Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 1 hour ago, esaj said: To be on the safe side, I'd suggest going higher, like 20-47k or such, but probably the caps should discharge pretty fast, so the power dissipation on the resistor shouldn't matter that much, unless going to really low values (a 0.25W can withstand higher power loss for a short while). I don't know the capacities of the capacitors, so I can't calculate how long it takes to discharge, but keep it there for a little while (10-20 seconds?), then check again what the voltage is. Once it's close to 0V, you can proceed with measuring the resistance. I used an led light to drain the voltage. It dropped to around 1.9- 2.0v in a matter of 2 seconds.I said in the video .9 but met 1.9v. 1 hour ago, esaj said: Once it's close to 0V, you can proceed with measuring the resistance. Probably there is a high resistance on the board, as otherwise the caps themselves should have discharged a long time ago... unfortunately then we're back to square one, what caused that huge sparking in the first place? Here is the video checking the resistance of the power leads at the main board. I used a 330 ohm resister to check the meter and it was dead on. So there is 0 resistance coming from the main board and no elevation in resistance after a few moments. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted April 30, 2017 Share Posted April 30, 2017 6 minutes ago, Rehab1 said: I used an led light to drain the voltage. It dropped to around 1.9- 2.0v in a matter of 2 seconds.I said in the video .9 but met 1.9v. Here is the video checking the resistance of the power leads at the main board. I used a 330 ohm resister to check the meter and it was dead on. So there is 0 resistance coming from the main board and no elevation in resistance after a few moments. It's possible the capacitors are relatively high capacity and the DVM resistance mode will take a long time to charge capacitor before it starts reading a resistance. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 14 minutes ago, Carlos E Rodriguez said: If you look there is no damage on the female connector. The male puns evaporated. Both male pins evaporated indicating that they shorted together. I believe my theory is that somehow during connection attemp the two male pins shorted physically. Another theory is that a smal arc ionized the air around the two male pins and that cascaded into a full blow short arc flash between the two pins. Tonprecent this, connectors need to be plugged in with commitment. If you do not slowly the arc would start and posibly cause the ionized air short. If you do it firmly the connector will be fully seated before it can form a full short. I believe you are correct on that point. My connection was not deliberate at all. Like @esaj pointed out it was like arc welder. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted April 30, 2017 Share Posted April 30, 2017 @Rehab1 do you have the tool to remove the female pins? i would like to see if the female pins have damage. If the female pins are not melted it would support the theory that the normal spark during reconnection created a plasma bridge between the two male pins before you had a chance to engage the connectors together. Once the plasma arc started the one battery pack with male pins fully shorted. 80vdc x 10 amps = 800 watts. 20amps is 1600wats. 40amps is 3200watts. Could a full short produce 100amps momentarily? 8,000watts. If the female pins have minimal damage meaning sputtering and no melted female pins like in the male, then I believe the two males experienced a full short circuit possibly initiated by air ionization during the connector mating and cascading into a plasma and then full arc flash of molten metal vapor and any nearby residues and posibly plastic. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted April 30, 2017 Share Posted April 30, 2017 11 minutes ago, Carlos E Rodriguez said: It's possible the capacitors are relatively high capacity and the DVM resistance mode will take a long time to charge capacitor before it starts reading a resistance. Considering you measured 60 volts I am Certain the capacitors are giving you the 0 reading. It does not mean yet that a short exists. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 Both pins are melted and I the ohm meter has been connected for 10 minutes with no increase in resistance. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted April 30, 2017 Share Posted April 30, 2017 @Rehab1 I noticed some crazy people recommended using plastic gloves. NEVER EVER DO THAT! an arc flash will ignite any flammable material. You skin is proof of that and your skin has moisture that protected you for a short period. But a flammable material exposed to a supper heated arc flash plasma pulse with flying melted copper would have burned the gloves on your skin. At work ,high voltage is handled with fire resistant silicon gloves and a second glove of leather on top. The leather protects again flash and also protects the silicon glove. The silicon glove is only to prevent electric conductivity and electric shock. Never use plastic as the primary shield for personal protection. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 Both pins are melted and I the ohm meter has been connected for 10 minutes with no increase in resistance. Link to comment Share on other sites More sharing options...
