Rectifier vs. Voltage Regulator

[Bighornbob]

Perhaps a dumb question, but could anyone tell me the difference between a rectifier and a voltage regulator. I understand the rectifier on my Force outboard (probably other brands too) changes AC current to DC current, and a voltage regulator manages that current. But I hear the terms used interchangably as it relates to outboard motors. Are they the same thing, or is the rectifier a part inside the voltage regulator? I run a '96 Force 120 if that helps. Thanks!

 

[fucawi]

Re: Rectifier vs. Voltage Regulator

if it just has a rectifier then the output is low and a charge current of say 3A is not going to do harm to a starting battery . If the output is higher say 50 A then you need a voltage regulator to limit the voltage that the battery can be charged to so you dont buggger the battery ...same set up as your car.

 

[Frank Acampora]

Re: Rectifier vs. Voltage Regulator

Really old Chryslers had "trip regulators" attached to a selenium plate rectifier. Old Chryslers had voltage regulators on the Motorola ignition systems., then older Forces in a cost saving move switched to rectifiers. I think Merc went back to regulators in the late 90s.

Rectifiers simply convert AC to DC while the more complex (and therefore expensive) voltage regulator will maintain about 13-14 volts. Force alternators put out about 16-18 volts. A 12 volt lead acid battery actually will show 13 volts at peak charge. (2.25 volts per cell). 13-14 is what is usually required to charge a 12 volt lead acid battery. So, under prolonged running and cruising, some of the battery water is going to "boil" off. You must periodically check the battery and add water if needed if your engine only has a rectifier. Engines with regulators require much less frequent checking of battery water level. An electronic regulator will have a circuit inside to rectify AC to DC and another circuit to step down the voltage to 13-14. More complex voltage regulators will also have a feedback circuit to taper off the voltage as the battery approaches peak charge.

 

[fucawi]

Re: Rectifier vs. Voltage Regulator

To charge a lead acid battery you must raise it to 14.4v at which voltage it does not gas.Any less and its life is seriously reduced.
A charged battery after standing 24 hrs will show at least 12.5v if below its suspect. The voltage of an off charge battery which has not been stood 24hrs is meaningless.
When supplied from a regulated supply at 14.4v the charge current is self regulating and will not excedd 20-25A whatever the current rating of your alternator..
Computer controlled regulators raise the battery voltage to 14.4v and then cut it back to 13.8v

 

[RRitt]

Re: Rectifier vs. Voltage Regulator

IMO, battery life and charging characteristics of regulator vs rectifier are of secondary importance in a boat. If you install a shut off switch then your battery is going to last a long time and give you plenty of advance warning so that you never get stuck. The difference in charging/starting between regulator and rectifier is small potatoes when compared to installing a switch. However, if you have expensive and sensitive electronics - including CDI ignition systems - then a regulator offers dramatically improved protection for them. If the battery cables is disconnected or if there is a corroded connection while the engine is running then your electronics will get a series of spikes with a rectifier and can be damaged. With a regulator, the spikes are limited to 14V and the harm is mitigated. However (again), a regulator is much less reliable than a rectifier due to heat issues. A properly maintained and operated engine with rectifier is less likely to break than regulator.

So there is no clear best. Pick the one you like the most. If it is a regulator make sure that the heat can be transferred away by air flow and mounting.

 

[Bighornbob]

Re: Rectifier vs. Voltage Regulator

Thanks to all for the info. There are some smart posters on the forum and this "Cadet" isn't one of them. So in case you happen to know, in my 1996 120 Force do I have a regulator or a rectifier? I think by 1996 Merc was putting all the same ignition systems in all thier 90 and 120 Force engines. At least that is what I've been told.

 

[ronhud]

Re: Rectifier vs. Voltage Regulator

Seems to be a lot of knowledgable people on here, so I have a question. Can you tell me what these leads are for on my voltage regulator. It is a Force 50 HP, 1997, ser OE262932. I have four leads coming out: two yellow, 1 red and 1 grey. Everything seems to work on the motor, but the back of the regulator is burnt around two of the wires. Like it got overheading from the engine, which as you know it is exposed to. I am having trouble with my Tach and it has a grey send wire. I wonder if the grey wire on the regulator could be going to the tach and causing it not to work. Due to running in thge bilge, I can't trace the grey wire.

 

[john from md]

Re: Rectifier vs. Voltage Regulator

The two yellow wires are AC voltage from the stator. The red wire is the +DC wire for battery charging. The grey wire is the tachometer feed wire. Your regulator is grounded to the case. If it is burn't on the back, it probably got cooked and that is why your tach is jumping around.