Battery load tester?

Now you will appreciate why an adjustable carbon pile load tester can resolve issues. I have found so many issues with dual battery Ford diesels using a load tester I lost track 30-years ago. A marginal terminal is REACTIVE to high amperage loads. it just doesn't sit there with the same impedance. Or milliohm resistance.

A friend of a friend had a 40' salmon boat. He was a retired PhD mathematician. You read about the other argumentative mathematician on a sailboat. Well Dean sat at the galley desk and tried his dandest to try and convince me his battery issue was so complex it defied explanation or resolution. Out came an impedance meter and an ohm meter. Then came the math. Diagrams and reams of calculations.

If X equals Y and O fits, it cannot be a bad connection. I listened to diatribe like this for hours.

I jumped on the dock and went to my pickup truck and grabbed my Auto Meter 800 amp load tester. Over his objections I connected the meter to a battery. The other 4 8-D's were in a forward compartment.

10-secods is all it took...

"STOP! FIRE! STOP! STOP!" he screamed. Smoke rolled out of a compartment forward.

Sometimes ya gotta take the BULL by the horns...

MrWizard wrote:
#2..no, impedance is battery impedance, not system load resistance

I was thinking of this approach:



V is just the no load potential on the battery. I see the method is very sensitive to the accuracy of the load resistor; probably too difficult to determine as it heats up.

I had the "left walking" experience with this old vehicle last winter and just assumed it was a battery problem - it turned out to be a corroded connection between the battery cables and their battery ends. Now a friend has given me a failed one year old battery from his motorhome, which was sitting with 11.5 volts on it. I equalized and reconditioned (desulphated) it and am using it in the old van but wondering if it is good enough for winter.

Take a group 27 R battery with 600 CCA rating at 25c. To obtain the BCI by substitution, a 300 ampere load would have to be placed on this one single battery for 15 seconds. With an adjustable load tester the load must be adjusted constantly to maintain a 300 ampere load.

Your starter motor does not consume 300 amperes. It's load varies at it heats up. So a test is a moot issue unless you like best-guesswork results.

A hydrometer is by far the cheapest and most reliable of the three test protocols. I hydrometer tested a battery six months ago and found two cells with smoky fluid. It soundly passed an impedance test. our months later it utterly failed. It was sudden. No drains and the battery tested 4.2 volts. The two smoky cells tested low on the hydrometer, the conductance of plate alloy in solution pulled the wool over the eyes of the impedance meter.

#2..no, impedance is battery impedance, not system load resistance
#3.. Don't know what to tell you on that one,
Capacity changes with temperature, aka because of the speed of the chemical reactions that produce the electrical energy
And cold weather cranking of an engine takes more energy
Best thing is fix it do it starts correctly, engine block heater ?

I see some advisors suggest watching the voltage while starting the vehicle as a load test. If the battery voltage dips below 9.6 volts, it fails. A bit awkward without a max/min feature on the meter.

MEXICOWANDERER wrote:
UNBEATABLE TRIO

1. Accurate hydrometer

2. VARIABLE (adjustable) amperage carbon pile load tester

3. Impedance test meter

Got 1.
2. Can I measure impedance by turning on the lights and dividing the voltage by the current?
3. Can I load test with the lights, too? I tried leaving the lights on for two hours while visiting my dentist and the vehicle wouldn't start. Is that a test failure? What constitutes a pass? I guess I could compare two batteries and see which can deliver more amp hours before hitting the dreaded 12.0 volts. But I'm really interested in how long it can crank in cold weather. Unplug the spark plugs and observe that directly?

Mex, I have some questions for you that I'll start in another thread. Don't want to hijack this thread/subject.

UNBEATABLE TRIO

1. Accurate hydrometer

2. VARIABLE (adjustable) amperage carbon pile load tester

3. Impedance test meter

With a hydrometer a person can see discolored or cloudy electrolyte FAR before a carbon pile or impedance tester indicates a problem.

The only way a battery can fail after passing all three tests is for a mechanical failure to pop up. Like my Johnson Out Of Control Wal-Mart special that fractured an intercell strap. Not the most common of failures.

A followup- I bought the HF battery analyzer- it *seems* to be doing a good job, though I need a bad battery to be sure. Tested the 9 Full River DC115-12 batteries, first with the cheapo 100 amp load tester- all tested fine. Then tested with the HF- you hook it up, enter the CCA capacity, it hems and haws for a minute, then gives voltage, resistance, percent of capacity remaining, entered CCA and calculated CCA. Every battery tested out at above rated capacity (770 CCA).

So- looks neat, if it is accurate, it could be handy. On the other hand- the readings could be off simply because these are AGM batteries. The customer said they were not lasting as long as usual, but we've added 12 volt loads, and when I checked, the charging algorithm had been changed to gel, from custom, so the batteries were not being fully charged at all.

I've learned SO MUCH from this thread, want to thank all of you!!!!!!!!!!!