Charging Voltage Low

Submitted: Tuesday, Jan 08, 2008 at 23:15
ThreadID: 53260 Views:8735 Replies:15 FollowUps:69
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Ive got a GQ Patrol fitted with a new 14V 120 Amp BOSCH alternator ,NOW when it is idling and the redarc has switched on to connect the deep cycle up the voltage sits at 13.6 volts with nothing on.

If i turn the aircon on it goes down to 13.4 ,if i then put the lights on FULL it goes down to 13.1 by this time the redarc has spat the dummy and disconnected the deep cycle so hence no charge to it.

I have run BIG cables from the alternator to the battery and to the second battery but the system voltage does not get anywhere near what it is supposed to according to the 14V that is stamped on the alternator.

What tells the voltage regulator to raise or lower the sytem voltage ,what is the sensing voltage taken from because this system is very low and i cant understand why.

Please help me!!!!!!!!!

Matt
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Reply By: Member - Matthew C (WA) - Tuesday, Jan 08, 2008 at 23:16

Tuesday, Jan 08, 2008 at 23:16
OH and it mnakes no difference what RPM the engine is set on the voltages DO NOT change.
AnswerID: 280538

Reply By: Member - bungarra (WA) - Tuesday, Jan 08, 2008 at 23:28

Tuesday, Jan 08, 2008 at 23:28
where are measuring the voltages?...at the battery terminals or at the alternator?.....
might be worth measuring at the alternator (if your not already) and if the voltage is ok there under load then hook the red arc up direct from there

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AnswerID: 280540

Follow Up By: Member - Matthew C (WA) - Tuesday, Jan 08, 2008 at 23:33

Tuesday, Jan 08, 2008 at 23:33
Measuring at the battery terminals and i have a gauge on the deep cycle at it says exactly the same voltage as the measurement taken at the primary battery.

What i am needing to do is raise the sytem voltage to around 14v under load,like when the redarc is connected otherwise when i hook the van up it wont charge that battery either and i really dont think it is too much to ask of a 120A alternator.

Any ideas.
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FollowupID: 544768

Reply By: Derek from Affordable Batteries & Radiators - Tuesday, Jan 08, 2008 at 23:31

Tuesday, Jan 08, 2008 at 23:31
Hi Matt

How old is the Redarc ?

It may be a early one that would disconnect close to 12.8V but the new ones are just like our DBi-120 and disconnect at 12.4 to 12.5 volts.

Your alternator may need a bot of a tweak but if the isolator is working correctly and the auxiliary battery is drawing amps it should stay engaged.

Have you got the serial number of the Redarc or send it to me to test.

What is the voltage at the main battery with the a/c and lights on and the engine at 2000 rpm ?

Regards

Derek.
AnswerID: 280542

Follow Up By: Member - Matthew C (WA) - Tuesday, Jan 08, 2008 at 23:35

Tuesday, Jan 08, 2008 at 23:35
Derek the voltage is 13.0 flat at 2000 with aircon on and lights on FULL.

My concern is not the isolator it is doing its job and saving the drive battery.

What i want to do is raise the sysytem voltage,this alternator should bleep this job in .

Matt
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FollowupID: 544770

Reply By: Derek from Affordable Batteries & Radiators - Tuesday, Jan 08, 2008 at 23:33

Tuesday, Jan 08, 2008 at 23:33
AnswerID: 280543

Follow Up By: Derek from Affordable Batteries & Radiators - Tuesday, Jan 08, 2008 at 23:38

Tuesday, Jan 08, 2008 at 23:38
Sorry I meant to include the DBi-120 specs too.



Most modern vehicles require this lower kick in / kick out voltage to stop the isolators disengaging at idle or with computer controlled alternators.

We have found the 13.2V on and 12.4V off is the best balance and the 120A rating covers most applications.

Regards

Derek.
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FollowupID: 544771

Reply By: Derek from Affordable Batteries & Radiators - Tuesday, Jan 08, 2008 at 23:49

Tuesday, Jan 08, 2008 at 23:49
OK Matt

Please give me these voltages with the engine at 2000 rpm and a/c and lights on.


1) Main battery (use the + and - posts)
2) Alternator (use the + on the alternator and the engine as the -)
3) Isolator input (use the input as + and the body as -)
4) Isolator output (use the output as + and the body as -)
5) Aux battery (use the + and - posts)

Now fit a earth jumper to the isolator (does any of the above voltages change ?)
Now fit a earth jumper to the aux battery (does any of the above voltages change ?)

Please make accurate notes and post them here or email me.

Regards

Derek.

AnswerID: 280546

Follow Up By: Member - Matthew C (WA) - Tuesday, Jan 08, 2008 at 23:55

Tuesday, Jan 08, 2008 at 23:55
Ok will do,

By earth jumper what do you mean???

Do you mean from the negative battery terminal to isolator,because the isolator has no negative connector.

And earth jumper to uax battery is from negative terminal to chassis or engine,main battery.

Thanks

Matt
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FollowupID: 544772

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 00:02

Wednesday, Jan 09, 2008 at 00:02
Many isolator problems are caused by the isolator simply not having a good earth so jump a new earth to the isolator (Should be a small black wire)

Many no charge problems on aux batteries are caused by a poor battery earth to the car body / chassis. Jump a new earth from the aux negative to the body.

