Question about sizing a battery charger to a 12v lead tractor battery

Discussion in 'General Electronics Chat' started by sternpirate, May 22, 2016.

  1. sternpirate

    Thread Starter New Member

    Dec 10, 2015
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    I am in the market for a battery charger. Since antiquity I have used car battery chargers on tractor batteries without issue but I have decided to upgrade to a model with short circuit protection so that the unending cycle of burning out chargers from internally shorted batteries and buying replacements can be broken. It seems that I need a switchmode type charger for that feature.
    http://www.ctek.com/ie/en/chargers/XS 3600 this is a charger that would be the right voltage for me, but it says Battery capacity 7–75Ah up to 120Ah for maintenance
    By my estimation I need a charger to handle a battery of 150AH but I don't need a high amperage charger as I have atv batteries and car batteries to charge also. I don't mind taking 2 days to charge a battery either as I have a boost charger to get me going in a hurry.
    So, can any of the techies here tell me can I use this charger on a larger ford/new holland tractor/bus battery without damaging it as ah rating is not something I ever worried about before in sizing alternators and chargers to the task.
     
  2. ronv

    AAC Fanatic!

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    I'm not sure it's big enough. I have that problem with my golf cart batteries and a small charger - It never turns off.
     
  3. #12

    Expert

    Nov 30, 2010
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    It's a bit slow, but you're not supposed to take your batteries down to dead flat before you charge them. As far as charging goes, a 150 amp-hour battery that's about half empty will act like a 75 amp-hour battery that's dead. If time doesn't matter much and the price is right, I say, "try it" for any vehicle that has an alternator in it.
    If you're going to run your atv down to where you have to push it to the charger, I wouldn't buy this one.
     
  4. tcmtech

    Well-Known Member

    Nov 4, 2013
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    And that using small chargers on long duty cycles to try and recharge big batteries is why you keep burning them up.

    The basic rule I have always used for sizing chargers it that it should be able to recharge the battery from near flat dead to full charge in under 4 hours and for alternators their continuous duty capacity should be no smaller the half main battery systems Ah rating.

    For a 150 Ah battery I would be looking at something capable of handling at least 50 - 60 amps continuous duty minimum and 4x - 6x that peak otherwise you are just going to burn it out trying to bring a large battery up with a small charger by letting it sit maxed out for hours on end.

    As for doing small batteries with large chargers is not really a problem just so long as the charger keeps its peak voltage under 15 volts once the charge rate has dropped under an amp or less. I have some homemade super charger units that can carry the better part of 100 amps continuous duty and top wel over 400 peak, if the circuit they are on can support i,t and I charge small batteries with them all the time without problems. The only trick behind it is that they top out a ~15 volts.
     
  5. sternpirate

    Thread Starter New Member

    Dec 10, 2015
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    i bought the larger ctek mxs 5.0 version which was all i could afford at the moment. thanks for all the responses.
    tcmtech, i would like to see plans for how you made your supercharger unit. i see many inexpensive server psu's on ebay that support 130A at 12v and mods on other websites to modify to 13.8 and 14.4 they would be ideal for charging. could i use an arduino to disconnect the charger then measure the battery voltage every few minutes or is some other way the correct practice? i thought larger chargers were frowned upon because cc/cv is the correct way to charge a fully flat battery. and your design does not sound like it supports constant current.
     
  6. #12

    Expert

    Nov 30, 2010
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    I found a sale on surplus torroids, 12V, 150W. $7.50 each:eek:
    I put 4 of them in an old toolbox, added rectifiers and a fan.
    Used 3/4 inch copper pipe for the terminals.:D
    What the h. They fit the jumper cable clamps just fine.:rolleyes:
    50 amps continuous, 200 amp surge, for less than $50.:cool:
    It's a bit high in the voltage department at almost 19 volts peak, but I never leave it unattended because you can start a car with it in 4 minutes.
    I have never seen a car battery accept more than 36 amps...even if its so far dead that it won't run the dome lights.
     
  7. Lestraveled

    Well-Known Member

    May 19, 2014
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    @sternpirate
    Most battery manufacturers recommend that the charger output about 10% of the amp hour rating of the battery. So, a 15 amp charger would be best for a 150 AH battery.
     
  8. tcmtech

    Well-Known Member

    Nov 4, 2013
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    They are just simple high current DC power supplies like any other dumb battery charger.
    Mine are based around old 2 - 2.5 KVA transformers with old multi-hundred amp arc welder diodes for the rectification.

    They work just like any common high power alternator does and don't bother with theCC/CV mode nonsense. Just make the peak output voltage so that it levels off at around 14.5 - 15 volts with a fairly low 1 amp draw and life's good.

    The simplest way to make one is to find a common 12/24 Buck-boost transformer and us that. Set it up as a center tapped 24 volt output and use two large diodes (preferably with ~ 1 volt forward drop ratings) in a half-bridge configuration and that basically it. Stick a big capacitor on the output and load it up with a good battery and see where it levels off at.

    If it's putting out more than 15 volts and 1 amp once the battery has been fully charged they you may need to add a third large diode in series with the others to reduce the peak output voltage down an another .5 - 1 volt.

    As for high powered charging you need to factor in that you will have a lot of small voltage drops in both the 12-volt side cabling and the 120 VAC supply cords as well which helps out as a sort of peak current limiter for charging large deep discharged batteries meaning that even if you hook it up to a tractor that runs a pair of group 31 batteries that are deeply discharged its unlikely that you will see much over a 150 - 200 amp peak charge current for more then a minute or two before everything starts to level off.

    Same with small lawn mower batteries. They can pull a 100+ amp peak if ran down far enough but it only lasts a few seconds before their voltage comes up high enough to drop them back to a more civilized charging rate.
     
