Wire diagram

[davy1010]

For my build I've figured out the wire diagram below, I'm an electrical newbie so I'm not sure if this will work / will not short my battery...

If you guys could give me your feedback, that would be great.

The battery kill switch is meant to switch of the whole system, the on/off switch is meant to turn the lights on and off.

 

[Philistine]

One thing I would point out is ideally you should have a precharge resistor for the kill switch. This isn't such a big issue with 48V, as the arc isn't so bad, but basically the arc created from constantly turning that kill switch on and off will eventually fry/pit the contacts. I run 84 volts, so the arc is much worse, but before I installed a precharge resistor, using that same kill switch, I eventually welded the switch shut after about 3-4 weeks of use. I am sure on 48V it would last alot longer, but putting in a precharge resistor is also better for your controller. The way I did it was to take a resistor (I used a 1,000 ohm 5w resistor, but I think you will need less resistance for 48v, do a search on here for the ideal resistor for that voltage), then take a button switch. THe button/press switch and the resistor sit in line over the kill switch, I press the button to start precharging the caps in the controller, then after a few seconds throw the switch. This stops the switch arcing and will preserve its life, as well as protect the controller from the in rush current. There is heaps of posts/threads on here showing how it is done. I thought it was unecessary until I welded my switch shut.

 

[davy1010]

One thing I would point out is ideally you should have a precharge resistor for the kill switch. This isn't such a big issue with 48V, as the arc isn't so bad, but basically the arc created from constantly turning that kill switch on and off will eventually fry/pit the contacts. I run 84 volts, so the arc is much worse, but before I installed a precharge resistor, using that same kill switch, I eventually welded the switch shut after about 3-4 weeks of use. I am sure on 48V it would last alot longer, but putting in a precharge resistor is also better for your controller. The way I did it was to take a resistor (I used a 1,000 ohm 5w resistor, but I think you will need less resistance for 48v, do a search on here for the ideal resistor for that voltage), then take a button switch. THe button/press switch and the resistor sit in line over the kill switch, I press the button to start precharging the caps in the controller, then after a few seconds throw the switch. This stops the switch arcing and will preserve its life, as well as protect the controller from the in rush current. There is heaps of posts/threads on here showing how it is done. I thought it was unecessary until I welded my switch shut.

Thanks a lot for your adivce, I've been looking into it and I believe this is how the diagram should look like with the resistor. I'm wondering, will the little on/off switch before the resistor not be affected by some sort of spark? I've calculated that I will need a 400 ohms 2 watts resistor (2 second charge) (http://www.scriptasylum.com/rc_speed/nospark.html).

On ebay I can find lots of resistor that fit the 400 ohms 2 watt (or more watts) standard. Are these all good or should I look for a resistor made from some special material?

I believe this would be the "power on" routine:
1. switch the resistors on/off switch on
2. wait 2 seconds
3. switch the battery kill switch on
4. switch the resistors on/off switch off
5. ride my bike
6. after riding switch the battery kill switch off (is there an arc when switching off?)

Your advice is appreciated

 

[AussieJester]

I am sure on 48V it would last alot longer,

I run exact same switch on 48v lipo setup, has been in use over 12 months no issues.

With your light/fan switch...you will only be able to have fan and lights on at same time
is that how you wanted it?

KiM

 

[auraslip]

There are two versions of that switch - the cheap $2 one from harbor freight and the more expensive one........... I am really curious to how they hold up. I've used mine at 48v for 8months, but with a precharge.

 

[Philistine]

How you have put it in your diagram is exactly how I have my setup. The small switch doesn't get stressed because the resistor is limiting the current flow, I use a button rather than a switch, so that once the precharge is caused, the main switch throws, and the "small" wiring/switch no longer sees any current if that makes sense.

But as Aussie Jester pointed out, perhaps it is not needed for 48V - if he has not had problems with his switch I guess it is fine. For example, I run 48V on one bike, that doesn't have a switch (I just plug and unplug the andersons for power, and put up with the spark). I could do that for months before having to replace the andersons from pitting. When I moved up to 84V, the spark/arc on the andersons destroyed them in a matter of weeks. So the arc on 84v is substantially more damaging. As I said, it caused my switch to stick shut after weeks (you could hear the arc happening inside the switch quite loudly).

But if you intend to move up voltages at some stage it might be worth putting in, otherwise you could always try without it and just get another switch and precharge setup if it does start sticking. I was just pointing out my experience.

 

[AussieJester]

There are two versions of that switch - the cheap $2 one from harbor freight and the more expensive one........... I am really curious to how they hold up. I've used mine at 48v for 8months, but with a precharge.

I bought mine local from JayCar (Electronics chain of stores in OZ) It was ~20 bucks. I have two of these
as mentioned one in use for over 12 months now, the second i have recently fitted to my new bike
i had to do some 'surgery' on it before instal which required dissembling the switch, it consists
of a sprng and a ~3mm thick copper bar that is pressed onto contacts when 'T' handle is turned
I considered momentarily about beefing this 'bar' up, but seeing it was as thick as the bus bars
i am using i left it be haha.. I only run 48v systems so can't testify to how well this switch will work
and for how long on higher voltage setups, where a pre-charge resistor is advantageous to both switch
and speed controller.

KiM

 

[davy1010]

I am sure on 48V it would last alot longer,

With your light/fan switch...you will only be able to have fan and lights on at same time
is that how you wanted it?

KiM

I want the fan to be on all the time, the on off switch is meant for the light only.

I thought if I put them in parralel this would work, how should I wire it then?

 

[Alan B]

Looks to me like the switch controls the light, the fan is on whenever the main power switch is on. The fan will also run during precharge, which may slow the precharge down and prevent it from completing, depending on the current drawn by the fan and DC-DC versus the current supplied by the precharge resistor. It is probably not a problem if the precharge resistor is low enough.