Let me know the results.

Regards

Derek.
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FollowupID: 544773

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 00:07

Wednesday, Jan 09, 2008 at 00:07
1) 13.3V
2) 13.63
3) 13.44
4) 13.44
5) 13.27 Waeco CF50 connected and cycled on.

Earths made no difference.


Seems that the system voltage is lower than expected for the 14V output of the alternator.

Test was done with only A/C and high beam no spot lights.They draw another .3V from the system.

Matt

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FollowupID: 544775

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 00:10

Wednesday, Jan 09, 2008 at 00:10
If i was to do it with the spot lights on the system voltage would fall below 13.0v and the redarc would disconnect.

Matt
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FollowupID: 544776

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 01:30

Wednesday, Jan 09, 2008 at 01:30
1) 13.3V This voltage is a lot lower then the Alternator - Check for a bad engine earth or poor connection between the alternator and the main battery - check the fuse or fusible link too.
2) 13.63 - This should be higher too. Around 14.3v - Alternator regulator may be faulty. But repair #1 first.
3) 13.44 - This does not make sense as it should be the same as the main battery - it should not be higher - check for a loose connection on the main battery earths - fusible link - or possible open cell on the battery.
4) 13.44 - This shows the isolator has no voltage drop and contacts are in good condition.
5) 13.27 Waeco CF50 connected and cycled on - This is normal - a 0.17v drop with the fridge running is very good.

I would say you must...

1) Make sure the wiring is in sound condition. There must not be a voltage drop between the alternator and the main battery. Replace as required.
2) Make sure the main battery is in sound condition and not causing the alternator to decrease its output.
3) Have the alternator tested - It should give you 14V even with a load at 2000 rpm.
4) Once all components are in working order you should have the same voltage at all points and only the aux battery will be slightly lower.

Regards

Derek.

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FollowupID: 544784

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 10:08

Wednesday, Jan 09, 2008 at 10:08
Derek last night i changed batterys to a different one that i know is ok ,its a N70ZZ.

Also fitted another new 120A alternator ,better but still low charge voltages.

The voltages at the alternator are the same on the B+ terminal and the D+ terminal which is the sensing point isnt it or the one for the light.

The alternator is brand new out of the box every time.

MAtt

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FollowupID: 544807

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 10:28

Wednesday, Jan 09, 2008 at 10:28
Matt,

How much better.

Please give me the voltages of 1,2,3 again.

No load at 2000 rpm and with load at 2000 rpm.

What make are these alternators ?
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FollowupID: 544809

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 10:40

Wednesday, Jan 09, 2008 at 10:40
Derek

That is with the NEW alternator,it would have been at least .5V lower with the old alternator.

They are BOSCH alternators.
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FollowupID: 544812

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 10:46

Wednesday, Jan 09, 2008 at 10:46
Hi Matt

Fit a heavy earth from the alternator to the main battery (-).

Fit a heavy cable from the alt (B+) to the main battery (+).

Then give me those readings again.
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FollowupID: 544813

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 11:51

Wednesday, Jan 09, 2008 at 11:51
Derek

I will do what you suggested when i get home.

So from what part of the alternator should i run the earth and i have already run another charge wire directly to the battery bypassing the connector plugs and fusable links on the battery terminal.

How heavy is heavy.

I still dont understand why the system voltage is low at the alternator,cause if it senses low battery voltage shouldnt it up the voltage at the alternator to compensate ????????


Matt
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FollowupID: 544821

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 12:13

Wednesday, Jan 09, 2008 at 12:13
Make the earth at least 8 B&S.

If the alternator is not properly earthed back to the main battery then it can cause charge and voltage problems.

Once this is done we can test the voltages.

I am hoping to see the voltage at 1,2 and 3 all the same and then we can look at alternator problems but then and only then.
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FollowupID: 544822

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 14:36

Wednesday, Jan 09, 2008 at 14:36
Derek

I ahve just fitted a big earth to the alternator and it seems to hold the voltage better under load.

I will fit a BIG charge wire when i get home cause there is still .25v drop from alternator B+ to battery terminal.

Thanks

Matt
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FollowupID: 544849

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 14:42

Wednesday, Jan 09, 2008 at 14:42
Great, clean up those battery terminals while you are busy. Make sure the cables are not corroded internally.
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FollowupID: 544852

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 22:43

Wednesday, Jan 09, 2008 at 22:43
Derek

I must thank you very much the problem is solvered i believe.

1) 13.69
2) 13.73
3) 13.7
4) 13.7
5) 13.58 once again i suspect fridge may have turned on.

These test were done this time with A/C on and ALL the lights on FULL boar instead of just the A/C and normal high beam lights on.

Now i fitted the BIG earth from main battery to mounting bolt of alternator and also fitted a BIG cable from the B+ to the main battery terminal.

Like these cables are 8-9mm copper wire size not OD.

Anyway i will hook up the van over the weekend and measure the voltages at the appliances and see how that goes.

Since you have helped me out and probably saved me hundreds ,i would like to purchase one of your caravan second battery systems so i can set that up correctly also.

How do i go about that.

MAtt
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FollowupID: 544999

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 22:45

Wednesday, Jan 09, 2008 at 22:45
Derek

Also how do i now raise the system voltage to a tad over 14V or do you think i dont need to with the results that i have.

