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  1. W

    better resistor, method for testing 12v lithium/lifepo4 batteries?

    I'm using a ZB2L3 battery capacity tester (all I have on hand at the moment) to test some 12v LiFePO4 batteries (4s8p A123 cells). First I used the included ceramic 5 watt 7.5 ohm resistor; it pulled ~1.5 A, got very hot (temp gun says 350 to 400+ F (177 to 204 C)), had a very unpleasant smell...
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    Powerjack inverter and charging board

    I have a Powerjack 15kw 48V to 120/240vinverter. I purchased thebattery charger board (both the 120v and 240v boards... not sure which one I willneed), but it doesn't come with instructions and I can't find anything onlineon how to install it. Anyone happen to know how to install it?
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    time of use -ish system?

    I picked up a 12kW automatic transfer switch (ATS) just because it was so cheap. I figured I could put it to use asI also have a 12 kW 48V inverter and a ton of 18650's (so I could make a DIY powerwall). How can I set it up so I can charge the battery bank from the grid/utilityduring off-peak...
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    better bins for organizing and storage during harvesting

    I'llbe processing a couplethousand of harvested 18650 cells. I started using the AkroBins to sort and store cells during processing (the 11 x 5 x 5 version, photo attached),but they only hold about 80 cells per bin and waste a lot of space if I want to store them safely. Any recommendation on a...
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    charge up to 8300 mAh, but get 6400 mAh in capacity test

    I'm capacity testing a Headway LiFePO4 38120 cell - charging puts 8300 mAh in, but capacity testing/discharging it only gives me6400 mAh (cut off is 2.5 volts). I've ran this test multiple times and get essentially the same resulting mAh's even after tryingdifferent charging current (12 A, 6 A...
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    I messed up, big spark, but not sure how

    I needed to quickly test a 48v inverter just to make sure it actually works, so I grabbed four (4) 12v batteries to put them in series. The first battery is aAGM car starter battery (automotive post terminal), the second one is a solar AGM battery (1/4" inserted screw terminal) and the last...
  7. W

    18650 for 48v powerwall - charging, discharging and currents?

    The project is a 48v 24-ish kWh 14s245p powerwall where I'm using harvested 18650 cells with around 2000 mAh. Based on my house's average energy consumption, I'm looking at roughly 215 mA of continuous current per cell. The 48v inverter I plan to get has shut down voltages at 42v (~3.0v per...
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    calculating current per cell for powerwall

    I'm losing my math somewhere and can't figure out where. I'm planning the battery config for my DIY 48 V powerwall using harvested 18650 cells. Let's say my baseline power usage is 2500 watts/2.5 kW, so 2500 W / 48 V isroughly 53 amps of current I need to pull from the battery/inverter (let's...
  9. W

    big DIY power supply

    I dabble in all types of DIY projects, butfind my 60V, 5 Abench power supply to be limiting. I do have six (6)12 V, 27 A(325 watts)server power supplies and it would be great to combine them all to get up to 72 V or162 A (1950total watts) for testing scenarios and components. I already...
  10. W

    use Li-on BMS on LiFePO4?

    I'm looking for a 16s BMS for LiFePO4 batteries, but the only ones in stock are from China anddelivery time is 30+ days. 16s BMS's for Li-on are in stock here in the states... I know there's a charging voltage difference (4.2 vs 3.6), butis there a way to use Li-on BMS's on LiFePO4, maybe in...
  11. W

    battery contact for high current LiFePO4 cells

    I have 30-ish Headway 38120 LiFePO4 cells with flat tabs/tops (not the screw style) and building a DIY battery holder for them so I can do some cell and packtesting (similar to the ones for 18650's:https://www.amazon.com/Battery-Case-Holder-4x3-7V-18650/dp/B01FSDKXRI). I was going to use D cell...
  12. W

    DIY powerwall in uninsulated garage

    I'm in the beginning stages of planningmy 48vDIY powerwall (harvest/used 18650s). I'm thinking of putting them in an enclosed rackmount server cabinet and placing thatin my detached garage which is not insulated. The garage walls are made up of6 feet of cinder blocks (pony wall) then 2 feet of...
  13. W

    why 80p for powerwall?

    I notice a lot of DIYers online (including YouTube) make 80p cellpacks/modules(/strings?) for their 24v or 48v power wall batteries. Why is 80p so common?
  14. W

    can't get bigger spot welder, can I layer strips instead?

    I picked up a couple of 38120L LiFePo4 based batteries packs(flat top Headway) and I'm trying to replace the dead cells with good spares. The batteries use0.5mm nickel strips, spot welded to make the pack (24v, 8s2p). I don't own a spot welder and the biggest readily available spot welder...
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    specs of these blue 38120 cells?

    Curiosity got the best of me and I picked up these 38120 cells off Craigslist (attached below). The seller said these were pulled from a electric forklift. Igoogled what I thought was the model number (a38120lie17) to get the specs, but got no results. Anyone happen to know the specs of these...
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    18650 in use 24/7 outside, how to prevent overheating?

    I'm building a solar panel (12 volts, 3 watts,250 mA)+ batterypowered weather station type of thing + autonomousgardeningwith arduino and sensorsat the heart of it. I need 12 volts for a couple of the components in this project as well as 5 volts for others, so I figured I'd throw 18650's in3s1p...
  17. W

    13s229p... wait, what?!!!

    So I was running numbers trying to calculate how many 18650's and which config I need to get 8 hours of battery runtime (500 Ah x48 v = 24 kWh)for my whole home. Using harvested laptop batteries and assuming the lowest capacity will be 2200 mAh I'd need a 13s229p config (about 3000 cells). I...
  18. W

    solar and battery config with 12/2 wire bottleneck?

    I'm thinking of doing a quick and dirty installation ofsolar panels on mydetachedgarage roof (roughly 20' x 12' installation area)and storage based oneither 18650 lithium ionbatteries ordeep cycle 12V sealed lead acid batteries. There's a 12/2 wire (20 amp circuit) ran from the house, buried...
  19. W

    need help figuring out Ah and watts of battery

    I picked up a handful of small 12V lead acid batteries (CSB HR 1221FW F2)and I'm having trouble figuring out the specs, namely the Ah and watts, so I can figure out what project they can be used in. The spec sheet says 12V (6 cells),21W @15min-rate to 1.67V per cell, 60/90A (5 sec) max discharge...
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    having trouble properly discharging, getting capacity

    I'm trying to get the capacity of18650cells I harvested from laptop batteries via fully charging and then fully discharging them, but the discharger stops and theresultingmAh's are much lower than the cell's rating and I even notice the resulting/resting voltages are around or above nominal...
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