Spark avoidance and precharge resistor

[groundproximity]

Anyone with a decent solution how to avoid the sparks if connecting a 16S LiFepo4 to the charger XLR connector.
I guess most of you guys use precharge resistors.
Could anyone explain how to make one. Maybe i missed the thread but most of the threads include coments of people who already know how to make one

Thanks,

Alex

[RVD]

i just built one last week.

it's fairly easy. just get a resistor by calculating it at: http://scriptasylum.com/rc_speed/nospark.html

for me, i just went to radio shack and bought a 100 ohm 1 watt resistor for a few bucks (came in a pack of 2) and it seems to work fine. i wait about 2-3 seconds and it doesn't spark anymore.

you just want to split up your pos(+) coming from your battery into 2 red wires. your red battery wire from the controller needs to also be split into 2 red wires. 1 wire will have the precharge resistor between it and the controller. so when this line is plugged in it will look like:

battery -> resistor -> controller

then you have a second red wire that you plug into the controller after waiting a few seconds...

battery -> controller (no spark!)

i'm not sure if the attached image will help since it has more things in it. you can ignore the whole key/ignition thing and just assume that is one wire connected. i also used a hub to simplify the Y splitter / connectors a bit.

[ZOMGVTEK]

Just buy or find a high power resistor (1-5+ Watts) at somewhere around 50-500 Ohms, and then put in in line with any wire going to the controller, and a separate connector. I run two sets of Anderson Power Poles. One has a pre-charge resistor on it, and I plug it that first, wait a few seconds, then plug the big power wires in to actually power the bike.

Its a resistor, which resists current flow. You don't want to put it on your standard power connector, since the bike wont work anymore since it wouldn't be able to pull any power through the resistor. You need a separate connector of any kind to charge the caps in the controller up before connecting your main power leads. It works the same as your standard power connection, so you need a plug on the controller AND battery, one of those sides needs a resistor in line with a + or - wire. Its that simple. You can leave it connected even after the bike is plugged in, no power will run through it after the initial charge.

I never ran one with 48V of lead and thin power wires. Now that I'm running over 100V hot off the charger of 24S lipo, thick wires, and beefy caps in the controller, the connectors get absolutely DESTROYED after only a few connections. I had a 500 Ohm 5W resistor laying around, and now theres essentially no spark or damage to the contacts on connection. 500 Ohms is a bit on the high side, but its still better than nothing, and works just fine at 100V.

EDIT: I see you're talking about a charger... This really shouldn't be a major issue, but the same principal applies. Most people only run them on the controller.

[groundproximity]

Thanks to all of you.
Even as a non electrician i should be able to build that.

Cheers,

Alex

[Dingo2024]

Hi Alex, I have a precharge resistor on the battery connection to the controller and works well although it has blown once (I think that was down to me doing stupid stuff though)

looking at your original question though....was it sparking on connection of the charger to your battery pack the problem My pack did so I coated both plugs (XLR) with die electric grease (actually I used Vasoline) and is much better now

Ian

[groundproximity]

Hey Ian,

electric grease... i think some years ago, when i started with my first build i ordered that from ebikes.ca.
...not knowing what the purpose of that could be
It just sounded like something i would probably need

So, i just dig both plugs into that stuff and thats it right - sounds easy.

Alex

[fechter]

If the spark is between the charger and the pack, try turning on the charger first before making the connection. Depending on the charger, it may resolve the problem.