Matt
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FollowupID: 545000

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 22:57

Wednesday, Jan 09, 2008 at 22:57
Hi Matt

Email me directly for any information required for the caravan system so we can design this to suit your application and existing h/ware.

I would not raise the system voltage right now as 13.7v under load is excellent and best to see what the regulator cycles back to once the batteries are charged and engine is at fast idle. If you still have 13.7 to 13.8 volts then great.

Do a test. Allow the main battery to discharge slightly by leaving the head lights of for 5 minutes and you should see the voltage of the main battery charging at 14 volts at fast idle with no load.

I would say all is well.

Please fit a 150A fuse to that new alternator (+) wire for safety.

Regards

Derek.
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FollowupID: 545004

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 23:33

Wednesday, Jan 09, 2008 at 23:33
Derek

Yeah with no load the main battery is at 13.94 or thereabouts so yeah all good i guess.

Ok mate will do ,can you supply the fuse as well.

What is your contact email.

MAtt
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FollowupID: 545010

Follow Up By: Derek from Affordable Batteries & Radiators - Wednesday, Jan 09, 2008 at 23:38

Wednesday, Jan 09, 2008 at 23:38
Click on my logo or Contact-Derek
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FollowupID: 545011

Follow Up By: Member - Matthew C (WA) - Thursday, Jan 10, 2008 at 00:21

Thursday, Jan 10, 2008 at 00:21
Email sent.

Cheers
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FollowupID: 545015

Follow Up By: Member - Mike DID - Thursday, Jan 10, 2008 at 08:42

Thursday, Jan 10, 2008 at 08:42
So which change actually fixed the problem ?

Above you say "Now i fitted the BIG earth from main battery to mounting bolt of alternator and also fitted a BIG cable from the B+ to the main battery terminal. Like these cables are 8-9mm copper wire size not OD."

But your original post said also you had big wires from the Alternator.
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FollowupID: 545035

Follow Up By: Member - Matthew C (WA) - Thursday, Jan 10, 2008 at 10:06

Thursday, Jan 10, 2008 at 10:06
Apparently not big enough cables when ALL the load was on,

The biggest change was from putting the BIG earth from the battery - to the alternator bracket.

What i thought was enough wasn't in the end so i replaced them and its all good.

MAtt
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FollowupID: 545047

Follow Up By: Mainey (wa) - Thursday, Jan 10, 2008 at 10:11

Thursday, Jan 10, 2008 at 10:11
Mathew,

That's the reason I use 2B&S (32mm²) battery cable on both (+) & (-) cables in my battery system and have zero voltage loss.
Mainey...
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FollowupID: 545050

Follow Up By: Member - Mike DID - Thursday, Jan 10, 2008 at 10:23

Thursday, Jan 10, 2008 at 10:23
"The biggest change was from putting the BIG earth from the battery - to the alternator bracket."

- that's weird. The heavy cable from the Battery Negative to the engine block is designed to carry the 200-300 amps of starter current. If you had no problems with a sluggish starter, then the connections on this cable must be ok.

Considering the big bolts connecting the Alternator to the Engine Block, I don't see how there can be high resistance there.

When the practice doesn't agree with the theory, I start wondering if there is a coincidental change.
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FollowupID: 545051

Follow Up By: Member - Matthew ,United Fuel- Thursday, Jan 10, 2008 at 16:32

Thursday, Jan 10, 2008 at 16:32
Mainey

Thats what i used as well 2B&S on both cables.

Mike DID: Not sure what if any were coincidentals but hey im happy now.

Matt
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FollowupID: 545105

Reply By: Tim HJ61 (WA) - Wednesday, Jan 09, 2008 at 00:35

Wednesday, Jan 09, 2008 at 00:35
Matthew,

I've got an adjustable regulator that makes things easier on my 61 series LC. You may be able to get one fitted to your vehicle instead of what I guess is a solid state regulator. There are also after market regulators around - three stage chargers - that might be helpful, sorry I don't have the links.

I also found Redarc would adjust the cutin/cutout voltages is you ask them nicely. You have to post the little black controller unit back to them after talking to them on the phone and seeing if they will still do it.

Tim
AnswerID: 280548

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 00:45

Wednesday, Jan 09, 2008 at 00:45
Ok thanks but i really dont think the redarc is the problem here.

The system voltage should be higher,like around 13.8V minimum so that this doesn't happen..

Where did you get the adjustable voltage regulator from and is that for the main battery system or aux one.


Am i right in thinking this because we all no that batterys dont charge very well at around 13.0v.


Matt
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FollowupID: 544783

Follow Up By: Member - Mike DID - Wednesday, Jan 09, 2008 at 08:43

Wednesday, Jan 09, 2008 at 08:43
No Lead Acid battery will charge fully at 13.0 volts and it will not last long due to sulphation.

At 13.6 volts it will charge fully, but it will take a LONG time.

Most cars (that don't use Calcium-calcium batteries) put out 14.4 volts until the Alternator warms up.
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FollowupID: 544791

Follow Up By: Tim HJ61 (WA) - Wednesday, Jan 09, 2008 at 08:59

Wednesday, Jan 09, 2008 at 08:59
Matthew,

I agree with you, the Redarc is not the problem - the low charge voltage is the problem.

