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-   -   Have I a duff battery (https://www.the75andztclub.co.uk/forum/showthread.php?t=315756)

macafee2 11th October 2021 09:43

Have I a duff battery
 
I took the battery off the car and put it on charge for a few days in the garage.
As soon as I took it off charge I measured the voltage and it was 12.8v, another battery that had been off charge for about a week measured 13.2v.

The above was about 3 or 4 days ago, I have just measured the suspected duff battery again and it is 12.57v. Not a lot of drop but as it was 12.8 when it came off charge I am suspecting it is duff.

Your thoughts please. If you too think it may be duff I will take it back and the shop can try a drop test.

macafee2

MSS 11th October 2021 11:20

I wouldn't say the voltage you have measured necessarily indicates a duff battery.

I would put a mild load on the battery for a while and recheck the voltage. An old 55W 12V headlamp bulb consumes nearly 5Amps and makes a good test load.

macafee2 11th October 2021 11:39

Quote:

Originally Posted by MSS (Post 2903178)
I wouldn't say the voltage you have measured necessarily indicates a duff battery.

I would put a mild load on the battery for a while and recheck the voltage. An old 55W 12V headlamp bulb consumes nearly 5Amps and makes a good test load.

At say 2 minutes, what would I expect to see voltage wise?

macafee2

MSS 11th October 2021 12:19

I would put the bulb on for 30 minutes. This will remove approximately 2.5Ah of charge from the battery which will have a capacity of around 70Ah for a 096 type when new.

You should get at least 12.5V which would indicate that the battery is at >90% fully charged.

If it drops to less than 12.5V, the battery is not as healthy as it should be.

MSS 9th November 2021 23:34

What was the measurement or conclusion in the end?

macafee2 10th November 2021 08:08

Quote:

Originally Posted by MSS (Post 2907297)
What was the measurement or conclusion in the end?

Result, undecided about the battery. The voltage seemed not to drop any further, always staying above 12v. I am wondering if the fault is on the car. I kept a headlight bulb connected for well over an hour as suggested but the voltage stayed above 12.
I have just taken the battery off charge and it is showing 13.04v.

macafee2

COLVERT 10th November 2021 15:35

The reading off charge won't be accurate.--It needs to be left for a few hours to settle.

12.57 is normal for most batteries.---:D

The very best way to check a sealed batteries capacity is to have a drop test done at a local garage.

Oh for those filler caps where you could test the specific gravity of the acid.

macafee2 10th November 2021 17:08

Quote:

Originally Posted by COLVERT (Post 2907380)
The reading off charge won't be accurate.--It needs to be left for a few hours to settle.

12.57 is normal for most batteries.---:D

The very best way to check a sealed batteries capacity is to have a drop test done at a local garage.

Oh for those filler caps where you could test the specific gravity of the acid.

ok thanks, I'll test it again in the morning

macafee2

patrolman pete 10th November 2021 19:48

An old way that the AA used to test batteries was to charge by running the engine for 5 mins , then disable the engine by pulling a fuse so that the car would crank but not start. Crank the engine for 15 seconds and listen to the cranking speed , and if it starts to drop , the battery is unserviceable . That is a live drop test and is pretty conclusive.

macafee2 11th November 2021 09:16

Quote:

Originally Posted by patrolman pete (Post 2907401)
An old way that the AA used to test batteries was to charge by running the engine for 5 mins , then disable the engine by pulling a fuse so that the car would crank but not start. Crank the engine for 15 seconds and listen to the cranking speed , and if it starts to drop , the battery is unserviceable . That is a live drop test and is pretty conclusive.

I can try that. What fuse to remove, fuel pump?
15 seconds continuous cranking seems a long time, I just timed it my goodness that is a lot of cranking

macafee2

MSS 11th November 2021 09:56

The 15 second cranking test was reasonable when most people were driving around in 1.3L or 1.6L petrol cars. A 2L diesel engine requires a lot more cranking current due to the higher compression. The starter solenoid as well as the starter motor would be in danger of overheating over 15 seconds.

