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Old 01-15-2021, 09:05 PM   #1
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RV / Auto "SMART" Battery Testing

Those with some 'tech' background will find this hard to believe. But it is true.

Some years ago I bought a new high tech battery tester.
Preforms the test w/o drawing a heavy load on the battery.

Much later when I bought new group 31 starter batteries, got them home, charged them and then tested. Neither one tested close to what it should.
I went back to the dealer (Interstate Battery) and explained. The guy w/o hesitation asked did you use lead testing terminals or just clip onto the screw threads. I said just clipped onto the screw post.

He brought out 2 lead adapters to screw onto the metal stud turning it into a normal car lead post battery. Then clipped his 'expensive' smart tester onto the battery and all tested well. He showed me the test. I thanked him and asked if I could test with my in-expensive Harbor Freight tester. My tester tested +- the same as his did when connected to the lead post.

Back at home I tried it again w/o any adapters, same results. Then I noticed like 1/32" of lead sticking up at the base of the threaded stud. I clipped onto that as best as I could and I got results that came in much closer to what the battery should show.

I have a history working in electronics, I don't have a clue why this happens. I also don't know anyone that has explained how a high tech battery tester works and why it needs to have a better connection than being clipped onto the metal threaded post.

Since then I have clipped onto the copper fittings on the battery cables and gotten results that appear to be in the some what normal range.
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Old 01-15-2021, 09:29 PM   #2
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The lead gives the alligator clip teeth something to bite into, on the steel bolt, the alligator clip rides on the surface of the steel and it arcs under the high amps. Copper is also softer than the steel teeth, it allows the teeth to bite into it
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Old 01-15-2021, 11:41 PM   #3
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Originally Posted by Jyrocharlie View Post
The lead gives the alligator clip teeth something to bite into, on the steel bolt, the alligator clip rides on the surface of the steel and it arcs under the high amps. Copper is also softer than the steel teeth, it allows the teeth to bite into it
It is NOT a load tester.
Smart battery testers draw little to no current.....
Each side of the battery clip has its own wire (4 wires) maybe 18 gauge wire. Like I said, I don't know how they work.....
Gives me CCA & micro ohm readings, along with voltage & % rating if you input the rated CCA. This is the link...
https://www.harborfreight.com/automo...zer-66892.html
Ad's info:
Digitally analyze the condition of your automotive battery with this easy-to-use battery analyzer. This unit checks voltage, cold cranking amps (CCA), resistance and overall battery condition and displays information on a large backlit LCD screen.
  • Checks voltage, cold cranking amps (CCA), resistance and overall battery condition
  • Continuous testing will not damage battery
  • Uses car battery for power, no extra internal batteries needed
  • Large backlit LCD screen
  • Includes removable rubberized protective sleeve
  • Easy-to-carry and durable design
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Old 01-16-2021, 04:37 AM   #4
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Interesting... will look into the HF unit as I'm not familiar with it. HF link failed... do you have a mfg model #?
I do have a Balmar SG (Smart Gauge) on my boat. It is the original version without a shunt like the newer version has.
https://marinehowto.com/smartgauge-b...nitoring-unit/
This guy is excellent with his reviews... very thorough.
I have been very pleased so far. In addition to very accurate V info on primary and secondary batty banks it provides SOC for the primary bank all via 14 AWG connections to batty terminals. They / he are very specific that connections must be made to the terminals vs a switch etc for best accuracy.
Threaded batty posts are SS and likely no the best conductors. When you fasten a cable terminal it bears on the lead "ring" or post around the base of the threaded terminal. Thats the reason for recommending the largest cable / highest A load be the first terminal on. Subsequent cable terminals contact the previous ones for conductivity. The threaded post and nut /washer provide the clamping force more than the primary conduction path.
When checking V w a meter always best to touch the lead vs SS thread for a good reading.
The newer Balmar SG200 includes a shunt and more bells & whistles including Bluetooth connectivity for remote monitoring.
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Old 01-16-2021, 11:23 AM   #5
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link etc

Harbor Freight SKU 66892, it is a Cen-Tech model, Pretty sure Cen-Tecn is only sold at Harbor-Freight. I know HF doesn't sell highest quality tools. But for me 'so far' everything I have bought from HF has met my needs and lasted WAY long enough for the money invested.


