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    Anyone------can I safely STORE Lifepo4 battery in cold weather

    Do you have a spec sheet for your batteries? For instance, here is an excerpt from the REPT sheet on my cells. Based on this, I am planning on disconnecting everything including the BMS and just let them get cold - they might get as low as -25C.
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    3P8S 840 AH build

    I considered he Midnite breaker but used a different one for the reasons you state. The TAIXI breakers I used have a shunt trip module that has auxiliary contacts that can be wired to de-energize the shunt once it trips. Works great. As far as he SOC alarm, I was going o use a NC relay but it...
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    3P8S 840 AH build

    Well, my battery has been in operation for a few months now and the only remarkable thing is that there have been no hassles at all. I have been monitoring it pretty closely, looking for issues, using the SBMSO on-board data log as well as some additional logging I can monitor remotely. The cell...
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    What do I need to make a 600Ah 25.6v battery pack? (BMS and balancing)

    you should go to these two sites that cover Electrodacus. I used one a few months ago and am very pleased. The implementation is a bit different than the FET types. https://github.com/bdlow/sbms0 https://groups.google.com/g/electrodacus
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    Is this battery cycle life calculator correct?

    Consensus in the literature is that one cycle is the sum of how every many cycles it takes to equal 100% of the battery's capacity. For example, one day from full to 80%, another from 90% to 40%, and another from full to 70% adds up to 100% = one cycle.
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    3P8S 840 AH build

    Just a followup now that the battery has been operating for a couple of weeks. THe following is the charging cycle, it is consistent from cycle to cycle. The cell to cell delta V is under 10 millivolts until about 5 minutes before the end when one cell hits 3.55 volts. During that 5 minutes or...
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    Is this battery cycle life calculator correct?

    They mention it is based on a particular Panasonic cell, in a paper published in 2015. Couldn't access the full paper so its not clear whether or not the analysis included correlation to actual testing. However, one way of looking at lifetime is to take the manufacturer's cycle life info ( in...
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    3P8S 840 AH build

    Battery was on charge today at 80 amps. I checked the delta V between battery terminals, across the bus and diagonally. It is really hard to repeatably measure such low voltages, but by using both a YR1035 and a multimeter, I came up with a set of measurements in the range of 0.2 and 0.9...
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    3P8S 840 AH build

    The breakers trip in a sequence, first disconnecting the panels, although the time gap is a couple milliseconds. In any case, according to a discussion on the Midnite forum, it isn't an issue. I have tested the shutdown a few times without any ill effect. Fwiw
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    3P8S 840 AH build

    The BMS I chose has two levels of control, one for controlling the charging and discharging within the normal battery parameters, and another for an emergency shutdown in case things (voltage, temperature) fall into a battery damaging area. The BMS balances anytime the voltage is below 3.55 and...
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    3P8S 840 AH build

    With the belleville spring washers, torque doesn't matter. Based on the spring rate and the force I wanted at the connection, I needed to compress the spring 0.5mm; 1/2 turn on a M6-1.0 bolt. The spring compression method is much more accurate than torque.
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    3P8S 840 AH build

    Probably best to get a quote from them - prices from a few months ago might not be current. I paid right around $100/cell, delivered to Canada. I dealt with Elodie Liu, who answered everything I asked, provided me with the REPTA spec for the cells, and accepted the changes I requested in the...
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    3P8S 840 AH build

    Have you done any measurement of internal resistance (and busbar connection resistance)? Based on the IR of the individual cells, the calculated IR of the battery is 0.671 milliohms. By measurement, using the same YR1035 as I used to measure the cells, the Neg to Pos IR is 1.15, a difference...
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    Weird bus bar idea

    6061 aluminum in the annealed state has slightly lower resistance than in the T6 state, so annealing doesn't do anything negative. Regarding the cable connections, I made up these: So that the distance from the cell terminals to the shunt connection is pretty close to equal.
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    3P8S 840 AH build

    Its a stationary application, and, by my analysis, above, the complications of properly constraining the cells isn't attractive. The cells are not secured, and have a space between them so any "breathing" will not move the cells around. As I said above, time will tell. Aluminum anneals around...
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    Weird bus bar idea

    https://diysolarforum.com/threads/3p8s-840-ah-build.24602/
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    3P8S 840 AH build

    The battery is for off-grid storage, replacing a 790AH 24V Crown industrial battery that is actually working quite well but the maintenance is tiresome. The maximum charge rate is 90 amps from a Midnite Classic controller fed by 3600 watts of panels in two fixed arrays. The maximum discharge...
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