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    kWeld - "Next level" DIY battery spot welder

    The kWeld will work with up to 30V but 12V is ideal. Here's a quote from the designer on this subject: "Desired current is 1500A. The resistance of the kWeld system is roughly 3.2 milliOhms (stock cables). The weld spot itself contributes another 1 milliOhm typical. This gives 4.2 milliOhms...
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    kWeld - "Next level" DIY battery spot welder

    The Drain to Source voltage is not 12 V when the MOSFETS are fully on. They would measure about 0.183 V @ 2000 A (2000 A / 6 FETs * 0.00055 Ohms). You should be looking at the "limited by Rds(on)" part of the graph.
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    Copper Strip DC Ampacity

    Circuit board trace width calculators are good for this. I'd keep the internal layer temperature rise under 20°C for the hottest days. Trace Width Calculator
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    kWeld - "Next level" DIY battery spot welder

    Read and understand the power supply requirements detailed on page 7 of the operating manual.
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    kWeld - "Next level" DIY battery spot welder

    I see the gold coloured negative terminal on pictures of protected NCR18650B cells. Are your cells 70 mm long instead of 65 mm? If so, you're trying to weld to a printed circuit board. It would be very thin copper plated with nickel, then gold.
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    Low Profile Connector Recommendations

    You could use the contacts from an EC3 connector and insulate them with heat shrink tubing. Similar 3.5mm bullet connectors are available without a housing but they often don't list the maximum AWG.
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    Replacement cells for automatic lawnmower battery packs

    Even if a 10A cell doesn't overheat, the voltage may sag too low when the blade spins up. The BMS low voltage cutoff may be triggered or the guidance processor may lose power.
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    Replacement cells for automatic lawnmower battery packs

    I would assume the designers had a good reason for choosing a 20A cell over higher capacity. The EVE 25P is a good budget replacement. I'd go with Molicel P30B if money was no object, they were available, and they fit in the cell holders.
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    Battery newbie in over his head.

    There are some transistor shaped solder pads missing components near the switch input, so I'd say the switch capability is missing from this BMS. I'm never going to recommend cutting a safety monitoring feature to disable the output.
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    help with identifying this fuse

    From estimating the dimensions, it could be any one of these: https://www.digikey.com/short/qf3rpvzb
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    such a thing as emmo 48v/50ah lead acid

    50 amp output is not 50 ah capacity. This battery is available in lead-acid with 20 ah capacity.
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    I guess I need to make 72v 35ah battery pack

    The bare minimum is 800 A for proper functioning. 1200 to 2000 A is the recommended range. 496 A is inadequate. That battery is very tired.
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    13s4p/48V/21700 DIY Questions - Samsung 50E okay for 750W BBS02? [Edit: Why is nothing in stock?]

    The 50E is perfect for this use case. I pull peaks of 7.5A from the 50E in an e-bike (30A @ 4P) and they don't even get warm. The cells go in and out of stock all the time. At least you know you are getting fresh ones!
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    Is there an equation for Battery interconnects

    I use a trace ampacity calculator for high current printed circuit board design. You may find it useful. The source code could probably be modified for nickel or steel as well.
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    Battery Capacity

    It's an unusual approach. I mentor budding electrical engineers who ask the wrong questions all the time. I always appreciate too much information over what they think is a concise question.
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    Battery Capacity

    The 50A and 25A packs use different cells, which is very relevant. I can't find the 20A pack. For your low current requirements, I recommend the 25A pack made with 50G cells. It will give you nearly identical run time and last for many more charge cycles. The 50S cells have a much shorter lifespan.
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    Battery Capacity

    Do these three packs have the same cells but differently rated BMS modules? If so, the highest current rated BMS will have the lowest resistance and be slightly more efficient for more ride time.
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    Battery Capacity

    Go with the highest energy density cell that supports your current requirements for the greatest cycle and calendar life. Read the last paragraph here.
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    Over 77 Fahrenheit ruining batteries?

    That temperature derating data would be better represented by a graph. Imagine a sloping line from 3C @ 25°C to 1.5C @ 55°C.
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    30S bms? (4,2 x 30)

    Here's one from my go-to supplier: https://www.lithiumbatterypcb.com/product/20s-21s-22s-23s-24s-25s-26s-27s-28s-29s-30s-lithium-battery-smart-bms-with-current-of-40a-to-100a-constant-
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    How to calculate maximum battery discharge current/rate?

    That's correct!
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    How to calculate maximum battery discharge current/rate?

    These cells are a bit of a mystery but test similar to the Samsung 50E2 by Mooch. A continuous rating of 10A and short peaks of 15A can be expected. Multiply that by 21 for your pack capability, assuming your BMS/collector busses/wires/connectors are up to the task. The pack capacity would be...
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    Are those blue batteries good for 1800w brushless motor build?

    If you're talking about UB12120 batteries, you'll get about 5 minutes runtime at 1800W, according to the datasheet. I suggest taking some time to save up money and learn more about batteries. I have 20 years of electronic design experience and still spent 2 months learning and planning my first...
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    21700 : Voltage [V] vs Charge (Capacity) [A•h] Discharge Curve : Samsung 50E, LG M50LT

    Samsung 50E test results LG M50LT test results 18650 Battery Store / Bulk Battery only sells new grade A cells. I have a very well matched pack made with their 50E2 cells.
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    Automatic 80% soc cutoff charger?

    LUNA CHARGER 48V ADVANCED 300W EBIKE CHARGER I have a 600W version of this and cannot for the life of me find where to buy another
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