On/Off switch for ebikes

gobi

10 kW
Joined
Jan 9, 2021
Messages
540
Greetings from west MI,

Finally we have some cool temps and this time of the year till we have snow on the ground is my favorite to be outside riding my bike.
The girls like the scooters better and have not really spent any time on the bikes after a few rides.

I have tried to adjust the brakes on one ebike with v-brake instead of the disk (front) and I threw in the towel, my skill are not there unfortunately.

I have xt60s on the batt side and have extension wire from the rear carrier to the controller. I use the connect/disconnect the xt60 to the take batt off to charge.

SHOCK/SPARK - the spark from initial connection (juicing the caps) scares me abit.
I want to put an INLINE switch.

1. What switch should I use?
2. The motor in question is a 300w bafang geared (uber take off) with 36v or 48v battery.

I thought about a breaker but a breaker is not designed to used as a switch.
 
You could switch to Anderson connectors or XT90 anti-spark connectors. They do sell marine battery cutoff switches, but I haven't used one.
 
RunForTheHills said:
You could switch to Anderson connectors or XT90 anti-spark connectors. They do sell marine battery cutoff switches, but I haven't used one.

I bought a pack of those anti-spark xt-90s, would be sufficient? I will solder one tonight and try it tomorrow..

I have a few of those marine battery switches, man those are BIG, something smaller out there?
 
https://ebikes.ca/switchwp.html

https://ebikes.ca/keyswitch.html

https://lunacycle.com/remote-on-off-solid-state-switch/
 
Disconnecting the battery is a good safety measure, and the spark when connecting does not damage anything but pitting the connector that should last very long before it’s pitted enough to replace it. Bigger connectors last longer, Andersons P75 will outlast the wire that is slowly corroding in winter conditions.

That said, you still should have a switch. The controller normally has a wire for a start switch. A breaker is a good safety for shorts but few would survive being used as a daily switch. Check Square-D breakers, I know they do but still, you have to install it on a safe dry place. Batteries are safer disconnected off anything at rest and the best way is to disconnect.
 
Without spending much money, I just took an old AC switch and rigged it for anti spark. Very little current goes thru the contacts when switched, so I believe the contact ratings is of less concern. This was when I first started using batteries w/o ON/OFF switches.

Then I tried XT90 anti-sparks. Worked fine.

Then I had so many battteries and bikes, I just live with the pop these days. Tells me the batteru has a charge.

anti-spark.jpg
antispark2 (1 of 1).jpg
 
When using the xt90 anti spark connectors you plug them halfway in first to energize the pre resistor then fully plug it in if you just fully plug it in ot doesn't have time for the resistor to pre-charge the controller to prevent spark
 
You can use a BMS that has an on/off function, like the speedict Neptune 15. This switches power in the mosfets so no Spark from charging caps.

The spark and associated erosion of connectors scares me too. some controllers seem to put up to 1000uF across the DC rails- don’t really know why you’d need this when parallel lithium ion batteries have such low impedance anyway!
 
docw009 said:
Without spending much money, I just took an old AC switch and rigged it for anti spark.
That resistor looks pretty crispy.

There are plenty of switches out there rated for very high currents - and when the arc is internal (and the switch is designed for the current) it's not much of an issue.
 
MadRhino said:
Disconnecting the battery is a good safety measure, and the spark when connecting does not damage anything but pitting the connector that should last very long before it’s pitted enough to replace it. Bigger connectors last longer, Andersons P75 will outlast the wire that is slowly corroding in winter conditions.

That said, you still should have a switch. The controller normally has a wire for a start switch. A breaker is a good safety for shorts but few would survive being used as a daily switch. Check Square-D breakers, I know they do but still, you have to install it on a safe dry place. Batteries are safer disconnected off anything at rest and the best way is to disconnect.

ok, yes, the spark is fine, but I am bit faint hearted, so more anxiousness of the impending "crack" is what I want to get rid off.

Square breakers sound good, I will check them out, I need something small that can sit behind the battery.
 
999zip999 said:
Okay doc but in his situation he might need a bigger resistor huh ? I don't know the formula but there is a formula.
docw009 said:
Without spending much money, I just took an old AC switch and rigged it for anti spark. Very little current goes thru the contacts when switched, so I believe the contact ratings is of less concern. This was when I first started using batteries w/o ON/OFF switches.

Then I tried XT90 anti-sparks. Worked fine.

Then I had so many battteries and bikes, I just live with the pop these days. Tells me the batteru has a charge.

anti-spark.jpg
antispark2 (1 of 1).jpg

Now I am curious, what is the math to figure out the size of the resistor?

I can 3m VHB tape an A/C switch sideways on to the battery with the resistor as in your pic, attached to the battery, it will be one less thing to hang.

FYI: I bought 15amp switches off amazon and not sure what I was messing with, but the switch welded shut.
 
electric_nz said:
You can use a BMS that has an on/off function, like the speedict Neptune 15. This switches power in the mosfets so no Spark from charging caps.

The spark and associated erosion of connectors scares me too. some controllers seem to put up to 1000uF across the DC rails- don’t really know why you’d need this when parallel lithium ion batteries have such low impedance anyway!
999zip999 said:
When using the xt90 anti spark connectors you plug them halfway in first to energize the pre resistor then fully plug it in if you just fully plug it in ot doesn't have time for the resistor to pre-charge the controller to prevent spark

I am using off the shelf 48v batteries with enclosed BMSs.

That is a neat way to prevent the spark, I like it, may I need to plan on making a 20a 48v battery with an JBD bluetooth bms that has an on/off switch.
 
JackFlorey said:
docw009 said:
Without spending much money, I just took an old AC switch and rigged it for anti spark.
That resistor looks pretty crispy.

There are plenty of switches out there rated for very high currents - and when the arc is internal (and the switch is designed for the current) it's not much of an issue.

Link to something I can buy off the interweb pls, my 15a amazon purchase smoked out :shock:
 
gobi said:
Link to something I can buy off the interweb pls, my 15a amazon purchase smoked out :shock:
I have used this one for several builds, including one that could be switched between 36 and 72 volts:

https://www.digikey.com/en/products/detail/nkk-switches/S732/1007152

But it's not available any more. I'll look around some more.
 
gobi said:
Link to something I can buy off the interweb pls, my 15a amazon purchase smoked out :shock:

I use one of these on my battery that has a switch:

https://www.ebay.com/itm/203592560317
s-l400.jpg


It's rated 300A and 60V, though power-on sparking will surely reduce its real capabilities over time.

I tapped the mounting holes with M5 threads to make my life easier.
 
Jack, that is a nice switch, 50a rated, little ching ching though.

Chalo, $8 works for moi,

Thanks for the input gentlemen!
 
Ships from United States. I'm 25 miles from Long Beach there's three tankers parked out in front of my Beach that means there must be about 68 tankers ready to unload or more. So forget about the slow boat from China method
 
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