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Replacing Flooded Battery With AGM

Discussion in 'Luhrs Yacht' started by Hot Rod, Dec 21, 2009.

  1. Hot Rod

    Hot Rod New Member

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    I am thinking about replacing my two 8 D flooded (wet) batteries with AGM batteries. I have a 2007 Luhrs Open Sportfish with twin Yanmar 480 HP engines and Hitachi 80 amp internally regulated alternators (all original equipment).

    Are these batteries a simple swap, or do I need to modify the alternators? Thanks
  2. Henning

    Henning Senior Member

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    No mods required, simple swap.
  3. Capt J

    Capt J Senior Member

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    Simple swap, but there may be a different setting for your battery charger for AGM. (Usually a dip switch or something similar). ALSO, most AGM's don't have anywhere's near the cold cranking amps of flooded, so check that before making the switch or they might have a hard time cranking over your Yanmar 480's
  4. Pascal

    Pascal Senior Member

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    simple swap, just set the switch on the charger as Capt J mentioned.

    not sure i see the point though, the only benefit is that you wont' have to add water to them, not really worth the extra $. they should last a little longer but not longer enough to offset the cost.
  5. Henning

    Henning Senior Member

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    You'd only flip the switch if you are changing from Gell Cell batteries. Flooded Cell and AGM operate at the same voltage, it's the Gell Cells that require lower.
  6. Hot Rod

    Hot Rod New Member

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    Many thanks for the advise on the AGMs.

    I plan on using 2 8D flooded (wet) for cranking the Yanmar 480s and 2 8D AGM batteries for the House/Electronics. I plan to have the House/Electronics bank batteries wired together in parallel with one of the Yanmar alternators providing charge while underway and its own dedicated battery charger set to "AGM".

    I plan to keep the 2 8D cranking batteries separate from each other except for charging, when I plan to use a voltage sensitive relay battery combiner. I plan to have the other Yanmar alternator provide charge while underway and supply the cranking bank with its own dedicated battery charger set to "Flooded".

    What are your thoughts and ideas about this preliminary plan? I currently have a stand alone battery to crank a 3 cylinder Yanmar powered Kohler 8-32EOZD generator. How do you think I should incorporate it into the system? I need to provide a charge to the battery when it is not in use? The current battery used by the generator is a standard marine sealed cranking battery.
  7. Henning

    Henning Senior Member

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    Unless you are staying with the flooded cell battery for cost reasons, there is no good reason not to use an AGM for cranking. I would suggest that you get a multi point charger with a desulfinator cycle built in. Provides a great extension to battery life.
  8. Hot Rod

    Hot Rod New Member

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    I reviewed the details of my ProMariner ProTech-4 battery charger to insure that it properly addressed the desulfate process. Here is what it says, "Stage 2 Absorption Charge/Conditioning Mode = Precision 14.7 V DC to Fully Charge & Desulfate Battery(s)." The dip switches are set to 4 hours for 8D batteries for this stage. The charger also has three 3 DC output connections.

    I discovered that this battery charger, which came installed on my 2007 Luhrs, has been discontinued. It has one setting for Flooded/AGM batteries (14.7 V Absorption, 13.5 V Float) and a second for GEL (14.1 Absorption, 13.5 V Float). That charger has been replaced by ones (ProTechi and ProNautic) that have three different battery type settings; Flooded (14.7V Absorption, 13.5V Float), AGM (14.4 V Absorption, 13.3 V Float) and Gel (14.1 V Absorption, 13.8 V Float). The AGM now has a different charging rate (.3 V lower for Absorption and .2 V lower for Float) and the GEL has a .3 V higher Float rate.

