Maine mentioned in a earlier post that Odyssey batteries where really great one. I am about to change out my batteries and was planning on going with Sams Club 6v Golf cart ones.... However after looking at the Odyssey site I was wondering if I might be better off with a single 31M-PC2150ST-M battery acting as the house battery instead. However, on the website they only mention 400 cycles..... I thought a good 6v could do more.... Any thoughts would be appreciated.... Thanks.. Jon
Odyssey batteries
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Jon,
Odyssey batteries are one of the premium AGM's, an excellent AGM battery, like Lifeline is. The big problem is they are anything but "drop in" replacements for typcal flooded batteries that were using a bare bones system. They require a particular charging regime that needs to be though of before just "plopping in" some AGM's..
400 cycles is to 80% DOD with Odyssey (IN A LABORATORY) but you would never see that in the real world if trying to cycle to 80% DOD. You are still going to be best to cycle Odyssey batteries to 50% DOD for the best life.
*You will also need a min of 40% of Ah capacity in charge current (120A for a 300Ah bank)
*The ability to charge to full after each discharge or as soon there after
*Temperature compensated charging on all sources
*Charge voltages of 14.7V Absorption > 13.6V Float, on all charge sources
Read the link below then decide if AGM batteries are a good fit for you...
AGM's - Making The Choice
The realities of cycle life and not at all what the lab numbers represent. Fairy tale best describes them.. Most boat owners barely break 140-150 cycles before their banks are dead and some don't ever break 100. We do the math at the beginning of every one of my electrical seminars based on owners boats whom are in attendance.... Don't get giggled up over the misleading laboratory data the manufacturers present. Lab data does not translate to the real world abuse sailors put these batteries through...
On top of that two 6V GC2's will give you 225Ah's and one PCM2150 will give you 100Ah's. You would need at least two PCM2150's to get to 200 Ah's.. Odyssey's can last a long time but it is more expensive and costly to get there then it is with flooded batteries.
This bank was very costly to build and do correctly and included a massive alternator, serpentine pulley kit, external regulator, temp sensors, temp compensated shore charger, solar etc. etc... The batteries alone were approx $1500.00 then there as another 2k plus in extra equipment. They are doing fine but it is not cheap to do correctly...
Maine;
You say that an AGM bank requires a "minimum" charge output of 40% battery capacity. Why? What does the battery bank care how fast it is restored? Certainly is great that the AGM can take a monster charge, but not a necessity. Getting to that kind of charge capacity for a 400Ah battery would require two big shore chargers (and the the relevant installation hassles). Or are you referring to a boat on moor relying on an alternator?
You say that an AGM bank requires a "minimum" charge output of 40% battery capacity. Why? What does the battery bank care how fast it is restored? Certainly is great that the AGM can take a monster charge, but not a necessity. Getting to that kind of charge capacity for a 400Ah battery would require two big shore chargers (and the the relevant installation hassles). Or are you referring to a boat on moor relying on an alternator?
Odyssey batteries want to see a minimum 40% of Ah capacity for optimal cycle life but 30-35% will be better than 20% etc.... Lifeline wants to see a minimum of 20% of Ah capacity but more is better. Neither company is willing quantify what the impact is but it can be comparable to DOD in effect on cycle life..
Odyssey Battery Technical Manual:
"Note the charger current in the bulk charge mode must be 0.4C or more."
The engineers at Odyssey/EnerSys don't mince words and actually use the word "must"..
The higher the charge current the better cycle life you get with AGM. Dave V., the head engineer at Lifeline, presented this data back in the 90's after conducting some studies on military batteries. Both Lifeline and Odyssey have minimum charge current guidance because they have studied it at length. I have had a number of conversations with Kalyan J. of EnerSys and Dave V. of Lifeline and both are fully in the "the more current the better" camp....
I am doing some testing for a new type of AGM that will be out pretty soon and Kurt, the head engineer, says the same thing. The PSOC testing I am conducting, for real world type of marine use, is being conducted at .46C. They initially wanted me to do these PSOC tests at 1C but that is simply not realistic and we want to have realistic data not lab type data. Even .46C is a stretch for most boats.
The sad reality is that many folks completely ignore the technical manuals, and instructions for charging, then get upset when a $1500.00 bank of batteries is dead in three years.
The basic take away of the study is from the abstract:
"The results show that cycle life is strongly affected by the rate of charge, as well as the depth of discharge."
Can you charge at lower rates? Yes, of course, but it will dig into cycle life. AGM batteries are a puzzle and all the pieces really need to work in concert to yield the best cycle life to dollar ratio...
Interesting, thanks. Could a case be made for a smaller AGM battery that better matched the charge capacity of a typical large 100A charger, then take the bank to 80% DoC (rather than 50%) before a robust recharge? It certainly would be nice to reduce the size of the battery bank.
I MUST replace my current 400Ah wet cell bank this year and they need to be moved into the saloon. So the final design strategy is underway and I really do not want two big shore chargers. An AC genset will be my supply out of slip. Is it still too soon for lithium battery technology?