Personally, I would never crank an engine on one of my cars for more than 5 seconds, which will feel like eternity when doing it.

A local garage will do the equivalent high-current drop test for little more than beer money!

TourerSteve 11th November 2021 11:55

With the sensitive electronics on most modern cars these days why would you risk a crank test when for not a lot of money you can get a drop / load tester that will determine the condition of a battery

https://www.machinemart.co.uk/p/clar...E&gclsrc=aw.ds

MSS 11th November 2021 12:35

Quote:

Originally Posted by TourerSteve (Post 2907463)
With the sensitive electronics on most modern cars these days why would you risk a crank test when for not a lot of money you can get a drop / load tester that will determine the condition of a battery

https://www.machinemart.co.uk/p/clar...E&gclsrc=aw.ds


Agreed.

I normally listen to the vigour with which a battery cranks an engine and replace the battery if it is getting a little tired. I consider this really important on say the Twintop where if the battery is depleted the roof and window drop-down/up-lift etc. could loose adjustment settings.

The older batteries get relegated to use with 12V LED floodlights for use when working on cars, lawnmowers, etc.

COLVERT 11th November 2021 16:07

Quote:

Originally Posted by patrolman pete (Post 2907401)
An old way that the AA used to test batteries was to charge by running the engine for 5 mins , then disable the engine by pulling a fuse so that the car would crank but not start. Crank the engine for 15 seconds and listen to the cranking speed , and if it starts to drop , the battery is unserviceable . That is a live drop test and is pretty conclusive.

Funny old lot the AA if that was standard procedure.---The engine running bit.---That would be of no use at all before the cranking test.----:shrug:

Quote.--- That is a live drop test and is pretty conclusive.



Also very bad for the starter motor. ( unless you have shares in the selling of starter motors.---:D:D:D )

patrolman pete 11th November 2021 19:46

You would normally hear it slow within 5 seconds if it was duff and I never blew a starter motor. They eventually equipped the patrol force with Midtronic battery testers which gave the member an informed choice of whether to replace the battery or take a risk :shrug:

macafee2 25th November 2021 22:14

measured the voltage and it is showing 12.8 which is pleasing

macafee2

COLVERT 25th November 2021 22:36

Quote:

Originally Posted by macafee2 (Post 2909628)
measured the voltage and it is showing 12.8 which is pleasing

macafee2

Was your check soon after charging or, perhaps, the next day ??



If the next day then that reading suggests a good battery.---:D

macafee2 26th November 2021 00:08

Quote:

Originally Posted by COLVERT (Post 2909631)
Was your check soon after charging or, perhaps, the next day ??



If the next day then that reading suggest a good battery.---:D

some days after

macafee2

Ducati750cc 26th November 2021 10:00

Quote:

Originally Posted by patrolman pete (Post 2907401)
An old way that the AA used to test batteries was to charge by running the engine for 5 mins , then disable the engine by pulling a fuse so that the car would crank but not start. Crank the engine for 15 seconds and listen to the cranking speed , and if it starts to drop , the battery is unserviceable . That is a live drop test and is pretty conclusive.


The important thing to note with the old type simple test is volt drop over a specific time from a reasonably, ideally fully charged battery, the cranking speed can be an indicator, but can be affected by engine faults.

Ducati750cc 26th November 2021 10:48

Quote:

Originally Posted by COLVERT (Post 2907485)
Funny old lot the AA if that was standard procedure.---The engine running bit.---That would be of no use at all before the cranking test.----:shrug:

Quote.--- That is a live drop test and is pretty conclusive.



Also very bad for the starter motor. ( unless you have shares in the selling of starter motors.---:D:D:D )




First rule of thumb when testing battery, cranking, charging, in fact anything electrical on vehicle systems.........start with a fully charged or as near as battery, hence the engine running bit, obviously at the roadside the only way to get some semblance of a charge in it and would be approx. 15 mins at a high idle..............you can't do a cranking test with a flat, or very low battery !



