Time taken to charge batteries VS alt size.

Discussion in 'OnBoard Electronics & Controls' started by DennisRB, Apr 16, 2010.

  1. DennisRB
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    DennisRB Senior Member

    Not if the boat never goes to marinas.
     
  2. capt littlelegs
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    capt littlelegs New Member

    The regulator doesn't get the voltage up, it keeps it down to the right voltage when the battery voltage rises from proper charging, it's really a voltage limiter. Your battery will take at least five hours to fully charge with sufficient charge current available. If the terminal voltage is constantly low below 14.5 volts then either the regulator is set at the wrong voltage, the output is too low or the battery too big, the running loads are too big leaving not much for charging, the charge time is too short, the wiring is too small or as I said before the battery is failing due to over discharge. Try a battery charger over a couple of days to see if that makes a difference. 12.5 volts three hours after charging indicates an 80% charge so if it's only charging at 12.5 volts then that means the battery is completely discharged (you should only go down to 50%) and probably knackered.
     
  3. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    Dennis the correct method to test the voltage regulator is to run the engine until the charge dcurrent from the alternator is below 10 A ..then measurde the battery volts with the engine running it should be at least 14.4v ignore all that 13.6-14.4v crap thats from the 1960s...If it does not come up to 14.4 and the warning light is out then the volt reg needs replacing
    personally I would reduce the number of batteries to 1 for the test . But charging with a battery charger to see if they come up and testing with a hydrometer are all good ideas...starter cable/welding cable for all connections at least 50 mm sq pref 75
     
  4. DennisRB
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    DennisRB Senior Member

    I will try to get the batteries out so I can charge them individually on the shore. Maybe this will show a dud battery. They are sealed units so we cant use a hydrometer. But the inbuilt crude ones do show a green window.

    I realize the regulator is there to keep voltage down, but when the voltage is always so low there has to be a prob somewhere. Either wiring too small or the alternator capacity is way too small or something. Its just not right.

    Someone turned the fridge on by accident and the stereo started cutting in and out because the voltage was getting too low. This was after it was only running for a couple of hours and we done 3 hours of motoring that day.

    We don't use a lot of power on the boat when the engine is not running. Just a few fluro lights and maybe a car stereo for a few hours. When the engine is running the only extra load might be an auto helm, sounder and GPS and running lights.
     
  5. capt littlelegs
    Joined: Apr 2010
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    capt littlelegs New Member

    What batteries, capacity, age etc. and alternator have you got and do you have a separate starter battery? I think more likely the batteries have had it or you are just not getting enough charge as you appear to be getting some charge in or both!

    You can work out your load x time to calculate how long your fully charged battery will last down to 50%, same with re-charging, you might be surprised to find how little you can use! Evaporator type fridges are a very heavy continous load.

    You can check the batteries individiually with the voltmeter for any obvious low ones then as said charge any good ones individually to see if they come up. If they are any good you should see the voltages as in the link after off charge for three hours.

    http://www.energy-solutions.co.uk/state-of-charge.html
     
  6. DennisRB
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    DennisRB Senior Member

    I will get my mate to take the batteries out so I can charge them and take look at them. I will get the capacities off them. Apparently they are only a few months old. Yes we do have a separate starter battery. We normally have all 5 batteries connected when the engine is running and isolate the starter battery when the motor is switched off.

    That chart is useful. Thanks.
     
  7. DaveJ
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    DaveJ Senior Member

    Make sure when you leave the boat that you isolate all batteries from each otherwise they will run themselves down. What that means if you have a bank of batteries connected is parralell they will try to charge each other but the end result is they end up discharging themselves flat in an effort to charge each other. Possible solution is to go out and buy a cheap solar battery charger and connect that up, so while your away from the boat the solar charger will hopefully replace any run down the battery might do to each other during the night, or isolate them from each other when you leave the boat.
     