What have the people that supplied or installed the new alternator said? I'd be checking to make sure the alternator regulator was working properly.

Some regulators are built into the alternator, others external and either adjustable like mine in my 89 Landcruiser, or more commonly solid state thingys that aren't adjustable. The solid state units are probably more reliable than the old style regulator in my vehicle.

Like Mike says, 14.2 to 14.4v is what you're looking for.

Why did you change over your alternator? or more to the point, what voltage was the old alternator charging at when it was working?

Is your alternator regulator external to the alternator or inbuilt?
If it is external, maybe buy a new one. If it's internal, then I'd be talking to the supplier/installer of the alternator as it's just not charging high enough voltage.

When I had low charge voltage problems in my cruiser, he noticed a voltage drop of a volt between the alternator output and my battery. He suggested running a separate dedicated cable from the alternator to the battery. In reference to your question about where does the alternator pick it's voltage from, I understand that unless there is a voltage sense wire to the battery, then it is measured internally and/or by the regulator. Given your voltage readouts, this doesn't seem to be part of your problem.

A trip to the auto sparky might be the way to go if you can't get anywhere with these suggestions.

Tim

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FollowupID: 544794

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 10:04

Wednesday, Jan 09, 2008 at 10:04
Ok this all started because i put in a deep cycle battery and purchased a caravan and needed the extra amps to run the van and deep cycle battery.

The old alternator was only making the same voltage but would fall away dramatically under load (it was the same type but 65A).

So i fitted this NEW 120A one and thought no more of it until i went away and the deep cycle and caravan voltages started to fall away during the trip.So i fitted a gauge in the dash to monitor it all and noticed that the charge voltages turned to bleep once load was applied,so i figured the new alternator regulator had failed.

I fitted ANOTHER NEW 120 A alternator that we had in stock last night and it is a little better but still way below the 14.1 volts i am looking for.

CAn i raise the charging voltage ????

Derek i will do what you say first then recheck it all.
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FollowupID: 544806

Follow Up By: Member - Mike DID - Wednesday, Jan 09, 2008 at 10:39

Wednesday, Jan 09, 2008 at 10:39
"Can i raise the charging voltage ????"
- see my message below.

Your problem is due to the Alternator - all you need to do is measure the voltage at the Main Battery. Forget about the Isolator voltages - it won't work properly until the Alternator voltage is right.

Are you using a proper multimeter ? Those dash-mounting voltmeters can quite inaccurate.
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FollowupID: 544811

Follow Up By: Mainey (wa) - Thursday, Jan 10, 2008 at 00:20

Thursday, Jan 10, 2008 at 00:20
As Mike R as said, "" it won't work properly until the Alternator voltage is right "" and I will add is 'regulated' correctly

I have only a 55 Amp Alternator, it's 'regulated' to put out 14.4 Volts
No battery problems... :-))

Mainey...
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FollowupID: 545014

Follow Up By: Member - Matthew C (WA) - Thursday, Jan 10, 2008 at 00:29

Thursday, Jan 10, 2008 at 00:29
Ok it looks like we have solved the problem with a lot of help from derek.

Not sure a 55 amp alternator would cope with the load that i have on this sytem.

What vehicle and what load are you using.

Mine has to run general car system with stereo/amps etc, charge main battery/80 A/Hr aux battery with CF50 connected all the time,run twin EL thermo fans @ 40 AMP start current/15 AMP Run/aircon and cooling fan/big driving lights and also keep 12V fridge going in caravan.I know that they are not all on at once BUT there is a hell of a load when it all happens .

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FollowupID: 545016

Follow Up By: Mainey (wa) - Thursday, Jan 10, 2008 at 09:46

Thursday, Jan 10, 2008 at 09:46
Toyota 2L diesel (2.4 Lt) the 55 Amp alternator puts out 14.4 Volts as I replaced the (Alternator) "regulator" for extra battery security as I needed to charge the 2 x 80 ah Calcium Deep Cycle batteries I originally used as the Accessory batteries, I still use one of them as my Cranking battery now.

All the items listed could be charged by my 'little' Alternator, because they take their current direct from your batteries, the Alternator only recharges those batteries as required.

The driving lights are only used out of town and at highway speeds and the thermo fans only use their large current at start up for just a few seconds, so they are never require their power at the same time.
Mainey...
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FollowupID: 545046

Reply By: Member - Mike DID - Wednesday, Jan 09, 2008 at 08:52

Wednesday, Jan 09, 2008 at 08:52
"What tells the voltage regulator to raise or lower the sytem voltage ,what is the sensing voltage taken from because this system is very low and i cant understand why.

Please help me!!!!!!!!!

Matt"

There are two types of Alternators -

- Internal sensing - most aren'et adjustable so you can't change anything.

- Remote sensing - these have a separate wire connected to the battery. If there's any resistance in the wire, it'll cause the Alternator to put out a higher voltage to bring the sensed voltage back to the setpoint. You can take advantage of this and put a Diode in series with this wire to raise the Alternator output voltage by 0.7 volts.
AnswerID: 280559

Follow Up By: Member - Olcoolone (S.A) - Thursday, Jan 10, 2008 at 08:04

Thursday, Jan 10, 2008 at 08:04
How does the diode increase the resistance?
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FollowupID: 545028

Follow Up By: Member - Mike DID - Thursday, Jan 10, 2008 at 08:17

Thursday, Jan 10, 2008 at 08:17
The diode will drop the voltage at the sensing circuit inside the Alternator by 0.7 volt below the battery voltage.

