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Post by Deleted on Jun 2, 2020 22:17:16 GMT
Got a multimeter? Here's some destructions. This is a very old-school analogue gadget that still gives practical useful results for lead-acid.
And here's some destructions ...
If you search the web you will see that several different companies sell this device with their badge on it. They are all a little bit different looking but all the same thing. Just the price differs.
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Post by Deleted on Jun 3, 2020 1:56:16 GMT
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Post by Deleted on Jun 3, 2020 6:29:46 GMT
I watched a youtube vid of a guy doing a group test of those things - major variance in price, and also results - most of them were absolute garbage.
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Post by Deleted on Jun 3, 2020 8:19:06 GMT
I've got the original Motorola conductance tester. Moving needle type.
I expect the cheap ones might be a bit pointless as you suggest.
Their main use is to allow garages to sell new batteries in place of not quite so new ones. A bit like the part worn tyre situation I guess.
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Post by Telemachus on Jun 3, 2020 15:58:49 GMT
The testers mentioned above are only useful to see if the battery could be used to start an engine. You stick a 110Ah starter battery in, you turn the key, maybe 400A flows for 3 seconds before the engine starts. That is 0.3Ah. So a starter battery just has to be able to provide a high current for a very short period of time, it doesn't need to have significant capacity.
Whereas a leisure battery needs to be able to supply a modest current for a very long time - the measure of its usefulness is the remaining Ah capacity. The only way to measure that is by a discharge test. You fully charge it, you put on a load of known amps (say 10A for a 110Ah battery), and you time how long it takes for the battery voltage to fall to 10.5v. You multipy the discharge current by the number of hours it lasted, and that is the Ah capacity of the battery.
The above gizmos are totally unable to give you any clue about the capacity of the battery, only its ability to deliver a high current for a short time.
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Post by Deleted on Jun 3, 2020 17:24:38 GMT
Is that a 'drop test' ? The battery place has a great tool that does just what you describe Telemachus ... no idea what it's called or how much it would cost ... I just let them do it for me Rog
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Post by Telemachus on Jun 3, 2020 17:45:59 GMT
Is that a 'drop test' ? The battery place has a great tool that does just what you describe Telemachus ... no idea what it's called or how much it would cost ... I just let them do it for me Rog A drop test is checking that the battery can produce a large amount of current for a short time, telling one that it will start an engine. It has nothing to say about the capacity of a battery for domestic use (ie small amount of current for a very long time). If someone selling you a battery for leisure use, uses a drop test to show you that the battery is in good condition, they are either trying to deceive you or they are thick.
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Post by JohnV on Jun 3, 2020 18:23:58 GMT
prefer a float test ..... but most canals are not deep enough
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Post by Jim on Jun 3, 2020 18:51:58 GMT
prefer a float test ..... but most canals are not deep enough Perhaps your bottom is too big?
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Post by Deleted on Jun 3, 2020 21:16:01 GMT
The above gizmos are totally unable to give you any clue about the capacity of the battery, only its ability to deliver a high current for a short time. Except that they are able to do this because they measure the battery's internal state ie whether it is nackered or not. A "Leisure battery" is just a lead acid battery it's not some kind of special item. You can start engines with a "Leisure battery" if you wish.
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Post by Telemachus on Jun 3, 2020 21:58:03 GMT
The above gizmos are totally unable to give you any clue about the capacity of the battery, only its ability to deliver a high current for a short time. Except that they are able to do this because they measure the battery's internal state ie whether it is nackered or not. A "Leisure battery" is just a lead acid battery it's not some kind of special item. You can start engines with a "Leisure battery" if you wish. No they don't. Well, they measure the battery's internal state only in that they detect whether or not the battery is capable of pumping out enough current to start an engine. They have not insight into the AH capacity of the battery. If you still insist they do, pray tell how they know. Other than by the label on the device which promises it does, as well as promising that you will have eternal youth if you plug it into your brain and an extra large nob if you connect it to your genitals no doubt.
