# Car battery tester.

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#### Wp100

##### Well-Known Member
Hi,

Seems the old ways to test a car battery with a dvm or load tester have been superseded by these "conductance " devices which would appear to be micro based.
http://www.ebay.co.uk/itm/Ancel-Bst...949361?hash=item4d4d744d31:g:WUQAAOSw44BYDQLT

Can find little about their circuitry as was wondering if the actual battery testing part of it was diy buildable to work alongside a DVM ?
Seems you also need a table etc to apply to the measurments to give the correct result.

Just that the price of these meters is almost the price of a new car battery , so not very cost effective for a one car family.

#### spec

##### Well-Known Member
Hi WP,

To answer your question , yes a home-brew microprocessor-based battery tester is a feasible project, but why would you want to do that, when all you need to do to check a battery is to charge it up and then pull some current and measure the battery terminal voltage with a digital volt meter.

spec

##### Well-Known Member
Just that the price of these meters is almost the price of a new car battery , so not very cost effective for a one car family.
I believe it is aimed at business use and if it can identify a few batteries as bad then it pays for itself like most tools used in a business. During the early 60s I used one. A large restive load with an analog meter across it scaled as Poor-Good.

Ron

#### spec

##### Well-Known Member
I believe it is aimed at business use and if it can identify a few batteries as bad then it pays for itself like most tools used in a business. During the early 60s I used one. A large restive load with an analog meter across it scaled as Poor-Good.

Ron
I worked part time at a garage where they had a 24 mili Ohm battery tester that comprised a metal bar, covered in fins. A huge voltmeter calibrated in amps connected to the bar. The battery tester dated from the 1930s and was a thing of beauty.

spec

#### Wp100

##### Well-Known Member
Hi WP,

To answer your question , yes a home-brew microprocessor-based battery tester is a feasible project, but why would you want to do that, when all you need to do to check a battery is to charge it up and then pull some current and measure the battery terminal voltage with a digital volt meter.

spec
Well they suggest that it can give the Crank Amps still available in a more accurate way than using a load /resistive method ..?

As just said, perhaps its overkill for a single car family.

Just been testing it and seems to keep above 10 v when cranking for 3-4 seconds.
Will have to disconect the fuel pump fuse to crank it for longer.

##### Well-Known Member
I worked part time at a garage where they had a 24 mili Ohm battery tester that comprised a metal bar, covered in fins. A huge voltmeter calibrated in amps connected to the bar. The battery tester dated from the 1930s and was a thing of beauty.

spec
I believe the one we had could make a good battery look marginal. Yeah, it was a classic. The idea being after the "tester" aided in selling a few batteries it paid for itself. About 25 years ago I bought a bore sighting device for my gun shop. It cost about $40 back then. I charged about$10 to bore sight a rifle. After I used it 4-5 times it had paid for itself. Like any tool, they pay for themselves.

Ron

#### MikeMl

##### Well-Known Member
I have one of the 500A Carbon Pile testers; works to discover if a starting battery needs to be replaced prophylactically.

They seem to have one of the newer "electronic" testers...

#### Mosaic

##### Well-Known Member
My full service regenerator does automated battery testing via internal resistance detection and linearization to determine CCA and HCA with fair accuracy in a couple seconds. I have calibration routines to match it with the conductance meters ...I use two brands to cross reference.

#### spec

##### Well-Known Member
Well they suggest that it can give the Crank Amps still available in a more accurate way than using a load /resistive method ..?
Hmm, I would be very interested to know how you can measure the crank amps still available.

The traditional restive load/voltmeter tester is pretty accurate because you know what current is being drained from the battery, as opposed to just cranking the engine, when you have no idea how much current is being drained from the battery.

I cant remember the details now, but the correct test to ascertain if an automobile battery is going to do its job is to reduce the battery temperature to zero deg C and make sure the battery will supply 500A with a terminal voltage of no less than 10.5V, for a given period. The current varies according to the application- some lorry batteries are well over 1,000A.

With a low temperature, everything is working against you: low battery terminal voltage, higher internal resistance, lower AH capacity, thicker oil, tighter moving parts.

