Odyssey weird

Thread: Odyssey weird

  1. flynlow said:

    Odyssey weird

    My RV8 has a Odyssey PC925 battery and it will drain after a week of inactivity. Yesterday I barely got a start and flew for 30 minutes and landed at Dodge City to pick up some parts. The battery was too low for a hot start on my IO360 so the A&P and I hook up the tug leads (800 amps) to the battery terminals....nothing. The mechanics said I had a starter problem or a loose wire.
    I disagreed and told them if we put a charger on the battery the engine would crank after 15 minutes or so. They thought I was crazy but gave me a charger to use. It worked and I was on my way. As soon as I put the charger on the volts went from 12 to 14 and increased, the jumper cable leads had no effect on my voltmeter?????
    A month ago the same thing happened, we attached jumpers off a pickup truck and nothing until we started the truck and the alternator started charging.
    I have no idea why jumper cables on the battery terminals won't crank the engine but as soon as a charger is added the battery starts to charge, doesn't make sense.

  2. behindpropellers's Avatar

    behindpropellers said:
    1. Check all grounds.
    2. Check solenoids.

    Checking voltage is not really enough, you need to know that you have sufficient amperage to crank your starter.

    Put a meter on the battery and then crank the starter while the battery is dead. If it goes below 12 you have no amperage.

    My guess is your battery is fried and will not hold a charge.

  3. Frenchy said:
    You can also check voltage drop between starter and battery
  4. flynlow said:
    If I keep a 'maintainer' charger on the battery all is well. If the battery sits for a week, it loses charge. I have a clock and gps that would likely use some parasitic drain but one week seems kinda short to drain a large battery like the PC925. If the battery is left on the trickle charger it will crank the engine for a looong time.
    I ordered a new battery and will install it but I am still meeting myself going in circles as to why jumping the battery won't achieve a start. A tug with enough amperage to spin a turbine to 13 grand shouldn't be a problem for my little io360. It would seem that this would eliminate the battery as the problem.

    A friend thought it may be that the tug's 12 volts may not be enough irregardless of amps because it may take 13 or so volts to open a solenoid. I am still clueless. I just don't understand that much about electricity.
  5. fobjob's Avatar

    fobjob said:
    It sounds like the battery has accumulated some internal resistance from sulphation. The key to this is discharge from small electrical drains on board combined with the long idle time between run times. Disconnect any drains when the aircraft is parked, no matter how small. Put a trickle charger on it while you are away. The sulphation should eventually go away. But, (if you let it go long enough) it's possible that lead whiskers can form between plates that will short a cell. Voltage fully charged with no load or charger should be 12.5 volts. If it's markedly lower, like 11.5 volts, then shorts have probably formed and you need a new one. It's possible to burn out the shorts with high current, but sulphation will prevent you from achieving high current, and since it's an AGM battery, it would Explode if you tried it. Don't try to charge it in service with more than 30 amps......what size alternator/generator do you have?
  6. ak2711c said:
    As far as your jumper cable problem. It sounds like your external power receptical is ether not wired properly or has a faulty relay. Even if your battery was shot it should have given you all the power you needed. I would study the schematic for that circuit and compare it to your plane, I think you'll find the problem. However I think that problem is not part of your battery problem.
  7. flynlow said:
    Shawn we were jumping directly to the battery terminals...after removing 2 thousand screws for access while in a position I wouldn't assume in California. The engine should have cranked, I am still scratching my head over this.

    fobjob, As long as I keep a trickle charger on everything works great. My alternator is 45 amps, I had it off and checked a couple weeks ago. I am guessing a new battery will solve the problem. When flying with minimal equipment on and a very low battery the alternator will show only 4-5 amps charge....perhaps this type of battery won't take much more charge rate than that?? When I switch on landing lights, boost pump, etc the charge rate goes up to 25 amps or so.
    I have a clock and gps that probably is responsible for the drain but for this big battery to drain in one week seems excessive.

    The new battery ought to be here in a day or two. When I replace the old one I'll sit it out fully charged and test it after a couple weeks just to be sure. Thanks.

    No one can explain why the engine won't crank with jumpers of over 800 amps attached to the battery terminals....just don't make sense!
  8. Jim Michael said:
    There is a systematic guide to troubleshooting starting problems on SkyTec's website - http://www.skytecair.com/Troubleshooting.htm I would also put a meter on the battery terminals with one terminal disconnected from the battery to determine whether drain is occurring. I did have the same hot start issue with my Stinson and that was due to the starter. Follow the t/s procedure in the guide and you should be able to isolate the problem.
  9. fobjob's Avatar

    fobjob said:
    Quote:..perhaps this type of battery won't take much more charge rate than that?? When I switch on landing lights, boost pump, etc the charge rate goes up to 25 amps or so.
    I have a clock and gps that probably is responsible for the drain but for this big battery to drain in one week seems excessive.
    If the battery has some sulphation, the internal resistance is higher and charge AND discharge current is limited. It sounds like you are talking about current from the alternator and not into the battery...sulphation is caused by letting your battery discharge....just a tiny bit will do it, (if repeated)...leave a trickle charger on it or get rid of those small current drains....
    Because I shouldn't give anyone advice at 2 AM, I combined two topics when I shouldn't have.
    TOPIC 2:
    Charge currents greater than 30 amps may damage AGM batteries....
  10. Clyde and Susan's Avatar

    Clyde and Susan said:
    If the charging source is voltage regulated at 13.8 to 14.2 volts, adjusted within this range by battery temperature, regardless of the charging source capacity, the charging current is determined by the battery. If the battery tries to draw more current than the charger can supply, the voltage output of the charger is lowered as much as necessary to limit the current to the maximum capacity of the charger. This will happen regardless of the consequences to the charger or the battery. Circuit breakers or fuses can provide some protection.

