A kill switch...How many amps?

rg12

100 kW
Joined
Jul 26, 2014
Messages
1,584
I want to add a kill switch between the battery and the controller.

Do i have to buy a big 40A switch in order for it to stand the current? or can i get a small normal size switch
and solder it to the negative cable? would that solve my problem?

Roy.
 
If you have an ignition wire, which is also called "key lock", "anti thief" and other names, put your switch on that, where you only need a small switch. You can also use one of the brake switch connectors for a kill switch. Just put a switch between the two wires. You can use the tiniest of switches on that one.
 
If you use the small red ignition wire on the controller as a permanent off, your battery will likely still have drain on it from the controller. If you want to prevent that you can use a few options.

One being a DC contactor rated for your application (this will be expensive and fancy) but allow a remote switch on your bars with small gauged wires controlled by your batteries voltage.
hzj100s-48_600_z1.jpg


Or a battery master switch for about $10 (they are fairly bulky but do the trick)
images


or a circuit breaker, but most of them on this side of the lake aren't DC rated and do not have line/load terminals
Front.jpg


Maybe add a pre charge resistor into the mix if you are going to this extent.
 
ElectricRider.com sells a 40A switch from crystalyte. It's great quality. I've used them on 7 or 8 bikes so far.
 
Are you looking for something that is a literal kill-switch, for emergency use? If so, just use a jumper wire you can easily reach that can be yanked out with one hand. One way to do this is a pair of SB60 Andersons: Wire up in either + or - of the battery output one of the SB60's, cutting the wire and putting one contact on either end. Securely bolt that SB60 to the frame or something, so it doesn't have to be held onto while you pull or push on the other one.

Then use the other SB60 with a loop of wire from one contact to the ohter, as the pull-out killswitch.

You can also use that as a security measure, since it's not highly likley anyone will have an SB60 laying around to plug in there as a shorting loop (although if htey knew what it was for they coudl also short across it iwth something else, they'd have to know first.).

Then you can use the "ignition wire" on the controller as the normal on/off switch. It isn't going to use much power when in this "off" state--unless you have something else besides the controller hooked ot the battery (like a DC-DC or Cycle Analyst, etc) that would still be on, it'd work fine. And if you power those devices off the ignition wire instead of the main battery power, then they'll be off, too, and you have nearly zero power consumption.

But it is not completley zero, so you would want to disconnect the battery if it's being stored for a while.
 
amberwolf said:
Are you looking for something that is a literal kill-switch, for emergency use? If so, just use a jumper wire you can easily reach that can be yanked out with one hand.

If you do this right, you should make it look like the eject handles on fighter jets :D
300x450_q75.jpg
 
amberwolf said:
If you power those devices off the ignition wire instead of the main battery power, then they'll be off, too, and you have nearly zero power consumption.
I like the sound of that. How much current can be drawn from the ignition wire on a typical controller?
 
Thanks Amberwolf. I was wondering if there could be anything else upstream that may pose a problem (resistors or thin traces etc.), but that's good to know.
 
:oops: I had a bit of brainfart actually: really it doesn't matter: you don't even have to replace the wire in the controller itself to get more amps to devices powered off of it, because you'd really be hooking them up before the controller anyway. The power doesn't actually come from the controller or thru it.

You could run whatever gauge you want from your "ignition switch" to each of teh devices powered only when the switch is on, and also just hook up the controller's ignition wire to that same point on the switch.

You *can* power them post-controller, but there's no need to, and you'd actually have to add a new wire inside the controller to be able to do that. :oops:


(what really is happening with the ignition wire is that it supplies the Battery+ to the low-voltage regulator section of the controller, instead of being directly supplied by the B+ that's at the FETs and so on inside it. That way you can either just hook it straight up to B+ externally, or you can use it to power off most of the controller (really all the stuff that uses up any significant power when not running a motor). I've also seen controllers that have this wire run internally straight to B+ (or to a switch on the case itself), but still have the wire so they do have the option of running a longer wire outside the case to use as a keyswitch/ignition somewhere else on the bike. )
 
Ahhhhh, of course, the feed comes straight from the battery doesn't it. Sorry, it was a stupid question to begin with. The switch would essentially just be serving multiple circuits. Good idea though.
 
