30V 60W Constant Current Electronic Load

Thread Starter

Lumenosity

Joined Mar 1, 2017
469
Hello,

I bought this battery capacity tester and there's one part of the instructions I don't understand. (In RED)
It's clear how to connect the battery, but I'm not sure what they mean by "four-wire clamp test" at the Differential Voltage Input. port.

3. Battery Capacity Test Mode:
*The test battery should be fully charged with a special charger!
*Energize the tester and enter into the battery capacity test mode, connect the battery current line to (P+/P-) positive and negative terminals; if you use four-wire clamp test, please connect the four-wire voltage test interface to (V+/V-) port.

If you can help thanks.

 

Sensacell

Joined Jun 19, 2012
2,628
A 4-wire connection means you connect the battery normally, but run 2 separate wires from the differential input directly to the battery terminals.

This prevents terminal and wiring resistance from mucking up the voltage readings when current is flowing in the main battery leads.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
469
A 4-wire connection means you connect the battery normally, but run 2 separate wires from the differential input directly to the battery terminals.

This prevents terminal and wiring resistance from mucking up the voltage readings when current is flowing in the main battery leads.
Thanks!

So I would just connect the battery as normal then run another set of wires from the batteries negative and positive to the differential voltage input?

Basically connecting the battery to two places?

OR...it really doesn't make much difference?
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
469
What do the instructions say?
Here is everything that was available.....

Battery capacity testing mode:
1. Please fully charge the battery before testing.
2. Turn on the tester with power supplied, enter the "Battery capacity testing mode". Connect the battery "+" & "-" to the test power input "P+" & "P-" port by cable. If you are using four-wire clamp for the test, please connect battery "+" & "-" to the "V+" & "V-" port.
3. Pre-set the current and lower limit voltage by adjusting the knob. (As "Electronic load mode") Press the Start-Stop switch after setting. The tester will check the battery and circuit firt. it will automatically detect if the wire is 2-wire (shows JS-2) or 4-wire (shows JS-4) and enter the test.
4. During the test, the display on the above will show the battery voltage, capacity(Ah) and power(Wh), the capacity data will flash and the buzzer will alarm after fully discharged.(the battery voltage should lower than the pre-set voltage)
5. Press the knob or Start-Stop switch will stop the alarm, you can rotate the knob to check discharge data of the battery, such as capacity (Ah), power (Wh) and voltage, press the Start-Stop switch again to delete the data and back to initial setting for testing the next battery.
 
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Thread Starter

Lumenosity

Joined Mar 1, 2017
469
I've used this puppy extensively now and it works well.
I even made a custom enclosure for it and bought several more.
With it I've been able to accurately determine the real capacity of my Sealed Lead Acid batteries.

It's surprising just how far off most battery capacity claims really are. Like others have already said, you're lucky if it has HALF the claimed capacity.
I suppose these and similar devices will eventually pressure battery vendors and manufacturers to become a bit more "honest in their claims.
But it will take time. Most people never had a clue how far off the claims on battery labels are.

CapTester_2.jpg

CapTester_4.jpg
 

crutschow

Joined Mar 14, 2008
25,647
It's surprising just how far off most battery capacity claims really are. Like others have already said, you're lucky if it has HALF the claimed capacity.
The capacity rating is typically for a 1/20 C discharge rate (discharge current is 1/20th of the AH capacity).
Is that the way you tested them?
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
469
Yes. However, I have a few batteries which have no indication of their capacity. Depending on the size of the battery, I used as close a C/20 rate as possible. Generally tending to err on the low side for the load.

However, batteries with a stated Ah capacity were of course easier.

If I had, for example, an 8Ah battery, I would apply a load of 8Ah/20=.40amps

20 being the 20Hour discharge rate

Not one of the batteries I have (and I have quite a few) come anywhere near their stated capacity at the C/20 discharge rate.
 
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Answering your question in another way.

V+ and V- are clearly labeled. They go to the battery/battery clamp In reality, you should have two separate leads to the post. One being high current and one really low.

This allows the charger to measure cuurent and the voltage across the battery removing the effects of contact resistance and the resistance of the current carrying wire.

Your supposed to use a Kelvin clip: e.g. http://muellerelectric.com/product-category/alligator-clips-insulators/kelvin-clips-ak/

This http://muellerelectric.com/wp-content/uploads/DS-BU-116K-@.pdf datasheet makes it obvious. The two jaws are independent./

New word: Kelvin; https://www.google.com/url?sa=t&rct...ements&usg=AFQjCNEq3DUfKe_54SX2H2BoxLayFBTWWA
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
469
Answering your question in another way.

V+ and V- are clearly labeled. They go to the battery/battery clamp In reality, you should have two separate leads to the post. One being high current and one really low.

This allows the charger to measure cuurent and the voltage across the battery removing the effects of contact resistance and the resistance of the current carrying wire.

Your supposed to use a Kelvin clip: e.g. http://muellerelectric.com/product-category/alligator-clips-insulators/kelvin-clips-ak/

This http://muellerelectric.com/wp-content/uploads/DS-BU-116K-@.pdf datasheet makes it obvious. The two jaws are independent./

New word: Kelvin; https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0ahUKEwjKiPL4rf3VAhWlK8AKHc3TBRwQFgg3MAI&url=http://www.tek.com/document/application-note/overview-two-wire-and-four-wire-kelvin-resistance-measurements&usg=AFQjCNEq3DUfKe_54SX2H2BoxLayFBTWWA
Ok. Just curious. Is this likely to significantly alter the results? Say, more than 20% ?
 
It could. It really depends on the length of the hi-current leads, the wire gage and the current.

The dual isolated contacts gets rid of contact resistance.

20% is surely possible.

You could look at 1/2 the lead drop and double it as the gizmo is doing it's thing.
 
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