This system was used, had to be used, back in the day but time has moved on, thankfully.


The resistive drop test is OK but doesn't tell a full story and on rare occasions when instructions haven't been followed, can cause a bit of fun with a bang from the battery.


My Midtronics battery tester does the following from connection to a battery, asks if it is on the car or off, asks if the test is being done on a remote jump start post or battery terminals, warns if the croc clips are making a poor connection, shows the ambient temperature, asks the type, regular, spiral etc, asks the capacity and if SAE, DIN, JIS etc, then if it's happy performs the test.


It will show as battery good, needs replacing, or simply recharging, if the volts are too low at the start it will tell me to charge then retest, if on the vehicle it will ask for the engine to be started, via a jump pack/leads, run at a high idle then say when to shut down, switch on headlights to remove the surface charge then when removed re-test.


The test results show volts at start of test, expected capacity and actual available capacity, state of charge and state of health of the battery, important bit these two, because you can have a battery that show say 12.6v so presumed to be good but the capacity has dropped from what it should be say 800A to 380A.


Whilst charging on the vehicle it will do a charging test, volts, look for diode ripple and so on.


It will also do a cranking test showing cranking speed, amps being pulled, volt drop etc. and from this to an experienced eye the condition of the starter motor can be determined to a degree, such as the odd one where the armature bearings are worn allowing it to rub on the magnet, modern sintered magnets or on the stator pole pieces.


Costs a bit but worth it's weight in gold.


But like any test equipment from a DVM upwards, only as good a the user.

polinsteve 26th November 2021 12:31

Quote:

Originally Posted by macafee2 (Post 2907441)
I can try that. What fuse to remove, fuel pump?
15 seconds continuous cranking seems a long time, I just timed it my goodness that is a lot of cranking

macafee2

Back in the day, (late 1960s buses) our Leyland Leopards would take several minutes continuous cranking in cold weather, followed by a clouds of acrid smoke.

COLVERT 26th November 2021 22:22

Quote:

Originally Posted by polinsteve (Post 2909689)
Back in the day, (late 1960s buses) our Leyland Leopards would take several minutes continuous cranking in cold weather, followed by a clouds of acrid smoke.

I guess you could call that proof of rubbish design.---:D

Fast tick over to put a charge into a nearly flat battery is no better than just letting the engine tick over.--The modern alternators will hold 14.4 volts even at tick over.---:cool:

Ducati750cc 27th November 2021 01:31

Quote:

Originally Posted by COLVERT (Post 2909798)
I guess you could call that proof of rubbish design.---:D

Fast tick over to put a charge into a nearly flat battery is no better than just letting the engine tick over.--The modern alternators will hold 14.4 volts even at tick over.---:cool:




Rubbish design from the 1960's compared to what exactly ? :shrug:



Fast tickover compared to idle tickover to put a charge into a nearly flat battery is the same you say.


Can I suggest you experiment on your suggestions with a modern alternator with both a voltmeter and an ammeter connected.


Then come back to report that the amps produced is exactly the same at both idle and a high idle.


Volts is only half of the story :shrug:

MSS 27th November 2021 09:38

Quote:

Originally Posted by COLVERT (Post 2909798)
I guess you could call that proof of rubbish design.---:D

Fast tick over to put a charge into a nearly flat battery is no better than just letting the engine tick over.--The modern alternators will hold 14.4 volts even at tick over.---:cool:


Up to the late 1970's most vehicles did not charge the battery well at idle. Motorcycles did not at all. When Honda launched the CX500 V-twin in 1978, they made a huge thing of the fact that its alternator charged the battery even at idle.

COLVERT 27th November 2021 11:28

Quote:

Originally Posted by MSS (Post 2909846)
Up to the late 1970's most vehicles did not charge the battery well at idle. Motorcycles did not at all. When Honda launched the CX500 V-twin in 1978, they made a huge thing of the fact that its alternator charged the battery even at idle.

