alternator overheating ?

[scoooby slayer]

my alternator voltage runs 14.2 volts when i start it and holds fine but once ive driven it hard for a while its dropping to 13.4 volts, sometimes 13.1, if i stand the car and let it cool its back to 14.2 again ?

 

i run a big single with a big header and the alternator sits right below it and there is no form of heatshield, could the heat be affecting it ?

 

are there heat shields available ?

[dude]

It seems to alternating nicely dude, thats whatv its supposed to do, it will alter output according to rpm (slightly) and battery voltage. 13.4 is perfect, in the 14's is a bit much, i remeber in the old days the lovely smell of cooking batteries when alternators overcharged them.

[scoooby slayer]

It seems to alternating nicely dude, thats whatv its supposed to do, it will alter output according to rpm (slightly) and battery voltage. 13.4 is perfect, in the 14's is a bit much, i remeber in the old days the lovely smell of cooking batteries when alternators overcharged them.

 

my fuel pumps sound perfectly happy at 14.2 volts but once it drops to 13.4 i can hear them get louder and fuel pressure has a slight dip which then causes slight leaning off if on lower boost than 2 bar.

[dude]

Adjust the pressure so it as you want it at the lower voltage then, you cannot stop and alternator alternating, thats what it does and 13.4 is pretty much bang on normal charge rate, im pretty sure you can get a gizmo to keep the voltage at 14v but as I don't get involved with any wiring you will need to wait for someone cleverer than me to chip in.

[jagman]

http://www.kennebell.net/accessories/boostapump/boostapump.htm

[dude]

Told you !!!!!

[jagman]

http://www.kennebell.net/accessories/boostapump/boostapump.htm

 

Its pretty much what Toyota do a stock -up the voltage under boost but this moves it higher up the voltage to 17 volts

Ive not read about anyone using one in the UK , and the unit looks robust and well made with adequate heat sinks by the size of it - I have one on order so will report on how they operate , going on my soarer as I have a boostlogic single to go on it (couldnt help myself Dude -lol)

[SupraP-Z]

thats wierd dude...normal charging rates on any alternator should be anything between 13.9 and above, anything below isnt very good especially if its dropping to low 13's. 14-14.4 is what they normally sit at on idle. If its dropping to low 13's then either something is drawing a lot of current from your alt, the heat is affecting it, or it may possibly be the regulator. Although as it idles fine at 14.2, it would point to something drawing a lot of current, or the heat.

 

The alternator is called an alternator because it actually produces an AC current, the rectifiers inside convert this into DC, its not meant to alternate voltage.

 

Atleast this is the impression i was under lol

[scoooby slayer]

thats wierd dude...normal charging rates on any alternator should be anything between 13.9 and above, anything below isnt very good especially if its dropping to low 13's. 14-14.4 is what they normally sit at on idle. If its dropping to low 13's then either something is drawing a lot of current from your alt, the heat is affecting it, or it may possibly be the regulator. Although as it idles fine at 14.2, it would point to something drawing a lot of current, or the heat.

 

The alternator is called an alternator because it actually produces an AC current, the rectifiers inside convert this into DC, its not meant to alternate voltage.

 

Atleast this is the impression i was under lol

 

this is my issue the car was mapped everything set up with 14 volts, so shes grumbling with lower voltage. im gonna check all the earths first and run a few more aswell alt to engine, alt to body and bat to body and go from there.

[jagman]

Alternators reguate for both speed of engine and state of battery charge so outputs vary depending on both these - lower output can simply be the battery is fully charged

[SupraP-Z]

Alternators reguate for both speed of engine and state of battery charge so outputs vary depending on both these - lower output can simply be the battery is fully charged

 

True, but you are talking about output of the alternator which would be the amperage it produces when under load. Obviously this does contribute to voltage drop as current is being drawn, but for it to drop down to as low as 13.1 on a run, and staying like that...to me that doesnt sound right, unless something is drawing a hell of a lot of current...even so the regulator should normally re-adjust the voltage back upto 14v and over asap.

 

Question to the OP...are you using the factory alternator? or an aftermarket one?

 

If you think it may be an issue with poor connections, try doing the BIG 3 upgrade, normally done in big car audio systems using 0 gauge wire.

