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Can somebody knowledgeable like @Jason McNeil, @esaj or someone else with knowledge about this have some input into connecting batteries without risking arching?

In my little world, the idea was that the only time you risk an arc, is when you close the circuit - but maybe I've been naive?

I know I've gotten "mini" arching when I've done the last connection, but I tend to do it as resolutely and smoothly as I can, to minimise the time where the poles are close but not connecting.

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The fat yellow cable between the batteries was the first thing you connected? Did you store the batteries with all 3 cables connecting them?

Can you get Ian to do the Monster repairs if you pay for shipping and possibly labor? Seems natural.

Also, both your wheels don't work properly? If the ACM was defective from the start, have the dealer care about that or return it.

Sorry to hear your situation. Definitely sucks:( Also $$$$$:cry2:

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5 minutes ago, esaj said:

The batteries themselves should be charged to the same voltage as close as possible before they're connected together to minimize possible sparking. Larger voltage difference between the connectors at time of connecting may cause large currents to flow, and the (partial) connection is the highest point of resistance, dissipating most of the power (voltage difference * current flowing through), which can get into really high values, enough to heat up the metal at the connectors to melt. 

Another point of risk is when connecting the packs to the mainboard. If the mainboard has been sitting unpowered for longer while, the large bypassing capacitors have discharged, and will charge up when connected. They can have as little internal resistance as a few tens of milliohms. I have simulated a capacitor bank I've been building for spot-welding purposes, and it can dish out >1000A at 12V. 

Technically, it's not as much arcing (the voltage isn't probably high enough to arc over the air gap), but a sudden large current flow heating up the connectors. If the contact is a few hundred milliohms (just as an example), the momentary current for full 84V packs and empty capacitors can reach values of hundreds of amps, dissipating kilowatts if not tens of kilowatts at the point of contacts, which have very little mass and heat up instantaneously to very high temperatures. The sparks flying are likely tiny pieces of molten copper flying, rather than just "electric" sparks.

To minimize the possible sparking:

-Measure the packs, if there's voltage difference (can't say what would be "critical" difference, but probably something like a few tenths of a volt isn't that bad) charge packs to same value before connecting, easiest way is to probably charge the packs full before connection so they're all sitting at same voltage
-Charge the bypass capacitors in the mainboard to same voltage as the packs before connecting. This can be done for example simply by putting a resistor (or resistors) between the connector pins of the mainboard and battery pack for a while so the capacitors charge up to full voltage with small current, something like 1K, even lower could do  (even if you don't have a power resistor, the power dissipation for the resistor will momentarily be high, but it's so short-lived that it shouldn't destroy even a 0.25W basic resistor, plus resistors cost <1 cent per piece)

Easiest solution is to use anti-spark / no-spark connectors that have the charging resistors built-in, the resistor will make contact before the actual connector pins do, and charge up the caps. NOTE: Do not use separate resistors or such connectors between the packs, if there's a larger voltage difference, there the current can be high for a longer while and destroy the resistor / resistor inside the connector, as they're only meant for short-lived high currents.

61690.jpg

XT90 anti-spark connectors. It's not too hard to do yourself either, although you won't get it as "clean" as those:

sparkgold4.jpg

sparkdeans4.jpg

Personally, I've for example put through hole-resistors on the connector pins and used those to touch the other side connectors (mind the polarity & don't short-circuit by accident! ;)) to charge the caps, then removed the resistors and pushed the connector in. No sparks.

 

 

 

 

 

Those XT90's look awesome!

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15 minutes ago, esaj said:

The batteries themselves should be charged to the same voltage as close as possible before they're connected together to minimize possible sparking. Larger voltage difference between the connectors at time of connecting may cause large currents to flow, and the (partial) connection is the highest point of resistance, dissipating most of the power (voltage difference * current flowing through), which can get into really high values, enough to heat up the metal at the connectors to melt. 

Another point of risk is when connecting the packs to the mainboard. If the mainboard has been sitting unpowered for longer while, the large bypassing capacitors have discharged, and will charge up when connected. They can have as little internal resistance as a few tens of milliohms. I have simulated a capacitor bank I've been building for spot-welding purposes, and it can dish out >1000A at 12V. 