I like the idea of using the brake wires the most.

I just need a kill switch for when the throttle is sticking etc...

My controller LCD can power on and off the bike by holding the main button on the screen for two seconds.
Doesn't that cut all the power and wastes zero battery? (this question is separate from the kill switch idea
which i'm going to apply to the brake wires like i wrote above)

Roy.
 
Instead of building a custom kill switch into the ebrake connector, why don't you just use an ebrake lever. This is almost the definition of reinventing the wheel...
 
mlt34 said:
Instead of building a custom kill switch into the ebrake connector, why don't you just use an ebrake lever. This is almost the definition of reinventing the wheel...

I have 200mm hydraulic disc brakes...i don't think putting a .99c lever would increase my safety.
 
rg12 said:
I like the idea of using the brake wires the most.

I just need a kill switch for when the throttle is sticking etc...
All you need is the ebrake switch in that case. You can add one to your existing brake handle or cable or whatever, by a number of methods. If you search for "*brake" and "switch" on ES you'll likely find a lot of posts and topics about doing that. Might be a wiki entry about it with links by now, too (if not, feel free to create one. ;))

My controller LCD can power on and off the bike by holding the main button on the screen for two seconds.
Doesn't that cut all the power and wastes zero battery?
No, the LCD itself is still using power to wait for the next button press to turn it back on. ;) It probably uses the "ignition wire" in the controller to turn it on and off, so again it still ends up with power across the FETs and main caps. There is almost no power usage in that case, but there is still a tiny bit of leakage thru the caps/etc., plus the little bit used by the LCD unit.

Easy enough to test how much by putting your multimeter set to A or mA (or wattmeter) in series with the battery + or - leads, and turnign the system on and off, to see how much is used in standby in either case. Then you know how many Ah it uses over time, and can calculate how long your pack would last before LVC point just sitting there with it in standby.
 
riba2233 said:
There are some DC breakers, just search ones for solar use.

For for $27 CDN, I've ordered a 50A solar use breaker to protect my DIY 72V 16Ah Sony 18650 triangle battery (in case of external short from controller or charger). It's good for up to 150V DC and I'll post how it turns out.

http://www.ebay.ca/itm/Midnite-10A-15A-20A-30A-50A-63A-DC-PV-Solar-Charge-Circuit-Breaker-Disjoncteur-/290853459161?pt=LH_DefaultDomain_2&var&hash=item43b83794d9&_uhb=1

This would also serve as a kill switch, though waterproofing could be a problem? I have a switch on my controller behind my seat which will serve as a kill switch, so the breaker will be in my battery bag.
 
Here you go guys, i ebayed it!

2 pin
http://www.ebay.com/itm/Heavy-Duty-Toggle-Switch-2-Pin-Chrome-50-Amp-VW-Camper-Beetle-Buggy-Bay-Bus-T1-/150830136744?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item231e2d3da8

3 pin
http://www.ebay.com/itm/Heavy-Duty-Toggle-Switch-3-Pin-Chrome-50-Amp-VW-Camper-Beetle-Buggy-Bus-Bay-T1-/160817038637?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item257171452d


So the ignition wire on all of those simple ebikes you see on the streets aren't really killing the power totally when turning the key off?
damn...gotta take care of my 6 beautiful zippy's...gonna stick that huge world war one air craft style switch on my bike.

EDIT: DAMN! up to 24v those stupid switched arrhh...What do all those commercial stealth bomber etc use for killing power?

Roy.
 
rg12 said:
Here you go guys, i ebayed it!