 

1) alternator positive to battery positive.

2) battery negative to chassis.

3) engine ground to chassis.

 

Either way, i reckon the heat in the bay isnt helping at all

Edited October 2, 2011 by SupraP-Z (see edit history)

[jagman]

Its not current regulated its voltage regulated -its output is voltage regulated not load or current regulated , the s or sense connection senses the battery voltage and adjusts the voltage to suit ie a low battery voltage ups the output of the alternator to add a charge current , it also looks at its stator output voltage due rotational speed if it gets to high it trims it down or vise versa

if a load got so high as to drop the voltage output it must be beyond the alts ability to produce that current output ie very high - an internal short in the battery or feed line to earth, any load that did this would blow the fuse quickly or you would get red hot wires .

In this case if the battery is fully charged then the regulator keeps the voltage close to the battery voltage and lessens the charge current -so a 12 volt battery at 13 volts would give close to 13 volts out

the speed of the alternator part of the reguator has now no requirement to regulate higher that this or overcharging the battery is the result and the circuits and bulbs etc only need 12 volts - you can get the situation where 13.1 or so is fine

[SupraP-Z]

I didnt say it was current regulated, you were talking about the output, the alternator produces current, this is the output. For there to be current there has to be voltage. Voltage drop = harder work for the alternator to produce the neccessary amps. As you mentioned it just regulates voltage.

 

What you have to remember is that the alternator is not only charging the battery but running all things electrical while the car is on, so it is constantly under load (Not very much load on idle). Although not a lot of current is drawn, it is effected nonetheless.

 

Let me give you an example...if you take a brand new fully charged battery and place it in the car, switch in on and measure the voltage...it will still read at 14.4 or whatever that particular vehicle normally charges at. I have a HO alternator in my daily driver and without there being any load on the car except for the onboard electricals, i can drive it for 5 hours pretty much straight, and it still reads 14.4v at the battery, and this battery is fully charged!

 

What you are saying makes sense, but every car ive driven - the alternator never drops the voltage unless under heavy load, and if the voltage drops, it dips into the battery reserve voltage and uses that, then of course it has to charge it back up, but thats different anyway lol

[dude]

I didnt say it was current regulated, you were talking about the output, the alternator produces current, this is the output. For there to be current there has to be voltage. Voltage drop = harder work for the alternator to produce the neccessary amps. As you mentioned it just regulates voltage.

 

What you have to remember is that the alternator is not only charging the battery but running all things electrical while the car is on, so it is constantly under load (Not very much load on idle). Although not a lot of current is drawn, it is effected nonetheless.

 

Let me give you an example...if you take a brand new fully charged battery and place it in the car, switch in on and measure the voltage...it will still read at 14.4 or whatever that particular vehicle normally charges at. I have a HO alternator in my daily driver and without there being any load on the car except for the onboard electricals, i can drive it for 5 hours pretty much straight, and it still reads 14.4v at the battery, and this battery is fully charged!

 

What you are saying makes sense, but every car ive driven - the alternator never drops the voltage unless under heavy load, and if the voltage drops, it dips into the battery reserve voltage and uses that, then of course it has to charge it back up, but thats different anyway lol

 

OK I have a large RV with 4 leisure batteries and 1 engine battery and none of these either charge or sit at 14.4 v, when driving both leisure and engine battery charge from the alternator at a max of 13.8, the moment the engine is stopped this settles to low 13's high 12's and the leisure batteries will power my inverter 40" LED tv, blue ray player and laptops all night. IMO a little more than 14.4 and you will be starting to get that nice stinky battery smell.

[SupraP-Z]

OK I have a large RV with 4 leisure batteries and 1 engine battery and none of these either charge or sit at 14.4 v, when driving both leisure and engine battery charge from the alternator at a max of 13.8, the moment the engine is stopped this settles to low 13's high 12's and the leisure batteries will power my inverter 40" LED tv, blue ray player and laptops all night. IMO a little more than 14.4 and you will be starting to get that nice stinky battery smell.

 

Thats because you are running 5 batteries! thats a hell of a lot! am i right in thinking you are running all of this of your stock alt? if you are, your stock alt wont be able cope to charge all of your batteries fully, it would take ages, plus having so many they would settle at a collective lower voltage.