I changed the dynamo on my 1970's Fiat 500 for an alternator with dramatic improvement.--It made a real improvement of the headlights from 10 glow worms to 100 glow worms.---The light actually managed to reach the road surface---:D

COLVERT 27th November 2021 11:33

1 Attachment(s)
Worth looking at.---:D-----Live and learn is my motto.-----;)






COLVERT 29th November 2021 23:48

I guess the above pdf was too complicated for most folk.---:shrug:

macafee2 30th November 2021 18:11

Quote:

Originally Posted by COLVERT (Post 2910291)
I guess the above pdf was too complicated for most folk.---:shrug:

I dont do well reading a lot of material like that. I'm not good at technical reading, I just cant take all the information in.

macafee2

Ducati750cc 30th November 2021 20:47

Quote:

Originally Posted by COLVERT (Post 2910291)
I guess the above pdf was too complicated for most folk.---:shrug:


A bit technical in parts but otherwise not bad.


Remember when you said......... " Fast tick over to put a charge into a nearly flat battery is no better than just letting the engine tick over.--The modern alternators will hold 14.4 volts even at tick over.-- "


And I said .........."Fast tickover compared to idle tickover to put a charge into a nearly flat battery is the same you say.

Can I suggest you experiment on your suggestions with a modern alternator with both a voltmeter and an ammeter connected.

Then come back to report that the amps produced is exactly the same at both idle and a high idle. "



Could I suggest you read the PDF, taking note of Fig. 3 and Fig. 7 where you will find that there is a noticeable increase in current output at higher idle ( fast ) speeds







MSS 30th November 2021 21:52

Quote:

Originally Posted by COLVERT (Post 2909867)
Worth looking at.---:D-----Live and learn is my motto.-----;)



Did you hope to initiate a discussion on the basis of the paper? If so, to what end?

COLVERT 1st December 2021 12:16

Quote:

Originally Posted by MSS (Post 2910407)
Did you hope to initiate a discussion on the basis of the paper? If so, to what end?

Thought never crossed my mind.

I was using the report to show that modern alternators had high outputs even at low engine revs.

Due to the difference in pulley sizes between the alternator and engine the alternator would be running at quite high output even at tick-over.

Revving the engine would make very little difference to the approx. 14 4 volts already being output.

MSS 1st December 2021 12:44

Quote:

Originally Posted by COLVERT (Post 2910445)
Thought never crossed my mind.

I was using the report to show that modern alternators had high outputs even at low engine revs.

Due to the difference in pulley sizes between the alternator and engine the alternator would be running at quite high output even at tick-over.

Revving the engine would make very little difference to the approx. 14 4 volts already being output.


The term output is ambiguous. Whilst alternators have a relatively constant voltage output vs engine RPM, their current output is related to the RPM by curve that roughly has the form of Imax(1-e^-(k*RPM)). The maximum current output is available at around 2500RPM.

It is the current that carries charge from the alternator to the battery meaning that the charging rate is dependent on RPM roughly in accordance with the shape of the above formula's curve.

Ducati750cc 1st December 2021 19:29

Quote:

Originally Posted by COLVERT (Post 2910445)
Thought never crossed my mind.

I was using the report to show that modern alternators had high outputs even at low engine revs.

Due to the difference in pulley sizes between the alternator and engine the alternator would be running at quite high output even at tick-over.

Revving the engine would make very little difference to the approx. 14 4 volts already being output.


But the report doesn't show what you say, quite the opposite, the charts / graphs, 3 & 7, I mentioned previously actually how low the output, in amps is at low engine revs



Talking about the difference in pulley sizes is irrelevant, the article and graphs are talking about output at engine speeds, RPM, not at the alternator rotor speed, RPM.


You are comparing apples with oak trees !


MSS explains the voltage, current thing excellently.

COLVERT 2nd December 2021 22:52

Quote:

Originally Posted by MSS (Post 2910449)
The term output is ambiguous. Whilst alternators have a relatively constant voltage output vs engine RPM, their current output is related to the RPM by curve that roughly has the form of Imax(1-e^-(k*RPM)). The maximum current output is available at around 2500RPM.

