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https://diysolarforum.com/threads/do-not-discard-a-dead-victron-mppt-100-30-or-its-kind.23289/

I'd second the suggestion for an aluminum heat spreader. To reliably read the internal temperature of the battery, you can epoxy the thermistor inside an (uncrimped) lug and add it to one of the battery terminals. Don't trust tape.. if the thermistor falls off it may read as cold while the...

Hard to see with the leaves there but it's maybe a GFCI?

Filling the center hole with caulk is another method to quiet (but not totally silence) those buzzers, and is a little more effective than tape.

The reason for my comment was prior experience with PLA-printed parts melting/warping in a hot car. Reprinted in ABS and those parts held up fine. YMMV

Looks great but I would not personally be comfortable with the choice of PLA. If a modest amount of heat is generated by a bad connection and/or being in a hot vehicle, those parts could start to warp or even liquify. ABS seems like a better material for this application.

Shouldn't it be possible to at least partially correct the power factor with an appropriately selected capacitor? e.g. https://electrical.theiet.org/media/1687/power-factor-correction-pfc.pdf

You probably want DDP, not DAP

IMHO, throw those alligator clips in the trash. The contacts are the flat, round surfaces on the battery itself. The stud is just there to provide a means of clamping something (e.g. a lug) against the contacts. If you care at all about the quality of a measurement you're taking, you ought to...

This looks like a bad connection to me.. A poor connection is exactly what would cause it drop out like that and then pop right back up to where it was before as the connection improves (through subtle thermal expansion/contraction), especially if you are using a 2-wire setup as opposed to...

I believe you are looking at the specs for LTO, not LFP. The relevant table is here (from Heltec's web site):

The way around this is to use a 4-wire load tester, for example the newest version of the Atorch DL24. Voltage is measured by a dedicated pair of sense wires connected directly to the battery terminals (that carry essentially no current and thus have almost no voltage drop), and current is...

P = I ^2 * R Getting the same power at 12 volts vs 48 volts involves 4 times the amperage, and power lost to resistance heating is a factor of 16 times higher. Everything is going to run much hotter, cables yes but especially terminals. It's difficult to properly implement protection with such...

During my capacity testing, I found that a poor connection at a terminal can cause heat to be produced at the terminal which is then conducted into the cell warming the whole case. Perhaps this is what occurred in the cell that failed and it then overheated the cell. It's not possible to...

Tell us about your charge termination parameters. Did you capacity test these cells prior to putting them into service as a pack?

In my case.. 61 days between payment and receipt of cells.

What loads are you planning to power with these?

Did you ask for threaded holes or welded studs?

I just started playing with my eight 280Ah cells and I'm trying to put together a test matrix so this is helpful information.. thanks. Currently testing one cell at a time and recording the discharge curve between 3.65v and 2.5v at ~17a. After that's done I'm planning to bring them back up to...

Would you be able to elaborate on your process here? I would guess it starts with formally capacity testing the pack, followed by incrementally discharging it to a percentage of that measured capacity, rest 24 hours, record voltage, repeat for each set point. That's a no small investment of time...

Thanks. Coulomb counters are high precision but have poor accuracy unless the initial conditions are well known. I suspect what's happening is that there's a coarse SOC estimation with a linear interpolation based on 6 voltages in the settings ("Single cut-off voltage", "20% Voltage", "40%...

Out of curiosity, what method did you use for top balancing?

I discovered today that for the Android app (the version from the overkillsolar web site), if you go to the Function Setting screen and then hit the "Reset Capacity" button, it will recalculate the SOC displayed on the main screen.

You decided not to top balance because the cell voltages were well matched. Voltage is a poor indicator of state-of-charge except at the very top (or very bottom). That's the whole reason for top balancing, to get above the flat part of the voltage-soc curve. Without a balanced pack, your...

Sounds like it could be poor cell connections.. remove lugs and bus bars, polish them up and try again?

There's your problem.

Nice setup, Domino. What gauge are your cable "busbars"?

Thanks for the write up. Can you elaborate on #3 (or point me to a thread)?

SOC = state of charge. The SI ACR is designed for lead acid voltages and will not perform its advertised function with LiFePO4. Rather than connecting or disconnecting when a charge source is present or absent, it will just stay permanently connected regardless unless the battery bank is...

Due to the higher resting voltage, the SI ACR (shown in your first attachment) will never disconnect from a LiFePO4 bank unless the SOC drops below 20%.

There are many resources about this already.. do a google search for "full time RV", "establishing a domicile", etc. Certain states are friendly to this lifestyle and others not so friendly. Texas, South Dakota and Florida are popular choices. Many mail services exist for this exact purpose...

Just for kicks I tried shifting the curve downward to align the testing start points on the y-axis rather than aligning the axis labels themselves. The accelerated capacity loss effect is still present but the crossover point drops to about 1000 cycles:

I'm new here.. Reviewing the datasheet I found here for EVE 280Ah cells, I was bothered that the cycle life with and without a fixture is plotted with different axes limits. So I did a crude stretch and overlay, aligning the tick marks visually to better compare the cycle performance curves on...