    Last edited: May 23, 2016
  9. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Give this a read:
    http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
     
  10. marcf

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    Dec 29, 2014
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  11. tcmtech

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    Nov 4, 2013
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    In ideal conditions for what are primarily stationary type systems (backup power and UPS type applications) that concept is fine but in day to day real life work where a person is dealing with the starting batteries of vehicles and equipment very little of the holds true.

    In a mobile application, the typical alternator or DC generator system only follows one rule. Charge at whatever amp capacity it can deliver or is demanded by the battery until the set voltage is achieved and then stay there whether the run cycle is 1 minute or non-stop until the next oil change is due weeks later.

    My personal experience is that when a vehicle or machine starting battery is to low to start the engine I don't have or want to spend 5 - 20+ hours waiting for an ideal charging rate unit to do its job. I want all the amps that battery can take on its own to be available until it's up to the point of starting the engine.

    Or if possible to have enough power available to start the engine without the battery contributing anything of significant value which if such an event occurs and it within reach of my welders leads that means setting my welder to CV mode and dialing down to ~15 volts and letting whatever needs it take all the amps it can give even if that means maxing out the CV mode on my welder at 600+ amps for a few seconds.
     
  12. ronv

    AAC Fanatic!

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    Yea, but. Why would you want to stress it with the high current and a voltage above the gassing voltage when you don't need to?
     
  13. tcmtech

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    I've never seen a battery outgas on a momentary high charge rate. IF it was a long term hard charge then yes agree they outgas but on a short high current limited voltage burst the time duration is too short too do anything serious.

    As I have mentioned even a large battery won't draw that kind of current for more than a minute or two before it's voltage starts to come up and limit the whole charging process. It's not any different that what a battery sees when it's attached to a high output alternator as in that several second period when the belts squeal if they are loose.

    Besides, if a battery has been run down so far that it can't start the engine the odds are it took on a bit of damage anyway. :oops:

    Also, do you call your boss and tell them that you are going to be 4- 7 hours late for work because your vehicle battery was dead and you want to give it it's ideal ~.1C charging profile rate rather than just pour the amps to it until the engine starts and go from there? I don't being I consider batteries a consumable item and I have far better things to do than fuss over one. :p
     
  14. Lestraveled

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    May 19, 2014
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    No one has mentioned sulfation. This is the reason why a battery should be charged at 10% of its amp hour rating. This is the reason why a battery needs to be held at 14.7 volts for a certain amount of time. These two charging parameters are geared towards maximizing desulfation. Charging a battery at too low of a current and never bringing the voltage over 13.7 volts is far worse than over charging a battery for a short period of time.

    If you use a charger, meant for an ATV battery, on a 150 AH tractor battery, then soon your tractor battery will only have the capacity to start an ATV.
     
    bwilliams60 likes this.
  15. ronv

    AAC Fanatic!

    Nov 12, 2008
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    I think 15 volts is a little gassy.

    [​IMG]

    I don't think of anything I pay a couple hundred dollars for a consumable. :rolleyes:
     
  16. tcmtech

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    Nov 4, 2013
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    I've never had a good battery overheat or boil out at 15 volts regardless of whether it was atiny 2 Ah backup battery or a 400+ Ah battery bank.

    Besides it's not like what I am charging stays at that voltage for weeks at a time. Usually, it's a hook it up in the morning or evening and come back to it 12 - 24 hours later.

    I've found that on the cheapo lawn and garden batteries that are more than a year old letting them sit for a good 12+ hours at 15 volts tends to improve their cranking capacity and ability to sit idle for extended periods. My guess is it's high enough to break down the sulfate but not high enough to cause any noticeable outgassing.

    I know it works. I 've been doing it for years.

    As far as I am concerned anything that is found at every major chain store like Walmart, Target, Sears, K-mart, your local gas station and so on, and not just dealerships or auto parts centers, that is made to be replaced in less than five minutes with nothing more than a basic hand tool is a consumable.

    Window wipers, filters, spark plugs, oil, tires, light bulbs and batteries. Those are consumables being in the typical life of a vehicle or machine it will go through at least several sets of those items in it's working life time.
     
  17. ronv

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    It's your money. Knock yourself out.
     
  18. Lestraveled

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    What happens when you over charge a battery is that the plate material gets eaten away. A little is OK. This is great for desulfating. A lot of over charging shortens the life of the battery.
     
  19. tcmtech

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    And what is your annual food and clothing expenses? I bet that's over a couple hundred dollars a year. :p

    So you never had to replace a single battery or a component that cost over a few hundred dollars in anything ever?


    So if you consider anything over $200 a non-consumable what do you classify tires on your vehicles as? Do yours never wear out?

    Still got the original batteries in everything that you have ever bought even if they are years or a decade or more in age?o_O

    Okay if so, what batteries are you buying that cost a couple hundred dollars and never go bad in the lifetime of the vehicle or piece of equipment?
    I'm just asking being I am fairly sure a number of us would love to have batteries that we never have to worry about going bad and needing to replace in the lifetimes of the equipment they are in even if they cost $200+ each.o_O

    By my standards a lawn and garden battery is good for 2 - 4 years and vehicle or heavy equipment batteries are good for 4 - 6 although I have had a few that made it over a decade.

    Still, anyway I measure it as anything that has a battery will likely go through multiple batteries in its working lifetime which by my definition makes them a consumable component of the machine as a whole.
     
    Last edited: May 25, 2016
  20. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Is there a point in here somewhere?
    Are you trying to say that treating batteries badly is a good idea?
    What happens to your batteries when you forget to remove them from the open loop charger? Does your line voltage ever go to the high side?
    I just consider these oversights as poor design.
     
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