2 pin
http://www.ebay.com/itm/Heavy-Duty-Toggle-Switch-2-Pin-Chrome-50-Amp-VW-Camper-Beetle-Buggy-Bay-Bus-T1-/150830136744?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item231e2d3da8

3 pin
http://www.ebay.com/itm/Heavy-Duty-Toggle-Switch-3-Pin-Chrome-50-Amp-VW-Camper-Beetle-Buggy-Bus-Bay-T1-/160817038637?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item257171452d


So the ignition wire on all of those simple ebikes you see on the streets aren't really killing the power totally when turning the key off?
damn...gotta take care of my 6 beautiful zippy's...gonna stick that huge world war one air craft style switch on my bike.

EDIT: DAMN! up to 24v those stupid switched arrhh...What do all those commercial stealth bomber etc use for killing power?

Roy.

24 V shouldn't be a problem, however I doubt it can really stand 50A, but who knows...

That solar breaker should be a better option, or this one:

images


This one can stand 100A continuously, but it's big.
 
Only brushed motors need a switch on the battery leads. Brushless just need a fuse there. Then a low current switch goes on the supply to the controller brain without which a brushless motor cannot run. The first line of defense is the ebrake switch, which tells the controller to cut power, but the controller is still on, and with that thin wire that flexes all the time when turning the handlebars and is pretty exposed to damage a failure in that line or cheap switch is foreseeable. That makes a secondary means of shutting down very needed, plus you want to turn your bike off when parked anyway so some little kid walking up and twisting the throttle doesn't hurt themselves. That's where a low current key switch comes into play. Put it where you can easily reach it while riding, and where the wiring isn't exposed like it would be up on the handlebar (who wants pack voltage going to the handlebar anyway?), and you're good to go. I use a generic switch for motorcycles, and since I don't draw big power on my DC/DC converter, the wiring and contacts are beefy enough to handle that current too on my bikes.
 
John in CR said:
Only brushed motors need a switch on the battery leads. Brushless just need a fuse there. Then a low current switch goes on the supply to the controller brain without which a brushless motor cannot run. The first line of defense is the ebrake switch, which tells the controller to cut power, but the controller is still on, and with that thin wire that flexes all the time when turning the handlebars and is pretty exposed to damage a failure in that line or cheap switch is foreseeable. That makes a secondary means of shutting down very needed, plus you want to turn your bike off when parked anyway so some little kid walking up and twisting the throttle doesn't hurt themselves. That's where a low current key switch comes into play. Put it where you can easily reach it while riding, and where the wiring isn't exposed like it would be up on the handlebar (who wants pack voltage going to the handlebar anyway?), and you're good to go. I use a generic switch for motorcycles, and since I don't draw big power on my DC/DC converter, the wiring and contacts are beefy enough to handle that current too on my bikes.

I didn't understand how exactly i can install a low current switch if i have a fuse...
I don't want to have the brake kill switch and another battery kill switch because i just need one switch to cut power totally by disconnecting the battery
but i can't find a way to place a normal sized low current switch on those thick wires. My max amp draw will be about 40-45 amps i guess at 60v.
 
rg12 said:
John in CR said:
Only brushed motors need a switch on the battery leads. Brushless just need a fuse there. Then a low current switch goes on the supply to the controller brain without which a brushless motor cannot run. The first line of defense is the ebrake switch, which tells the controller to cut power, but the controller is still on, and with that thin wire that flexes all the time when turning the handlebars and is pretty exposed to damage a failure in that line or cheap switch is foreseeable. That makes a secondary means of shutting down very needed, plus you want to turn your bike off when parked anyway so some little kid walking up and twisting the throttle doesn't hurt themselves. That's where a low current key switch comes into play. Put it where you can easily reach it while riding, and where the wiring isn't exposed like it would be up on the handlebar (who wants pack voltage going to the handlebar anyway?), and you're good to go. I use a generic switch for motorcycles, and since I don't draw big power on my DC/DC converter, the wiring and contacts are beefy enough to handle that current too on my bikes.

