testing batteries

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Buck Parrish

Buck Parrish

Senior Member
Location
NC & IN
They make a battery tester that can simulate the battery having a load on it. Such as it starting an engine.
I have one it was about $40 .
The auto supply houses will ussually test it for free.
 
MarkyMarkNC

MarkyMarkNC

Senior Member
Location
Raleigh NC
It's been my experience that cheap SLA's, like you find in an emergency fixture, reach the land of no return once they've dropped down to somewhere between 65% and 80% of the rated voltage. Once you get to less than that, chances are one of the cells has completely crystallized, and its time to replace it.

ex. 12V SLA battery

10.6 V - probably still good, just discharged
9.1 V - Could still be re-chargable, or could make a good paperweight
6.6 V - Send on to battery heaven

Car batteries I don't have enough experience with to make an educated statement.
 
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wptski

Senior Member
Location
Warren, MI
Just using voltage without a load is a poor way to check any battery. Some battery impedance testers use a 1kHz signal and in general the lower the impedance the better the cell or pack condition. Car starter batteries check around 1/2 milliohms.
 
brian john

brian john

Senior Member
Location
Leesburg, VA
We perform battery service and inspections.

Voltage
Specific gravity (if a flooded lead acid)
Internal resistance or impedance.
temperature.

We perform DC resistive load test based on manufactures published ratings.
 
dereckbc

dereckbc

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Staff member
Location
Plano, TX
Load testing is the only way to determine a batteries health. However chaecking the State of Charge for SLA, FLA, and VRLA can tell you immeditely if it is bad or not if you now how to take the measurement. If SOC passes it does not tell you how good of shape the battery is in, but you can tell if it is shot or not.

For example for a 12 volt lead acid type be it FLA, SLA, or VRLA you charge the battery up, disconnect it from the charge source and load, or in other words open cicuit and let it rest for 4 to 6 hours. Then you measure the voltage. If the battery is in bad shape it will read less than 12. 4 volts it is toast as that only indicates a 50% SOC. Put a load on it and it will faill very quickly. If it reads around 12.65 it is probable OK, you just do not know the capacity.
 
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wptski

Senior Member
Location
Warren, MI
Load testing isn't the only way to check a battery's SOH or SOC. Conductance type testers have been around for years and you don't have to discharge the battery to test it either using this technology. Poke around at Midtronic's site, they've been in the battery testing business for twenty years.
 
ELA

ELA

Senior Member
Occupation
Electrical Test Engineer
wptski said:
Load testing isn't the only way to check a battery's SOH or SOC. Conductance type testers have been around for years and you don't have to discharge the battery to test it either using this technology. Poke around at Midtronic's site, they've been in the battery testing business for twenty years.
Click to expand...

Thanks Wptski - that was very interesting. I included a charger as part of the design of a piece of equipment a while back. It included a dummy load for testing the batteries.
I never liked having to dissipate so much power to perform the test.

If I should do anther I would definitely look into the conductance testing method.
 
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wptski

Senior Member
Location
Warren, MI
ELA said:
Thanks Wptski - that was very interesting. I included a charger as part of the design of a piece of equipment a while back. It included a dummy load for testing the batteries.
I never liked having to dissipate so much power to perform the test.

If I should do anther I would definitely look into the conductance testing method.
Click to expand...
ELA:

Did you catch the video in the Technology section, I think it was, where they use the automotive OBD-II port for commands? They had a bunch of articles that one could read on-line but I couldn't find them some time ago already!:mad:

I take that back, I was able to find all those articles again, very good reading!
 
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dereckbc

dereckbc

Moderator
Staff member
Location
Plano, TX
wptski said:
Load testing isn't the only way to check a battery's SOH or SOC. Conductance type testers have been around for years and you don't have to discharge the battery to test it either using this technology.
Click to expand...
Yes they have been around for years and were developed for SLA and VRLA batteries where there is no way to measure specific gravity and internal temp, nor will they tell you much about the capacity. There biggest drawback is unless you have a baseline measurement when the batteries were new and after the forming charge, the readings don't tell you a whole lot because you have no reference to measure against.
 
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wptski

Senior Member
Location
Warren, MI
dereckbc said:
Yes they have been around for years and were developed for SLA and VRLA batteries where there is no way to measure specific gravity and internal temp, nor will they tell you much about the capacity. There biggest drawback is unless you have a baseline measurement when the batteries were new and after the forming charge, the readings don't tell you a whole lot because you have no reference to measure against.
Click to expand...

The Midtronic's site states that many battery manufacturers now publish conductance reference or base-line values. If not then, there are other suggestions for doing so in their manuals.

Hey, if you'd rather take a battery out of service to test it, have at it. I'm just suggesting that there are other ways that are quicker and easier that are getting more accurate day by day.
 
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