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  1. G

    Question about regenerative braking

    Also, when you do have a regen brake, the numbers pan out differently. If it's set up correctly, it'll start regenerating before the mechanical brakes engage, so all the brake energy goes to regen when you brake gently, and the mechanical brakes only engage at all when you brake heavily.
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    "Copper/nickel sandwich" buses for series connections

    That looks neat. .2mm is probably overkill though. I used .1mm on the cells and .15mm for interconnects. I only used .15mm where I could solder it, as it didn't weld well with my capacitor welder. With .1mm I had no worries about the energy deposited into the cell when welding. Edit: I also used...
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    "Copper/nickel sandwich" buses for series connections

    Looking good. Maybe I'll try lanthanated W when my current stick runs out. Do you know why that one was recommended? Did you have any issues with using it? My only issue (after increasing the clamping force on the electrodes) is copper sometimes sticking to the probes and having to be ground...
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    BMS for regenerative braking. How do i know ?

    I can happily report that my build (20s17p battery for a 3kW EU moped) is now complete, and that the common port BMS handles regen without any issue at all. The only annoying thing is that the event log of this smart BMS fills up with "charging" events for every time I brake. Edit: if you want...
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    "Copper/nickel sandwich" buses for series connections

    I'm using 1.6mm diameter sticks, and I found that when I shortened the electrodes and increased the clamping force, I could go from a 41 ms to a 1.5ms welding pulse. Before, there were shims around the electrodes, and tightening the screws squeezed the shims more than the electrodes. Without the...
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    "Copper/nickel sandwich" buses for series connections

    I've had quite good results now with the tungsten electrode+0.1mm copper foil, though it took some experimentation and tweaking. I'm using a pure tungsten TIG stick. Which is quite brittle, but can be cut and polished with a Dremel cutoff wheel without cracking. Here's the beginning of the...
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    BMS for regenerative braking. How do i know ?

    It has a common port for power and charging, so it should be able to treat the regen voltage as a regular charging input, provided the regen current doesn't exceed the max charging current. That's my guess; I've not tested this myself yet. I'll try it in my next build.
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    BMS w.bluetooth - question

    The ?? wires are probably for an NTC thermistor or a high temp cutoff. If they're shorted, it's a cutoff.
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    "Copper/nickel sandwich" buses for series connections

    Here are a couple of rows of test welds on some junk cells using 1.6mm pure tungsten TIG stick probes. The offset welds on the lower row are just an artefact of sloppy cutting of the test ribbons. The upper row of welds is on the positive pole. Edit: my inspiration for trying tungsten came from...
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    "Copper/nickel sandwich" buses for series connections

    I used both at the same time; 0.13mm nickel-plated steel on top of 0.1mm copper to be precise. I tried infinite and non-infinite slots in only the copper, only the nickel, and both. I got good welds sometimes, but not consistently, on used cells with some nickel remnants. The best welds were...
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    "Copper/nickel sandwich" buses for series connections

    I never could get the sandwich method working reliably with my capacitor-based spot welder and copper electrodes. I suspect that this welder is a bit anemic, because even at the highest pulse lengths and infinite slots in both the copper and the nickel-plated steel, the copper just didn't stick...
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    Air-cooled for 18650 Li-ion battery pack

    Conducting heat out safely is probably easier than getting air in safely. If you want a meaningful amount of air to enter through a filter, you need a pretty beefy fan. Think vacuum cleaner territory. And you still need to keep moisture from condensing inside. Oil immersion cooling would...
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    General Question about charger

    For SLA, you can do without a BMS, and connect the charger directly to the batteries. They're less explody and can handle overcharging. Those and up-front costs are pretty much the only advantages of SLA. Converting to Li-ion would give you more range AND less weight. I've done several...
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    Dissimilar batteries:

    Switching between packs is the easiest. Paralleling packs with the same voltage using diodes comes next. You can also diode parallel packs with different voltages, as long as you accept that one will drain before the other, each one has a low voltage cutoff, they're charged separately, the load...
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    Looking for recommendation: 20s 40-60A smart BMS with 5 or more NTC inputs

    They're tiny bimetal clickers (which should make them as mechanically distinct as microswitches or tactile pushbuttons) with a guaranteed max contact resistance after 10k clicks. I'll put all of them (NC contacts) in series and connect them to the on/off input of the BMS. If any thermostat trips...
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    Looking for recommendation: 20s 40-60A smart BMS with 5 or more NTC inputs

    Useful information, thanks. The voltage drop at 100mA balancing current would be <.005V, so measurements shouldn't be too affected, and I'm going to use a smart BMS (not that this guarantees which situations it can handle), but I understand it's safer overall to keep this fusing separate, so I...
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    Looking for recommendation: 20s 40-60A smart BMS with 5 or more NTC inputs

    Thanks for the tip; I didn't realize bimetal switches came in such small size and cost. Those should work. I could save on wiring by connecting them in series with the balance wires, so that if any one of them trips, the BMS thinks the battery is off kilter and shuts down. That'd give me four...
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    Looking for recommendation: 20s 40-60A smart BMS with 5 or more NTC inputs

    I've considered a separate temp cutoff, and it's still an option, but if I can have it integrated it's better. If you have a separate one to recommend, I'm interested. One of the BMSes I'm considering has a on/off input, so a separate cutoff could signal to that instead of being capable of...
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    Looking for recommendation: 20s 40-60A smart BMS with 5 or more NTC inputs

    I'm building a 20s Li-ion moped battery divided into 5 IP67 waterproof boxes of 4s each, and am looking for a BMS that can measure at least one temperature in each box. I have 4 unused pins in my chosen balance connector to each box that can be wired for temperature sensing. I've looked at Daly...
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    Troubleshooting ebike battery

    If you try to draw any power from the 25V output, does it deliver power, or does it collapse to 0V while delivering less than a mA? If it collapses, this means the BMS has shut off the output. IDK why, but some BMS models will show half the battery voltage on the output when they have turned...
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    using Liitokala Lii-500

    Charge: charges the battery. It will display the number of mAh put into the battery. Fast test: drains and then charges the battery. It will display the number of mAh drained from the battery. Nor test: charges the battery, drains it, and then charges it again. It will also display the number of...
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    BMS

    The BMS normally handles overvoltage, undervoltage, overcurrent and short circuit in addition to balancing. Check out the specs to see that the one you buy actually does all that. 36V is the nominal voltage, which is the voltage when the battery is about half full. You ned 42V to get it...
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    looking for recommendations for BMS upgrade

    Best of luck to you, hope the cells are fine. The auction listing says lithium iron, which means LiFePO4 (Lithium Iron Phosphate). All voltages point to this (3.5V balancing, 2.0V LV cutoff, 48V 16S = 3V nominal per cell). All rechargeable lithium batteries are really Li-ion batteries, but in...
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    looking for recommendations for BMS upgrade

    Start by discharging the cells down to 3.6V. This voltage is safe bor both Li-ion and LiFePO4. Then check with the manufacturer to see what you actually have got. I don't know if it's possible to charge LiFePO4 to 4.1V cell voltage, or if the voltage is an indication that you have Li-ion after...
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    3D printed copper compression battery

    Both tape and rubber (natural an silicone) ages with heat and time. Scotch 8884 is made for securing objects during shipping, so no regard has been taken to long term stability. The best you can do is to do this reasarch yourself. Get the tape and the rubber bands you want to use, and find the...
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