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  1. #1
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    Default 12v lead-acid battery tester recommendation

    I seem to accumulate a few 12v batteries around the place.
    Cranking batteries, deep cycle ones, traditional wet lead-acid, AGM, VRLA etc and ranging from small 6Ah ones through to about 150Ah. I usually avoid anything larger than that as they are just too friggin heavy to move around!!

    Some are definitely dead, but others are fine and were replaced due to misdiagnosis, or simply weren't big enough for the job.
    Typically what I do is to put them on my 15A Projecta smart charger, and leave them for a few days to go through the automatic charge and "recondition" process.

    I don't have any way of testing them though other than the typical "if they are dead flat again in a couple of days they're definitely scrap".
    I've also found that the black/green/clear condition window on some batteries is mostly just a gimmick. I've got batteries here that are dead - but still showing green.

    Any batteries that aren't scrap typically get appropriate uses found for them around family and friends, but definitely get a few that seemed OK but didn't hold up in use.

    Hence I'm looking for recommendations on a reasonably priced battery tester....

    Definitely needs to be able to test Ah capacity for deep cycle batteries, and ideally also do load testing for cranking performance.
    If its more appropriate to have two testers - one for deep cycle capacity and the other one for CCA then so be it - but would be nice if the one device did both.
    Budgetwise, hoping to get something reasonable for under $150??

    I've had a bit of a look around online, and came across these ones that look promising:
    Altronics one that will test up to 80Ah - but no crank testing function
    https://www.altronics.com.au/p/q3215...attery-tester/

    Sydney tools one that only does crank testing, but says you don't even need to charge the battery ??
    https://sydneytools.com.au/product/s...ranking-tester

    This one looks like it might do both, but probably have to read the manual as the advertising vomit isn't 100% convincing ..
    https://www.jcinstruments.com.au/pro...ry-load-tester

    Any thoughts or recommendations?
    Steve

  2. #2
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    Sep 2012
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    Default

    Hi Steve,

    All those instruments are basically useless ! Non of them actually do the real battery test that you want, which is "Do they hold up under load".

    Load testing requires that the battery can supply the required current under the conditions that it will be subject to in use. Normally a load tester is a high powered, low value resistance that is applied across the battery, whilst measuring the voltage across it.

    Normally a car starter battery will have to supply around 400 amps for a few seconds whilst the engine is started. A load tester will pass about 25 amps across its load resistor and use an ordinary volt meter to measure the battery voltage.

    Getting a sufficiently high powered resistor is very difficult ! The proper commercial tester uses a strip of copper bar folded into a zigzag shape between the battery terminal probes and a volt meter, usually calibrated in amps as well as volts to measure the battery voltage. This give a good indication of the state of the battery. Bearing in mind its actual state of charge. A fully charged battery in good health will show a lower voltage drop than a battery that is only partially charged or starting to fail.

    You can easily make a drop tester using a length of copper tube rolled flat into a strip and a simple multimeter to measure the voltage. Using Ohms law, Voltage divided by current, an Ohmmeter/Multimeter will get you into the resistance ballpark.

    You can get an idea of the resistance value of your copper tube by measuring the resistance between two points along its length before you cut and flatten it into a strip. The only reason to flatten it, is so you can fold it up to take less space. And its easier to bolt your battery probes to it.

    https://www.sealey.co.uk/product/563...ry-drop-tester

    Far too expensive but quite pretty !
    Best Regards:
    Baron J.

  3. #3
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    Mar 2011
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    Southern Flinders Ranges
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    Default

    A load that represents about 10% of its C10 discharge rating like a globe and a multimeter, and 15 minutes of your time.

    Measure the voltage under load, a good battery will dip as the surface charge is knocked off then rise very briefly then start the relatively linear (for the time you are likely to test it) progression downward. Provided it doesn’t drop off a cliff the first 15min you’re on a winner.

    I prefer the battery testers that inject high frequency AC into the battery as it’s simultaneously under load to graph the plate resistance while it load tests. Gives a very good idea of the state of the battery if you know what you’re looking at. They are a bit above your desired price bracket though..

    For what you’re doing a few bulbs and old headlights with a multimeter while you neck a couple of cans one night will get it done

  4. #4
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    Thanks John.

    I generally agree with what you're saying in regards to testing start/cranking batteries.
    I don't see that it applies directly to deep cycle batteries though, where its capacity that you're more interested in. Traditional deep cycle batteries aren't designed to deliver high currents, and hooking them up to a crank style tester is likely to make them unhappy (even if they were OK to start with).