 

to get the most out of it, you need 0 gauge running throughout to maximise electron flow from ur stock alt, and proper ground. most people with that many batteries tend to use thick buss bars to make a collective ground, then you just may notice the batts settling at a higher voltage.

 

tbh 5 batteries that are almost fully charged would power a huge sound system running 5-7kw for a good hour or two, maybe even longer depending on if you play it on full tilt or not. they would have no problem powering everything you mentioned.

 

disconnect all of the leisure batts and then measure the voltage of the engine batt, guaranteed it will be over 14volts.

[jagman]

each cell in a battery has a nominal voltage of 2 volts hence a 12 volt battery , discharged battery is at 1.75 volts per cell ,fully charged is 2.12 volts per cell or 12.7/8 volts , however during charging ,(a reverse of current flow)it can rise to 2.7 volts per cell -

as soon as the charge current is removed it rapidly drops to its full charge 2.12 volts , due the battery internal resistance

.any load on the battery will futher drop its voltage towards its nominal voltage .

 

The alternator has to put out over 12.8 to fully charge the battery , the more over the 12.8 the more charge current to the battery ,if this were permanently 14.5 volts , the current charging heats the battery , reducing the electrolyte and warping the spongy lead plates - thats when you smell the gases given off - this is now controlled by the regulator so at idle the charge voltage is reduced -depending on the battery charge and increased at high rpms again depending on the battery charge

the load from circuits varies , but say a 80 amp alternator can suppy 80 amps load with no drop off in voltage ,the regulator almost instantly maintains voltage , this adds the load to the engine as torque

some things such as motors ,wiper,heater, draw large start current until the build back emf ,at these time the voltage drops off for a few seconds then stabalises (not so much with wipers stop starting -you see the volts rise/fall)

If the load was 150 amps ,then the alt cant keep up,its output volts drop and once at or below the battery voltage the battery supplies the load and discharges the battery can supply hundreds of amps to the load , well for a while .

duff brushes7slipping belts, for example reduce the alts ability to provide enough power , but load wise its got to be a large and usually obvious problem .

temperature also affects the charge current /voltages but this is the battery temp ,some cars such as the Jaguars used to fit a fan to the battery case to keep this as constant as possible ,keeping the battery internal resistance in limits

[dude]

Thats because you are running 5 batteries! thats a hell of a lot! am i right in thinking you are running all of this of your stock alt? if you are, your stock alt wont be able cope to charge all of your batteries fully, it would take ages, plus having so many they would settle at a collective lower voltage.

 

to get the most out of it, you need 0 gauge running throughout to maximise electron flow from ur stock alt, and proper ground. most people with that many batteries tend to use thick buss bars to make a collective ground, then you just may notice the batts settling at a higher voltage.

 

tbh 5 batteries that are almost fully charged would power a huge sound system running 5-7kw for a good hour or two, maybe even longer depending on if you play it on full tilt or not. they would have no problem powering everything you mentioned.

 

disconnect all of the leisure batts and then measure the voltage of the engine batt, guaranteed it will be over 14volts.

 

I can and do disconnect the leisure from engine battery and it never charges at more than 14 volts, the 4 leisure batteries are normally fully charged because the RV is always left hooked to the mains, the onboard generator charges them in about an hour. I did use very good quality cable when I installed them with good terminals.

 

Reading up on RV sites they ALL say a fully charged battery will read 12.7/8 volts, remember battery life is the holy grail of RV's its what they all strive to do as well as possible.

[scoooby slayer]

it should sustain 14 volts on a good alt regardless of battery charge. it is definately a heat issue as if i stop the car while its hot and voltage has dropped and wait 10 mins then restart the voltage is still around 13.1 - 13.4, but if i leave it an hour or 2 so

as the engine bay has cooled right down and start it shes straight back up to 14.1 - 14.3 volts. i may try heat wrapping the alternator as its prefect until it overheats.

[dude]

it should sustain 14 volts on a good alt regardless of battery charge. it is definately a heat issue as if i stop the car while its hot and voltage has dropped and wait 10 mins then restart the voltage is still around 13.1 - 13.4, but if i leave it an hour or 2 so

as the engine bay has cooled right down and start it shes straight back up to 14.1 - 14.3 volts. i may try heat wrapping the alternator as its prefect until it overheats.

