At the battery I have 15+ volts. It was going to 18-19 before new regulator.
Exactly where are you measuring the battery voltage? If you place your test leads directly on the battery
posts (NOT the lead battery cable ends connected to the battery) , you will read battery voltage.
When the engine is off, it should be approx 12.5v for a fully charged battery.
If you read a higher voltage (on the battery POSTS) when the engine is running (approx 13-14.5v) the alternator is charging. and producing enough current to overcome the internal resistance of the battery AND provide sufficient current to operate all the accessories.
If the battery is "healthy" (and the right size) the correct alternator will usually not overcharge (or produce enough current to overcharge) the battery.
This all assumes all connections are clean, and tight.
If either battery cable end is corroded, and/or the posts are corroded, that corrosion(in the form of lead sulphate) will introduce resistance between the actual cable end connector and the lead post. (lead sulphate is a rather poor conductor)
You can actually measure this resistance in the form of voltage drop (or voltage across) the cable-end --- post connection.
I.E, place your test leads on the actual post and the connector when either charging or discharge(operating accessories with engine off) and you will measure voltage between the post and the cable end connected to it......it can be a few tenths of a volt to a couple of volts depending on how corroded it is and how much current is flowing) on BOTH terminals! A two volt drop on each connectors would add up to 18v total!
If you draw a LOT of current (like cranking a starter for 30 sec or so) the terminal will actually get HOT if there's a lot of corrosion and a poor connection. (high resistance + high current produces HEAT, sometimes enough to actually melt lead!)
Remove the battery connections and clean them to shiny metal. then use a spray sealant or grease to "seal" them. You want to prevent vaporized sulphuric acid from contacting the exposed lead.
Corrosion can result in very slow cranking. But the BIG problem is once you get the engine started, the alternator will try to charge the battery through a high resistance and will increase current accordingly. A defective regulator makes it worse!
This can produce high enough voltages to damage or destroy electronics. (like your fish finder, stereo, or your engine ECM/IGN module etc.....
DO NOT allow your battery terminals (or GROUND connections) to become loose or corroded or both (ever!) ! Corrosion can occur in any connection especially in crimped connections close to the battery.
Cheers,
Rick
