a single proper 100-0 cycle or occasional full cycles shouldn't have any meaningful negative impact to the best of my understanding.I see on youtube everyone seems to do a %100 discharge to check battery capacity. Does this not harm a new battery to drain it like that?
The tests you see are discharging until the internal Battery Management System (BMS) does a low voltage cutout. The individual ceslls inside the battery are not being 100% discharged - only down to the cutoff voltage set in the BMS.I see on youtube everyone seems to do a %100 discharge to check battery capacity. Does this not harm a new battery to drain it like that?
Very true when it comes to packs with the BMS installed but some people are doing it with individual cells.The tests you see are discharging until the internal Battery Management System (BMS) does a low voltage cutout. The individual ceslls inside the battery are not being 100% discharged - only down to the cutoff voltage set in the BMS.
I believe the cheap little testers with the fans/heatsinks many people use for capacity testing single cells do have a configurable low voltage shutdown so they can be set to automatically disconnect. Personally I would want to verify it works correctly and is accurate before trusting it, but then this is a good idea with a BMS as well.Very true when it comes to packs with the BMS installed but some people are doing it with individual cells.
It's probably best to have a discharge system that cuts off at a certain voltage when doing this.
what the voltages were for the state you want.Would DL24 work to test capacity for AGM batteries?
@meetyg - I just stumbled upon this video from Will Prowse about Battery capacity test and the first pinned comment says that this cutoff voltage/low voltage protection doesn't work. Can you please share info if it works in your case? And if it is working, what version of DL24 are you using?The DL24 is programmable, so I don't see why you couldn't use it with SLA batteries.
You just need to set proper cutoff voltage for your batteries, and probably run it in constant current mode.
Thanks for the chart @chrisski. Last night I did some reading about DoD and battery cycle life, and in this article read the following:Going to 50% gets 1500 cycles, but going to 10% gets you 100 cycles
Here is the image that this statement was referring to:The yellow region past 50% is not overly damaging to your batteries, but consistent cycling to this level will shorten their lifespan. Clearly, the red region past 80% should be avoided unless absolutely necessary, say in case of emergency.
How does one add more batteries to the existing ones, if capacity testing is not worth it? Or the statement that low capacity batteries would damage the new ones isn't true?To me I read between the lines saying capacity testing a lead acid battery is not worth it.
I'm using the one with the color display (DL24P)@meetyg - I just stumbled upon this video from Will Prowse about Battery capacity test and the first pinned comment says that this cutoff voltage/low voltage protection doesn't work. Can you please share info if it works in your case? And if it is working, what version of DL24 are you using?
Thanks for the chart @chrisski. Last night I did some reading about DoD and battery cycle life, and in this article read the following:
Here is the image that this statement was referring to:
View attachment 100559
Although this is a chart for wet/flooded batteries, does this also translates for SLA batteries? If so, then it shouldn't be a problem to discharge it once to let's say 20%?
How does one add more batteries to the existing ones, if capacity testing is not worth it? Or the statement that low capacity batteries would damage the new ones isn't true?
I can’t say. I would only say that if it were me, the only time I’d do the capacity test would be if I could replace the entire bank if things went wrong.Although this is a chart for wet/flooded batteries, does this also translates for SLA batteries? If so, then it shouldn't be a problem to discharge it once to let's say 20%?
I’ve done this two years and instead of adding additional capcity with lead acid, I went to lithiums because what I researched said the older batteries drug down the newer ones. With an RV build, I also needed less weight.How does one add more batteries to the existing ones, if capacity testing is not worth it? Or the statement that low capacity batteries would damage the new ones isn't true?
There is a notion that internal resistance is related to capacity, but this is false. The resistance of modern lead acid and lithium-ion batteries stays flat through most of the service life.