    In a typical vehicle generator (alternator), battery, and load (lights, radio, ...etc.) circuit, an ammeter that reads both charge and discharge will indicate only the current into (+) or out of (-) the battery. The current drawn by the load but supplied by the generator will not show on the meter. In a circuit that has an ammeter (load meter) reading only from zero to some maximum value (0 to 60 for example with a 60 amp generator/alternator) will indicate the sum of all currents delivered by the generator/alternator.

    As has already been noted in another post above, any time that a lead-acid battery remains for any length of time in a partially discharged state it will become progressively sulfated. The only way that a battery in this condition can be restored (there is another time consuming and impractical way to do it with non-sealed flooded batteries) is to charge it using high voltage pulses that average a nominal 14 volts. This type of battery charger can restore the original capacity to a badly sulfated battery. Fortunately, this type of charger is available and the prices are becoming more reasonable as time goes on.

    ...Clyde Davis
  11. Clyde and Susan's Avatar

    Clyde and Susan said:
    Quote Originally Posted by flynlow
    Shawn we were jumping directly to the battery terminals...after removing 2 thousand screws for access while in a position I wouldn't assume in California. The engine should have cranked, I am still scratching my head over this.
    If you connected directly to the battery and it still wouldn't drive the starter, the problem could be the ground cable from the battery or any of the wiring between the positive terminal of the battery and the starter. That would include any contacts in that part of the circuit such as the starter relay. I would check the ground lead first. One way to do that is to connect a voltmeter with the positive lead connected to the airframe and the negative lead connected to the negative battery terminal. While the voltmeter is connected try to crank the engine with the starter. If the cable is good there will be no more than a few hundredths of a volt or so depending on the length of the ground wire and the amount of current drawn. If the ground cable from the battery is bad the voltage could be as much as 12-volts when the starter is engaged and drawing current. The positive lead to the battery can be tested in a similar way by connecting the positive lead of the voltmeter to the positive terminal of the battery and then moving the black (negative) lead of the voltmeter along the circuit toward the starter until there is a large voltage measured when the starter is engaged. You can find the problem very quickly that way. ...Clyde Davis
  12. Clyde and Susan's Avatar

    Clyde and Susan said:
    One more thing I should have mentioned that you should do first. Connect the voltmeter directly to the battery terminals. Make the connection to the battery terminals, not to the cable ends. Try to make the starter crank the engine. If, as soon as you try to crank the engine with the starter, the voltage drops to a very low value, you can stop right there and replace or charge the battery. ...Clyde Davis
  13. flynlow said:
    Thanks for all the input. A new battery should arrive today.
    I will keep a trickle charger on it.

    A friend mentioned that this problem only occurs when the airplane sits for a extended period of time. He said it's nothing 20 gallons of LL and clear skys won't cure.

    Thanks again.
  14. dpearce said:
    Had a similar problem on a car some years back. The battery had good voltage, the alternator showed good charge, the battery leads tested for continuity. But, couldn't jump from an idling car. Could jump from a car at high idle or after charging briefly. Problem was traced to a disintegrating positive battery lead. The lead jacket had a pinhole in it that had apparently allowed water in and corroded the lead to powder but left some surviving strands. So there was a high impedance path with a few strands to show continuity but not carry much current. Replaced the lead and all was well with the world. Found this after replacing battery, solenoid and alternator.
  15. flynlow said:
    I'll recheck the positive leads and the negative also.

    I recently had a ford pickup that would spin the stater but wouldnt engage to start the engine. I hooked up jumpers to see if I wasn't getting enough electricity to engage the starter gear with the flywheel...still no joy.
    Went into the house to rethink with a cup of coffee, sometimes that helps. As I was thinking I looked out to the driveway and noticed the starter hanging by the cable under the truck A couple new bolts and I was good to go.
  16. mike mcs repair's Avatar

    mike mcs repair said:
    Quote Originally Posted by flynlow

    ....and noticed the starter hanging by the cable under the truck
    ah.... wish all things in life were that easy to diagnose! the smoke rolling out last summer of my working car alternator was another easy one to know that might need replacing soon too....

    oh, and the broken crankshaft on the 185 in my avatar.. we thought just a the cable broke/slipped or bad prop governor when it went flat pitch in flight, the pilot stopped at bible camp on bacharoff lake, we went down adjusted cable flew it around patch, Ok..then all of a sudden flat pitch again... land change prop governor, same result... except this time it oversped and threw alternator belt too.. my stepfather had figured it out by then, taxied up got out and walked up to the prop and could 'move/twist' it front to back some, pulled oil screen it was packed! of course this was a plane we bought pretty much sight unseen a month or so before, with "missing" engine log and affidavit of times and such... they must not have liked that prop strike entry... we had 200 hours since we bought it...

    the crack in the crank was probably 5 inches long up front spiraling through/from the hole in side of crank where the transfer collar is.....