Using flooded lead-acid deep cycle battery as engine starter

Discussion in 'The Projects Forum' started by djbuggybee, Jul 29, 2013.

  1. djbuggybee

    Thread Starter New Member

    Jul 23, 2013
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    Hello all!
    I am wondering how one goes about using deep-cycle flooded lead-acid batteries to start up a car/truck. I am aware that this is not an ideal application, but I am interested in them because I want to replace electrolyte and perform comprehensive battery maintenance. This is part of a bigger project on lead-alum battery conversion and off-grid power.

    Somebody else asked this question in another off-site forum, and all they got was a bunch of "Why in the world would you want to do that?" and "That is not a good idea".
    Well, the answer to those statements is fairly obvious: Flooded deep cycle batteries will last longer and (In my opinion) are easier to maintain and service than a typical automotive battery if treated correctly.

    Because the situation does not pertain to lead/lead oxide plates in sulphuric acid, but instead to lead/lead oxide plates in aluminium sulphate hydrate, I need an answer relevant to P/I/E requirements and not "See manufacturer datasheet".

    Okay, now my question is really about converting a known aH to an unknown CCA, but those values do not really convert into each other, being a factor of manufacture process (I.E. Sponge plates versus solid plate, plate separation, etc...) How many aH from a flooded deep cycle battery are needed to turn over the ignition on say, a FORD F-150? A replacement F-150 battery is group 65, rated for 850 CCA; Do I need to have 12v 850aH minimum (NOT factoring discharge rate in C) available from my cells?

    The main reason I ask is because I want to use lead-acid batteries in an off grid power box/wagon, one of the features of the unit being car starting, and there is basically zilch information on this topic. I could contact manufacturers to determine CCA, but this will be next to useless to me once I have converted to lead-alum.

    The system I want to develop is not simply for powering the engine ignition, however, it should be capable of performing such a task repeatedly if necessary, after all, my designs seek extensibility.

    With my experimental lead-alum battery, which is rated for 6v 2aH (XT6N2-2A UNV), considering the original rating, I have roughly 80% E and 50% I , OR 4.8V and 1A output, yielding ~4.5w. I do not plan on starting a vehicle with this particular battery.

    Thanks in advance for your comments, questions, and answers! I look forward to your response!
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Automotive batteries are designed to supply large bursts of current for short periods of time, and then to be immediately recharged. Their plates are much thinner than that of deep-cycle batteries, as that allows for much greater surface area in the allowable space.

    This also means automotive batteries weigh far less than a same-capacity deep-cycle battery would. Attempting to change to a deep-cycle battery would likely add a considerable amount of weight to the vehicle, and it would most likely be in a undesirable location (far forward and to one side) which would have negative effects on handling, braking and fuel economy.

    You say the new electrolyte reduces the AH rating by ~50%, and the output voltage by ~20%. At that rate, the engine would turn over about as fast as if it were powered by an automotive battery that was completely discharged.

    If you properly maintain a standard automotive battery, you can have them last in excess of six years. If a battery cost $100, that's less than $17/year.
     
  3. #12

    Expert

    Nov 30, 2010
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    LOL! Not in Florida:D

    I haven't had a battery last 5 years in the 40 years I've lived here.
    It doesn't matter what brand or what the "warranty" is, Diehard, Interstate, whatever. The goal nowadays is to get an honest "pro-rate" on the warranty time because you KNOW it isn't going to last 60 or 72 months.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    Same in Southern California. I've never gotten more than about 4 years out of a battery.
     
    #12 likes this.
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    A ford F-150 starter will draw between 150 and 200 amps from a fully charged battery at a standard temp of 68ºF.

    Seldom, if ever, is this the situation. A car trip of less than thirty minutes will leave a battery less than fully recharged after a single starting load/demand. If you make multiple stops in less than thirty minutes and restart the vehicle at every one, you may need several hours of driving time to fully(FULLY) recharge the battery. This, in and of itself, is the main reason a battery will not last for its full rated lifespan. Recharging with a trickle charger over night if you have this type of driving pattern will greatly extend your batteries lifespan.
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    The CCA rating is a comparison value. meaning the battery can deliver 'somewhere in neighborhood of' 850 amps for a very very very short time and still maintain a voltage above 11.5 to 12 volts. Like most manufacturers these numbers are often greatly exaggerated.