Yes I know what a leisure battery is dumdum. The term, when applied to el cheapo batteries, arises from the usage of the battery, not from the constuction of the battery. That said, you can get "proper" leisure batteries that have thick plates, thus are less able to give very high currents for short periods and more able to give sustained modest current to a low SoC that would rapidly trash a re-badged starter battery. Not good as a starter but good as a leisure battery.
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Post by Deleted on Jun 3, 2020 22:09:38 GMT
It might not give you the actual Ah rating but it will show whether the battery is generally nackered or not compared to another similar one. Of course this would require new and used similar batteries to be fair. as you don't seem to know how they work this is actually quite an interesting Q&A and does mention that UPS systems operators use conductance testing. Not just car batteries. www.skylark.co.uk/CONDUCTANCEQ-A.htmAdmittedly this is with professional conductance testers not Micky mouse Chinese things. "Various test data have shown that at low frequencies, the conductance of a battery is an indicator of battery state-of-health showing a linear correlation to a battery's timed-discharge capacity test result. This can be used as a reliable predictor of battery end-of-life." Conductance testers do work on Lead Acid batteries of all kinds " Why test conductance? A. Through years of laboratory and field-based research, conductance has been found to correlate directly with battery capacity as measured in a timed discharge test. This correlation is nearly linear, meaning that if conductance can be measured, timed-discharge capacity can be predicted. Since voltage and specific gravity testing are not predictive, timed discharge testing is very time-consuming and expensive, and impedance testing does not correlate directly and linearly with timed discharge capacity, conductance testing is a very effective and economical alternative." Like I said it's an interesting Q&A and I don't reckon it's marketing bollocks.
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Post by Deleted on Jun 4, 2020 2:18:19 GMT
The testers mentioned above are only useful to see if the battery could be used to start an engine. You stick a 110Ah starter battery in, you turn the key, maybe 400A flows for 3 seconds before the engine starts. That is 0.3Ah. So a starter battery just has to be able to provide a high current for a very short period of time, it doesn't need to have significant capacity. Whereas a leisure battery needs to be able to supply a modest current for a very long time - the measure of its usefulness is the remaining Ah capacity. The only way to measure that is by a discharge test. You fully charge it, you put on a load of known amps (say 10A for a 110Ah battery), and you time how long it takes for the battery voltage to fall to 10.5v. You multipy the discharge current by the number of hours it lasted, and that is the Ah capacity of the battery. The above gizmos are totally unable to give you any clue about the capacity of the battery, only its ability to deliver a high current for a short time. Tomsk's enquiry was concerning whether or not a battery was still functioning as desired or was instead scrap. Thats all. Both those tests provide an answer to that question quickly - very quickly in the case of the second gadget and with a degree of accuracy beyond the 'charge it up and leave it for a bit' method (which is also a valid test). You could do the hydrometer test to get much the same answer IF you can insert the tube (which on many LA batteries these days you of course cannot). But perhaps you would prefer the one that does the two-step as well. PS is a multimeter a 'gizmo'?
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Post by Andyberg on Jun 4, 2020 4:23:59 GMT
Like I said it's an interesting Q&A and I don't reckon it's marketing bollocks. Thatβs all marketing bollocks! π
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Post by bodger on Jun 4, 2020 6:57:51 GMT
I don't know what al the fuss is about. I have 6 cheapo leisure batteries to power my leccy boat and occasionally do a discharge test. Each battery is connected to a car headlight bulb (keep the bulb clear of anything inflammable - it gets very hot!) and left for, say, 5 hours. Before the test and after the test (allow an hour for the battery to settle down) I measure the battery voltage. A simple calculation using the bulb's wattage will show how many Ah have been consumed, which can be compared with the chart of battery voltage against % discharge. Working backwards, the apparent Ah rating of the battery can be calculated - this will indicate if the battery has lost significant capacity.
Isn't that all the the OP is asking?
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