48v through a 24v on/off switch ?

[1000watt]

I am running a 48v 1000w Golden Motor with a 48v 10AH LifePo4 battery. I trimmed the shunt so amp peak is only 19.6A on my WattsUp meter, even on a steep hill it never goes over 20A. The positive lead on the battery goes to a 30Amp fuse then to a 24V 25A rocker switch. I haven't had any problems running 48v through the 24v switch yet. I read that maybe I should add a 1K, 5W resistor to the switch... I only have about 40 miles on this setup. So do you think the switch will be ok?

Sorry for the blurry pic.

 

[Lock]

...a 24V 25A rocker switch

I believe it depends on the switch... So, this is intended to break full loads? Rated as DC? (Huge diff. between AC and DC ratings...)
Only to be used once-twice-never?
tks
Lock

 

[1000watt]

I don't see any ac or dc marking on the switch, If I had to guess I would say it's DC. I use the switch to turn on the battery under no load then after riding I flip switch to off under no load.

 

[Lock]

If always NO load, I would only look at the size of the contact surfaces and any electrical pathways. That they don't heat up under full loads... No heat and you are good-to-go...

 

[1000watt]

On my next ride I will feel the switch for heat. Thanks

 

[adrian_sm]

The in rush current to charge up the capacitors in your controller might slowly kill the switch contact faces.

Do you notice a different sound when you flip the switch after it has been off for a while. Might be a spark jumping the gap, and pitting the contact faces.

 

[StevenR]

Yes, there is a big surge when the caps charge on initial start-up which will cause a spark at the contacts of the switch. A pre-charge resistor is used to slowly bring the caps up to voltage and supress the initial spark. The pre-charge resistor and low-current switch would be put in parallel with the main switch. Turn on the precharge switch, wait a few milliseconds for the caps to charge, then turn on the main switch. You probably want to put a small fuse in there somewhere too or accept burning it up if you forget the main switch.

I don't use pre-charge resistor and had just a key switch on a 48V40A controller. It held up for several thousand miles but had a bunch of char on the contacts. The switch should probably last a while on that rig. If not and it is weak, it deserves to die! Put powerpoles on either end so that when it dies, you can just unplug it and bypass.

I am now running so much current that I have taken the switch out.
Q: What DO you use for 5kW DC that is cheap and light?
A: NOTHING!
I use the switch on the controller and accept the parasitic load when it is off. If it is going to be off for a long time (weeks, not days), I break the power poles right at the battery negative, but it is rarely that long. If it will be a real long time, I take the BMS sense plugs off to remove the BMS and have the battery totally isolated from everything. I get a spark when I reconnect the powerpoles but I don't do that often.

 

[Russell]

I used a 12V/50A toggle switch from RadioShack with good results on 48V/15-22A. I added a precharge resistor (200 ohm) and momentary switch across the main toggle switch contacts. Press momentary switch, wait 1-2 seconds, toggle main switch on and release momentary switch. This is a good way to go to preserve the main switch contacts.




I also have a key switch which has held up well. You can buy a Crystalyte key switch like the one pictured below from a number of ebike vendors for around $15. ( http://www.electricrider.com/crystalyte/x-ks-01.htm )




I also have tried a 30A (80VDC) version of the marine/RV circuit breaker pictured here. Unfortunately the breaker can trip with a slight touch or good mechanical shock so it's not my favorite.




I also got this heavy duty battery disconnect switch for less than 10 bucks on eBay but haven't used it yet because it's kinda overkill for my bikes.





-R

 

[VSkudarnov]

Car Audio circuit breakers should perform well, they are 12/24V and 50-300A. Cost $10-15 on Ebay.

 

[John in CR]

StevenR has it right. The on/off switch doesn't go on the battery main. That safety feature is only needed for brushed motors. Your switch goes on the wire that supplies the current to the brain of the controller, which draws less that .1A, and doesn't feed the main caps. Switching the mains each time you turn on not only will wear those contacts over time, but it also slams your capacitors with the inrush of current which reduces their life and can cause certain surface mount components on the controller's main board to fail. No only are the big expensive switches a waste of money, but wiring that way can actually cause breakdowns. It's one of the most common errors on ES, because it perpetuates when others chime in about the switches they use. They'll all fail in time, since each time they're switched the contacts are scarred a little bit, while even the cheapest switch will work on the low current supply wire almost indefinitely.