    And, concerning the deep cycle battery portion of this post.

    They would not function well if multiple starts are made in a short period of time, they take longer to recharge to a completely full state, and, in a positive way, they would not suffer as much damage from delays in recharging as a starting battery would.

    The high amperage the automotive alternator delivers to a battery with low voltage would not be ideal for the deep cycle battery. It is designed to quickly charge a starting battery. Deep cycle batteries need lower amperage over a longer period to properly recharge for maximum life cycle.

    As for the Alum based electrolyte. I assume it is still an experimental development or it is an older tech that was tried and abandoned by manufacturers as inferior. Either way, I would not suggest it's use. Very little data is available concerning the lead/alum couple.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    A starter draw of 200A for 10s (a long start) will draw 2000 amp-sec from the battery. For a typical generator charge rate of perhaps 20A and a 50% charge efficiency it would require 2000 / 20 x 2 = 200 seconds or a little over 3 minutes to recharge the battery. How did you arrive at 30 minutes? :confused:
     
  8. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    You could try to charge a shallow discharged deep cycle battery that fast but it would kill it quickly and boil the electrolyte from the heat of the plates being unable to accept that much energy on the surface of the thick plates because the voltage needed to maintain that bulk current would quickly rise above the recommended charging voltage.

    For a typical deep cycle battery used in a starter type application only the surface charge on the thicker plates is converted from chemical energy to electrical energy and there is usually much less actual reaction surface (and a higher internal resistance) exposed directly to the electrolyte at any given time compared to a starter battery so more heat is generated internally at the same current draw. The internal hot spots can warp the separators and generate much larger sulfate crystals that are harder to reconvert to pure lead again during the charge cycle. Doing this more than a few times usually results in permanent loss of capacity or a shorted cell.
     
  9. LDC3

    Active Member

    Apr 27, 2013
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    I want to point out that deep discharge batteries usually have a wider gap between plates to decrease the likelihood of shorted cells. Also, the plate are position higher to accommodate more fallen particles from the plates.
     
  10. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    All that assumes they are being charged correctly using a normal bulk to a set voltage, regulating a set absorption voltage until the proper ends amps is met and float cycles to reduce heating effects and maintain full charge. The quickest way to murder a good deep discharge battery is to short cycle charge it like a starter battery.

    I using 4 6vdc golf cart batteries for solar energy power storage that have lasted many years with hundreds of full discharge cycles so yes they can take abuse during discharge but I'm always careful on the recharge cycle because that's usually where they are killed from either over or under charging.

    My solar project over the years: http://www.flickr.com/photos/nsaspook/sets/72157622934371746/with/6822479182/
     
    Last edited: Jul 31, 2013
  11. Brownout

    Well-Known Member

    Jan 10, 2012
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    I've had a deep-cycle lead-acid battery starting my '98 f-250 for two years. Being the truck is an old diesel, it often takes alot of cranking before it starts. There are no issues using this battery.
     
  12. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    I don't know what type of (flooded) battery you're using but if it's got a CA/CCA rating then it's usually not a 'true' deep-cycle battery like the traction/EV batteries I use for solar power storage. If you install a oversized 'true' deep cycle-battery that can supply the needed cranking amps while staying under it's rated discharge capacity and have a (multi-stage) charging system designed for that type of battery that's ok. I admit that the term has been twisted by marketing to mean anything with slightly larger plates but there still is a technical difference between the two with 'flooded' cell construction. If it's a AGM battery then the overlap in construction between the types allows for deep-cycle starting batteries but the recharge cycle must be optimized (voltage limited to avoid gassing) for that type instead of a flooded cell for long life.

    http://www.aussiebatteriessolar.com.au/deep-cycle-battery-info/
    http://en.wikipedia.org/wiki/Electric_vehicle_battery
     
    Last edited: Jul 31, 2013
  13. Brownout

    Well-Known Member

    Jan 10, 2012
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    It's a true deep cycle battery. But it's probably an AGM type, as most lead-acid batteries sold in the US are nowadays. Definitely deep-cycle though.
     
  14. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    AGM batteries are great (pricey too) but DON'T ever short one because the internal resistance is so low they can generate thousands of amp and melt a wrench in half within seconds. (I've done it :eek:)

    http://www.sunxtender.com/otherpdf/SunXtender_Internal_Resistance_Short_Circuit_Current.pdf
     
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