I didn't understand how exactly i can install a low current switch if i have a fuse...
I don't want to have the brake kill switch and another battery kill switch because i just need one switch to cut power totally by disconnecting the battery
but i can't find a way to place a normal sized low current switch on those thick wires. My max amp draw will be about 40-45 amps i guess at 60v.
That is a low switch to work on high current? No- high current switch for high current, low amp rating switch on the 'ignition' wire only because it only carries a low current.
 
I like these circuit breakers, works great if you are putting them in an enclosure. Big selection.

http://www.bluesea.com/products/7220/A-Series_Black_Toggle_Circuit_Breaker_-_Single_Pole_30A


Blue Sea might be on Amazon as well.

http://www.amazon.com/Blue-Sea-Systems-A-Series-Circuit/dp/B000MMH27K/ref=sr_1_14?s=sporting-goods&ie=UTF8&qid=1409108890&sr=1-14&keywords=blue+sea+systems+circuit+breaker
 
I'll go over it one more time before giving up. The battery leads carry the primary current and with brushless motors only a fuse is needed there to cut the battery supply in the event of a short. The low current switch goes on the supply for the BRAIN OF THE CONTROLLER. This is commonly a separate wire on our controllers that connects to Battery positive. This is a very low current connection, often less then 1/10th of a amp, that turns the controller itself on to supply the MCU it's power to switch the power mosfets (solid state switches in the controller connected to the battery mains) on and off in a manner that supplies an alternating current to the 3 phases of the brushless motor. Without this low current supply to the MCU (the brain of the controller), the motor cannot run. That means turning that low current supply off, cuts motor power, period.

If you have a DC brushed motor, then the only way to shut down in every possible failure event that could result in a runaway condition is to cut battery power completely. Brushed motors used to be the norm, and that old school thinking that battery mains need a switch originated. High current switches, contactors, etc are required for brushless motors, but they're expensive and bulky, but thankfully unnecessary for the brushless rigs the overwhelming majority of us have.

While about once a year some try to defend their use of big, unnecessary, failure prone switches on the battery mains using brushless motors, I put them in the same category as people who think it's convenient to remove their battery pack after every use, and break it apart to recharge. I wouldn't even ride an ebike if it was that detail oriented and failure prone. Who wants a hobby called fiddling with ebike batteries? I take due care in making my battery connections correctly about once every 2 years, and that corresponds with the same number of times I would need to use a money wasting, resistance adding, failure prone switch on my battery leads. On that basis my "switch" is either a bolt together connection or a soldered connection of large gauge wires. What do I know though? Despite being one of the heaviest guys on the forum, I've got the only 100mph capable electric bicycle, and in 6 years not a single under $10 switch I've used has ever failed, and the keys for them fit nicely on a regular key ring. Had I fallen for the concept that my switch needed to be on the battery leads, there's not doubt in that time I would have been left stranded by a failed contactor at least once, and had to replace others with failure emminent, wasting hundreds of dollars in the process.

Adopt the KISS principle and do things the simple way. I'd bet most using switches on their battery mains don't even have fuses on them, so guess what will happen a worst case scenario, a short of the battery mains? You got it, the contacts of their switch will weld together in the closed position, while they can only stand there and watch their bike go up in flames. Worse yet some idiot with an iPhone will record the event, and it ends up on the news, hurting the cause like any EV fire made public.
 
Im not sure what current or voltage you are running but this one is rated for 80volt dc and 63a current :
http://uk.mouser.com/ProductDetail/Altech/2D63UM/?qs=sGAEpiMZZMvNllHT6Fj2fuIX06sKXks1KXbFNSveDmQ%3d

I have a circuit breaker on mine and its rated at 80v dc and 120a or 150a current as im running quite a bit of power, it works fine as a switch and I never hear any arcing inside it when its flipped, I connected that after I crapped myself having to do it manually, as pushing the cables in by hand can draw an arc if your not careful.
 
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