Cheking battery output?

Discussion in 'Mechanic and Repair' started by bligh61, Jan 15, 2008.

  1. bligh61

    bligh61 LawnSite Member
    Messages: 240

    Can anyone advise how to check battery output or voltage, my 2000 ford f250 has been starting a little hard since the cold weather. I believe it is the original battery, I cleaned the posts but still the same. I have a volt meter but not sure how to use it to test the battery. thanks.
  2. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,824

    1 to pos , 1 to neg , should be giving you about 13.7 or so.If its original , its time for a new one.
  3. GravelyNut

    GravelyNut LawnSite Bronze Member
    Messages: 1,594

    Shouldn't drop under 10V when cranking.
  4. bligh61

    bligh61 LawnSite Member
    Messages: 240

    Meter on dc mode?
  5. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,824

    yes dc= direct current as in battery , a/c alternative current as in made somewhere else and brought in thru wires
  6. bligh61

    bligh61 LawnSite Member
    Messages: 240

    Meter reads 11.4, then when engine is running it reads 14.5, after i shut it off the meter reads 13.2 but then drops down again. Does this show that its charging but unable to hold a charge? I also trickle charged last week with no luck. thanks
  7. MarcSmith

    MarcSmith LawnSite Fanatic
    Messages: 7,157

    not holding a good charge or you got a draw somewhere. 8 year old batty most of good for 5-7. grab a new one...I recommend an Optima. I'm going on 10 years now...and it on its second vehicle.... I'm sure thats pretty unique...but of course now that I said that I'll be getting a call from my wife needing a jump start tonight...
  8. Ridin' Around

    Ridin' Around LawnSite Senior Member
    Messages: 266

    The only way to really check a battery is to do a "Load Test" on the battery. The voltage while running shows you only that your charging system (alternator) is in working order. Most auto parts stores or Battery stores will gladly do the load test no charge. They may expect the battery sale in return though!
  9. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    A low battery must me charged for a hour or two depending on how low it is. Then taken off charge and let sit for no less than a half hour. This will let the surface charge dissipate, Then the battery can be checked for proper voltage and load tested.
  10. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Look, it sounds a little low but it will always be around 12v when not running, even a battery with a dead cell will register 12v, it might be weak but voltage in itself isn't enough here.

    So, grab yourself a good 100 dollars (with some change), take the required tools along and run on down to your local Advance Auto Parts store. Once you get there, pull the battery and ask them if they could load test it.
    This process takes about 20-30 maybe 45 minutes, so in that time start price-shopping their 1,000 cca batteries, for a 3/4 ton you want 1,000 cca's. Matter of fact I like running those in my cars too, they're nice and strong, last a good 5 years, 1k cca.

    If by the time the test is done it turns out the battery is good, explain to them the problem and ask if they can alternator / load test your truck after you re-install it, either way re-install your old one and hope for the best.

    But if it turns out like I think it might (bad), then go ahead and buy a nice new 1,000 cca battery and since you got your old one refund the core charge right there, this will run you between 80-120 maybe 140 dollars, but if you price-shopped 100-120.
    Now stick the new one in your truck and your problem is most likely fixed.

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