So the Alternator compensates by increasing its output voltage, so that the voltage at the sensing point is the same.
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FollowupID: 545032

Reply By: Mike Harding - Wednesday, Jan 09, 2008 at 09:08

Wednesday, Jan 09, 2008 at 09:08
A failed diode (or 2) in the alternator?
AnswerID: 280560

Reply By: Member - Mike DID - Wednesday, Jan 09, 2008 at 11:26

Wednesday, Jan 09, 2008 at 11:26
"NOW when it is idling and the redarc has switched on to connect the deep cycle up the voltage sits at 13.6 volts with nothing on."

- most cars while not put out much current when idling - to do a voltage test you really need to have the engine at 1500rpm at least.

My NS Pajero Diesel will put out 25 amps at idle, but since Diesels have lower peak revs than a petrol engine and better low-revs power, it's easier to design a Diesel to charge at idle.
AnswerID: 280570

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 11:48

Wednesday, Jan 09, 2008 at 11:48
The charge voltage DOES not chanmge more than .1V with higher RPM than idle.
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FollowupID: 544820

Reply By: TD100 - Wednesday, Jan 09, 2008 at 20:43

Wednesday, Jan 09, 2008 at 20:43
Matt,

i had a similar problem with one of my older commodores,i put the later voltage sensing alt on it and didnt improve it much,a mate suggested running the volt sense wire to the ignition as losses occur in the wiring as they get older.problem solved after that,better charge volts with lights on at idle.cheers Paul
AnswerID: 280669

Follow Up By: Member - Matthew C (WA) - Wednesday, Jan 09, 2008 at 21:30

Wednesday, Jan 09, 2008 at 21:30
That is what i was talking about earlier,can i move the sensing point to raise the system voltage.

Anyhow i am about to finish off the mods that derek has suggested and then i will retest the system.

Matt
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FollowupID: 544972

Follow Up By: Member - Mike DID - Thursday, Jan 10, 2008 at 08:08

Thursday, Jan 10, 2008 at 08:08
Moving the sensing point will make a small difference - to raise it by 0.7 volt, my suggestion was above -

"- Remote sensing - these have a separate wire connected to the battery. If there's any resistance in the wire, it'll cause the Alternator to put out a higher voltage to bring the sensed voltage back to the setpoint. You can take advantage of this and put a Diode in series with this wire to raise the Alternator output voltage by 0.7 volts."

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FollowupID: 545030

Reply By: Member - Steve Y (NSW) - Friday, Jan 11, 2008 at 14:47

Friday, Jan 11, 2008 at 14:47
The voltage and current are two different things. You should alway get close to 14.4 when the truck is running. You are right that the current (AMPS)is lower at idle but only becasue the amount of current required to the stato to create enough magnetic feild to create enough amps is not there. IE, the quicker you can get he alternator spinning the more amps with less amps requird from the batery to make those charge amps, it can be a cycle of loss if there is damage to the charge system, that's what the regulator does work out how much power to provide BACK to the alternator to help creat amps to chage and run the system.

The amps put out at a rev range is all in the winding. not petrol verse deisel though. It is a common mistake that ideling your truck will while on camp will really do much good. You will get a few amps but not the full amput, But, you will get 14.4 volts but that's not what relaly runs that fridge.

Have you taken it through any mud - dirt etc lately, You may have some muck in the bushes or some interfering in the rotor/stator which is limiting the amount of pwer that can be produced
AnswerID: 280991

Reply By: Member - Steve Y (NSW) - Friday, Jan 11, 2008 at 15:15

Friday, Jan 11, 2008 at 15:15
The voltage and current are two different things. You should alway get close to 14.4 when the truck is running. You are right that the current (AMPS)is lower at idle but only becasue the amount of current required to the stato to create enough magnetic feild to create enough amps is not there. IE, the quicker you can get he alternator spinning the more amps with less amps requird from the batery to make those charge amps, it can be a cycle of loss if there is damage to the charge system, that's what the regulator does work out how much power to provide BACK to the alternator to help creat amps to chage and run the system.

The amps put out at a rev range is all in the winding. not petrol verse deisel though. It is a common mistake that ideling your truck will while on camp will really do much good. You will get a few amps but not the full amput, But, you will get 14.4 volts but that's not what relaly runs that fridge.

Have you taken it through any mud - dirt etc lately, You may have some muck in the bushes or some interfering in the rotor/stator which is limiting the amount of pwer that can be produced
AnswerID: 280998

Follow Up By: Member - Matthew ,United Fuel- Sunday, Jan 13, 2008 at 23:37

Sunday, Jan 13, 2008 at 23:37
Steve

No i havent been through any mud or sirt or whatever. The problem STILL is low system voltage.The problem has reooccured after a few days it is back to the original problem.

NOW it would seem that the system voltage drops the more the battery is charged up by driving .If i drain the battery by leaving the lights on then when i restart it the voltage is 14+ Volts,.

Why cant i keep it up there all the time.

