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Old 06-12-2008, 14:12   #1
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AGM vs Gel cells

Just wanted to hear some opinions and would like recommended brand names of both types.
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Old 06-12-2008, 15:10   #2
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AGM's are the better refinement of Gel batteries. The lower internal Resistance means it takes a charge faster. You save on engine time and that saves fuel. I had some Concorde Lifelines that were really nice. You can put them in any position. The group 4D's are easier to lug up and down the companionway. They have gotten expensive. The price of lead has gone sky high so cost will be an issue. Two group 4D's make a nice 400+ amp hour bank.

The other alternative is some of the large industrial lead acid batteries. They make a 1200 amp hour that is being used more. The plates are wicked thick and would last a very long time.
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Old 07-12-2008, 17:42   #3
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I agree with Paul. I replaced some gels with AGMs and I love them. The AGMs really soak up the charge quickly and are a little more robust with respect to charging voltages than gels. Gels require a fairly narrow charging voltage range. See the link for a comprehensive discussion.

http://www.eastpenn-deka.com/assets/base/0139.pdf

In addition to the Lifelines, I would recommend East Penn Dekas. They are sold under a variety of brand names. Whatever you choose, make sure that you have a well-regulated charger and that your alternator, if it does not have a multi-stage external regulator, charges within the voltage specifications for the battery.

If you can, you can save a bundle buying at a "Battery Warehouse" or some other distributor (away from the shoreline) that carries a wide line of batteries for autos, marine, golf carts, etc. I think I saved about 50%

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Old 07-12-2008, 18:27   #4
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An interesting newer AGM brand is Odyssey. These are made by Hawker who does a lot of military batteries.

These have "virgin lead" which is supposed to provide "faster charge acceptance". They are capable of ...cranking pulses in excess of 2250A for 5 seconds as well as 400 charge/discharge cycles to 80% depth of discharge" (I wonder what kind of writing the Odyssey marketing writer does in his/her off hours..)

If they have greater cycle life and faster charge acceptance than other AGM's that would be a real plus. Anyone who has dealt with AGM's knows that it's very important to reguarly get them all the way back to full charge.

Anyways, Nigel Calder has put them in his new boat. I read somewhere recently (but can't remember where) that he was happy with their performance but waiting to see how they lasted.

I believe (but am not sure) that in the US the Sears Diehard Platinium are rebranded Odysseys.

I don't have Odysseys but continue to consider them.

Does anyone have updated experience with these batteries?

Carl
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Old 08-12-2008, 08:31   #5
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Carl...Calder wrote an article on the new battery technology here:
Professional BoatBuilder - February/March 2008
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Old 08-12-2008, 08:43   #6
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And about his use of Odyssey Batteries:
Blog - Malo visit #1
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Old 08-12-2008, 08:59   #7
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His latest comment:

"The Polar Power generator is wired to a 144v bank of ‘Odyssey’ batteries from EnerSys. These are a variant of AGM lead-acid technology with very thin, pure lead, plate grids (Thin Plate Pure Lead – TPPL) which results in astonishing charge acceptance rates. The first time I ran the batteries down a bit and then cranked the generator, their charge acceptance rate immediately drove the generator to its full 22 kW output! We can put 24-hours worth of ‘house’ energy in these batteries in about 20 minutes!! "
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Old 10-12-2008, 02:19   #8
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Batteries - What Type? ~ by Chuck Husick
Chuck Husick on BoatUScom

“... A boat used six months of the year will experience about 60 battery cycles, about one for each day of use. A light/medium duty battery good for 200-300 cycles will last about three years. Use the boat almost every day of the year and you will accumulate about 200-250 cycles. A medium/heavy duty grade battery will provide 500-750 cycles, or about three years use. A sailor off on a world ranging voyage can put 700-1000 cycles on a battery in one year. The price of a 3000 cycle life very heavy duty battery will be a bargain for his boat but will give you a non electric shock. Remember, batteries wear-out even when not being used. Buying one that whose cycle life won't be consumed for 10 years is not a good idea ...”

More:
boatus.com/husick/techno01_01.asp
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Old 10-12-2008, 03:30   #9
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one should keep in mind that ODYSSEYs require higher charge voltage
than "usual" batteries (~ 2,45 Vpc = 14.7 V per battery);
also much higher currents are required.
A standart alternator may be not good in the case - at least I will have
to replace my ISKRA with something more sophisticated.
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Old 10-12-2008, 04:16   #10
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When "they" refer to battery cycles, what actually does this mean?

For example does it mean using up 25% of capacity and then a recharge? Could it be as little as using 5% and then recharging?