    That's why I was thinking that the 2 different types of testing (ie cranking and capacity) were required depending on the battery (and its potential use).
    A cranking battery that was rated at 700CCA and may have degraded to 350CCA might not be good enough for the vehicle it was in - but if it holds charge and still has the capacity to deliver say 5A for 10hrs then it may still have an alternative use eg with a small solar panel for a security light.

    Does that make any sense?

    That Sealy tested you linked to is an unfamiliar style down this end of the world (at least in my experience). I've never seen one with just rigid probes on it.

    The old school ones down here for testing typical cranking batteries are like this: https://www.batteriesdirect.com.au/s...88/blt100.html
    Internal load resistor, and pretty much what you described.

    The serious ones were carbon pile up to 1000A load (and higher) - and seems they are still around too - but not cheap!! https://www.batteriesdirect.com.au/s...19/blt300.html

    Steve

  5. #5
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    Quote Originally Posted by racingtadpole View Post
    A load that represents about 10% of its C10 discharge rating like a globe and a multimeter, and 15 minutes of your time.

    Measure the voltage under load, a good battery will dip as the surface charge is knocked off then rise very briefly then start the relatively linear (for the time you are likely to test it) progression downward. Provided it doesn’t drop off a cliff the first 15min you’re on a winner.

    I prefer the battery testers that inject high frequency AC into the battery as it’s simultaneously under load to graph the plate resistance while it load tests. Gives a very good idea of the state of the battery if you know what you’re looking at. They are a bit above your desired price bracket though..

    For what you’re doing a few bulbs and old headlights with a multimeter while you neck a couple of cans one night will get it done
    I have tried that a few times in the past, but TBH what normally happens is I get bored watching it, get distracted with something else, forget about it, go inside, then remember in the middle of the night the light bulb is still hooked up to it, can't be faffed getting up and by morning its flat as a maggot....

    I'm hoping technology can help overcome my personal shortcomings

    Steve

  6. #6
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    Sep 2012
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    Hi Steve, Guys,

    The probes on that Sealey one are movable they pivot to allow for different sizes.
    Notice that the meter is center zeroed so you can put it on a battery either way round.

    Its a bit heavy for testing Leisure batteries though ! A much smaller load should be used for those. The C10 rating works but is time related. I've never seen a problem using a load tester, but then mine are continuously on trickle charge from the solar panel.

    One battery that I did replace on the old van, developed a bad cell. It was shorted, probably from a collapsed plate. The other cells would boil if you load tested the battery for more than a few seconds. I still use it for testing various items.

    The copper strip resistor works very well if you wanted to make a load tester, and you can choose the load you want !
    Best Regards:
    Baron J.

  7. #7
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    I spent 4 months towing a load bank trailer along the most of the length of Dampier Bunbury pipeline in WA from Badgingarra to Karratha in 2008 load testing standby batteries at Alinta’s comms sites. I completely understand your apathy…..

  8. #8
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    Hi Guys,

    Just a quick note on some of those battery testers.

    What they actually do is measure the internal impedance of the battery ! They don't actually tell you very much. A low internal resistance doesn't necessarily mean that the battery is any good. A duff battery can still show a low impedance but won't supply the current wanted or needed.

    Good for capacitors though !
    Best Regards:
    Baron J.

  9. #9
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    For a low resistance, high capacity resistor an electric stove element may be the go. I snagged a few from the bin at the previous place for a vac former I intended to make but one of the guys suggested that they would be good for providing resistive loads too.

    Michael

  10. #10
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    Hi Michael,

    Electric stove elements are too high a resistance for loading a 12 or 24 volt lead acid battery ! They are usually around 3.5 Kw at 240 volts ac, so will be around 20 Ohms or so. That would only be about 0.650 ma at 13 volts.
    Best Regards:
    Baron J.

  11. #11
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    Default

    Back in my youth we used the old nichrome wire wound radiant heater elements as rheostats for charging motorbike batteries from dumb car battery chargers. Normally to use as spotlighting batteries.

    From memory the batteries could only take about 2A without getting cooked - so we’d connect a heater element in series. One wire to the end of the element and the move the other wire along the element until we got the desired current then clamp it there somehow.
    Not useful for battery testing but Michael’s post about using oven elements brought back memories.

    Steve

  12. #12
    Join Date
    Dec 2023
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    Adelaide South Australia
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    Default Battery tester

    I raid the scrap metal place and bring one of these with me - https://www.ebay.com.au/itm/16660580...AtiSyR16t8DzJn
    It is a proper load/ voltage tester, and will load up a battery and show CCA's. Only used it on standard lead/acid batteries, not sure if it would show anything significant with other types of batteries.

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