    The question is, what is the affect of this change in charging rates on the AGM battery? Is it worth the investment in the newer model (ProNautic or similar brand) battery charger?
  9. Henning

    Henning Senior Member

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    They will charge at a slightly slower rate, not get quite as warm and offgas at a slightly lower rate. I have never had an issue using old style battery chargers on AGMs, so I don't know if it would be worthwhile to get the new charger, but dropping the float to .1 volt above lead/acid batteries full charge sure won't hurt anything, and with the desulfation cycle you might get some impressive life span out of them. I had a desulfator circuit that I'd use on my airplanes battery and got over 7 years out of it (typical is 2-3) and it was still going strong when I sold the plane.
  10. Hot Rod

    Hot Rod New Member

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    Thanks to everyone that has participated in this post to date. I now feel that I am headed in the right direction with the selection of AGM batteries for the House/Electronics battery bank. I just purchased a ProMariner Pronautic model 1260 marine onboard battery charger. It has all of the features that have been pointed out to be necessary to prolong AGM battery life. I needed a second battery charger anyway, as I am going to dedicate my current ProTech 4 charger to the 2 8 D Wet (Flooded) cranking batteries.

    The Pronautic 1260 has 60 amps of charge, 7 user selectable charging algorithms, employs battery balance which allows smaller group size batteries to be charged along with larger battery types, allows 100% of the available charging amps to be used by any one or combination of three banks, provides an individual charge/conditioning time based on the status of each of the three charge outputs resulting in a 100% charge while desulfating batteries, includes an automatic reconditioning mode every 10 days and last, has remote true temperature compensation from a remote battery temp. probe.

    I still have some concern about using standard marine alternators with the AGMs, but in reality, the amount of time running the engines on the water being charged by alternators Vs the amount of time attached to the onboard battery charger is minor. So now that I have a charger that is ideal for AGMs, it's on to battery selection!

    I would like to hear comments as to the best AGM for the investment and the best deal that can be had. Thanks
  11. Henning

    Henning Senior Member

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    Deka Batteries
  12. Capt J

    Capt J Senior Member

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    I would recommend two things with your setup.

    1. A Battery switch so that you can connect (parallel) the house batteries with the starting batteries in a dead battery situation, if one is not already installed.

    2. I would use a battery isolator on the port engine, that way you can use the alternator to charge both house batteries and engine batteries and one battery bank would not backfeed the other. That way, you could run on only the port engine in an emergency situation or whichever.
  13. wingless

    wingless Member

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    When I recently replaced my six group 31 batteries I used the published specifications for rated ampere-hours, cycle life and cost to caclulate the lifetime cost per ampere-hour delivered.

    That caclulated lifetime cost was a wash between the flooded cell and the AGM battery.

    The flooded cell has the benefit of a lower initial cost, about half.

    On this swap I remained w/ flooded cell.
  14. Hot Rod

    Hot Rod New Member

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    Does anyone know if it's possible to direct the alternators' output to a high capacity battery isolator and then to the starter bank and the House/Electronics bank? This would produce a .6V lower alternator max charge rate by going through the isolator's diode. That would provide the reduced (desired) output for the AGM batteries in the House/Electronics battery bank. The reduction in the max. charge rate for the cranking battery bank could be corrected when the batteries are charged by the onboard battery chargers without going through the isolator. Will each alternator need a separate isolator, or can both alternator-charge-outputs be attached together to the isolator's charge-source-terminal?

    If this works, it may be simpler than having my internally regulated alternators, converted to alternators with external regulators.
  15. Capt J

    Capt J Senior Member

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    Yes, you can run your alternator's output directly to a high capacity battery isolator. I would think that you can run both alternators to 2 different isolators and 2 different battery banks. I wouldn't worry about your engine alternators producing too much voltage for the AGM's.
  16. Hot Rod

    Hot Rod New Member

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    Thanks to all on this site that helped me with the redesign of the battery/electrical systems for my 36 Luhrs. The problem with the original factory system was that the cranking and house/electronic batteries were all combined into one bank and I was often surprised with batteries too drained to crank the 480 HP diesels. I use the boat to fish 50 miles offshore, so that is an outcome that had to be addressed.