It is the current that carries charge from the alternator to the battery meaning that the charging rate is dependent on RPM roughly in accordance with the shape of the above formula's curve.

Don't like to disagree but your post is ambiguous.--:D

Alternator output ( voltage ) is a straight line graph and is related to rpm when not being being controlled by a voltage regulator.

As I said, the regulator controls voltage in the car's electrical circuits but not current which varies according to demand.

As more items are switched on the voltage input to the armature varies.--This variation changes the strength of the armature's magnetic field.

The armature has about 6 amps being fed into it to give maximum output.---Perhaps even up to 100 amps or so output.

This input ( 1 to 6 amps. ) is what varies the current coming out of the alternators field coils which are bolted to the inside of the casing.

Your 2500 speed is vague as you don't quote a specific alternator type or output.

All my input ( information. ) is specific to the types of alternators fitted to the R75.





PS. Merry Xmas.-----:snowball::new_year:

Ooooops. nearly forgot.--;) ( Which vary very slightly according to the make and model fitted. )

It would also be nice if you explained what the letters mean in your complex formula.

COLVERT 2nd December 2021 23:00

Quote:

Originally Posted by Ducati750cc (Post 2910479)
But the report doesn't show what you say, quite the opposite, the charts / graphs, 3 & 7, I mentioned previously actually how low the output, in amps is at low engine revs



Talking about the difference in pulley sizes is irrelevant, the article and graphs are talking about output at engine speeds, RPM, not at the alternator rotor speed, RPM.


You are comparing apples with oak trees !


MSS explains the voltage, current thing excellently.

Look at the first graph on page 172.

Read the title underneath it.---It says alternator speed.---:duh:




PS. I'm sure everybody has heard of --"oak apples"--Lol.

Plus, you've left a word out in your first sentence.

COLVERT 2nd December 2021 23:06

Got to go now as my coach has just turned into a pumpkin.---:D---And those mice can run faster than I can.--( What with my stick and all. )

COLVERT 6th December 2021 13:09

[QUOTE=Ducati750cc;2910403]A bit technical in parts but otherwise not bad.


Remember when you said......... " Fast tick over to put a charge into a nearly flat battery is no better than just letting the engine tick over.--The modern alternators will hold 14.4 volts even at tick over.-- "


And I said .........."Fast tickover compared to idle tickover to put a charge into a nearly flat battery is the same you say.

Can I suggest you experiment on your suggestions with a modern alternator with both a voltmeter and an ammeter connected.

Then come back to report that the amps produced is exactly the same at both idle and a high idle. "



Could I suggest you read the PDF, taking note of Fig. 3 and Fig. 7 where you will find that there is a noticeable increase in current output at higher idle ( fast ) speeds

Just found your post.

Five amps is a reasonable regulated charge rate both by the alternator or a battery charger.
Any more than that and the battery will start to overheat and lose water vapour from the electrolite.

The level of electrolite will start to fall reducing the amount of the plate taking part in the chemical action. Capacity is therefore lowered by overcharging.

On the car the battery is shielded from engine heat by having a casing around it. Engine heat too can cause vapour loss making the battery less efficient.---:shocked:

I believe you are looking at the capabilities of an alternator and not what it is actually doing when in a controlled operation on a car.

COLVERT 6th December 2021 23:10

Good thread this one and we might be closing in on the factual truth. I really enjoy these kinds of searches.----:chat:

MSS 7th December 2021 00:25

It's a bit late now but I'll see if I can make it less enjoyable for you tomorrow. :laugh:

COLVERT 7th December 2021 14:58

Quote:

Originally Posted by MSS (Post 2911210)
It's a bit late now but I'll see if I can make it less enjoyable for you tomorrow. :laugh:

Party Pooper.------:snowball::snowball::snowball:

MSS 7th December 2021 15:49

Quote:

Originally Posted by COLVERT (Post 2911296)
Party Pooper.------:snowball::snowball::snowball:



The best! :snowball1::snowball1::snowball1:


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