battery recommendations

Discussion in 'General' started by Powder Monkey, Mar 17, 2008.

  1. Powder Monkey

    Powder Monkey Active Member

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    Looking for recommendation on a battery distributer and type for my Baltimore class hull weight may be an issue not sure on my build yet but have heard from other captains of this class

    thanks guys
     
  2. crzyhawk

    crzyhawk Well-Known Member

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    I'd be interested in this info myself so I can apply it to my USS Salem. Depending on the weights, I might be able to use the same batteries etc for my Salt Lake City.
     
  3. djranier

    djranier Well-Known Member

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    I found 6v, 5 amp, sla batteries at Home depot, back in the lighting section, used for emergency lighting, for like $9.50 or so each. Should work great for cruisers, plus very light weight.
     
  4. Powder Monkey

    Powder Monkey Active Member

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    is there some place I can go to read up on or can some one give me the ins and outs I get the volts and amps but stuff like what is sla and what charger to get
     
  5. Bob

    Bob Well-Known Member

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    SLA stands for Sealed Lead Acid. The battery type, like NIMH is nickle metal hidride. NICAD is nickle cadnium. SLA & NIMH are the two most common battery types in the hobby. SLA is cheaper. NIMH cost more but you get more amp hours for the same weight as an SLA.
    A local battler has a Baltimore. He started with 7 amp hour SLAs, too heavy went to 5 amp hours. I think the ship is now under powered. He's trying to cut weight in other places to go back to the 7 amp hour. Power Sonic makes a 6.5 amp hour battery that is a great shape to fit in a ship. Nice and square.
    For the Des Moines class that I think Salem is part of they could go with a 12 amp hour, if you build light. They get 3 or so more pounds the Baltimore.
    The large cruisers like Baltimore & Des Moines should have 550 motors, stinger motors on large pumps and larger batteries. The smaller cruisers can go with 380 motors, the small pump and smaller batteries.
    The 10000 ton cruisers like Salt Lake City typicaly have a 5 amp hour battery.
     
  6. JohnmCA72

    JohnmCA72 Member

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    Battery tech should be worthy of an entire topic. "What battery" is a question that just about everybody asks, at least once.

    JM
     
  7. Powder Monkey

    Powder Monkey Active Member

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    So would a gel cell be the sla? Or is that a totally different animal
     
  8. JohnmCA72

    JohnmCA72 Member

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    Gel cell = Sealed Lead Acid (SLA), i.e. same thing.

    Pretty much like a car battery (i.e. a box of lead plates in an electrolyte solution). The electrolyte is a gel instead of liquid.

    http://en.wikipedia.org/wiki/Gel_battery

    JM
     
  9. klibben

    klibben Member

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    I recommend SLA's if you have room, if not (as is the case for many non-capital ships) I recommand NiMhs ... I don't ever recommend NiCds due to their memory.
     
  10. JustinScott

    JustinScott Well-Known Member

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    Why does everyone like 6V batts? I have my reasons for liking 12V, but I'm curious what "I'm missing"...
     
  11. GregMcFadden

    GregMcFadden Facilitator RCWC Staff

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    Part of the 6V love is that you can generally run the RX off of it, and if you do put a diode in there to drop the voltage, it will not generate as much heat as with a 12V system. Part of it is what one can get cheaply (when I was pricing out my tirpitz, there was a substantial cost savings for the same energy storage going 6V rather than 12V). I.E. Two 6V 12AH cells were cheaper than two 12V 6AH cells. Two 6V 12AH cells were also cheaper than one 12V 12AH cells... (that can change depending on when you purchase). Part of it is flexibility. With multiple 6V cells, I can play with it and run what is best for each system, be it 6V or 12V. With 12V cells, I get 12V only as a base voltage.

    For example, I found that with my ole tirpitz, I wanted 6V to efficiently run the propeller, but 12V to the pump. And I could easily set it up that way with a bank of 6V batteries.
     
