

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If you use the follow the money of what is best you would to accept the GC2 golf cart type battery is best. The millions of golf cart batteries being used makes the boat market a waste of effort. if the 12v batteries were better the golf courses would know it.
I've heard this argument before and I don't get it.

Are you suggesting there are more golf carts in North America than there are boats, RVs, and automobiles? I don't think so.

But even if there is, if golf cart batteries are so much better, why didn't the boat and RV manufacturers adopt them? (PS, some golf carts run on 12 Vdc batteries.)
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Old 15-12-2016, 17:10   #12
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Re: Are GC2s really better than Grp 27s?

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Show me an amp hour that is cheaper than a Sams Club or Costco golf cart battery, even if they don't last longer, they are cheaper to buy
But are the uber cheap GC2s actually good batteries? If they cost 20% less and last 20% less long as a comparable Grp 27, where are the savings other than initial cost?

But then again, with the initial cost one has to factor in the cost to change out the battery boxes and cabling, so the initial installed cost of the cheapest golf cart batteries, may actually be higher.

And then of course there's the issue that if one goes bad you have to take out 2 until you make get a replacement.
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Old 15-12-2016, 17:15   #13
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Re: Are GC2s really better than Grp 27s?

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Reasons for sticking with Grp 27s instead of GC2s

1. Availability. 12 Vdc Grp 27s are available everywhere. GC2s, not so much.

2. Usable voltage. Small (or independent) systems: If a single 100 A-hr Grp 27 is plenty for the intended app (say bow thruster), for GC2s it would take two batteries to make the necessary 12 Vdc.

3. Loss of capacity on failure. If a house bank consists of 2 x GC2's and one develops a shorted cell, 100% of capacity is lost, whereas 2 x Grp 27s, you can run on one and only loose 50%. For 4 x GC2s if one goes down 50% of capacity is lost as two have to be taken off the bank, whereas for 4 x Grp 27s, only 1 battery (25%) capacity is lost.
Rod I dont know where you shop for batteries but I can purchase grp whatever 12 olt bat tree eries as well as gc2 batteries ( in every walmart sams club costco and auto parts store in america. Bet its about the same in most of Canada as well
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Old 15-12-2016, 17:18   #14
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Re: Are GC2s really better than Grp 27s?

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Reasons for sticking with Grp 27s instead of GC2s

1. Availability. 12 Vdc Grp 27s are available everywhere. GC2s, not so much.

2. Usable voltage. Small (or independent) systems: If a single 100 A-hr Grp 27 is plenty for the intended app (say bow thruster), for GC2s it would take two batteries to make the necessary 12 Vdc.

3. Loss of capacity on failure. If a house bank consists of 2 x GC2's and one develops a shorted cell, 100% of capacity is lost, whereas 2 x Grp 27s, you can run on one and only loose 50%. For 4 x GC2s if one goes down 50% of capacity is lost as two have to be taken off the bank, whereas for 4 x Grp 27s, only 1 battery (25%) capacity is lost.
My thoughts on these points:

1. That's a pretty tenuous argument, Rod. I've found GCs fairly easily now for nearly thirty years of cruising, often in third world venues. There are golf courses in the most surprising places! Sometimes Trojans have been scarce, but other brands were available. And finding G-27s of good quality isn't so easy, either, in many places. At least, when you buy a GC2 there is a good chance that it is actually designed as a deep cycle battery. This is not so true of G27s labeled as such!

2. I agree about this.

3. Well, your math is correct, but the implication that you should base your choice of battery style on this fails to convince me. We've never had a catastrophic failure of a battery. Gradual sulphation, sure, but loss of capacity has always lead to replacement before abject failure, so the smaller deficit of capacity you quote does not seem important to me. For others, perhaps...

At any rate, your philosophy seems better grounded than the new tech at all costs crowd's. I hope that your customers appreciate it!

Jim
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Old 15-12-2016, 21:05   #15
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Re: Are GC2s really better than Grp 27s?

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Rod I dont know where you shop for batteries but I can purchase grp whatever 12 olt bat tree eries as well as gc2 batteries ( in every walmart sams club costco and auto parts store in america. Bet its about the same in most of Canada as well
Just did a search on Costco and Walmart sites, lots of 12 Vdc batteries, not one 6 Vdc. No Sam's Club in Canada. We do have Canadian Tire, a huge automotive / all house wares chain; lots of 12 Vdc / no 6 Vdc batteries listed.

Meanwhile, there are about 20 places in Peterborough (pop. 78,000) where I can buy 12 Vdc batteries. There are 6 Vdc batteries at TSC (I guess some old tractors had 6 Vdc starting systems). Are these quality deep cycle batteries? Prolly not.

A few marine retailers, within 100 mile radius stock 6Vdc batteries (Crown, Trojan, etc) but who knows how old they are, and they are super expensive. Do they even have enough to set up a 4 x GC2 house bank without having to order them in?

So just because 6Vdc batteries may be prevalent in some locales, don't assume you can get them easily anywhere; at least here it sure isn't so, and I've heard cruisers outside USA say they can't find them, when there are 12 Vdc batteries everywhere.
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