Matt
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FollowupID: 545810

Follow Up By: Mainey (wa) - Monday, Jan 14, 2008 at 08:26

Monday, Jan 14, 2008 at 08:26
Matt, you post-> ""NOW it would seem that the system voltage drops the more the battery is charged up by driving .
If i drain the battery by leaving the lights on then when i restart it the voltage is 14+ Volts""

The Aux battery "float charge" should be maintained at about 13.6v (wetcel) when the battery is 100% State of Charge, if your getting this and the battery will charge at 14+ Volts under the conditions you nominate above, it's normal.

If it's less Voltage and is also intermittent, and you have replaced the Alternator and it still persists then it indicates it's probably not the actual Alternator.
Maybe it's the (external) regulator or even a faulty battery could be considered, as could the electrical connections to the charging system.

To "fix" a 12v problem as you have, is a 'hands on' situation, all we can do is give you our idea's based on the information you supply, hence the persistence of the problem, if the problem was concidered as 'fixed' when you changed the charging cables, then it reoccured, maybe it's as simple as something to do with the charging cable connections?
Mainey...
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FollowupID: 545824

Follow Up By: Member - Mike DID - Monday, Jan 14, 2008 at 09:25

Monday, Jan 14, 2008 at 09:25
As I wrote above

Member - Mike DID posted:
"The biggest change was from putting the BIG earth from the battery - to the alternator bracket."

- that's weird. The heavy cable from the Battery Negative to the engine block is designed to carry the 200-300 amps of starter current. If you had no problems with a sluggish starter, then the connections on this cable must be ok.

Considering the big bolts connecting the Alternator to the Engine Block, I don't see how there can be high resistance there.

When the practice doesn't agree with the theory, I start wondering if there is a coincidental change. Mike R
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FollowupID: 545833

Follow Up By: Member - Mike DID - Monday, Jan 14, 2008 at 09:34

Monday, Jan 14, 2008 at 09:34
Matt

Any auto electrician should be able to explain that this progressive drop in voltage is totally normal.

All modern Alternators are temperature compensated so that batteries will be fully charged and not overcharged - whether the air temperature is -20 degrees or +50 degrees.

Around 20 degrees the Alternator will put out 14.4 volts and then as the Alternator gets hot from generating electricity and from drawing in air from behind the radiator, it regulates its output voltage down to 13.6 to 13.8 volts.

This brings the Alternator output close to that of a 3-stage charger - but WITHOUT actually sensing the battery state-of-charge. When you start the car it quickly replaces the lost charge and then goes to float charge voltage to avoid overcharging.
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FollowupID: 545838

Follow Up By: Member - Matthew ,United Fuel- Monday, Jan 14, 2008 at 12:08

Monday, Jan 14, 2008 at 12:08
Mike

That seems to fit due to the lower voltages over time .

BUT shouldn't the SYSTEM remain at around 14V all the time.Maybe i need to move the sensing point to the deep cycle battery so that it senses that battery which is always lower than the main due to the fridge.

Just never thought that the voltage output of the alternator dropped once the battery was cfharged??????

MAtt
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FollowupID: 545857

Follow Up By: Member - Mike DID - Monday, Jan 14, 2008 at 12:22

Monday, Jan 14, 2008 at 12:22
Great car alternator/battery myths
- a car alternator will never charge a battery above 70% capacity
- a car alternator changes its output voltage as the battery approaches full charge
- etc
- etc

"Just never thought that the voltage output of the alternator dropped once the battery was cfharged??????"
- NO !, read what I wrote again and you will see that the Alternator reduces its voltage as the Alternator warms up.

In MOST CASES this will happen when the battery is approaching full charge, but there is no sensing of battery state-of-charge.

If you are charging a deepcycle battery, the output voltage will drop long before it approaches full charge.

Unless you have very thin wires, the voltage will be the same everywhere.

I have already written twice above on how you can over-ride the control and raise the output voltage by 0.7 volts.
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FollowupID: 545860

Follow Up By: Member - Matthew ,United Fuel- Monday, Jan 14, 2008 at 14:09

Monday, Jan 14, 2008 at 14:09
Ok

I will see how it goes for a bit and go from there.

This alternator has the regulator in the back so im guessing i cant modify it at all????

Matt
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FollowupID: 545872

Follow Up By: Member - Mike DID - Monday, Jan 14, 2008 at 14:31

Monday, Jan 14, 2008 at 14:31
As it's an External Sensing Alternator, you don't need to modify it to increase the output voltage.
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FollowupID: 545877

Follow Up By: Member - Matthew ,United Fuel- Tuesday, Jan 15, 2008 at 20:36

Tuesday, Jan 15, 2008 at 20:36
Mike

I am still not getting this whole charge voltage thing.

The system is now sitting on 13.3 idling with a/c on .

If turn the lights on low beam it drops to below 13.0,tell me why now the SYSTEM doesnt compensate and raise it back up to around 14.0 like it says on the regulator.

It Just doesn't add up.

Matt
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FollowupID: 546181

Follow Up By: Member - Mike DID - Tuesday, Jan 15, 2008 at 20:45

Tuesday, Jan 15, 2008 at 20:45
Like any Generator, at idle speed the Alternator just isn't spinning fast enough to put out much power. The regulator has applied maximum current to the field coils, but there just isn't enough energy available.