    I have redesigned the system and attached it as an Adobe .pdf. The new system was designed to function as follows:
    > Separate battery banks for main engine cranking, house/electronics and generator cranking
    > 2 parallel 8D AGM batteries for house/electronics loads with a dedicated 60 amp "smart" battery charger setup for AGMs
    > 2 separate 8D Wet batteries for cranking loads from the 480 HP Yanmars with a dedicated"smart" battery charger setup for Wet batteries
    > Utilization of a Sure Power battery isolator that allows the cranking and house/electronic battery banks to be charged simultaneously by the two main engine alternators. The diode principle will reduce the alternators' output by .6V, which is ideal for not overheating the AGMs on the 50 mile trip out and back from the fishing grounds. The Wet batteries will be compensated for when charged by the onboard battery charger cycle
    > Parallel start solenoid for the two main engine cranking batteries
    > Parallel start solenoid for the generator and main engine cranking batteries, providing extra security for the generator

    I tried to keep the redesign simple so there would be less to go wrong. I am requesting feedback from the electronic experts on the following:
    > The basic system, ways to improve it, etc.
    > Knowledge of anyone's use of the Sure Power battery isolator (2 alternators and three battery sources)
    > How to disconnect my Hitachi, internally regulated, alternators' power output and connect it to the battery isolator. Is it as simple as disconnecting the battery wire from the battery terminal on the back of the alternator and connecting this wire to one of the output terminals on the isolator, and running a new wire from the charge input post of the isolator to the battery terminal on the back of the alternator? I have read that some other functions like tach output, etc. rely on the alternator charging function.

    Thanks again for all the help,

    Carl
  17. Hot Rod

    Hot Rod New Member

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    Added PDF File

    Adding PDF attachment for the post above

    Attached Files:

  18. Hot Rod

    Hot Rod New Member

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    Warning! Not All Alternators or Battery Chargers Work With Battery Isolators!

    I spoke with Gary Felipe of Sure Power and learned that my Hitachi alternators would not work with their battery isolators. He said, "For an alternator to work, it needs a separate battery sensor wire that connects directly to the battery." Gary went on to say that "Battery chargers are a little different and vary by make. Some have adjustable regulator settings to compensate for diode drop etc. Some do not work at all with battery isolators and need to see the battery directly in order for them to even turn on."

    This being said, I have been forced to rethink my alternator charging scheme. The simplest redesign to my system is to have each alternator charge its own starting battery and eliminate the battery isolator subsystem. The new ProNautic charger, that I recently purchased, is totally dedicated to the house AGM batteries and cranks out 60 Amps. The only time that the alternators would have been helpful to the house battery bank would have been on the ride back in after a day of fishing. Now that I have been forced in this direction, I think that they will be charged just fine by the onboard battery charger, which is activated by the Genset which is cranked up and running during the return trip and with onshore power once I get to the dock.

    I have attached the redesigned system. What are your thoughts or maybe other solutions?

    Attached Files:

  19. Capt J

    Capt J Senior Member

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    The Pronautic charger only puts out 60 amps if you bridge the 3 leads together.

    Could you run the isolator between starting battery bank and the house battery bank, and run the alternator straight to the starting batteries.......

    I had a friend now come to think of it that hooked his yamaha EFI 200 to an isolator and then 2 battery banks and it made the engine run weird.
  20. Hot Rod

    Hot Rod New Member

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    Gary Felipe was talking about his dual alternator to 3 battery output, Sure Power battery isolator. The Hitachi alternator will work with a battery combiner.

    There are three reasons for not using a battery combiner for charging the Cranking Battery Bank with the House/Electronics Battery bank:

    > I plan to use Wet or Flooded 8D Deka batteries for the cranking function and AGM 8D Deka batteries for the house/electronics loads. The battery manufacturer advises against charging dissimilar battery types together.
    > I have dedicated an onboard ProMariner ProTech-4 battery charger with a specific Wet/Flooded charging pattern to charge the cranking battery bank and the new ProMariner ProNautic smart battery charger with a specific AGM charging pattern to charge the house/electronics battery bank. If I were to combine these two banks, it would defeat the separate charging programs.
    > The cranking battery bank's discharge will be minor and require only maintenance levels of charging. The house/electronics battery bank will be exposed to heavy, long term loads (if the fish are biting) and require heavy and long charging. This can be most effectively performed by two separate charging systems.