  12. djranier

    djranier Well-Known Member

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    Lighter weight, for the same capacity. My Daughters, Iowa has 6v batts at 48 amps capacity. Her boy friends Yamato use 6v, with 60 amps, it runs all day.
     
  13. JohnmCA72

    JohnmCA72 Member

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    I like 6V because I can run everything - drive motors, rotation motors, pump, receiver, servos, misc. electronics - without needing what amounts to multiple, separate electrical systems. No need to use a BEC, either, which can cause trouble sometimes.

    I'm curious: What's so good about 12V?

    JM
     
  14. crzyhawk

    crzyhawk Well-Known Member

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    Another nice thing about 6v is interchangability. Since more people have them if you have a battery die on you, fail to take a charge or simply forget to charge it, there is often a loaner available from someone who was better prepared then you. 12v doesnt often have that luxury.

    Aren't most of the NiMH battery packs 7.2 volt? What does that do to motor RPMs and acceleration?
     
  15. Renodemona

    Renodemona Well-Known Member

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    I like 6V for the reasons said above, although I personally prefer to run my radio off a seperate 4.8V system. That way (hopefully) I may lose main power but at least the radio is still powered and I should be able to fire back while immobile. Of course in my Fuso I also have a 24V bus for the solenoids since they were a purchase of convenience (ie free) rather than anything practical. ;)
     
  16. JohnmCA72

    JohnmCA72 Member

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    Generally yes, for off-the-shelf packs. I've got some 6V NiMH packs that I made up myself for my cruiser (4 @ 1.5V cells). What's common us driven by popular usage, which includes transmitters & go-fast boats, but you can build whatever you want (within limits, based on available cells); it's not very hard to do.

    Speed is definitely dependent on voltage. Any motor will run faster on 7.2V than it will on 6V. Every motor is different in terms of what voltage it runs at most efficiently. The key is to set up your entire system (props, gearbox (chain, belt, or other transmission, if used), motors, & power supply to let your motors run as close as possible to their most-efficient speed.

    Acceleration is more a matter of how quickly you can increase power to the screws. This is a function of power vs. load. You can increase acceleration by increasing the power in (i.e. higher voltage), or by reducing the load (shallower prop pitch, smaller-diameter prop, steeper reduction gearing, etc.). It's the same as with a car. If you want to get off the line quicker, you can increase the horsepower of your motor or you can change your rear-end gearing. More horsepower also means higher top-end speed which, if your max. speed isn't limited, is probably a good thing. In a car, greater horsepower also usually means greater weight, which affects both acceleration AND top speed. With an electric drive, that means greater power consumption, which translates to either shorter run time or more battery needed. For a combat warship, where top speed is limited, I prefer to choose the load-reduction option vs. greater power. Top speed is a known, fixed value, so I try to pick components that get me high efficiency at that speed, which tends to favor acceleration & runtime as well.

    All else being equal, a ship with a 7.2V supply will accelerate more quickly than one with a 6V supply. That creates a problem with your top-end speed, though. It would be possible to build a speed control that delivers higher power during acceleration, then cuts back once top speed is achieved. That requires knowing actual speed (not just counting shaft RPM), or it could be implemented with a timed "burst" based on certain assumptions.

    It's all a matter of balance & compromise, & simplest is often best.

    JM
     
  17. Powder Monkey

    Powder Monkey Active Member

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    Jez the more I learn the more confused I are

    [​IMG]
     
  18. CURT

    CURT Well-Known Member

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    I find that in terms of physical size a 6V 12amp battery is not as thick as a 12V 7AMP. Also with the weight and space saving I get more amperage for longer running time.

    I use a seperate battery for the receiver. A NimHD 3600Mh pack. It's out lasted my TX battery.It provideds 4.8v. Brand name is a Hydrimax Ultra . You can get them at Hobbico.com
     
  19. Knight4hire

    Knight4hire Active Member

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    Check with you club first.
    Some places do not allow the Lead/Acid battery to be used
     
  20. crzyhawk

    crzyhawk Well-Known Member

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    That seems a little crazy. Is there some kind of safety issue with the SLA batteries?