Charging Coils For Small Engines

Hi guys,


On a small engine ( regardless of brand , horsepower or cylinders or age ) , does the charging rings with a diode in the harness put out more or less voltage than one with an external regulator box . I'm talking about the ones with two wires for outputs from charging ring that are the same color that go to an external regulator box. I say the ring that goes to the external box puts out more voltage. I know the position of the throttle makes a difference , but other than that which one puts out more voltage ? How many volts should safetly be going to a 12 volt battery to safely charge the battery ? I say 15 volts . Long story but thanks to all who reply . Any and all help appreciated .

Thanks,
Whizkid

There are no hard & fast rules to eng charging systems due to fact most eng mfg design charging systems to work with a specific flywheel,alt stator & inline diode or ext rectifer/regulator to determine ac output voltage/current,especially briggs.

If you look in many of the briggs service manuals for different mod eng you'll usually find 4-6 different alt stators listed & in some case's 2-3 different size flywheel magnets & a different pn for rectifer/regulator as internal design/componets of same are designed to be used with a specfic alt stator/flywheel depending on DC amp output.

On single/dual output alt stators with inline diode these systems are half wave charging systems & AC output voltage can be 15-18v,on stators with 2 wire output & ext rectifer/regulator these are full wave charging systems & AC output voltage can can be 18-35v/more depending on how eng mfg designed charging system,this is why it's important to have service manual for eng to id charging system/parts in same & troubleshooting guide as AC output voltage of stator can be different on different mod eng by same mfg.

Should be in the 14.0-14.5 volt range. Hal

As a follow up on inline diode charging system,the DC voltage output is usually 1.1-1.5v lower than AC stator output,this is due to internal voltage drop in diode,most 1.5-5A charging systems are unregulated,the actual DC charging voltage/current is determined by specific gravity/resistance of acid in battery as this changes with level of battery charge & condition of battery cells as acid acts as a half fast regulator for alt output,when battery new & all cells in good condition acid limits voltage/current charge to battery,as battery ages & cell(s) get weak due to internal breakdown of cell plates & cell(s) can't accept a full charge the gravity/resistance of acid changes along with AH capacity of battery,this will allow a higher voltage/current flow to battery up to max voltage/current rateing of charging system,in some cases it may blow the inline diode.

The major problem with an unregulated system is it tends to shorten battery life due to overcharging as battery being charged all the time,many tractor mfg will spec DC alt output to 3-5A,if tractor has an electric pto they will install a dropping resistor on pto sw to limit charge voltage/current to battery when pto off,then resistor is bypassed when pto turned on to provide max voltage/current to clutch/battery or if mower manual engage they will install a current limiting resistor in wiring harness/at ign sw to limit max charge current to battery.

So does that mean that it's ok to charge a 12 volt battery , no matter the batterys age or condition , with 30 volts DC, regardless if it's comming from a regulated or not or a full or half wave bridge source ?


Thanks,
Whizkid

NO-IT IS NOT ALRIGHT to charge a 12v battery with 24-30V DC source regardless if regulated/unregulated,doing so can cause battery to boil & possibly explode.

As Hal said normal charging voltage is 14-14.5v for a regulated system & 14-15.5v for an unregulated system,normal charging voltage for 12v lead acid batteries is normally 2-2.5V more that voltage rateing of battery,most eng mfg service manuals tell you if charge voltage in a regulated system over 15V DC to replace regulator/check alt stator.In an unregulated charging system the charging voltage can run 14-16v DC,this is after you subtract 1.1-1.5v drop thru inline diode from AC voltage of alt stator output & any possible current limit/voltage drop resistor after inline diode,this is why battery life is somewhat shorter with an unregulated system as battery is maintained at a full charge/slighty overcharged condition most of the time.