I gave up on LVD. First, especially on solar, I build a large enough batter that it should never get that low. If it does, I want the system to keep working with the hope that the sun will soon be out. And you need to keep your telemetry running even if the batts are low. Ended up tripping so few times at the 26 or so sites we had them in and when they tripped they never came back alive gracefully so I eliminated LVD from the picture. Just engineer it with the right size batts and add generators.
From: Adam Moffett Sent: Wednesday, December 02, 2015 11:39 AM To: [email protected] Subject: Re: [AFMUG] Calculating battery bank size There seem to be different opinions on the appropriate cutoff point for LVD also. I recall a 12V Morningstar solar controller had an 11.2V LVD. On one of the common DIN UPS modules it's 10.9V (Traco I think, though I might be muddling that with a Meanwell spec sheet in my head). That's roughly speaking 75% discharge vs 90% discharge. Either way it affects your run time and you ought to plan on it. Some here have expressed that they would rather buy new batteries than be down, so they avoid LVD completely. On 12/2/2015 1:24 PM, Ken Hohhof wrote: A good way to avoid confusion is to convert to convert to watt-hours. I’m assuming when you say 400Ah, you probably have 12V batteries and are adding up the Ah ratings of all the batteries. Like maybe 4 batteries, each 12V and 100Ah. Although there are certainly other common battery voltages like 2V and 6V. So I look at a typical 12V battery rated 100Ah, multiply them and get 1200 watt-hours. If you have 4 of them, it’s 4800 watt-hours no matter how you hook them up parallel, series, or some combination. That’s how much energy is stored in those batteries when fully charged. So in rough numbers, a 500 watt load will drain a ~5000 watt-hour battery bank in ~10 hours, assuming you are running the loads directly off the batteries, with no conversion loss due to an inverter or DC-DC converter. And as someone pointed out, you need to check what depth of discharge the 100Ah is rated at. If that’s 100% discharged, the battery life is going to be severely degraded. Also likely you may have a low voltage disconnect (LVD) that will disconnect the loads before you get to that point, in order to protect the batteries. From: Bill Prince Sent: Wednesday, December 02, 2015 12:05 PM To: [email protected] Subject: Re: [AFMUG] Calculating battery bank size wrong. bp <part15sbs{at}gmail{dot}com> On 12/2/2015 10:04 AM, Josh Luthman wrote: If you do 4x 12v 100ah batteries and do 24v it's twice the time as 48v Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Dec 2, 2015 1:01 PM, "Bill Prince" <[email protected]> wrote: What voltage? bp <part15sbs{at}gmail{dot}com> On 12/2/2015 10:00 AM, TJ Trout wrote: How long will 500w load last on 400ah?
