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Lifeblue uses 12 parallel 25 Ah cells (per "cell") in their 300 Ah batteries.

NREL recently changed the file format of the hourly solar data that they provide for your choice of location. Rather than re-write the whole spreadsheet, I added a sheet that moves the new data into the format required by my original spreadsheet. This sheet is called Kludge. Also, because...

The National Renewable Energy Laboratory in Denver that makes PVWatts available has changed the hourly solar data file format making it unusable in this spreadsheet. I will work on fixing this and update when this is done.

Charging to less than the battery manufacturer's recommended voltage is a bit risky unless you know the balancing parameters for the BMS. Some BMS do most or all of the balancing at a voltage not much below the recommended minimum bulk/boost voltage. With these, charging to less than the...

Lots of detail here ... skip to the last paragraph for the crux. Keep in mind that no SOC monitor on a LiFePO4 can simply measure SOC. All it can do is track changes in energy in and out over time and accumulate those. So, that 83% reading only tells you there has been some charging since...

Really need more information to help. I think key is what voltages you are seeing and under what conditions. I.e., are you using voltage readings to back up the SOC readings. And confirm that the four stacked batteries are remaining in balance.

I did this search (link below) and the first image shows capacity vs temperature. It's a bit difficult to use but was the only one I found in a quick check. I also found in other threads in this forum the suggestion that rated capacity of Eve cells is at 25C. It seems that at 15-20C a cell...

I wonder, are you folks adjusting for cell temperature when you do the capacity test? Cooler LiFePO4 cells have significantly lower capacity. It would take 0C or 32F to get close to a 10% capacity drop, but a cool battery might be a few percent low. Does putting a few cycles on the battery...

Are there still non-inverter units on the market?

If I'm reading correctly, you are saying that a faulty low temperature alarm is the problem. And I gather it is curtailing charging prematurely? If that's the case, and you are comfortable working inside of a battery, you could replace the BMS with an after market one. Or try just detecting...

It's not all in the amps (power draw). SEER is a seasonal rating and is based on miniscule amount of cooling (a lot of cycling) in some hours (spring and fall) and running hard mid-day for cooling in summer, less in evening, etc. And is based on Denver weather. SEER is effectively a cooling...

This is available in the "submittal" sheets that each manufacturer must provide. A search should turn up the submittals for each brand and unit. For example ......... https://www.fujitsugeneral.com/us/support/downloads/halcyon/submittal-sheets.html

The Mitsubishi units were a bit costly per K of capacity, but that SEER 33 and small size and DIY made the deal. All mini splits can "modulate" down to a level that can be as low as 1/6 of rated capacity (a Gree with SEER 38 was the first one) though more typical is 1/4 of rated capacity...

I'm just east of Sacramento in the very hot Sacramento Valley. 30 days over 100F in summer and average January low is 24F. When I went all-electric with mini-splits, I installed two 12K single-head units in the great room, one at either end. Those are SEER 29 and do somewhere over 90% of my...

The paper you referenced is clearly the source of the images I linked to above (that I randomly found on the web). It would be nice to have some other reference with similar results. I found a half dozen papers that might contain that but most were not accessible without some login or didn't...

You nailed it. I keep my "reconnect" at 13.4V to be sure I get into bulk and to 100% each day. Since the full charge resting voltage of a LiFePO4 battery is about 13.34 volts, 13.4V does the job. More than you wanted to know: The voltage read out by my BMS (sum of the four cell voltages)...

I have found LFP short-circuit current graphs. Enter "lithium battery short-circuit current" into your search window and click on "images" and look for something like this link...

Yup. 17ka at 48V could certainly cause some fireworks. Not something to be taken lightly!!! I think I'm glad I stayed with 12V!!! And 400Ah.

Replying to Ampster and Matt .............. My point was just just as I stated (and not included in your extraction). 12 pages of discussion of fuse types and their operating characteristics and ability to quench an arc, and no mention of how a Class T operates or one of it's significant...

Lots of discussion of fuse types in this thread but nothing on how Class T fuses work or that they are "current limiting." Or that BMSs are current limiting on high short-circuit currents. A Class T fuse, is, or used to be, filled with sand that surrounds multiple parallel fuse elements...

It sure would be nice to have some references for this assessment. I've long assumed that the BMS leads and circuit board traces and FETs will limit current considerably, but I'd like to see a BMS maker state this based on tests.

katsikas, I'm a bit puzzled. You mention charging at what looks to be a bulk level for the solar that you have (though it could be from the 13.8 float if the battery is severely discharged). Are you watching close enough to know that the MPPT charger is not going into bulk?. Voltage will...

The answer depends. A Class T fuse on the inverter isn't a bad idea, but makes only limited sense if there's significant short-circuit exposure (wire) between that fuse and the battery or batteries. A severe short-circuit in the inverter or more likely on the incoming terminals of the inverter...

Right you are on the AC rating. However, these are "current limiting" fuses (when current is high enough) which means they open in a couple of milliseconds or less. As such they "chop" the rising current quickly and usually well before it hits full or peak level. If you compare the current...

I agree. I ran my Overkill BMSs just below their 130 amp setting for 20 minutes, then increased the load slightly to force a disconnect. I checked unit overall temperature (it was warm to the touch but not hot) and declared them ready for service.

Indeed. My son has 2 kW of solar on his old motor home, along with a 9,000 BTU-hr mini split (EER=16.5). On sunny days his batteries are usually topped off early enough to get a few hours of heating in before the sun is down. This is in fall and spring on the CA west coast. If the forecast...

I think it's credible to do some analysis on winter heating potential to evaluate options before investing. PVWatts via the "NREL International" solar data base can provide hourly solar and ambient temperature data. Combining this with known or projected loads other than space heating would...

See title

This is a significant update from the original spreadsheet ("workbook"). It has more sophisticated propane heater motor energy use calculations (including morning warm-up following heat night set-back). 12V fridge duty cycle is a function of ambient temperature (outside if no space heating...

I'd say it depends ..... on what you paid. If you paid a grade B price and the cells all test out as usable, you may wish to keep life simple and live with them. If you paid a grade A price you may want to raise a ruckus. I haven't been keeping up, but 310 Ah are new to me. I only recall...

CORRECTION: ..... Change that 14 NM to 4 NM. Also, after measuring voltage drop in the #2 welding cable at my max charge current (60 amps), I remade the jumpers with 1/0 welding cable. The #2 voltage drop was up around 5 mV. Not large in the overall scheme of things, but when the target...

That's unfortunate. And I guess I'm not dying.

I'm probably too far outside of the box here, but a couple of alkaline batteries in series with the voltage sense lead would raise that 8 volt threshold to 11.2V. Three would take it to 12.8V. If your system runs above 13.0 V except at idle, three 1.61 volt alkaline cells would do the job...

Thinking outside of the box a bit .... I presume this large storage system will involve a solar array. How about a solar panel or two charging/powering the 12V system. I.e., a couple of panels and a solar controller. Solar controllers are generally up around 95% efficient. Simple and small...

I've changed my mind on some of the above. My old as dirt burnishing files seemed a bit course for the aluminum terminals. I.e., leaving the terminal surface a bit rough (as though I had used too course sandpaper). I was careful to use a finger centered and lightly pressed on the terminal to...