Suitability Of Ganged 6v Batteries as a Large House Bank

[S/V Alchemy]

I am in the lucky situation of having a custom steel full keeler, lucky in the sense that I have few of the usual restrictions on battery capacity or placement. We are heading offshore and have multiple (solar, wind, two alts, two portable gensets) charge sources and the means to control them for optimal charging. I am therefore considering the "ideal" of having five to six days of windless, cloudy days at anchor without having to run the engine or the gensets to charge the batteries.

I figure I need about 850-1000Ah of capacity for this, given a fridge and all LED lighting and the occasional SSB use.

Generally, I would stay near fully charged, however, assuming I stay in the tropics or near-tropics.

Because I have space and access, I am leaning away from things like Northstar AGMs and toward the more robust Trojan L-16 family. Six of those, ganged into two 12 VDC banks, would give me what I seek, at a mere 750 pounds or so, not a big deal close the the CG of the boat on the centerline, and it's a 16 tonne beast, anyway. I could even go up to eight.

Has anyone used the L-16 line on boats and what have your experiences been? I started with two T-105s when I bought the boat, and they were amazing given their extreme age (18 years). Anything I buy has to last just five to six years. I know how to keep lead-acid batteries happy.

[CharlieJ]

I have installed L16 banks on client's boats and they work well.

With 6 x L16P in series parallel, you will have a total of 390Ahrs x 3 = 1170Ahrs total; 585Ahrs useable.

That said, flooded lead acid batteries (FLA) have a charge acceptance of between 15 and 20% of the capacity of the battery in Ahrs (C). Trojan is currently specifying 0.17C. AGM batteries have a higher charge acceptance rate and thin plate pure lead (TPPL) AGMs like the Northstar batteries have an acceptance rate of 1.0C. Nigel Calder has performed an analysis and found that charging batteries by genset is incredibly expensive so minimizing generator run time should be a design goal.

Charlie

[Bash]

Golf cart batteries are happiest being charged overnight, just like how they do it at the golf course. That's great for a daysailor that plugs into shorepower every night.

With solar, wind and two alternators, you may want to take another look at AGMs. Instead of thinking about weight not being a problem, think about acceptance rate.

[S/V Alchemy]

Thanks, guys. The charge acceptance issue deserves more scruntiny, certainly, although I believe my charge sources are varied and energetic enough to overcome them.

I would prefer golf cart-style not only for reasons of cost, but for reasons of durability...hence the 6V preference. 1170 Ah as a big ol' house bank actually exceeds what I had hoped to have, but that's a "problem" I would enjoy...having 100 Ah a day for five days before I get close to 50% discharge.

As I will essentially be lifting a big lock-down lid to access them, I am not really needing the "no maintenance/lie 'em down" aspect of AGMs, although that did attract me to the Northstars originally, because they would fit with little problem on their sides under the floorboards into bolt together racks.

But I do have concerns about the price premium and the availability should one or more go bad, so I'll have to balance off the fact that they charge faster and at higher voltages against the "simplicity" of lead-acid.

Realistically, I would run the engine with its two 100 amp alternators before I would trot out a brace of Hondas, but that's just to illustrate how many (potential) charge sources I have.

There are many roads to "enough". Thanks for the guidance.

[SV Demeter]

Originally Posted by S/V Alchemy

Thanks, guys. The charge acceptance issue deserves more scruntiny, certainly, although I believe my charge sources are varied and energetic enough to overcome them.

I would prefer golf cart-style not only for reasons of cost, but for reasons of durability...hence the 6V preference. 1170 Ah as a big ol' house bank actually exceeds what I had hoped to have, but that's a "problem" I would enjoy...having 100 Ah a day for five days before I get close to 50% discharge.

As I will essentially be lifting a big lock-down lid to access them, I am not really needing the "no maintenance/lie 'em down" aspect of AGMs, although that did attract me to the Northstars originally, because they would fit with little problem on their sides under the floorboards into bolt together racks.

But I do have concerns about the price premium and the availability should one or more go bad, so I'll have to balance off the fact that they charge faster and at higher voltages against the "simplicity" of lead-acid.

Realistically, I would run the engine with its two 100 amp alternators before I would trot out a brace of Hondas, but that's just to illustrate how many (potential) charge sources I have.

There are many roads to "enough". Thanks for the guidance.

Similar setup on my boat. I am going with Trojan T-145's, 8 of them in my case. Each one is 260AH so (8) in a series parallel config gets me 1,040 AH bank and should weigh about 580lbs.

http://www.ebatteriestogo.com/SpecSh..._Batteries.pdf


I predominantly charge from solar with honda and 150amp ac charger as back up, along with engine alt 100amp as last resort. Im choosing lead acids because with the exception of my honda/AC charger I dont have any means to take advantage of the high charge acceptance rates. My 100 amp alternator trying to put back 500AH is just never going to get high enough output to make it worth the $$ for AGM. My solar at 400watts wont get there either. Lastly AGMs NEED to be floated pretty often or they will die a short life. I was worried about my ability to regularly float a 1K AH bank. So for me lead acids make the most sense.