Technically, it's not as much arcing (the voltage isn't probably high enough to arc over the air gap), but a sudden large current flow heating up the connectors. If the contact is a few hundred milliohms (just as an example), the momentary current for full 84V packs and empty capacitors can reach values of hundreds of amps, dissipating kilowatts if not tens of kilowatts at the point of contacts, which have very little mass and heat up instantaneously to very high temperatures. The sparks flying are likely tiny pieces of molten copper flying, rather than just "electric" sparks.

To minimize the possible sparking:

-Measure the packs, if there's voltage difference (can't say what would be "critical" difference, but probably something like a few tenths of a volt isn't that bad) charge packs to same value before connecting, easiest way is to probably charge the packs full before connection so they're all sitting at same voltage
-Charge the bypass capacitors in the mainboard to same voltage as the packs before connecting. This can be done for example simply by putting a resistor (or resistors) between the connector pins of the mainboard and battery pack for a while so the capacitors charge up to full voltage with small current, something like 1K, even lower could do  (even if you don't have a power resistor, the power dissipation for the resistor will momentarily be high, but it's so short-lived that it shouldn't destroy even a 0.25W basic resistor, plus resistors cost <1 cent per piece)

Easiest solution is to use anti-spark / no-spark connectors that have the charging resistors built-in, the resistor will make contact before the actual connector pins do, and charge up the caps. NOTE: Do not use separate resistors or such connectors between the packs, if there's a larger voltage difference, there the current can be high for a longer while and destroy the resistor / resistor inside the connector, as they're only meant for short-lived high currents.

61690.jpg

XT90 anti-spark connectors. It's not too hard to do yourself either, although you won't get it as "clean" as those:

sparkgold4.jpg

sparkdeans4.jpg

Just make sure to connect the other side over the resistor first.

Personally, I've for example put through hole-resistors on the connector pins and used those to touch the other side connectors (mind the polarity & don't short-circuit by accident! ;)) to charge the caps, then removed the resistors and pushed the connector in. No sparks.

 

EDIT: Oh yeah, Rehab1 sent me his dead ACM board. Don't know for sure if it was the huge sparking when he connected the batteries that killed the board, but the MCU was dead. Maybe a high voltage strike-through from cable inductances when the large current was flowing? Apparently it's possible that the sparking can kill the entire board.

 

 

 

Thank you @esaj  :)

I was re-connecting them as I saw others in various You Tube videos so it must be the charge difference. I literally had the batteries disconnected for an hour or so maybe and the Monster was showing 30% prior so it sounds like I'd have been better charging to 100% first but I thought lower would be better. :( 

I'll give charging the batteries to full a try. I presume I just connect each one, one at a time, to the cable that goes to the charging port without connecting to the board?

Also I may give the XT-90 connectors a try. Would it be best to replace all the XT-60's or just replace the damaged ones? It's been many years since I soldered anything like this so I'm not looking forward to it.

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25 minutes ago, TremF said:

Thank you @esaj  :)

I was re-connecting them as I saw others in various You Tube videos so it must be the charge difference. I literally had the batteries disconnected for an hour or so maybe and the Monster was showing 30% prior so it sounds like I'd have been better charging to 100% first but I thought lower would be better. :( 

The percentage may not be that trustworthy as an actual voltage measurement. Still, it sounds a bit odd that the voltages would have drifted that far apart in just an hour. Faulty cell in one of the packs?

 

Quote

I'll give charging the batteries to full a try. I presume I just connect each one, one at a time, to the cable that goes to the charging port without connecting to the board?

I don't know about how Gotway cabling, but I'd expect them all to be connected on the charging side, so that should work. Do note that if there is a faulty cell in one of the packs and it drops the voltage to a lower value once taken off charger, it will spark again when you connect them. I'd suggest measuring the pack voltages to check if one of them is clearly at a lower value.

Quote

Also I may give the XT-90 connectors a try. Would it be best to replace all the XT-60's or just replace the damaged ones? It's been many years since I soldered anything like this so I'm not looking forward to it.