  8. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    dennis ...charge them off the boat ...then stand overnight and measure voltage if its gone below 12.5 that battery is suspect...bad idea being sealed. If you can prise the tip off do so and you may find one cell has no electrolyte ......often I have drilled the top to get the hydrometer in and to top them up ...post a photo of the battery top and I can advise .Even though not very old if they have been left connected in parallel and discharged they could all be sulphated though the green in the one cell hydrometer is a good sign....
     
  9. DennisRB
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    DennisRB Senior Member

    Dave. I leave the house and engine batt in parallel when we leave the boat. I know this is not the best when batteries are just sitting but we have a solar panel and wind gen. When we get there voltage is usually somewhere in the low 13s.

    Pistnbroke, I am going to charge them on shore and measure the voltage 3 hours later as you describe. I have never liked the idea of sealed batteries in terms of maintenance either. I have never thought of drilling them though. How would you seal it later?

    What do you make of this article? It basically alludes to the best battery to use on a boat which gets used sometimes (like every few weekends etc) is a standard non sealed lead acid battery. It reckons all the other types of batteries are massively overpriced for what they are. Including most listed as "marine" or "deep cycle". With the only exception being the true deep cycle traction batteries. However these are still a waste of money unless you are living on the boat where ordinary starter batteries will die in 6-8 months and a traction battery will last 10+ years.

    http://www.sterling-power.com/support-faq-2.htm
     
  10. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    12 HRS LATER NOT 3 ..some of the sealed batteries are only sealed in that the strip top of stoppers is glued down and under a label... If its a drill job I use blind grommets ...you need a tube around your drill so you can only penetrate 1 cm and you take your positions from the mould lines in the top ...photo !!! No need for hosting on this site

    If your wind generator has held them at 13v + and they are still no good sounds like they are sulphated ..high on charge voltage ...gassing ...SG wil not go over 1150 thats the symptoms ....you need them isolated and 4 diodes in the output of your solar so they all get a charge but are not in parallel..

    need to know how its all regulated
     
  11. DennisRB
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    DennisRB Senior Member

    OK 12 it is. The link you provided said 3 minimum. I will get some pics when my mate takes the batteries out. So I will only know if they are sulfated if I take an SG reading? Can this be cured?

    The wind gen has its own reg as does the solar as far as I can tell. Do need to go the the effort of the isolation and diodes if all the batteries are in equal condition?
     
  12. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    charge for at least 2 days ..stand for 12 hours ..read voltage ....connect a headlamp bulb and see how long it stays on before the battery goes below 10.8v......around 20 hours would indicate about 100ah ...if it stays on substantially less then its sulphated .very often only one cell has failed ..no cure scrap..tear top off to confirm

    I did not send any links
     
  13. DennisRB
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    DennisRB Senior Member

    Sorry, capt littlelegs sent the link regarding reading the voltages vs charge.

    So that head lamp is a 60W load then, eg a automotive headlamp low beam?

    My charger is a "battery link fully automatic charger" 14000ma, with 55000ma engine start mode. 12v fast charge and 12v trickle charge. Its fairly cheap and heavy, not like a light fully electronic one, and doest come with any real documentation.

    Should I just use the fast charge function? Can I use the engine start function to boost the crap out of them at the start providing the voltage doesn't go over 14.8? (I have done this with large batteries before and put it down to fast charge once the voltage went up, I'm sure its not the best for the charger).
     
  14. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    yes all good ..put it on fast charge and if it shows a charge current then leave it ...if no current then try the boost to get it started but thats not a good sign,,,,,,dont you just love batteries .....as these baatteries are probably junk I would not worry about the charge voltage 15.5v as a max
     

  15. DennisRB
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    DennisRB Senior Member

    Yeah mate its a pain in the arse. What is going to suck is getting the batteries off the boat by dingy.

    How much do new batteries cost anyhow? Where do you get them (for a good price) and do you agree that cheap arse starter batteries are the best option for a boat that gets occasional usage like the link in my last post suggests?
     
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