HELP!! Tried to connect battery and it sparks

H

hennez

100 µW
Joined
Jun 12, 2014
Messages
9
Hi Everyone,
I have put a 1680w Cyclone mid mount motor kit on my giant reign and hard wired all the connections between the motor and controller to get rid of a bit of excess wire. I received my 20R cell 48v 16.5ah battery from EM3EV today and got home and went to connect the battery up, plugged the negative in and when i went to plug the positive in it did a pop flash sort of thing and i nearly poo'd. :oops:
I pulled all the electrical tape that i had put on off and could not see anything that would be causing this... :roll: I don't know if anyone has ever had this problem before or would know how to fix it as i'm not much of a sparky and don't really want to blow up my 2k of bike bits. I'm almost 100% sure that all the wires were connected back up to the right ones when i hard wired them but you never know. Any help would be awesome as i'm seriously keen to get the beast going!!
 
It's normal. It will happen every time you connect the battery when the capacitors in the controller are drained.

If there was really a short the connectors would explode and spray molten metal. Extremely violent.
 
Yep. If your fingers turn black and you're temporarily blinded by the flash, then there's a problem. otherwise, it's fine. No worries. :mrgreen:

As Tahustvedt explained, it's just a rush of power to fill the controller's capacitors. Its all perfectly normal, although it will slowly destroy your connector, that may not happen in the bike's life time. Connectors are disposable anyway.

You can cure the problem with an Inrush resistor, also called an anti-spark resistor. It's just a second positive wire and connector, only that wire has a resistor of around 1000 ohms in it. you plug in the negative, then you plug in this resistor wire, wait a couple seconds, and then plug in the main positive wire, and no spark! This is mostly pointless though.
 
Drunkskunk said:
Yep. If your fingers turn black and you're temporarily blinded by the flash, then there's a problem. otherwise, it's fine.
Click to expand...

I totally agree with Drunkskunk, if you have a direct short on the battery lead it will be very obvious:

Burntfingers.JPG


BurntConnector.JPG


A direct short works just like a pacemaker - it instantly starts your heart pumping again. :shock:

Alan
 
I have an em3ev battery, it has been built with a pre-charge resistor. I was under the impression that all their triangle and rectangle packs were all built with the pre-charge. A precharge allows a small amount of current to fill the controllers capacitors, before you connect the main power. This prevents any noticeable sparking or sound.
Your battery plug should be 3 Anderson connectors. Green, black and red. Make sure you connect the green(pre-charge resistor) first and allow it a second or two before connecting red.
If you already knew this and are still having this issue, apologies. Just thought I'd throw the obvious out there. :wink:
 
Did you plug in the pre-charge tail last? The tail has a pre-charge resistor in it that will prevent the flash from occurring. It the tail is plugged in last, then the spark should be avoided or at least minimized.

Pre-charge Tail2-500x500.jpg
 
I noticed HK are selling anti spark connectors. :?
Not sure how they are meant to work except for the heavy plastic covers so maybe you just don't see the spark.
If someone tries them it might be worth a review.

http://www.hobbyking.com/hobbyking/store/__42825__7mm_AS150_Anti_Spark_Self_Insulating_Gold_Bullet_Connector_2_Pairs_.html

I note my connectors are getting black around the ends from the sparking but I am not sure it is making any difference yet apart from being un sightly. I use the HK HXT 4mm connectors

http://www.hobbyking.com/hobbyking/store/__9283__HXT_4mm_Gold_Connector_w_Protector_10pcs_set_.html

The only way I know of preventing the spark is a smaller plug with a limiting resistor plugged in first to charge the capacitors.
 
tstephens said:
Did you plug in the pre-charge tail last? The tail has a pre-charge resistor in it that will prevent the flash from occurring. It the tail is plugged in last, then the spark should be avoided or at least minimized.

Click to expand...


You need to make sure the green connectors touch first or you will get a spark, Did your kit from Paul come with this type of connector?
 
thanks for the replies!
I contacted Cyclone about it and yeah they said it was totally normal....
I think it was just because i was connecting the bullet connectors which make quite a visible spark etc.. if i had of had them already plugged in and connected the large waterproof plug i probably wouldn't have thought anything of it :lol:
 
Even if they say it was totally normal, i would still invest in a pre-charge solution to increase the lifespan of your controller.
The constant inrush of current/voltage will eventually damage it.
 
Racer_X said:
Even if they say it was totally normal, i would still invest in a pre-charge solution to increase the lifespan of your controller.
The constant inrush of current/voltage will eventually damage it.
Click to expand...

Yes but we are talking about a 50 cent item.

The only reason the capacitors are there at all is to allow high peak current when the FETs switch on and prevent volt drop for the control circuitry. In theory you could put the capacitors on the battery side of the connector and keep the controller lead very short and fat eliminating the spark.
These things are usually fitted on a production ebike with up to 2 feet or 600mm of cable going to the battery. The manufacturer of the controller has no way of knowing how his controller is going to be fitted in a bike so the capacitors are an easy way to eliminate some variables. I might give it a try on my next project and see how it goes.
 
Modbikemax said:
Yes but we are talking about a 50 cent item.
Click to expand...

Thanks for the capacitors information, did not know that.

For me the big trouble I had was the wearing of the contacts due to constant spark upon connection, though i agree it is only a 50 cent item. That 50 cent item can cost you when you least expect.
 
I have removed the large capacitor(470uf) at the input to the controller on 2 bikes now with no perceptible difference.
I am running 250 geared hub motors with a suitable controller on 10s Lipo so 42v when fully charged. I am using 12AWG silicon RC cable no longer than 500mm with 2 gold RC connectors on each cable. There is still a spark but not as big. There are several smaller caps on the board charging up. I have fitted a 75amp pull switch on one bike, I'll see how long that lasts. Removing the cap should help the life of the switch.
 
It's been a year now and I have 3 ebikes all with 250 watt motors and controllers. I have removed the large capacitors on all the controllers. The sparking is a non issue now with connectors and switches all working well. Cables from the battery to the controller are kept short with a nice heavy gauge.
 
tahustvedt said:
Here's why you need caps: http://www.rcgroups.com/forums/showthread.php?t=952523&highlight=kill
Click to expand...
The devil is in the detail.
The RC guys hammer their equipment much more than ebikes.
RC motors generally run at much higher frequencies and currents than ebike motors.
The electrolytic capacitor in the average ebike controller would have little or no effect on the motor inductance.
It is just a storage bank of charge to deliver a peak current when the fet turns on since its at the front end of the controller. To have an effect on the motor it would need to be on the motor side. I believe thereare some smaller caps on the board which may have something to do with impedance matching. But that's not what this thread is about.

I am pretty confident the commets in the RC thread have little bearing on this discussion.
If I have a controller failure I will let you know.

In the mean time if people are unsure use the the charge resistor method it has merit too.
I am just letting everyone know my findings.
 
Modbikemax said:
In the mean time if people are unsure use the the charge resistor method it has merit too.
I am just letting everyone know my findings.
Click to expand...

like.png
 
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