# Sparks? Final connections... need some help now.



## soon2bEV (Mar 14, 2011)

ALLrighty.
Starting small to learn the discipline needed for the EV obsessive I now am. I got an old 'industrial' trike with a big aluminum box over the rear. Just what I was looking for to start, just some metalwork a little reinforcing and nothing to it. 
The system specs: Unite 48v 1000w motor (I will be going bigger after this). 4x 50ah 12v MK gel batts in series. controller 'made' for the motor is yiyun, bought from an ebay seller in LA that has not been helpful and after a lot of searching found out what wires went where since it's all written in chinese. no matter, I couldn't understand more than + or -. I found the specs for it on electric scooter parts dot com. 
So, I had everything together and went to connect the - terminal to the battery and a spark flew. I didn't think that was normal. I checked that my switches were still off. I have 1 on/off sw at the + motor lead and 1 on the throttle controller. Checked my wiring, then tried again, same thing, sparks. 
Now when I checked cont. on the batt leads to the controller my meter gives a momentary cont beep then show a resistance that slowly falls from 1000 to 700 ohms maybe. Did I get a bad controller? Anyone have some ideas. Negative terminal is not grounded when I am connecting it, is that right? Or do I need to have the neg. connected to ground initially then removed after completion of the circuit.
There is a cover for the batts, dont worry, just not pictured.
Also, I am replacing and rewiring the busbar since the connections are so close I thought it prudent.
Here are the pics.


----------



## Ziggythewiz (May 16, 2010)

A single spark is pretty common when making a final connection. You are completing a ciruit even if the controller and motor are off. Even the 12v accessory battery in a car typically sparks when connecting it, and you're running 4x the voltage.

Just be sure to calculate the max amps your system can pull from the batteries and have an appropriate sized fuse or two in series next to the battery pack. THat should protect your motor and controller (and you!) should you wire it up wrong or have another complication.

In summary, a momentary spark when connecting your battery is normal, ongoing or violent welding type sparks are not, and fuses are essential.


----------



## soon2bEV (Mar 14, 2011)

Thanks Ziggy, that puts my mind to rest. I have a healthy respect for electricity and take caution at every turn. When hooking up multiple batts I will use a large towel and cover everything except what I am working on. Also, I forgot to mention and take a picture of the 35 amp breaker I have on the battery neg lead as well. The docs I found on the controller on the electric scooter parts dot com web site listed a 35a breaker as a necessity for my operating voltage. My cowboy math had it around 30a. Would it be overkill to put a breaker on both batt leads? 
I will also be adding in an ammeter and charge/fuel meter for the front dash console.
SO close, I would've taken a test drive last night if I wasn't put off by the sparks.


----------



## Ziggythewiz (May 16, 2010)

soon2bEV said:


> Would it be overkill to put a breaker on both batt leads?


Since it's a safety feature, I believe the correct term would be underkill 

For highway EVs it is usually recommended to have one on each end plus at least one in the middle, but for your application one should be sufficient.


----------



## soon2bEV (Mar 14, 2011)

Ok, so one breaker on each batt lead makes sense. Where would the 'middle' you speak of be located? Would the middle be between the controller and motor?. Also, would you put two in series in case one locks and doesn't trip (from an earlier response here). A sort of safety-safety so to speak
Thank you for your help!
-D


----------



## Ziggythewiz (May 16, 2010)

In a typical EV, the middle is the mid-voltage wire that connects the front battery pack to the rear pack, as most vehicles can't fit them all in one place.

In your case, the batteries are all in one pack, so you only need to fuse it at one (or both if you want) end. All fuses will be in series, just like your batteries, though not right next to each other. You don't need to chain them together in case of failure, they're designed to fail and break the connection and made to be quite reliable.

There should be nothing between the motor and controller.


----------



## soon2bEV (Mar 14, 2011)

Got it... Should I then remove the on/off switch I have on the (+) motor lead? I was just putting one there for the security aspect. Not that it would stop anyone from taking it, just something to slow them down if they had eyes for my bike.
That or I wire in a zapper that will zap unless remotely disengaged
I'm sure that wouldn't work given the handle grips are plastic.


----------



## Ziggythewiz (May 16, 2010)

Any on-off switch you have should cut power to the motor controller, not the motor directly. Your switch is likely not rated for the power the motor will draw anyway.


----------



## soon2bEV (Mar 14, 2011)

Thank you for that!
I was concerned about that aspect of my circuit design, and since I am recrafting my busbar will make the design easier. And yes the sw was definitely on the fringe of rating, I had my doubts. 
Since I am using a PM motor, do you know if there is a small controller that does regenerative braking as well? Sort of off topic, but I thought I'd ask here first.
Thanks for helping me keep my stuff from melting.


----------



## Ziggythewiz (May 16, 2010)

I don't know of any small controllers that do regen, usually regen comes with a hefty price tag and is not worth it for a DIY build.


----------



## soon2bEV (Mar 14, 2011)

Thank you Zig! I am starting a new thread with new questions now that I am past this phase.. It's back to the lab


----------