esaj Posted April 30, 2017 Share Posted April 30, 2017 33 minutes ago, Rehab1 said: I used an led light to drain the voltage. It dropped to around 1.9- 2.0v in a matter of 2 seconds.I said in the video .9 but met 1.9v. Well, that worked Did you have any resistor with the LED? Surprised it didn't burn out with that high voltage. The voltage won't drop below 2V or so, because apparently that's the forward voltage of the LED (it will stop conducting once the voltage drops to that value). Quote Here is the video checking the resistance of the power leads at the main board. I used a 330 ohm resister to check the meter and it was dead on. So there is 0 resistance coming from the main board and no elevation in resistance after a few moments. 4 minutes ago, Rehab1 said: Both pins are melted and I the ohm meter has been connected for 10 minutes with no increase in resistance. I don't know how autoranging-meters work, maybe it stops giving out any current once it detects a short-circuit, and that's why the value won't start to rise... I doubt there's an actual short-circuit there, as otherwise the caps should have discharged by themselves very rapidly. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted April 30, 2017 Share Posted April 30, 2017 6 minutes ago, Rehab1 said: Both pins are melted and I the ohm meter has been connected for 10 minutes with no increase in resistance. Actually your meater is Saying open circuit. 0L is infinite resistance. Check the leads Open air and short them so you see the difference in the reading. Link to comment Share on other sites More sharing options...
meepmeepmayer Posted April 30, 2017 Share Posted April 30, 2017 I feel sorry for you, another involuntary detective case you must solve (so it does not repeat) and things you must learn and do (connectors) you could have done without... Some general stuff: 1. There's always a small "brzz"/tiny flash when you connect the complete battery system (all batteries connected by all cables/plugs) to the board plug. Had that equally with both ACMs, so I don't think that is a problem (just maybe questionable electrical design). 2. Why didn't the BMSes stop the sudden discharge? What good is a BMS if it doesn't M the Bs? Is it because that function is disabled for safety (so a sudden increase in demand won't shut the wheel down, this was mentioned on this forum occasionally)? Link to comment Share on other sites More sharing options...
esaj Posted April 30, 2017 Share Posted April 30, 2017 31 minutes ago, Carlos E Rodriguez said: Actually your meater is Saying open circuit. 0L is infinite resistance. Check the leads Open air and short them so you see the difference in the reading. Good point, probably it's showing infinite resistance instead of short-circuit. Otherwise it wouldn't make any sense how the capacitors could have stayed charged. I doubt the mainboards' at fault. 26 minutes ago, meepmeepmayer said: I feel sorry for you, another involuntary detective case you must solve (so it does not repeat) and things you must learn and do (connectors) you could have done without... Some general stuff: 1. There's always a small "brzz"/tiny flash when you connect the complete battery system (all batteries connected by all cables/plugs) to the board plug. Had that equally with both ACMs, so I don't think that is a problem (just maybe questionable electrical design). There are bypass capacitors in the board to help with voltage fluctuations, act as "energy reservoir" in case parasitic inductance in wiring etc. is limiting current change speed, and possibly to filter out high-frequency noise from the main voltage line. If they're completely empty (or at low voltage), a large current will flow to charge the capacitors when the wires are connected, which then can cause sparking. There are anti-spark (maybe it was called "spark arrestor" or something like that) -connectors available, that have a structure where the other side of the connector first connects through a resistor before making small resistance connection, to charge such caps with current limited by the resistor, before the low resistance-connection is made, so at that point there shouldn't be (at least large) voltage difference anymore. In the above picture, the "Small Polarized Connector" is meant to be connected before the actual Deans-connectors. More "professionally" made anti-spark connectors have the resistor inside the original connector next to the other pin, and that pin is slightly shorter, so the resistor makes contact before the actual pin. Quote 2. Why didn't the BMSes stop the sudden discharge? What good is a BMS if it doesn't M the Bs? Is it because that function is disabled for safety (so a sudden increase in demand won't shut the wheel down, this was mentioned on this forum occasionally)? There might not even be short-circuit protections (this was the case at least on some older Gotway BMSs), or the BMS does not react immediately, there's usually at least slight delay there: That's just some random BMS spec, but it says "5-20 ms" delay in over current protection, 200-500µs (0.2-0.5ms) delay in short-circuit protection, but those values can vary a lot from one BMS to another (I think at least the earlier BMSs I had in my custom-packs had something like 5-10ms delay in short-circuit, although not sure anymore). And like said, some BMSs might not even have the protection. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 32 minutes ago, meepmeepmayer said: I feel sorry for you, another involuntary detective case you must solve (so it does not repeat) and things you must learn and do (connectors) you could have done without... Don't be buddy! This is an interesting project and if others( including myself) are enlightened along the way...Great! 36 minutes ago, Carlos E Rodriguez said: Actually your meater is Saying open circuit. 0L is infinite resistance. Check the leads Open air and short them so you see the difference in the reading. Ok I will check tomorrow. Thanks! 38 minutes ago, esaj said: Well, that worked Did you have any resistor with the LED? Surprised it didn't burn out with that high voltage. The voltage won't drop below 2V or so, because apparently that's the forward voltage of the LED (it will stop conducting once the voltage drops to that value). It worked indeed. I wanted a visual of the voltage depletion and the led held up well! 19 minutes ago, esaj said: In the above picture, the "Small Polarized Connector" is meant to be connected before the actual Deans-connectors. More "professionally" made anti-spark connectors have the resistor inside the original connector next to the other pin, and that pin is slightly shorter, so the resistor makes contact before the actual pin. I like that idea but being the polarized connectors are temporary how do you connect those leads without damaging the battery lead insulation? Link to comment Share on other sites More sharing options...
Scully Posted April 30, 2017 Share Posted April 30, 2017 I haven't read the whole thread yet - but Mine did exactly the same thing. I disconnected the battery when I was repairing a puncture - as I tried to put it back together - poof' the exact same thing. I took it to an auto electrician, who fitted a standard 'screw in' terminal block. I presumed I'd been too slow as I tried to join the cables together - which caused the spark. Now I'm scared to death every time I have to take them apart. Edit. Here is my report from before. Actually, I don't think I've taken any batteries off since then - I do everything I can to leave them alone. On 12/13/2016 at 10:42 PM, Scully said: I've done a whoopsey though. I disconnected my battery - I thought it was good practice when working on these things. I just tried to re-connect it, the 1st side (motherboard) went back fine - then 2nd side, big spark, now the XT60's are fried, I dis-connected the mother board side, dis-connected that battery then tried to re-connect the 'fried' side. The XT60's won't physically go back together. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 25 minutes ago, Scully said: I haven't read the whole thread yet - but Mine did exactly the same thing. I disconnected the battery when I was repairing a puncture - as I tried to put it back together - poof' the exact same thing. I took it to an auto electrician, who fitted a standard 'screw in' terminal block. I presumed I'd been too slow as I tried to join the cables together - which caused the spark. Now I'm scared to death every time I have to take them apart. Any photos of the mod? Did your connectors melt in any fashion? Link to comment Share on other sites More sharing options...
Scully Posted April 30, 2017 Share Posted April 30, 2017 1 minute ago, Rehab1 said: Any photos of the mod? Did your connectors melt in any fashion? Just normal household block connector. I went to a model shop and took him some new XT60's - but he said he'd prefer to use these. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 33 minutes ago, Scully said: Just normal household block connector. I went to a model shop and took him some new XT60's - but he said he'd prefer to use these. Thanks! I just ordered this and it is assembled with XT 60 connectors! NO-SPARK High Current Arming Switch With XT60 connectors and Heavy Duty 12AWG Wire With Genuine XT60 Connectors and HD 12AWG Wires PART # 6996 No More Damage to your Expensive Battery Connectors You won't have to uncover your hardware to unplug the battery to turn your vehicle off EASY TO INSTALL! A must for Electric RC airplanes. Simply Mount the No-Spark push button where you can grip the plane and press the pushbutton with one hand for one hand use. Connect the ESC, remove arming jumper, then connect your battery. Ideal for High voltage Configurations A MUST for 8S or Higher Simply hold down push button for 2-3 sec to charge the capacitors with limited current. This will eliminate the nasty arching when the arming plug is plugged into the Arming Switch. XT60 Connectors HD High Current 12 AWG Wire Flush Mounting Plate (Black color) Fully Pre-Assembled EASY to Install EASY to Use This pre-assembled No-Spark arming switch is GREAT for electric RC airplanes, helicopters, boats, cars or anything using a battery pack. With the pre-installed XT60 connectors it is SUPER EASY and FAST to plug in your battery pack and ESC (electronic speed control) AND there is no soldering required. You won't have to uncover your hardware and unplug the battery to turn your vehicle off. Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted April 30, 2017 Share Posted April 30, 2017 How are your hands today, Rehab1? Putting on my crazy detective hat, I've got a few questions for you... Where did you have the control board sitting when you plugged the batteries in? Was it mounted inside the wheel? Do you have electrical tape covering the end of the wires that go from the control board to the motor? In the one video it looks like you have the end connectors removed? You aren't working on a metal work bench, are you? Did you connect the batteries without having the plug from the power switch connected to the circuit board? With an open power switch circuit, do these control boards default to an on state? I wonder if after you plugged in the first battery that activated the control board to start balancing. When it being flat on a table it should have detected the orientation and not have tried sending power to the motor though. Does anyone have the link to the Msuper disassembly and assembly video to check the connection sequence they use when connecting the battery packs? I remember seeing them connect things in a particular order. Maybe Ian at Speedyfeet can shed some light on what happened. Maybe packs should always be joined first together before doing the final connection to the control board, and the power switch connector should be plugged in before doing so. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 Just now, Hunka Hunka Burning Love said: How are your hands today, Rehab1? Just a big blister and Rhino skin. 3 minutes ago, Hunka Hunka Burning Love said: Putting on my crazy detective hat, I've got a few questions for you... Where did you have the control board sitting when you plugged the batteries in? Was it mounted inside the wheel? Do you have electrical tape covering the end of the wires that go from the control board to the motor? In the one video it looks like you have the end connectors removed? You aren't working on a metal work bench, are you? You will see in some of the recent videos I have an elevated circuit board stand so nothing will short out the bottom of the board. No connectors on motor wires as they have been completely severed awaiting the new motor that will be hard wired. 8 minutes ago, Hunka Hunka Burning Love said: Maybe packs should always be joined first together before doing the final connection to the control board, and the power switch connector should be plugged in before doing so. That is what I did the first time and there was no arching. There was an arch when I connected the batteries to the pos/neg pig tail on the board. That scared me so I took a different route that ended up...well not so good. The high current arming switch I just bought will be perfect as others in the RC using large batteries have experienced similar issues. Better yet the seller is only in Ohio so only 2 day shipping! Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted April 30, 2017 Share Posted April 30, 2017 Some good notes I found on reputable papers on battery safety. Conservative approach in determining the short-circuit current that the battery will deliver at 25°C is to assume that the maximum available short-circuit current is 10 times the 1 minute ampere rating. ===================================== Arc-Flash Hazard • An arcing fault is current flowing through air. – Temperatures up to 35,000 F (4x times the surface temperature of the sun) – All known materials are vaporized at this temperature. When vaporized they expand in volume Copper: 67,000 X; Water: 1670 X – The air blast can spread molten metal to great distances with force. • Incident energy is the energy dissipated during an arc fault, or arc flash event. – Arcs [“arc blasts”] produce intense heat, IR/UV radiation, sound blast and pressure waves (i.e. an explosion), and intense light. ========================================= In the arc flash tables, NFPA 70E 2012 identifies arc flash hazards for dc voltages above 100 volts. However, there may be arc flash potentials at much lower voltages, even voltages below 50 volts as shown in the calculations section. While 50 volts nominal is the cutoff for shock hazard concerns, it is NOT the minimum voltage for arc flash concerns. With large UPS cells, the short circuit can exceed 30,000 amps which can, in theory, create an arc blast causing 2nd degree burns at voltages as low as 10 volts using the NFPA 70E formulas. An arc has to be initiated with a short circuit or a ground fault and must be sustainable for up to two seconds to create the energy used in the sample calculations. If the arc is only sustained for 20 milliseconds, the energy will only be 1/100th of the energy shown in the sample calculations. ============================================= The energy of the arc is dependent on how long the arc is sustained. With ac systems, the time of an arc event is determined by the trip time of the overcurrent protection device (OCPD). Within a battery, this time is indeterminate since there is no interrupting device internal to the battery. The time depends on an interconnection meltdown, material burn back and/or arc self-extinguish. A time of two seconds is recommended if there is not an interrupting device. Within two seconds, the technician is either blown back by the pressure wave