If you can take advantage of the high charge acceptance rates the AGMs have AND you are certain you will be able to routinely float them then I would say spend the money and go with the sealed AGM. As always this is advice is worth what you paid for it...

[Vasco]

Originally Posted by Bash

With solar, wind and two alternators, you may want to take another look at AGMs. Instead of thinking about weight not being a problem, think about acceptance rate.

Whatever you do stay away from AGM's. Typically when cruising you're at anchor most of the time. And again, typically you will draw the batteries down to 50%. When charging after 85% full, it takes a long time to top up the batts, it's not economical to keep on charging to get the last 15% in. So most of us end up using the band from 85% to 50%. AGM's do not like this, they like to be fully charged, often. My AGM's lasted two seasons. I went back to flooded. AGM's are great if you're in a slip with shorepower but if you're out cruising they're a waste of money. Here's a recent thread on this.
Beneteau stock batteries or AGM upgrade? - BeneteauOwners.com

[btrayfors]

Alchemy,

You've already got it figured correctly. L16's are fine, and will last longer than T-105's.

No matter what Trojan says, these batteries will accept about .25C when 50% discharged, or in your case about 250A. That's a lot more than you can provide continuously, so with your setup you'll be fine.

AGMs, as stated above, are NOT appropriate for your setup and cruising plans. AGMs can easily accept 5XC for the first few minutes when deeply discharged and about 1.25C when 50% discharged (or 5,000-1,000 amps in your case!!!). And, as stated above, they need to be fully charged frequently or you'll shorten their lives. Also, their longevity is considerably less than good flooded batteries, like the L16's or the Rolls/Surette flooded batteries.

Bill

[ReMetau]

Originally Posted by Vasco

Whatever you do stay away from AGM's. Typically when cruising you're at anchor most of the time. And again, typically you will draw the batteries down to 50%. When charging after 85% full, it takes a long time to top up the batts, it's not economical to keep on charging to get the last 15% in. So most of us end up using the band from 85% to 50%. AGM's do not like this, they like to be fully charged, often. My AGM's lasted two seasons. I went back to flooded. AGM's are great if you're in a slip with shorepower but if you're out cruising they're a waste of money. Here's a recent thread on this.
Beneteau stock batteries or AGM upgrade? - BeneteauOwners.com

Same thing happened to us with Northstar AGMs. Northstar thought we got a bad batch and replaced all three of them plus the starter bat for free and paid shipping to the Keys. All of our charging systems were checked and gone over. After the replacement, we went through that set too. We switched to T-105s before going to the Bahamas and have not had a problem since.

[ka4wja]

Alchemy,
Here is just a brief reply, with some links that you may find helpful...

Originally Posted by S/V Alchemy

Because I have space and access, I am leaning away from things like Northstar AGMs and toward the more robust Trojan L-16 family. Six of those, ganged into two 12 VDC banks, would give me what I seek, at a mere 750 pounds or so, not a big deal close the the CG of the boat on the centerline, and it's a 16 tonne beast, anyway. I could even go up to eight.

Has anyone used the L-16 line on boats and what have your experiences been? I started with two T-105s when I bought the boat, and they were amazing given their extreme age (18 years). Anything I buy has to last just five to six years. I know how to keep lead-acid batteries happy.

1) If you in fact DO have the space and you can acommodate various size and shape/form-factor batteries, you are indeed in a "lucky situation"....

And, you have a wonderful opportunity to understand that there are MANY things about deep-cycle batteries that effect their "capacity" and "lifespans" (such as positive plate thickness, plate construction/metalurgy and water/electrolyte resivoir/capacity...)


Whether you choose 2-volt, 6-volt, or 12-volt, and at whatever size and capacity you require, you will find success if you do your homework....and here the manufacturers' websites are your friends, as you'll find lots of good info there!!!!




2) If you have a look around at the tech specs of some of the better industrial/commercial/marine battery manufacturers, you can see the positive plate thickness of batteries vary greatly....
As example, Rolls/Surrette L-16's have 0.170" thick positive plates, vs. 0.090" thick plates on the Trojan L-16's, vs. 0.200" thick plates on the Concord L-16's.....

And, since positive plate thickness is one of the biggest factors in battery longevity, so can see how your choice of battery manufacture and model, will have a big effect on their lifespan (and reliability)....





3) Also understand that some manufacturers make many models of batteries of the same / similar size, for various applications.....
As example, Rolls/Surrettes make many different L-16 sized batteries, some for the marine maket w/ heavier/thicker cases and plate support structures (such as the 350 A/H, CH-375M) or others for alternative energy / indoor industrial market, like the Trojan L-16's (such as the 400 A/H, S-530 or the 450A/H, S-600)





4) Have a look at this thread here on Cruiser's Forum, where you'll learn a lot...and have a look at the tech specs of different batteries and
http://www.cruisersforum.com/forums/f14/rolls-versus-agm-batteries-62379-2.html



http://rollsbattery.com/products/18
http://rollsbattery.com/products/17


http://rollsbattery.com/public/specsheets/CH375.pdf
http://rollsbattery.com/public/specsheets/S-600.pdf




I hope this helps you out....





