Pop sound when attempting to connect the battery

[rick_p]

Hi,

I’m building a bike from a kit and I double checked all the connections to make sure they were correct before attempting to connect the battery. The battery does not have an on/off switch, so the discharge connector is hot. Everything looked good on the other connectors so I started to make the last connection of the battery to the controller. As soon as the leads touched it popped louder than I might expect. Given there is power on the battery connector it makes sense to me that there might be a light arcing when making the connection, but with that pop I made no further attempt to make the connection without seeking opinion/guidance from those with a lot more experience than I. Please advise.

Rick

 

[markz]

It is completely normal.
If you want to save your connectors, just buy some Hobbyking Anti Spark XT connectors.

Hi,

I’m building a bike from a kit and I double checked all the connections to make sure they were correct before attempting to connect the battery. The battery does not have an on/off switch, so the discharge connector is hot. Everything looked good on the other connectors so I started to make the last connection of the battery to the controller. As soon as the leads touched it popped louder than I might expect. Given there is power on the battery connector it makes sense to me that there might be a light arcing when making the connection, but with that pop I made no further attempt to make the connection without seeking opinion/guidance from those with a lot more experience than I. Please advise.

Rick

 

[HK12K]

What markz said, especially if you plan to disconnect and reconnect frequently. That arcing will eat the contacts or possibly weld them together.

 

[LewTwo]

Better yet put in a switch or circuit breaker in the power line.
I have blown the resistors out of those anti-spark connectors.

https://endless-sphere.com/forums/viewtopic.php?f=2&t=110347

 

[rick_p]

It is completely normal.
If you want to save your connectors, just buy some Hobbyking Anti Spark XT connectors.

What markz said, especially if you plan to disconnect and reconnect frequently. That arcing will eat the contacts or possibly weld them together.

You guys were completely right. What I did was, I pulled the inline fuse out, connected the slip connector, and then let the arc happen at the fuse.

I do want to be able to remove the battery from the bike so I’m going to have to work something out with that. What about an inline switch between the fuse and the slip connector instead of the anti-spark connector?

I took it for the first test ride and I’m pretty happy with the kit, the bike is fast. There’s no speedometer on the bike yet but I think I hit around 30mph. It’s a 1k watt motor, with a 48v 14ah battery.

The kit came with a rear hub motor wheel with a disc rotor, but the frame didn’t have a mount for a disk brake, so I built a custom bracket to mount a caliper. I’ll take some pictures and post the whole project in the bike build section after I clean up some of the temporary work I did just to make sure the thing ran before I got all fancy with wiring and other mounts.

Thanks for your help!!!! Much appreciated

 

[rick_p]

Better yet put in a switch or circuit breaker in the power line.
I have blown the resistors out of those anti-spark connectors.

https://endless-sphere.com/forums/viewtopic.php?f=2&t=110347

Ha, you must have posted this while I was typing, I just asked about a switch. I’ll check the link now. Thanks!!

Yeah, that’s the hot ticket, and I bet I can pick one up at the marine supply store near me. Thanks again!

 

[Chalo]

Better yet put in a switch or circuit breaker in the power line.

I just disassembled a 300A disconnect switch that was damaged in a battery fall, and found severe contact erosion inside. If it's that or Powerpoles, well I suppose it's easier to replace Powerpoles.

It would be considerate of controller manufacturers to incorporate solid state anti-spark features for us, but I'm not holding my breath.

 

[HK12K]

Agreed. Using a switch simply transfers the arcing to the contacts in the switch. A precharge resistor, such as the aforementioned antispark connector, is the best way to avoid this. If the resistor should fail the connector will simply work like any other connector.

That said if you don't mind potentially replacing a DC circuit breaker from time to time, or potentially having it refuse to break the connection because the contacts are welded together internally, that will do the job.

Having both could be ideal, assuming you only flip the breaker without the battery connected. This will prevent contact damage in the breaker, while offering overcurrent protection should a dead short happen to occur.