The anti-spark connectors should not be used between battery packs, only between the mainboard and the packs. Again I don't know how Gotway cabling goes, but I'd presume there's a single connector going to the mainboard. The anti-spark connectors have low-value resistors, that can take the very momentary high power dissipation when the capacitors charge (fractions of a second), but probably not for a longer while if between two packs in different voltages (or they don't have enough time to balance the packs when pushed in).

If you feel unsure doing it yourself, something like a local RC-shop will probably be happy to exchange the connectors for you, for a small fee.

Edited by esaj
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@Linnea Lin Gotway @Jane Mo  Is there a proper sequence for connecting the batteries?  I wish @Rehab1 could comment as this very thing happened to him, but he was able to reconnect successfully later on.  He did get pretty bad burns though.  I don't know if he connected all the cables first to the control board (power, hall, motor, etc, battery lead) before connecting one pack then the other?  Is there a mandatory sequence?

I see the theories that have been posted, but I wonder there is something more going on.  Could it be that people are connecting battery packs together first before connecing to the main board?  In Speedyfeet's teardown video he unfortunately skips some of the reconnecting process.  I was watching specifically to see what he did but was disappointed there.

Could it be somehow BMS related where one triggers an overload detection, cuts voltage output while the other pack maintains voltage and boom the difference results in the explosion?  I don't see how connecting two battery packs of fairly equal voltage should spark that much.  Is there an extra wire coming from the packs?  What is that wire for?  Balancing voltages?  It would be nice to know for the record or else other people will end up getting hurt and damaging their wheels.

Can Gotway post up a video for reference?

BTW :  Sorry to hear this happened to you TremF.  I can imagine how frustrating it can be.  Hang in there - I'm sure things will get sorted out.  They really should provide warnings or a sheet of detailed instructions as this sort of thing is really hazardous just judging by Rehab1's photos of his experience.  It doesn't take much to give a video link, a website page of instructions, a photocopied sheet of step by steps?  Com'on guys, even generic printer toner refill companies provide paper instructions and a website how to video.  :eff04a58a6:  This really shouldn't be rocket science.  If there is risk for injury if not done correctly they should declare an important read me first sheet.  Sorry for the rant, can you tell I'm upset?  :furious:

 

Edited by Hunka Hunka Burning Love
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Ian has offered to sort it out if I send it back to him so i have opted for that rather than risk making things worse. I was quite anxious about messing about with the cables and connectors and causing even more damage to the Monster or myself.

It's now booked with UPS for pickup Friday and will get to him Monday. Hopefully, as he knows what he's doing, it shouldn't take too long to sort and in no time I will have my Monster in it's nice shiny new Purple shell back and be out and about enjoying long rides in the sun :) 

Thanks all for the advice. My mind is at ease knowing it will be safe in Ian's hands.

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5 minutes ago, TremF said:

Ian has offered to sort it out if I send it back to him so i have opted for that rather than risk making things worse. I was quite anxious about messing about with the cables and connectors and causing even more damage to the Monster or myself.

nice- yeah, if something like that happened i'd probably send it to someone.. the extent of my skills involves strategic duct-taping

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I had a boom too, when my MSuper was 2 weeks old, I tried to dismantle it and fix a puncture. 
I connected m/board, then the 2nd battery. 

Afterwards, reading on here I realise it's best to connect batteries first - then join the motherboard.

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7 minutes ago, Scully said:

I had a boom too, when my MSuper was 2 weeks old, I tried to dismantle it and fix a puncture. 
I connected m/board, then the 2nd battery. 

Afterwards, reading on here I realise it's best to connect batteries first - then join the motherboard.

I hadn't connected the batteries to the board when this happened. I connected two of them and when I went to connect the third it blew.

Anyway I'm letting someone with a lot more experience sort it for me and will look at getting the slime for the tire just to make sure I don't get a puncture and have to open it up again though in my two years of riding I haven't had a puncture yet.

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2 hours ago, Rehab1 said:

@TremF I remember you asking by about the proper battery/MB reconnect sequence after my incident. Hopefully your hands are ok!

Since my arcing accident I have installed the XL 90 spark arrest connector between the packs and the mainboard. I have performed the following reconnect sequence over 6 times within the last month:

1)Connect both battery packs and secondary leads together

2 Reconnect the joined packs to the main board. There will be a pop and slight arc but nothing like the huge arc that burned our fingers! The problem with the existing XL 60 connecter is that everytime you reconnect your packs to the mainboard that little sparking activity will begin to eat away at both the male and female unions literally pitting the material. 