My Alternator can put out 25 amps at idle, but most have trouble putting out any current at idle.

You need to increase engine RPM to around 1500-2000 to get regulation while drawing reasonable current.
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FollowupID: 546184

Follow Up By: Member - Matthew ,United Fuel- Tuesday, Jan 15, 2008 at 20:57

Tuesday, Jan 15, 2008 at 20:57
Ok i understand all that BUT why when i apply several loads to the system the voltage is not regulated up to around the 14V.

Im not worried about what it does at idle, i want to make sure when its loaded that the volts are stable at around 14v,i mean its a 120AMP alternator for gods sake and it cant keep up 14V running two batterys and a minor draw from the system.

Matt
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FollowupID: 546187

Follow Up By: Mainey (wa) - Tuesday, Jan 15, 2008 at 21:12

Tuesday, Jan 15, 2008 at 21:12
Matt, sorry to jump in here..
but look at it another way, a fully charged (wetcel) battery is ~12.66 Volts.

From what I have read of your recent posts, your battery does not go below 13 Volts, even with the loads you have applied to it.

Your battery does not have to be charged at 14 Volts, because it's being maintained at 13 Volts, which is above the fully charged Voltage anyway, no problem unless it's discharging, and it is not.

Check your battery Voltage 3 or 4 hours after vehicle being run and if it's 12.6 Volts or above, you have a battery that is "fully charged"
Mainey...
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FollowupID: 546194

Follow Up By: Member - Mike DID - Tuesday, Jan 15, 2008 at 21:31

Tuesday, Jan 15, 2008 at 21:31
"Im not worried about what it does at idle, i want to make sure when its loaded that the volts are stable at around 14v,i mean its a 120AMP alternator for gods sake and it cant keep up 14V running two batterys and a minor draw from the system."

Modern Alternators are temperature compensated.

When the Alternator is at 20 degrees it is DESIGNED to put out 14.4 volts to charge the battery quickly.

When the Alternator is at 60 degrees (a typical engine compartment temperature) it is DESIGNED to put out 13.8 volts to avoid overcharging the battery.
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FollowupID: 546202

Follow Up By: Member - Matthew ,United Fuel- Tuesday, Jan 15, 2008 at 21:41

Tuesday, Jan 15, 2008 at 21:41
Mainey

I will do that tonight before i go to bed!



Mike

So why when it is loaded at operating temp it falls to around 13.2.

Is it because the alternator senses that the battery is still charged ok.

MAtt
0
FollowupID: 546204

Follow Up By: Member - Mike DID - Tuesday, Jan 15, 2008 at 22:01

Tuesday, Jan 15, 2008 at 22:01
I've answered this SEVERAL TIMES in my posts above.
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FollowupID: 546211

Follow Up By: Member - Matthew ,United Fuel- Tuesday, Jan 15, 2008 at 22:14

Tuesday, Jan 15, 2008 at 22:14
Ok

I know youve said to fit a resistor in the sensing line to reduce the voltage so the alternator will increase its output but how do you do that when there is NO sensing wire.

MAtt
0
FollowupID: 546216

Follow Up By: Mainey (wa) - Tuesday, Jan 15, 2008 at 22:18

Tuesday, Jan 15, 2008 at 22:18
Matt,

don't worry or do anything till you check the 'rested' Voltage tonight...
Mainey...
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FollowupID: 546220

Follow Up By: Member - Matthew ,United Fuel- Tuesday, Jan 15, 2008 at 22:44

Tuesday, Jan 15, 2008 at 22:44
Ok

Will do,but can you see what im going on about.?????

Matt
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FollowupID: 546233

Follow Up By: Mainey (wa) - Wednesday, Jan 16, 2008 at 08:35

Wednesday, Jan 16, 2008 at 08:35
Matt,
So... what was the 'rested' battery Voltage last night and/or this morning ??

Mainey...
0
FollowupID: 546287

Follow Up By: Member - Matthew ,United Fuel- Wednesday, Jan 16, 2008 at 09:54

Wednesday, Jan 16, 2008 at 09:54
12.4V this morning.

The problem seems worse in the afternoon when its hotter tha in the morning.

I guess that is what mike has been saying all along but it bleep s me that i cant keep a steady 13.8 ish volts to the deep cycle.

Matt
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FollowupID: 546312

Follow Up By: Mainey (wa) - Wednesday, Jan 16, 2008 at 10:22

Wednesday, Jan 16, 2008 at 10:22
Matt,
Yes, you have a problem at only 12.4 Volts

If you are saying the battery voltage changes during the day, with-out touching it, maybe the battery will not hold it's charge and should be checked out to make sure.

(for comparison, my van now sits in a garage and after 2 days is still showing ~12.9v, but is AGM, and they do hold higher Voltage)
Mainey...
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FollowupID: 546320

Follow Up By: Member - Mike DID - Wednesday, Jan 16, 2008 at 10:40

Wednesday, Jan 16, 2008 at 10:40
"12.4V this morning."

Did you ensure that all loads were disconnected ? Was the Interior Light and Door Lights off ?

