Safe max voltage from alternator

**jjonphl** · August 6th, 2011 02:24 PM

Hi guys,

I had the alternator of my Crosswind (2001) replaced couple of years back. I remember we measured it at around 13V when idle and 14-15v when revving. Last night I measured it at 17v when idle. Is this safe? How did this happen?

Thanks!

**niky** · August 6th, 2011 03:46 PM

The voltage shouldn't go over 14v. Possibly the voltage regulator is shot.

**light2light** · June 28th, 2012 11:48 AM

niky is right. sometimes, even when everything is ok, you'll measure the pulses from the alternator( this is definitely an error measurement)

for diesel, if the battery is suddenly disconnected, (regulation is lost)the voltage may go up to over 18-24v. Lahat ng electronic devices mo, including all lights will be busted. this is the reason why many jeepneys are running without lights. there is a defect in the system design (assembled). do you notice that the driver will turn off the key and pull a lever to switch off the engine?
if the driver turn off the key to off and lately pull the lever, regulation is lost and the battery voltage will go as high as 18v.
if he is late in pulling the lever, air intake is still sucked-in by the engine and the engine will keep on running until he pulls the lever.
the time difference of 2-5 secs, all bulbs and electronic devices are busted.

The solution? rewire the charging system and install solenoids/relays, so that turning off the key and shutting off the air intake is simultaneous. A small tip for jeepney drivers.

**Thumbdrive** · June 28th, 2012 12:26 PM

Originally Posted by light2light

for diesel, if the battery is suddenly disconnected, (regulation is lost)the voltage may go up to over 18-24v. Lahat ng electronic devices mo, including all lights will be busted...

^is this without the voltage regulator functioning or without voltage regulator at all?

**light2light** · June 29th, 2012 06:59 PM

for diesel engines only: assuming everything is working properly, if the battery is disconnected, even temporarily, even for a few seconds, the voltage will go skyhigh; 18-24v, the headlights will flash like a camera! that's why it is important to maintain battery terminals for corrosion.

for gasoline engines: most engines will stop when the battery is disconnected.

**Retz** · June 29th, 2012 07:06 PM

Originally Posted by jjonphl

Hi guys,

I had the alternator of my Crosswind (2001) replaced couple of years back. I remember we measured it at around 13V when idle and 14-15v when revving. Last night I measured it at 17v when idle. Is this safe? How did this happen?

Thanks!

I think your battery will deplete more quickly if it is overcharge. Not to mention other accessories that is utilizing electricity.

**cocoy** · June 30th, 2012 11:07 AM

Originally Posted by light2light

for diesel engines only: assuming everything is working properly, if the battery is disconnected, even temporarily, even for a few seconds, the voltage will go skyhigh; 18-24v, the headlights will flash like a camera! that's why it is important to maintain battery terminals for corrosion.

for gasoline engines: most engines will stop when the battery is disconnected.

why doesnt this happen to my car when i take the battery off with the engine running?

**Ry_Tower** · June 30th, 2012 01:04 PM

For diesel engines afaik puwede tanggalin battery basta umaandar na. Ganun din sa kain eh, no fluctuation in voltage and amperes.

**yapoy86** · June 30th, 2012 01:34 PM

Originally Posted by light2light

niky is right. sometimes, even when everything is ok, you'll measure the pulses from the alternator( this is definitely an error measurement)

for diesel, if the battery is suddenly disconnected, (regulation is lost)the voltage may go up to over 18-24v. Lahat ng electronic devices mo, including all lights will be busted. this is the reason why many jeepneys are running without lights. there is a defect in the system design (assembled). do you notice that the driver will turn off the key and pull a lever to switch off the engine?
if the driver turn off the key to off and lately pull the lever, regulation is lost and the battery voltage will go as high as 18v.
if he is late in pulling the lever, air intake is still sucked-in by the engine and the engine will keep on running until he pulls the lever.
the time difference of 2-5 secs, all bulbs and electronic devices are busted.

The solution? rewire the charging system and install solenoids/relays, so that turning off the key and shutting off the air intake is simultaneous. A small tip for jeepney drivers.

kalokohan.... mga jeepney bumabyahe ng walang headlight dahil sa mis aligned ang head lamp nila at pag bukas ito.. masisilaw yung nag aabang na pasahero at hindi makikita yung signboard nya at hindi din makikita kung maluwag pa yung jeep.. yan lang ang dahilan..

yung mga diesel engine na may MANUAL CHOKE pa like isuzu C-190, pag naka start na kahit disconnect mo ang battery pwede... pero yung sa mga naka AUTOMATIC CHOKE, hindi pwede kasi mamatay yan...

ang alternator, self-exciting yan.. to produce electricity, battery must be present!.. check nyo yung alternator tester ng mga alternator shops... ikakabit muna nila sa battery bago paikutin yung alternator.. so kapag wala na yung battery unti unti din mag diminish yung charge ng alternator or worse masunog

masyado ka concerned sa mga jeepney drivers... dapat nga masunog na yang mga bulok na jeep para mapalitan naman.. yun bus nga pinapalitan eh.. taxi pinapalitan yung jeep forever