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Old 11th November 2021, 09:56   #11
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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!
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Old 11th November 2021, 11:55   #12
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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
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Old 11th November 2021, 12:35   #13
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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.
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Old 11th November 2021, 16:07   #14
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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.----

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.--- )
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Old 11th November 2021, 19:46   #15
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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
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Old 25th November 2021, 22:14   #16
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measured the voltage and it is showing 12.8 which is pleasing

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Old 25th November 2021, 22:36   #17
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measured the voltage and it is showing 12.8 which is pleasing

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



If the next day then that reading suggests a good battery.---
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Old 26th November 2021, 00:08   #18
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Was your check soon after charging or, perhaps, the next day ??



If the next day then that reading suggest a good battery.---
some days after

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Old 26th November 2021, 10:00   #19
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Quote:
Originally Posted by patrolman pete View Post
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.
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Old 26th November 2021, 10:48   #20
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Quote:
Originally Posted by COLVERT View Post
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.----

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.--- )



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.
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