 

Also when you leave it the battery has discharged a bit hence it will charge higher, still you have made your mind up so good luck with it.

[SupraP-Z]

Also when you leave it the battery has discharged a bit hence it will charge higher, still you have made your mind up so good luck with it.

 

The alternator will charge the battery at the same rate no matter what the battery voltage is at, as scooby slayer mentioned it will sustain 14 volts on a good alternator regardless of battery charge.

 

Dude, i am not familiar with electrical systems of RV's so i am not in a position to say what the alternator in your RV will be charging at, it may just be made that way. It may charge at just under 14 volts as some automotive charging systems prefer lower absorption voltages, like your case at 13.8V, to reduce water consumption and wet Low Maintenance (Sb/Ca) starting batteries to reduce cost. This will over time, undercharge the battery and electrolyte layers will build up, which causes the battery to gradually loose capacity because of the accumulation of lead-sulfate. Thus why you are having to use a charger to keep the batteries topped up. Ive got to admit though, one hour and the batteries are fully charged? pretty impressive! I guess they are not fully discharged though, which would make sense.

 

I have charged batteries on a c-tek charger and have seen a batt over 13 volts when fully charged (off the charger of course), but yes normally fully charged batteries rest at around 12.7 upwards to around 13.2 or so, it also depends on the battery itself.

 

Ill give you another example, you mentioned that when the RV is on...you dont see above 13.8 volts? So presuming the batts have already been fully charged by the onboard generator, when the engine is on you still see 13.7/13.8 volts at the battery right? The alternator doesnt drop the voltage down to 13.1/12.8 volts or anything like that does it? It remains constant, unless you put a load on it in which case voltage will dip and then rise back to normal, as stated by Jagman.

 

Heres how it works:

 

When the battery is weak, the electromotive force (voltage) is not strong enough to hold back the current from the alternator trying to recharge the battery. As the battery reaches a state of full charge, the electromotive force becomes strong enough to oppose the current flow from the alternator, the amperage output from the alternator will drop to close to zero, while the voltage will remain at a constant rate.

 

Back to the OP....is there any way you could direct some air towards the alternator? via some plastic ducting through the front bumper or anything like that? I would imagine not being a big single....but its worth a try. Heat wrapping may be an option...never heard of it being done to an alt though. There are moving parts inside so if it was me, that would be low down on my list of things to try, but kudos to you if it works!

Edited October 3, 2011 by SupraP-Z (see edit history)

[jagman]

"The alternator will charge the battery at the same rate no matter what the battery voltage is at, as scooby slayer mentioned it will sustain 14 volts on a good alternator regardless of battery charge."

 

 

 

 

3) Three-wire alternator. This is the most effective configuration. Essentially a closed loop "feed back" system. It uses a large battery wire, an ignition and or warning light connection and a voltage sensing wire. The advantages are a) the regulator is activated by the ignition/warning light wire, b) the sense wire, connected directly to the battery, continuously tells the voltage regulator the charge condition of the battery. (this information is significantly more accurate when sourced directly at the battery.) The voltage regulator infinitely varies the alternator output based on this information. No other configuration charges the battery as effectively."

 

http://www.chargerr.com/Alternators/ALT.HTM

 

If you are constantly making 14.1-14.3 , then it is possible that the s sense wire has a poor contact or high resistance , the battery may be 12.8 volts but the s wire at the alternator connector sees only say 11.5 volts due a volts drop (poor contact at either end) so it pushes up the output voltage constantly to a higher value (14.1-14.3) this will eventually knacker the battery .

If a cell is down on the battery a similar thing can happen , it needs checking on load to see if this is the case

[dude]

Regulated output of the alternator @ 110 centigrade is 13.2 - 14v, more at cooler temp, so the alternator is behaving correctly but will put out more IF you can keep it cooler, BUT cooler means 70 degrees cooler. I doubt the fact its single is making too much diff to the temp of the alternator. Your ecu should have a correction against battery voltage facility to allow for this. The battery runs the electrics not the alternator.

[Chris Wilson]

There will be (should be....) a compensation map in the ecu to adjust injector duty time against voltage. So varying fuel pump output V alternator output is compensated for by altering the injector on time.