I MUST replace my current 400Ah wet cell bank this year and they need to be moved into the saloon. So the final design strategy is underway and I really do not want two big shore chargers. An AC genset will be my supply out of slip. Is it still too soon for lithium battery technology?
Not really because now you are discharging deeper and discharging more frequently. You can discharge to 80% DOD but you accelerate the demise. Even in the lab at 80% DOD they only get 400 cycles yet at 50% DOD they get approx 750 cycles and at 40% DOD they are at 950 cycles.
The bigger bank will last longer and is usually a compromise between charge rate and bank size. With Lifelines and a 400Ah bank 20% of C is only an 80A charge source.
Better yet go GEL, get even longer cycle life, and they don't require massive charge current..
It's been a while since I researched all this but the bells that immediately ring are:
First the 31M-PC2150ST-M is a marketed as a dual purpose battery not a deep cycle. That can be important if your plan is really to use them as deep cycle batteries. The design is different and that will determine how many times you can deep cycle the things. You don't need a starting battery/dual purpose design unless you have a really big engine and then I'd really recommend getting a dedicated starting battery.
Second at 75 lbs the 31M-PC2150ST-M doesn't come close to the 126 lbs the two deep cycle golf cart batteries will weigh. That weight isn't there to keep the batteries in place but give you extra capacity.
All this info is online. Just spend more time researching it if you're interested.
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First the 31M-PC2150ST-M is a marketed as a dual purpose battery not a deep cycle. That can be important if your plan is really to use them as deep cycle batteries. The design is different and that will determine how many times you can deep cycle the things. You don't need a starting battery/dual purpose design unless you have a really big engine and then I'd really recommend getting a dedicated starting battery.
Second at 75 lbs the 31M-PC2150ST-M doesn't come close to the 126 lbs the two deep cycle golf cart batteries will weigh. That weight isn't there to keep the batteries in place but give you extra capacity.
All this info is online. Just spend more time researching it if you're interested.
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The Odyssey marine batteries are marketed as a deep cycle battery, high cranking starting battery and dual purpose because they do it all very well. They are very good performing AGM batteries in a deep cycling application, if charged correctly.
The EnerSys TPPL technology yields the ability to cycle deeply, provide massive pulse loads for things like thrusters, inverters, powered winches etc. all with minimal voltage sag due to the low Peukerts exponent the technology yields..
As AGM batteries go they are one of the best and one of the fastest charging. Like any AGM they still need proper charging to yield maximum cycle life..
First Thank you Maine, Claude and Ken. I've decided to stay with the 6v golf batteries.
One more question, I've done some research and am not completely clear as to what defines a cycle or a deep cycle for a Flooded Battery... Is it the same as the AGM? For instance the majority of my sailing consists of a going out for a few hours returning back to the dock and then letting the 20AM charger top the Flooded bank off. Does this constitute a cycle?
Thanks
One more question, I've done some research and am not completely clear as to what defines a cycle or a deep cycle for a Flooded Battery... Is it the same as the AGM? For instance the majority of my sailing consists of a going out for a few hours returning back to the dock and then letting the 20AM charger top the Flooded bank off. Does this constitute a cycle?
Thanks
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I can't say that this is scientific or what might happen with other boats but we had a lot of cycles with our Lifeline AGM batteries - 6 golf carts - 220 Ah - for a total of 660 Ah at 12v. The main charging was from a 120a engine alternator with double 1/2 belts. Solar panels helped keep engine runs down but we ran the engine a lot to keep the batteries up while we cruised full time for 5 years, with only occasional dock AC charging. The alternator charging was regulated by a Balmar 612 programmed for AGMs. We got a Honda 2000w generator at year 3 and charged the batteries with that through our 2000w Freedom inverter/charger, also programmed for AGMs. We also had 300w solar through a Morningstar regulator, also set for our AGM charge profile. But our primary charging was by the engine alternator. We charged them whenever the voltage got down to 12.1-12.2v and would charge them until they got to float (mostly). On passages we motored often for long periods so the batteries were well-charged under those conditions. I really don't know how many cycles we got but it well over 500. And the new owners used them for another 2 years after we sold the boat.
To say that we were pleased with the setup and batteries would be an understatement. I don't recall ever equalizing the batts. This may have been unusual as I met several cruisers who managed to ruin their AGMs in two years of cruising and bad-mouthed them to whomever would listen. I am happy that our "new" boat has Lifeline AGMs although I don't like 8D's if I ever have to move them. I would go with golf carts again. The Odysseys sound very good and I would put them on my list to consider if I replace what we have (unknown age and use/charging).
BTW - that is a beautiful installation in the pic that Maine posted.
To say that we were pleased with the setup and batteries would be an understatement. I don't recall ever equalizing the batts. This may have been unusual as I met several cruisers who managed to ruin their AGMs in two years of cruising and bad-mouthed them to whomever would listen. I am happy that our "new" boat has Lifeline AGMs although I don't like 8D's if I ever have to move them. I would go with golf carts again. The Odysseys sound very good and I would put them on my list to consider if I replace what we have (unknown age and use/charging).
BTW - that is a beautiful installation in the pic that Maine posted.