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Old 01-17-2021, 10:25 AM   #6
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I think the main difference between one of these "digital analyzers" and a traditional load tester is that the analyzer measures battery internal resistance rather than amps under load. Both types measure voltage in the same way, but the load tester is able to measure voltage drop under a high amp load.

Depending on what is wrong with a battery, one method or the other might give more useful results. If there is nothing wrong, either should give a good report.

Battery internal resistance measurement should easily show common battery problems such as a shorted or high resistance cell. Should also show a battery post that is faulty and not making good contact inside the battery case.
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Old 01-17-2021, 01:53 PM   #7
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Gary not sure I can totally agree. Interstate Battery in my city appears to only use a smart tester. A good friend loaned me his carbon pile tester. Where you adjust the load for the battery rating and test for a few seconds. That IMO appears to be a good test... When I bought my RV the RV dealer (large business in S. AZ) used a in expensive hand held load tested not much larger than my smart tester. PLUS they would charge the battery & immediately test it. The test was a good/bad test and my batteries tested good every time. No way I could convince them that their $20 tester was not really testing. The service manager was not interested in anything I had to say. In his point of view, his tester proved the batteries were good. I begged the technician to charge the batteries, let them set over night then test. Tested that way neither battery even came close to passing. Smart tester showed the batteries defective and showed it on the display.
I would say a good technician using a good load tester can get a good test.
BUT anyone using a smart tester will get a good test (if they use lead posts to connect to the battery).
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Old 01-19-2021, 08:20 AM   #8
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Not sure what you don't agree with, ronnie. Each type of tester is better at finding some faults and not so good on others. Neither is a perfect test, but both will find the most common problems. Your battery apparently had one of the more obscure issues, but without learning exactly what it was, we can only conjecture why the load test didn't find it.


Most tests are calibrated to work with a fully charged battery. The voltage and internal resistance both vary with the state of charge, so good vs bad is affected by the SOC.
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Old 01-19-2021, 02:19 PM   #9
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Yea, after I wrote the response it dawned on me that I did agree....
Tried to edit, but had timed out :-)

REALLY the reason for the post was to let everyone know if they use a smart tester it has to be connected through a lead post. Clipping on to the threaded terminal will not give a valid reading.

My battery would self discharge over night to about 7V and that's while attached to shore power and a trickle charger. Connect it up to a shop battery charger & immediately test it on a hand held go/no-go load tester and it would pass. In reality the problem was the RV dealer selling the unit. They just wanted me to go away and buy new batteries on my own.
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Old 01-19-2021, 09:05 PM   #10
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Well,
I'm by far, nowhere near an expert on any part of this. But, I'd sure as heck like to know WHY a steel post, on a battery, would not conduct the same exact reading on a tester, as a lead adapter which, is attached to the SAME STEEL POST? Something's not making sense here.
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Old 01-20-2021, 03:03 AM   #11
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Well,
I'm by far, nowhere near an expert on any part of this. But, I'd sure as heck like to know WHY a steel post, on a battery, would not conduct the same exact reading on a tester, as a lead adapter which, is attached to the SAME STEEL POST? Something's not making sense here.
Scott

Exactly, that's the reason for the post.
To let those that might come in contact with a smart tester know they require connecting via a lead post.


I'd like to know how a smart tester works.....
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Old 01-20-2021, 08:57 AM   #12
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The smart testers rely heavily on accurate resistance measurements, so the quality of the connection between the test leads and the battery is critical. In my opinion, there is nothing inherently wrong with connecting via the screw post, but the chance of a poor quality connection may be greater than any lead post. A soft lead surface scratches easily to expose clean and unoxidized metal for best electrical contact.



A threaded post nearly always makes a good connection when the wing nut is tightened down on a ring terminal, but alligator clips don't always do the same.
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