The discharge resistance decreases. The charge resistance increases.
On Wed, Jun 7, 2023, 3:14 PM <dmmoff...@gmail.com> wrote: > I get what you’re saying. Sounds like the worst outcome I can get is > warm batteries. > > > > Where I’m confused is I’m reading that resistance decreases as state of > charge rises (and also decreases from heat). If resistance is dropping, > and we’re at a constant voltage, why is the current also dropping? I’ve > certainly seen a car battery charger do that, so it’s not that I’m > disbelieving it, but what’s the mechanism causing it? > > > > -Adam > > > > > > *From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Chuck McCown via AF > *Sent:* Wednesday, June 07, 2023 2:03 PM > *To:* AnimalFarm Microwave Users Group <af@af.afmug.com> > *Cc:* ch...@go-mtc.com > *Subject:* Re: [AFMUG] battery overcharging > > > > Another metaphor would be inflating a tire to 32 lbs with the compressor > pressure set to 32 lbs. Once the tire is full the air will stop flowing. > > > > *From:* Forrest Christian (List Account) > > *Sent:* Wednesday, June 7, 2023 11:58 AM > > *To:* AnimalFarm Microwave Users Group > > *Subject:* Re: [AFMUG] battery overcharging > > > > Ignoring the overvoltage for a minute.. > > > > A normal battery, when charged at a normal voltage, will take less and > less current until full. It doesn't matter how much current is available, > it will only take what it needs. Generally you want to limit the current > based on the size of the array, but that's for the start of charge, but > the end of it. That is, an empty battery array will take all the current > you can give it, and too much can cause damage to the battery and maybe > wiring. > > > > As far as the overvoltage goes, that's far more dangerous as overvoltages > tend to cause "boiling" of the battery which is just another way to say > that the battery is producing lots of hydrogen and oxygen which can cause > explosive atmospheres around the battery, or in an extreme case can cause > sulphuric acid steam to escape the battery. Combine this with no > overcurrent or time limit and at the bare minimum you should expect swollen > and destroyed batteries. > > > > On Wed, Jun 7, 2023, 1:05 PM <dmmoff...@gmail.com> wrote: > > So I was looking at a rectifier config and trying to imagine the worst > possible thing I could do. > > > > With some creativity I could start an equalizing charge that will run for > 48 hours at 58.5 Volts. Normally it would stop when charge current hits a > configurable fraction of the C10 Ah rating of the battery, but by > intentionally misconfiguring the size of the battery and that fraction of > Ah I could ensure that the equalizing charge runs until the maximum time > limit…..which I can set as high as 48 hours. > > > > I could also disable the battery current limit, disable the over temp > shutoff, and disable the temperature compensation. > > > > If I’ve disabled the current limiting feature in the rectifier, what > determines the current that will go into the battery when I’m on a constant > voltage charge? The charger can do up to 100A, but would it put 100A into > the battery for the full 48 hours, or would some other factor limit it? > > > > The spec sheet for the batteries lists an internal resistance of 3 > *milli*ohms. > V=IR tells me they could take thousands of amps at 58.5V. Is there any > other limit here besides resistance. If nothing else stops this machine > from dumping it’s full 100A into the batteries for 48 hours I’m pretty sure > I could start a fire or explosion with this rectifier if I wanted to. I’m > not trying to commit an act of sabotage by the way, I’m just wondering if a > creative idiot could do something terrible. > > > > > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > ------------------------------ > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
-- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com
