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ContinuousWave: Small Boat Electrical
Unregulated charging into an AGM - Evinrude 88SPL
|Author||Topic: Unregulated charging into an AGM - Evinrude 88SPL|
posted 10-14-2010 09:43 AM ET (US)
A 2" dash mount Faria voltmeter was put in and wired from the ignition accessory post through a 0.5 amp fuse. Power plant is a 1996 Evinrude 88SPL. When running, meter is pegged at 16 volts. Checking with a known quality handheld meter, charging voltage at the battery @3000 rpm is 17.5-18 volts. After reading past posts on charging systems, it became apparent that some motors don't have voltage regulation, mine included. The engine has a 6 amp rectified unregulated charging potential, according to the Clymer manual.
Problem is that early on a new Optima marine AGM was installed to replace the long dead existing battery. After reading past posts and the repair manual, that was a mistake. Wet cell batteries are recommended for unregulated systems. Education is sometimes costly.
While perusing repair manual, the solution *may* be to retrofit the charging system with an Evinrude regulator-rectifier, though the ones specified at that time were for 9 amp systems and up, and I have no idea if the powerhead will properly accept one. They appear be attached at the water jacket for cooling, and will soon die if not cooled. Naturally, it would be desirable to have regulated charging. Is there some way to accomplish this? The simple solution may be to get a flooded cell battery and re-task the expensive AGM before killing it. Also, I don't know what will happen to a 16 volt gauge running at 18 volts.
Another possible problem with an unregulated charging system would be that sensitive electronics could be negatively impacted. Nothing sophisticated is on board right now.
posted 10-14-2010 09:53 AM ET (US)
"Also, I don't know what will happen to a 16 volt gauge running at 18 volts."
That was mis-stated. It is a 12 volt gauge, with 10-16 volt range, always pegged because of an 18 volt input while motor is running. Apologies, ---->bruce
posted 10-14-2010 10:16 AM ET (US)
I would be looking for a way to regulate the charging voltage. With a flooded cell you will be constantly topping off the electrolyte. You definitely can't use any type of sealed battery with charging voltage this high.
Regarding the meter, it is hard to say. At some level an over-voltage will overheat the coil. I doubt that 12% over-voltage would damage the meter.
posted 10-14-2010 11:44 AM ET (US)
You may be able to fit a regulator into the charging system of the Evinrude 88 SPL. Check on SHOP.EVINRUDE.COM in their excellent parts section to see if there is an accessory available.
posted 10-14-2010 02:30 PM ET (US)
Thanks Dave, Jim,
I'll leave the meter hooked up for now, and maybe that will be alright. I checked Evinrude parts and they show the rectifier-regulator as being available for the 25" shaft, but not the 20", which comes with a rectifier only. That's odd. Bolt pattern on the power head should be the same, so it should be possible to uninstall the existing rectifier and replace it with the combination unit.
posted 10-15-2010 12:18 AM ET (US)
Just look at the parts list for the same year 90hp and order the regulator and gasket from that.
posted 10-15-2010 12:35 PM ET (US)
Just as a note from the practical experience side, I had the same unregulated situation on my OMC 70. When I bought the boat it had a sealed, wet battery. I ran it for 2 years with no problems, and who knows how long the previous owner ran it. 6 amps isn't much - remember people used to run 2A trickle chargers indefinetely.
Also, you can get an accessory, external voltage regulator to protect any sensitive electronics - in fact I have one, but sold the motor before I got around to using it.
posted 10-18-2010 11:15 AM ET (US)
Thanks Tim, Seahorse,
Come to think of it, dear old Dad ran the boat unregulated for 25 years without much battery trouble that I recall. AGM's were not available though. I'm not sure which way to go with it yet. Tim, do you have a source for that external regulator? Would you consider selling yours?
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