Last winter the battery (3 year old Odyssey PC680) in my Hatz was getting weak and had to be jumpstarted a couple of times, so I bought a new battery in May. But as the weather warmed, it always started, even if it seemed to be struggling, so I never got around to installing the new one.
Come November, once it got cold again the battery wouldn't crank the engine, so I put the new one in. Worked for a [short] while, then again needed jumpstarting on the couple of times it was warm enough to fly.
Went to fly yesterday (first time in a couple of months due to surgery) and of course the battery was dead. Well, sort of... open circuit voltage was 12.7, which according to Odyssey should indicate 75% capacity, but as soon as I tried to crank the engine it dropped to 8V.
Strangely, after sitting on the bench since November the original battery was indicating 12.9V which means fully charged, so I reinstalled it... it managed to crank the engine through one revolution, that was it. At this point I used my portable jumpstart battery which effortlessly cranked the engine (indicating that the starter and associated wiring are OK) and I went flying for a half hour or so. After filling up with gas post flight, it cranked slowly but did start.
After starting, the ammeter indicated it was charging, and it showed 14.2V (Odyssey says the alternator has to put out 14.2-14.5V to properly charge the battery). But just before shutting down, it was at 13.9-14.0V with the engine at 1000 rpm.
With the batteries' voltage indicating a good charge but dropping instantly under load, it's clear they're both bad. It wouldn't be the first time I got a bad brand new Odyssey battery, unfortunately I purchased it almost a year ago, so I'll only get partial credit if any.
But the alternator only putting out 13.9V hints at a deeper problem. Most sources say 13.5-14.5 is OK, but Odyssey says 14.2-14.5... yet lots of people are using these batteries with standard alternators. Or am I overthinking this?
Come November, once it got cold again the battery wouldn't crank the engine, so I put the new one in. Worked for a [short] while, then again needed jumpstarting on the couple of times it was warm enough to fly.
Went to fly yesterday (first time in a couple of months due to surgery) and of course the battery was dead. Well, sort of... open circuit voltage was 12.7, which according to Odyssey should indicate 75% capacity, but as soon as I tried to crank the engine it dropped to 8V.
Strangely, after sitting on the bench since November the original battery was indicating 12.9V which means fully charged, so I reinstalled it... it managed to crank the engine through one revolution, that was it. At this point I used my portable jumpstart battery which effortlessly cranked the engine (indicating that the starter and associated wiring are OK) and I went flying for a half hour or so. After filling up with gas post flight, it cranked slowly but did start.
After starting, the ammeter indicated it was charging, and it showed 14.2V (Odyssey says the alternator has to put out 14.2-14.5V to properly charge the battery). But just before shutting down, it was at 13.9-14.0V with the engine at 1000 rpm.
With the batteries' voltage indicating a good charge but dropping instantly under load, it's clear they're both bad. It wouldn't be the first time I got a bad brand new Odyssey battery, unfortunately I purchased it almost a year ago, so I'll only get partial credit if any.
But the alternator only putting out 13.9V hints at a deeper problem. Most sources say 13.5-14.5 is OK, but Odyssey says 14.2-14.5... yet lots of people are using these batteries with standard alternators. Or am I overthinking this?