or will move out of danger voluntarily A conservative approach in determining the short-circuit current that the battery will deliver at 25°C is to assume that the maximum available short-circuit current is 10 times the 1 minute ampere rating. ================= – battery enclosures can increase incident energy as much as 3 times • i.e., “arc in a box” ==================================== Battery Hazards • Chemical • Electrolyte • Shock • 100 Vdc per NFPA 70E • 50 Vdc per NFPA 70 (NEC) • Thermal – Molten splatter • Arc Flash: Heat, light, sound, pressure • Least information available • Greatest potential hazard =========================================== Why are rules so tough? • Because we don’t even know what we don’t know. • DC Arc Flash has not been characterized – In the absence of knowledge, code writers respond to fear • IEEE & NFPA have conducted testing to characterize ac arc flash – No funding has be provided for dc – Our knowledge of dc arc flash is about where it was 20 years ago for ac arc flash ============================================ Bill Cantor - DC ARC Flash.pdf Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted April 30, 2017 Share Posted April 30, 2017 Found one video... Interesting, he seems to have the power button wiring connected and then connects the battery cabling with the batteries disconnected so he must connect them one at a time afterwards (not shown in video). Maybe the key is to have the power button and motor wiring connected already before doing the batteries last? Edit: That no spark XT60 took me a while to figure out in my head. I think maybe those connectors with the spark arrestor resistor might be easier to use as they don't involve a push button and jumper. https://electricbike-blog.com/2015/10/29/xt60-xt90-with-spark-arrestors-why-you-should-make-the-switch/ With the button you have to keep it pressed while you insert the jumper plug with the other hand. Without it mounted in an easy to get to area, it might be tricky to do one handed. Link to comment Share on other sites More sharing options...
meepmeepmayer Posted April 30, 2017 Share Posted April 30, 2017 Old (67V) and maybe no longer up to date (the motor connector is different in the 3rd video) but maybe helpful and directly from Gotway.. Link to comment Share on other sites More sharing options...
Rehab1 Posted April 30, 2017 Author Share Posted April 30, 2017 16 minutes ago, Hunka Hunka Burning Love said: Interesting, he seems to have the power button wiring connected and then connects the battery cabling with the batteries disconnected so he must connect them one at a time afterwards (not shown in video). Maybe the key is to have the power button and motor wiring connected already before doing the batteries last? Yes having all of the cables connected including the motor wires to the motor will definitely be my next method before rejoining the battery connectors. Link to comment Share on other sites More sharing options...
Scully Posted April 30, 2017 Share Posted April 30, 2017 Good luck, I hadn't touched any of the other connections when I did mine. Link to comment Share on other sites More sharing options...
Chris Westland Posted April 30, 2017 Share Posted April 30, 2017 Sorry to hear about this @Rehab1... that just looks seriously painful. I've had some experience with connectors in RC quads and helis. XT60s are simply re-packed bullet connectors, as are EC3's, and they are small -- 3mm or 3.5mm with thin lantern shaped conductors and small contact points. They are pretty convenient, cheap and reliably hold together, which is why you see them in RC electrics so often. I'm not sure they are optimized for the higher power, and hours at a time duration of EUCs. I personally think Deans Ultra Plug connectors are more reliable than the XT60s or EC3s and they ideally handle a lot more DC current because they have a lot more contiguous copper. Another choice, perhaps, is Andersen Power Poles which offer current handling up to 350A (standard is 30A). EC3 should handle continuous 10A draws at 84V (800W ~ 1 HP)(3.5mm bullets) and I wouldn't trust 3mm XT60s for anything more. Deans Ultra Plugs can probably handle 30A draws; they also have less resistance (according to their website) including the solder joints, than an equivalent length piece of 12 gauge wire. But all of this is predicated on the quality of a particular manufacturers product; and on the quality of the solder joint produced by the EUC manufacturer (or owner if you are into DIY) The downfall of any connector can be the solder connection. Deans Ultra Plugs are hard to solder and have a tendency to drop connection to the V Regulator when twisted or sometimes just touched. It is (IMHO) harder to get a good soldering junction on the Deans because there is more metal, and thus they require more heat. With these small connectors you always run the struggle of keeping the heat high enough to get a good solder joint, but low enough not to melt the plastic. I've heard of solderless APP and TE connectors, but have no experience. Apparently they can take higher loads, and maybe this is worth investigating for the larger wheels. Link to comment Share on other sites More sharing options...
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