 

[markz]

7mm bullet connector anti-spark
https://hobbyking.com/en_us/7mm-as150-anti-spark-self-insulating-gold-bullet-connector-2-pairs.html?queryID=f4b4beafcd61a8de4622c24fa61b218f&objectID=5083&indexName=hbk_live_products_analytics

OSE 8mm Anti Spark Connector
https://www.offshoreelectrics.com/proddetail.php?prod=ose-qs8-anti

https://www.kontronik.com/en/products/accessories/speedcontroller/connector/anti-spark.html

https://shop.jetiusa.com/Jeti-AFC-Anti-Spark-Connectors-8mm-300A-p/jetisp8.htm

Anti-spark XT90

https://hobbyking.com/en_us/xt90-s-anti-spark-connector-2pairs-bag.html

 

[rick_p]

Using a switch simply transfers the arcing to the contacts in the switch. A precharge resistor, such as the aforementioned antispark connector, is the best way to avoid this. If the resistor should fail the connector will simply work like any other connector.

Ah ha, that makes perfect sense, a switch won’t stop the arcing it will merely happen inside the switch until it fails. I’m guessing my store bought bike must have the anti-spark built into the battery pack, which would explain why I never noticed any arcing when I inserted/removed the battery.

I’m really liking the XT90-S and OSE 8mm connectors, I’ll go with one of those.

Thanks again everyone.

 

[E-HP]

I have about 3K on/off actuations of my $5 40A home depot AC circuit breaker that I use as my switch, and still functions fine. Since it's AC, it won't trip under load (100A+ without tripping), but works well for an on/off switch. About 1/3 of the actuations are when running 72V. Just don't turn it on/off under load, so the arc is minimized.

 

[LewTwo]

Using a switch simply transfers the arcing to the contacts in the switch.

True but good quality switches are built to to tolerate a number of operations (usually in the thousands). Of course switching under FULL load will eventually burn anything out. Remember those old 'foot operated' starter switches that cars/trucks had in the 1940s and 1950s? Even those eventually had to be replaced (though I can recall folks taking some of them apart and sanding down the contact plate to resurrect them them).

It would be considerate of controller manufacturers to incorporate solid state anti-spark features for us, but I'm not holding my breath.

Or for manufacturers to build low voltage switch circuits into their BMS (along with the option to totally switch off the BMS so that there is no phantom discharge). I believe my six year old GM rack battery does the former already.

 

[electric_nz]

if the controller has a wiring for an on/off switch (low current) then you could just use that and leave the battery permanently connected. it means that part of the controller will still be energised at very low current but that won't be an issue; you'll only need to remove the battery when storing it for an extended period.

 

[fechter]

You can put a resistor (around 1k ohm) across any switch to make a pre-charge. This will save the switch contacts, but doesn't completely turn off the power to the controller. For long term storage or if you need it really off, unplug the battery.

 

[rick_p]

I have about 3K on/off actuations of my $5 40A home depot AC circuit breaker that I use as my switch, and still functions fine. Since it's AC, it won't trip under load (100A+ without tripping), but works well for an on/off switch. About 1/3 of the actuations are when running 72V. Just don't turn it on/off under load, so the arc is minimized.

I happened to have an old but known working 20 amp single pole breaker, so I decided it was worth it to do the extra wiring so I could use the bike while I wait for the anti-spark XT90-S connectors to arrive. It works great, just like you said. I don’t hear an arc when I flip the switch, but I’m sure that doesn’t mean there isn’t one, I just can’t hear it :lol:

For future readers, I’ll explain that I kept the inline fuse in place. So, the positive line from the battery passes through the original fuse, then goes to the breaker, and then on to the controller. I feel this is important to point out because an AC breaker is not a substitute for a fuse. You could do that with a properly rated DC breaker, but it’s not worth it for me to go out and buy that for a temporary situation because in the end, the arcing will likely wear out the DC switch anyway, it doesn’t prevent the arcing that the XT90-S will.

 

[velias]

Use this, its been working great for me for the past 2 years.

https://github.com/msglazer/Anti-Spark_Switch

Send the gerbers off to oshpark.com get 3 circuitboards for about 20 bucks.
Order the parts and build it.
screw those anti spark connectors, they eventually arc and fail.