To measure the state of the battery in your car (automobile) just permanently fit a fast-acting (not thermal) voltmeter and watch the voltage as you crank the engine (motor). To do a proper job the the two voltmeter leads should connect directly to the lead terminals of the battery.

By the way, if you are having cranking problems change your oil to Mobile 1. It will give you easier cranking, longer engine life, more miles per gallon, less oil consumption, a cleaner engine, a quieter engine, and more power. I have some Mobile 1 sprinkled on my corn-flakes every morning at breakfast.

spec

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#### Mosaic

##### Well-Known Member
I use a high response speed electronic load under uC control which translates the result via the ambient temp into usable CCA. Calibrated with a professional conductance meter and crosschecked with a load pile 'oldstyle' tester.
1024 samples are done and averaged, after a surface clearing discharge (e-load again, is complete).
I detect volts down to two decimal places (instrumentation diff. amp) and current discharge down to 1 dec place with a ACS series linear hall sensor.

#### spec

##### Well-Known Member
I use a high response speed electronic load under uC control which translates the result via the ambient temp into usable CCA. Calibrated with a professional conductance meter and crosschecked with a load pile 'oldstyle' tester.
1024 samples are done and averaged, after a surface clearing discharge (e-load again, is complete).
I detect volts down to two decimal places (instrumentation diff. amp) and current discharge down to 1 dec place with a ACS series linear hall sensor.
Wow! Sounds pretty sophisticated Mosaic, but you are talking about the professional side there, involving many man-hours of development work which I think you have mentioned.

spec

##### Well-Known Member
By the way, if you are having cranking problems change your oil to Mobile 1. It will give you easier cranking, longer engine life, more miles per gallon, less oil consumption, a cleaner engine, a quieter engine, and more power. I have some Mobile 1 sprinkled on my corn-flakes every morning at breakfast.
I was going to comment that Mobile 1 is so good you can put it on your morning corn flakes but you had that covered. Actually I use Mobile 1 in everything including mine and my wife's trucks and my bike as well as a lube for guns.

Ron

#### spec

##### Well-Known Member
I was going to comment that Mobile 1 is so good you can put it on your morning corn flakes but you had that covered. Actually I use Mobile 1 in everything including mine and my wife's trucks and my bike as well as a lube for guns.

Ron
Yes, Mobile 1 is truly magic stuff, but not cheap, in the UK anyway.

It completely transformed the engine on my Peugeot 406. I used Mobile 1 from 30K miles and the car has now done 120K miles and, if anything the engine, is better than when nearly new. It does not use a drop of oil and when you change the oil it comes out like... oil, rather than ditch water.

spec

#### Diy1995

##### Member
We used that kind of tester when I worked for Citroen service. It's nice when you can determine if battery is bad in one minute. It was even nicer when I was bringing home batteries that were still good and tester claimed for them to be bad.

##### Well-Known Member
It was even nicer when I was bringing home batteries that were still good and tester claimed for them to be bad.
The tester designed to sell batteries? That tester? Anymore if I buy a 60 Month or 72 Month battery I only had one fail within a week, all of the rest seemed to run out their life course, just about down to the month. That includes the warm summers and the bitter cold winters. Myself and my neighbor just put our bikes (motorcycles) in winter storage a month ago. We leave a small battery charger on each battery for the winter just to keep the batteries fresh in storage. The battery in my generator (emergency house backup) runs on a constant trickle charger also. They actually call the small trickle chargers a battery maintainer or battery tender.

Ron

#### Diy1995

##### Member
The tester designed to sell batteries? That tester? Anymore if I buy a 60 Month or 72 Month battery I only had one fail within a week, all of the rest seemed to run out their life course, just about down to the month. That includes the warm summers and the bitter cold winters. Myself and my neighbor just put our bikes (motorcycles) in winter storage a month ago. We leave a small battery charger on each battery for the winter just to keep the batteries fresh in storage. The battery in my generator (emergency house backup) runs on a constant trickle charger also. They actually call the small trickle chargers a battery maintainer or battery tender.

Ron
Hehe, no actual tester, i cant remember the brand.

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