Alternator and battery issues

[olivier74]

The alternator on my R5 is playing up, or at least I think it is. Here are the symptoms.

Car started once this morning, but 20min later it didn’t. Faint lights on the dash, a vague click at the starter motor when trying to start but not enough to turn the engine. Concluded the battery was flat.

Jump started OK, but engine would die when large electric load is applied (headlights).

I got the following voltages at the battery:
13V at idle, 15-16V at high revs and 12.5v with engine stopped. Also managed to rev the engine and turn the lights on without the engine dying and after many kms of driving. Not possible at idle though, so battery is not charging.

Thinking the alternator needs attention with brushes probably ok since I can get high volts, but regulator gone. Battery may be ok but it clearly isn’t charging enough at the moment.

Are you getting to the same conclusion?

Thinking of sourcing a regulator from Europe or a second hand alternator locally.

 

[The Gonz]

16 seems damagingly high so I would agree at least your regulation is off. 13 at idle is probably not enough for charging.

 

[COL]

There is definitely a problem there somewhere. Does the alternator have an internal or an external regulator? It does look like the regulator is at fault and is giving the alternator full excitation causing the over charging.

Is the battery the type that you can check the electrolyte levels or is it a seal type? Over charging is not good for a battery and will boil off electrolyte. The battery have its capacity to hold a charge diminished by the over charging.

What I would do is if its the type of battery you can check electrolyte levels, do that and then put the battery on a battery charger and charge it up over night. If the battery is not the type that you can check electrolyte levels the battery is probably no good and needs replacing.

You will need another regulator whether it is internal one or an external one and replace that. You should be then good to go.

 

[olivier74]

The battery picked up some charge, but nothing useful other than making the dash lights brighter, so the mixture of 13 to 16V didn’t do anything.
No means of checking or topping up the water sadly. The regulator is part of the alternator unit, but should be replaceable if I can get hold of one.

 

[COL]

The regulator is most likely held in with 2 or 3 screws. The brushes will also be incorporated into the regulator.

 

[PeterT]

16 seems damagingly high so I would agree at least your regulation is off. 13 at idle is probably not enough for charging.

A lead acid battery starts charging at 13.1V.

 

[Greenpeace]

I'd be confirming the battery is serviceable before I did anything else.

Late model cars have a reasonable electrical load at idle even before you turn the headlights on. Fuel pump/s, injectors, ignition system, computer/s, I'm guessing you probably had the driver's door open while you were experimenting with the lights? So the interior light and door ajar light could possibly be added to that list?
A healthy battery is there to "cushion" the normal flutuation in charging voltage coming from the alternator.
I'd be seeing if the battery will hold charge after charging it from an external source or swap in a known good battery and see if the symptoms persist before I started fiddling with the alternator.

 

[jaahn]

hi olivier there is a problem and at first look it seems like the regulator. You must have a multi meter I guess so wire the leads to the battery terminals or jam them in the clamps so you can read the voltage while you test things. Check the clamps are good and clean and earth points are clean and low resistance. Then charge the battery and then test. You could swap the battery to a good car for charging or use jump leads.
What is the brand and type number of the alternator. Any auto electrical supplier or auto electrician will probably be able to supply a regulator with new brushes fitted for most brands of alternators if you supply the details of the alternator for them. They have reference lists but possibly not for an R5. Sometimes easy to fit in a couple of minutes sometimes not so easily accessible.
Good luck Jaahn
There are thousands of utube videos on testing an alternator and changing the regulator.

 

[olivier74]

Thanks Jaahn. The alternator is a Ducellier 7577. Battery is on charge, I’ll try that next

 

[baldrick56]

Had an ongoing battle (years) with my alternator overcharging, symptoms were when driving with headlights on they'd suddenly go brighter for a few seconds then dim down again at intervals. The car "ate" batteries - they'd fail after 12Mths max. The other really weird one was the plastic cap to the coolant bottle 'dissolved' - where's the coolant bottle - right behind & under the battery. Eventually traced the problem & in 2020 replaced the regulator unit, I bought one online (using the part No. stamped on the existing), it was a 'Hella' branded unit for a Bosch Alternator so was a bit sceptical but fitted perfectly - couple of screws BUT I did need to make one soldered connection for the main generator output cable.

 

[olivier74]

Changed the battery and all seem to be back in order, ie the voltage doesn’t seem to fluctuate anymore. I’m surprised to be honest, will keep an eye on it.

 

[Greenpeace]

Changed the battery and all seem to be back in order, ie the voltage doesn’t seem to fluctuate anymore. I’m surprised to be honest, will keep an eye on it.

The electrical system runs off the battery, the alternator's job is to charge the battery.
If the battery won't hold charge the alternator is now trying to run the electrical system, ie: it's trying to perform outside of its job description.
Some cars will tolerate this scenario and some won't. The later Valiants with electronic ignition, would develop a misfire with a tired battery regardless of how good the alternator was charging.