These voltage-vs-charge tables are only meaningfull if there has been no charge or discharge to the battery for several hours.
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FollowupID: 546322

Reply By: disco1942 - Wednesday, Jan 16, 2008 at 18:42

Wednesday, Jan 16, 2008 at 18:42
Correct me if I am wrong, but I have not seen anyone suggest disconnecting the auxiliary battery circuitry or Matthew state that he has tested the alternator with it disconnected. This is the first thing that should have been done. If the load placed on the alternator by the auxiliary circuit is too great it does not matter what you do to the regulator - you will not get full voltage.

Disconnect the Redarc and run the truck for a few days and see if the charging circuit acts OK. Make up a lead to connect your volt meter to some 12V source that is not affected by voltage drop by other accessories on the same circuit when they are switched on. I have used the cigarette lighter socket successfully in some vehicles. Connect and switch on the meter before starting. Shortly after starting the meter indication should rise to over 14V. The voltage should then commence to drop as the engine compartment heats up and when you have driven for half to one hour it will drop to somewhere between 13.6 and 13.9V. Monitor this whilst you are driving for the next few days until you are getting the same peak reading when the motor is cold.

If the the alternator has been shown to work without the extra load then your problem is in the auxiliary circuit. The problem will will probably the Redarc (least likely) or the battery (most likely.) You may need to take your battery to someone with a good battery charger or purchase a three stage charger for your van and use that. Perhaps you should do that whilst you are testing your alternator, take it to a supplier of deep cycle batteries and get it worked over before it sulphates up.

PeterD
PeterD
Retired radio and electronics technician

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AnswerID: 281975

Follow Up By: Member - Matthew ,United Fuel- Wednesday, Jan 16, 2008 at 21:01

Wednesday, Jan 16, 2008 at 21:01
Peter

Some sound advice there mate.I have not disconnected the aux battery and tested it but i will.Are you suggesting it should read between 13.6 and 13.9 with no load at say 2000rpm???? or loaded.

I have a three stage charger and will also charge the deep cycle fully and try that.

Matt
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FollowupID: 546448

Follow Up By: disco1942 - Thursday, Jan 17, 2008 at 00:09

Thursday, Jan 17, 2008 at 00:09
Matthew

I don't know what you mean by the "or loaded" bit. The voltages I gave were the voltages you would expect when you are driving along at traffic speed. The voltage will be higher when the motor is cold and lower when hot. For instance my Navara is 14.5V when first started in the morning when the motor is reved and 13.9V or less after I have traveled for 3/4 of an hour - My Disco is 14.5 down to 13.6V.

PeterD
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FollowupID: 546497

Follow Up By: Member - Matthew ,United Fuel- Thursday, Jan 17, 2008 at 00:18

Thursday, Jan 17, 2008 at 00:18
What i mean is with headlights on or aircon going etc etc.

Matt
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FollowupID: 546499

Follow Up By: disco1942 - Thursday, Jan 17, 2008 at 00:46

Thursday, Jan 17, 2008 at 00:46
Without the auxiliary circuit there should be extremely little change in voltage with a few things like that running.

PeterD
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FollowupID: 546502

Follow Up By: Mainey (wa) - Thursday, Jan 17, 2008 at 08:26

Thursday, Jan 17, 2008 at 08:26
Matt,
Why not take it to a qualified "AUTO ELECTRICIAN"

It appears you have been given advice you obviously can't comprehend, said nicely :-)))
Mainey...
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FollowupID: 546518

Reply By: Member - Matthew ,United Fuel- Thursday, Jan 17, 2008 at 15:29

Thursday, Jan 17, 2008 at 15:29
Mainey

I can comprehend it all BUT i was just expecting a little more from the system than i am getting and would like to upgrade the charge voltage when loaded.

Like today its 39 degrees here as you know and the thing wont charge over 13.2 with aircon on,i mean how much is it going to drop down to if the thermo fans come on or the fridge cycles.

Very frustrating because i know that it should perform better.

Matt
AnswerID: 282092

Follow Up By: Mainey (wa) - Thursday, Jan 17, 2008 at 15:43

Thursday, Jan 17, 2008 at 15:43
Matt,
for a "visual" look at what I am saying click on my members Rig & Profile
right at the bottom of the page it shows the solar system is producing 12 Amps, but only 3 or so amps is going to the battery.
Looks like a waste of Amps but the battery is full and is 'regulated'

If your Battery is not faulty and the Alternator is not faulty and yes the Regulator is not faulty and again the wiring is not faulty...
and the battery is "fully charged" it's terrific.
Mainey...
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FollowupID: 546595

Reply By: Member - Matthew ,United Fuel- Thursday, Jan 17, 2008 at 16:33

Thursday, Jan 17, 2008 at 16:33
Yeah i know what your saying ,i just like to see bigger numbers when i got a lot of stuff running.

I am going to disconnect the deep cycle and drive it for a few days over the weekend and see how it goes on that alone.

MAtt
AnswerID: 282104

Follow Up By: Mainey (wa) - Thursday, Jan 17, 2008 at 17:44

Thursday, Jan 17, 2008 at 17:44
Matt,
disconnect the Redarc at the Cranking battery (+) terminal, so your running as original equipment with only the Cranking battery receiving charge.

Disconnect ALL loads from the Deep Cycle battery for the weekend.
Measure the voltage of both batteries, at their terminals, when disconnected after 3 hours.

At the end of the weekend BEFORE you reconnect them measure and post the Voltages again.
Mainey...
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FollowupID: 546609

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