Batteries capacity changes as they age (apparently) in use. They seem to discharge quicker over time, which seems to equate with reduced capacity.

So let's say you have a 500AH bank and use your autopilot for 5 hrs with a brand spanking new battery. At the end of the 5 hrs the voltage might read say 12.6. Do the same with the battery after 5 yrs of use and it might read 12.4 (even though the starting voltage for both was 12.7. Assuming the load (drain) was the same, this means you battery capacity has been reduced it might be only 250 AH. I don't know how to do these calculations, but that seems to be what happens as batteries age - they shrink in "capacity" but continue to weigh the same!

So suppose you have plenty of charging capacity and you are topping off at the same rate as you are draining down. This would be NO CYCLES! Or more realistically your cycles would not be very deep. Is this good or bad?

We're also told that getting the last bit of recharge into a battery is much harder than the first bits so it like getting to the peak of a parabolic curve, which flattens out as you move alone the X axis (time). And of course your charge regulators don't or can't push lots of amps in to almost charge batteries since they base their charge regimen on sensed voltage and if it's high they cut back. It's lke filling a glass of water, as it gets to the top the tap slows to a drip.

What I would like to know is how to best maintain a battery to get the most out of it (matching my needs) for the longest term. Do I let it go way down before charging it back up? Or do I try to maintain it as full as possible with constant trickle charging and high output charging sources? How about smaller capacity (cheaper and lighter) and more frequently replaced batteries? If you had a spare to use, when bank A went south, you could then go to Bank B which is all new and waiting and then replace bank A. Not switch back and forth between A and B? The thought of replacing large batteries is not a pleasant one.

Does anyone actually know the best strategy?
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Old 10-12-2008, 05:15   #11
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Quote:
Originally Posted by defjef View Post
When "they" refer to battery cycles, what actually does this mean ...
In battery “marketing” literature, a cycle is a somewhat arbitrary term used to describe the process of discharging a fully charged battery down to a particular state of discharge, then fully recharging it.

Battery cycle life is defined* as the number of complete charge - discharge cycles a battery can perform, before its nominal capacity falls below 80% of its initial rated capacity; or the number of cycles the battery can perform before its internal resistance increases to 1.3 times its initial value when new.

* "They are the "BCI". The performance and life characteristics of batteries are typically determined using testing procedures specified by the Battery Council International Technical Manual:
Section 8: BCI Recommended Specification for Cycle Life Testing of Deep Cycle Marine/RV Batteries

Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it may last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it may last about 5 times as long as one cycled to 50%.
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Old 11-12-2008, 05:47   #12
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This whole cycling thing seems like it needs a little monitor to plot the voltage in the Y axis and time on the X axis and you can display it on a lap top or plotter and look at all the peaks and valleys and so forth. I don't know if this sort of history would reveal anything of usefulness, like knowing when you will be getting new batts, but I am sure some clever engineer will market such a device and we can all look at the graphs.

As I have said before, batteries are the telephone poles of high technology. When can we get rid of them?
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Old 11-12-2008, 07:51   #13
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Quote:
but I am sure some clever engineer will market such a device and we can all look at the graphs.
You can use a battery monitor to determine where in the discharge cycle you currently are as well as the current amp load (charge or discharge) and amps consumed. Charting on a day by day basis gets more complicated as far as storing samples over time and making the graph in a device. It could easily be done but requires a small computer device to store and display the data. I'm not aware of any monitors you can buy that have a digital output. The monitor itself is exceptionally valuable since it can tell you how much power you have used over a period of time and act as a fuel gage for the battery. Without saving historical data I find mine to be invaluable. if you can understand one day you can understand a week.

Quote:
batteries are the telephone poles of high technology. When can we get rid of them?
When we no longer need to store power batteries will be useless. Batteries right now are the most efficient method of storing electrical power. The chemistry of batteries is quite well understood and has been for the better part of 60 years. Processes for manufacturing batteries have advanced and has shown some new battery "packages" like the AGM and some tiny sized packages such as silver halide. Should we become able to create devices more energy efficient the batteries required could have more extended lifespans and get smaller and reduce their mass.
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Old 11-12-2008, 08:03   #14
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Just installed 5 Odyssey 2250s for a house bank this week. Sears didn't go that large. I did replace the two cranking batteries with the larger Sears Platinums. Will see how it goes.
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Old 23-12-2008, 16:26   #15
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Kirk,

Any early reaction to your new Odyssey battery bank?

I'm most interested in whether their high charge acceptance claim really translates to quicker full charges. I also noticed that the literature recommends charging at 14.7 volts. Are you going that high?

Thanks,

Carl
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