Re: An Alternator/Battery Charging Question
If the battery has a shorted cell the charging circuit voltage may not come up.
Sorry, I am trying to debug a charging problem, and didn't put in all the details (trying to avoid confusing everyone). Basically, I have a setup like this, except I have an outboard (2004 Evinrude E-TEC):
http://www.westmarine.com/images/wa/chart.jpg
It has worked fine for a number of years. Recently, however, I noticed that the voltage level as reported on my digital sonar unit (which is hooked directly to the starting battery) was dropping, with the sonar unit reporting under 9.8V many times during the day, even with the motor running. The voltmeter on the dash would sometimes read low as well, but not always.
I was pretty sure the starting battery was not at 9.8V, because the battery could always turn over the motor, and if the battery was really only at 9.8V, it would be completely dead.
So I assumed that the voltmeter on the sonar was bad, and that the meter on the dash, because of the erratic response, was suffering from some corroded connections.
What seemed like further evidence that the meters were off was that if I set the switches to run off the house battery, the voltages read the same, even though the house battery was supposedly under less load, and isolated from the starting battery.
So I eventually got under the dash, cleaned all of the connectors to bare metal and reattached, then started the motor on the garden hose, and checked output voltage from the engine. I could measure 13.0-13.1 volts at the engine /battery lugs in the transom, across the battery switches, at the lugs on the starting battery, even all the way to the output pins of the sonar power cable.
The sonar unit was now reading 11.8 - 12.1V, but it was erratic, creeping up/down a few tenths of a volt every few seconds. So I assumed the sonar unit voltmeter was bad. The dash meter read 13V.
HOWEVER, on my last trip, both meters continued to show 9.8-10V most of the day, even though both batteries were fully charged by the on-board charger (Guest 2632) the night before. I ran the boat all day, mostly trolling, and what do you know...when I shut off the motor at 2:00pm to do a little bait fishing, the starting battery was dead. I switched over to the house battery, and it was also dead. I could not initially start the motor (large pucker factor, as we were 30 miles offshore).
Fortunately, by letting the system sit for a few minutes, I managed to scrape up enough volts to turn over the motor a couple of times, and thanks to E-TEC magic, the engine started and we were able to get home.
When I got home, I let the batteries charge again, and put a load tester on them yesterday. Both batteries appear to be OK, recovering to 12.4V after two separate load tests.
I'm beginning to suspect the combiner, as it is the only thing other than the on-board charger which is continuously connected to both batteries, and could have the potential to discharge both batteries simultaneously. However, for something to drain enough current to kill both batteries, I would have expected something to be smoking, or at the least extremely warm. No sign of anything like that.
Any thoughts? Suggestions? I hate having to disconnect everything and do trial-and-error debugging, but it's looking like I have no choice.