 

[The Gonz]

The more accurate depiction is that the alternator is providing all the power while the vehicle is running. Its output feeds the ignition, pumps, accessories, etc. It also charges the battery while doing this. However, the finer point is that if the battery is failing, it can either not accept enough charging current and the alternator load may be unbalanced towards too much into systems like the ignition (overvoltage) or the failed cells in the battery draw too much current, becoming an excessive load and exhibiting a system-wide undervoltage.

While we're on the topic, for clarity, when you get a battery light on your dashboard, this is a lamp driven by battery voltage being higher than alternator voltage while igintion is on, which is why you see it before cranking the engine. If you still see it with the engine running, the alternator is simply not generating more than the battery.

 

[RINGER]

The electrical starter system runs off the battery, the alternator's job is to charge the battery.
If the battery won't hold charge the alternator is now trying to run the electrical system, ie: it's trying to perform outside of its job description.
Some cars will tolerate this scenario and some won't. The later Valiants with electronic ignition, would develop a misfire with a tired battery regardless of how good the alternator was charging.

My understanding is quite different & it is the electrical starter system starts with the battery, then when started @ above idle the alternator nearly immediately restores the battery to full charge ~ then the alternator provides all necessary current for all electrical needs. Why we no longer have 55amp alternators or less.
Only if the current needs exceed the alternators capacity does the battery need to be called upon.
I agree this goes out the window with a bad battery [if open & not mtce free check each cell for bubbling while cranking with safety glasses on].

 

[Greenpeace]

My understanding is quite different & it is the electrical starter system starts with the battery, then when started @ above idle the alternator nearly immediately restores the battery to full charge ~ then the alternator provides all necessary current for all electrical needs. Why we no longer have 55amp alternators or less.
Only if the current needs exceed the alternators capacity does the battery need to be called upon.
I agree this goes out the window with a bad battery [if open & not mtce free check each cell for bubbling while cranking with safety glasses on].

Yes I probably worded it a little wrong. However even though it can run a car without a battery, the alternator is is designed to the operate in conjunction with a good battery. I've seen the battery referred to as a "load/voltage stabiliser" in electrical text. Unless things have changed the charge wire off the alternator still goes to the battery and the electric system comes off the battery doesn't it?
Small Honda motorcycles are a case in point. They will kickstart and run perfectly without a battery, however bulbs tend to have a limited life if you use the bike without one.

 

[RINGER]

I did not say a vehicle will run without a battery.

It might be easier to say one needs a battery to start, then one needs supply [alternator] to maintain that battery's full charge & run all components needing supply.

If the supply needs exceed alternator amps, then battery draw happens & when load decreases battery fully recharges & alternator takes control again.
No argument just understanding is important

 

[Greenpeace]

I did not say a vehicle will run without a battery.

I didn't say you did?

It might be easier to say one needs a battery to start, then one needs supply [alternator] to maintain that battery's full charge & run all components needing supply.

If the supply needs exceed alternator amps, then battery draw happens & when load decreases battery fully recharges & alternator takes control again.
No argument just understanding is important

I think I said in my first post on this thread that I wouldn't be looking at anything else until I was certain the battery was good.
I've known lots of people that start replacing alternators and regulators because their vehicle is doing "weird things" only to find out it's actually the battery that's RS.

 

[RINGER]

If possible, all who choose to read ~ currently we have gr8 [even excess] supply [read alternator] with our gas & coal powered stations.
The alternators are being closed & frankly, batteries don't exist in Australa except the Snowy 2 boondogle.
How long until those who will end up paying wake up? Many of us [canaries] will be gone.

 

[jaahn]

Yes I probably worded it a little wrong. However even though it can run a car without a battery, the alternator is is designed to the operate in conjunction with a good battery. I've seen the battery referred to as a "load/voltage stabiliser" in electrical text. Unless things have changed the charge wire off the alternator still goes to the battery and the electric system comes off the battery doesn't it?
Small Honda motorcycles are a case in point. They will kickstart and run perfectly without a battery, however bulbs tend to have a limited life if you use the bike without one.

I would not use small motorbikes as an example of a proper car battery/alternator system. Small Jap bikes cheated and usually had several windings on the alternator that were switched on with the lights to match the power required, and the regulator for the system was just a zenner diode load dump for any excess power.
When I was teaching the theory was for cars the alternator carried the load and recharged the battery to replace the starting current. The regulator provided all the stabilisation required normally.
I was told by a Bosch tech expert that back in the 80/90s era the new cars came out of the factory and were driven to storage with no batteries. That is when Bosch stared to fit zenner power diodes in the alternators which would clip any voltage spikes. Batteries being age sensitive in storage they were only fitted when the cars were to go out of storage.
Probably with the advent of computerised everything later vehicles may be different and just in time supply planning may solve new car storage problems. However it is true in my experience that a bad battery will cause wierd problems and dash lights coming on in late model cars. First check point !
Jaahn

 

[Greenpeace]

Here's an excerpt from a battery manufacturer's
website.
I guess people can take from it what they will.
The last point is what I am trying to emphasise.