In my opinion the XL90 anti spark connectors are excellent for this application. They do take up a bit more room inside the shell but the outer shell did not have any difficulties closing properly. I also drilled a small hole in the little molded plastic tab on the shell and inserted a zip tie that now holds the XL 90 connector securely in place.

 

Thanks for the feedback @Rehab1 

I was doing exactly as you mention you do. I was connecting the 3 batteries together before connecting to the board I connected the small leads first and then the XT-60. As I connected the third battery that is when it arced. It only effected my right hand and it burned my thumb slightly but nothing severe.

I was contemplating replacing the XT-60's with XT-90's throughout but was advised, and read elsewhere, it was best just on the connection to the board. Seeing as I had the problem before connecting to the board I decided to take Ian up on his offer of sorting it for me. IF I need to disconnect the batteries for any reason, going forward, I will definitely swap to the XT-90 based on your experience.

 

Edited by TremF
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Does anyone have some photos of the battery packs and wiring setup?  If they are all identical 84V packs in parallel, why would there be any spark if they are connected first?  Maybe the small leads have something to do with it?   Has anyone tested the voltages prior to connecting to make sure all three packs match?  Then connect two and check the voltage and polarity on either side of the last connector?  I'm just baffled as to why there is such a huge spark.  Is there a polarity incongruency somewhere?  Say if you connected positive to negative accidentally on the packs instead of positive to positive that would create a huge arc-weld spark explosion as the batteries would discharge at high current.

Maybe the parallel connector has a specific pattern that isn't visually obvious so it would be wise to label each wire to match each battery pack?  With a sharpie, simply draw a one on the connector and one on the matching connector.  Draw a two on the next and so forth.  Label the small connectors as well.  Before connecting double check voltages and polarities on each side of the connectors?

Edited by Hunka Hunka Burning Love
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25 minutes ago, Hunka Hunka Burning Love said:

Maybe the parallel connector has a specific pattern that isn't visually obvious so it would be wise to label each wire to match each battery pack?  With a sharpie, simply draw a one on the connector and one on the matching connector.  Draw a two on the next and so forth.  Label the small connectors as well.  Before connecting double check voltages and polarities on each side of the connectors?

I did use a sharpie to identify the connectors first before disassembly...along with lots of photos and videos. After the mini explosion I checked the voltage on each battery like @esaj had suggested and both batteries were of equal value. My issue was the reconnection sequence where I reconnected the last pack after the  MB was connected. That will never happen again!

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On 6/21/2017 at 3:54 AM, Scatcat said:

Are those XT90's powerful enough that I can use them on my GT16 with 84V? I suppose so, just asking to be sure. Better a stoopid question, than tears later.

Yes the XT 90 connectors were used on my 84v ACM 1600. They have a much  high voltage/ amp rating than the existing XL60s.

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Just now, Rehab1 said:

Yes the XT 90 connectors were used on my 84v ACM 1600. They have a much  high voltage/ amp rating than the existing XL60s.

Then that is the way to go.

I'll have to see if they're sold anywhere locally. I think I have a component store nearby, I will ask them.

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6 hours ago, Scatcat said:

Then that is the way to go.

I'll have to see if they're sold anywhere locally. I think I have a component store nearby, I will ask them.

I purchased mine on Amazon. https://www.amazon.com/gp/aw/d/B06XW63S87/ref=mp_s_a_1_3?ie=UTF8&qid=1498148465&sr=8-3&pi=AC_SX236_SY340_QL65&keywords=xt90+anti+spark+connector&dpPl=1&dpID=41-1l4p7vyL&ref=plSrch

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  • 2 weeks later...
54 minutes ago, Hunka Hunka Burning Love said:

Did he mention why there was such a large spark?  Is there some special connection method to avoid it?

I suppose it was the initial connection between the packs and the board. If you are deliberate in that connection it will spark but not like the 4th of July fireworks I had. The connection posts inside the XL60s will start to degrade if the procedure is performed too many times. I don't believe @TremF ever posted a post spark photo of the connector.

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