Fair winds...


John
s/v Annie Laurie

[S/V Alchemy]

Originally Posted by SV Demeter

Similar setup on my boat. I am going with Trojan T-145's, 8 of them in my case. Each one is 260AH so (8) in a series parallel config gets me 1,040 AH bank and should weigh about 580lbs.

http://www.ebatteriestogo.com/SpecSh..._Batteries.pdf


I predominantly charge from solar with honda and 150amp ac charger as back up, along with engine alt 100amp as last resort. Im choosing lead acids because with the exception of my honda/AC charger I dont have any means to take advantage of the high charge acceptance rates. My 100 amp alternator trying to put back 500AH is just never going to get high enough output to make it worth the $$ for AGM. My solar at 400watts wont get there either. Lastly AGMs NEED to be floated pretty often or they will die a short life. I was worried about my ability to regularly float a 1K AH bank. So for me lead acids make the most sense.

If you can take advantage of the high charge acceptance rates the AGMs have AND you are certain you will be able to routinely float them then I would say spend the money and go with the sealed AGM. As always this is advice is worth what you paid for it...

Actually, no. We anticipate being at anchor and hardly ever on shore power. I can anticipate shelling out for a blast of equalization charge on occasion, but other than that, it will be four 135 W panels on a cambered arch, a 400W wind gen, and the aforementioned two circa 100 A alts.

I anticipate running the diesel with intent every three to five days, but not often on passage and not ever (unless for safety reasons) at anchor.

I have a 100 amp charger also and the capacity to run 60 amps to it (hey, room to grow!). I plan to echo charge the starter and the windless batteries (which may in fact be AGM, at least the windless) to avoid long heavy gauge runs of wire.

So maybe I'm back to lead-acid with that logic!

Frankly, from straw polls I've taken, our usage will not be particularly high, with a well-insulated fridge being the biggest draw. Unless we are on the "plus side" or actively charging big-time while motoring, it's all LEDs, rechargeable radios, charged laptops and foot pumped water....

"Movie nights" and "extended time with SailMail" will be entirely dependent on the state of charge and the estimated time to get back to fully topped up.

Thanks for the comment and real-life experience.

[S/V Alchemy]

Originally Posted by btrayfors

Alchemy,

You've already got it figured correctly. L16's are fine, and will last longer than T-105's.

No matter what Trojan says, these batteries will accept about .25C when 50% discharged, or in your case about 250A. That's a lot more than you can provide continuously, so with your setup you'll be fine.

AGMs, as stated above, are NOT appropriate for your setup and cruising plans. AGMs can easily accept 5XC for the first few minutes when deeply discharged and about 1.25C when 50% discharged (or 5,000-1,000 amps in your case!!!). And, as stated above, they need to be fully charged frequently or you'll shorten their lives. Also, their longevity is considerably less than good flooded batteries, like the L16's or the Rolls/Surette flooded batteries.

Bill

Thanks, Rick and Bill. Given I will have the ability to shunt power at preset voltages to various battery types (such as an AGM forward for the windless and perhaps an AGM start), would you consider that a large bank of lead-acids with a pair of AGMs can be made to play nicely with echo chargers or direct charges from a decent MPPT like the Outback FX-60?

You may have guessed that I prefer the belt-and-suspenders approach to passagemaking, with the option, should the house bank somehow fail, to lash the AGMs together to start the engine and keep the ice cubes for the rum solid. A man must plan his priorities.

[S/V Alchemy]

Originally Posted by ka4wja

I hope this helps you out....





Fair winds...


John
s/v Annie Laurie

Thanks, John. I haven't ruled out the Rolls line, and I understand the positive aspects of plate thickness, particularly on a boat I don't intend to spare from rough seas and generally getting thrown about.

And yes, a custom boat has some advantages in this respect. I don't have a second head, basically just a Lavac in something about 1.5 times the size of a shower stall, and instead of a V-berth, the saloon stops at a collision bulkhead, meaning the first seven feet of the boat is a triangular workshop.

The "upstairs/downstairs" aspect of a pilothouse boat means there's the feeling of separate cabins, as opposed to the "long saloon" of the typical production boat. And yes, the full keel means I can build a angle-steel frame to support a number of batteries over the keel tanks on the centerline. I just have to rebuild the saloon stairway. The steps provide access.

[sailinglegend]

Originally Posted by ReMetau

Same thing happened to us with Northstar AGMs...............

Northstar only make deep cycle AGMs for Telecom or Solar off-grid systems where they will be regularly re-charghed to 100%. I would suggest that they are not suitable for cruising boats.

NOT ALL AGMs ARE THE SAME!!!!

[S/V Alchemy]

I appreciate the comment. Even if I had the means to charge to 100%, which is a dodgy prospect on an anchored or passagemaking boat, I did not require the price premium AGMs command for the purposes of laying them down in a five-inch high space.

I am freed from that particular constraint.

AGMs for start batts and anchor windlasses make sense, however, to me.