48v eBike Battery Isolation Kill Switch

[Donut]

Hi. Hoping someone with more knowledge than me on DC currents will give me a hand here. Don't want to be riding atop a fireball or have my ebike explode in the house while fast asleep.

I hope to be able to use a battery isolation switch on my ebike so it doesn't 'pop' when I change batteries which as you know degenerates the connection.

I have two identical (48v 20Ah 1000w 13S3P) Lithium ion Battery Packs.

Recently found an isolation universal battery switch rated specifically for 48V DC at 600amp.
https://www.aliexpress.com/item/1005001436584952.html

I was planning to encase the two batteries and switch in a light steel, heat insulated, lockable box, on a trailer attached to the bicycle. Summers here get over 40C.

Like to be sure this switch is the right thing to connect between my battery and the ebike controller. What's your thoughts please?

 

[Tommm]

You either work hard or work smart. A massive breaker is the hard way. Your BMS contains exactly the functionality you are trying to reproduce, it cuts off power on low voltage, over voltage or what have you. A switch on the bms to toggle the FETs is the smart way.

There are 3 types of BMS:
Physical contacts for a power isolation switch (current flow is a few mA on that switch, you can see them as red switches on the side of hailong packs)
Bluetooth app with power off command
No contacts or bms app (trash tier bms)

Do it the smart way.

 

[e-beach]

Looks like over-kill to me. However it would work.

What it really depends on is the amp draw of your controller. If you have a switch that meets or exceeds the volts and amps of your system, you should be fine.

What is the maximum amp draw of your controller?

 

[Donut]

You either work hard or work smart. A massive breaker is the hard way. Your BMS contains exactly the functionality you are trying to reproduce, it cuts off power on low voltage, over voltage or what have you. A switch on the bms to toggle the FETs is the smart way.

Pardon my ignorence, I built it and ride it, I don't know how it works, technically.
I presume "BMS" is battery management system but am not aware if I have one, or not. Have no idea what "FET" is. So the balance of your obviously very helpful information is totally lost on me.

I understand how a kill switch works, which is why I want to use one.

 

[Donut]

What is the maximum amp draw of your controller?

Sorry, don't know the "amp" answer just know the battery and controller work togeather. The motor and controller are also supposed to be 1000w 48v.

 

[Tommm]

So if the only reason you want the isolation switch is to not pop when charging, try connecting the charger to your wall plug before putting it on the battery. If you are doing it this way already, try the opposite.

 

[Donut]

Looks like over-kill to me. However it would work.

Thank you, I finally feel I've made the right decision.
I'm fine with over-kill, its the under kill I worry about.

 

[E-HP]

https://www.amazon.com/XT90-S-Female-Connector-Battery-Charge/dp/B00RVM8U5W/ref=sr_1_10?dchild=1&keywords=xt90+anti+spark&qid=1602085783&s=toys-and-games&sr=1-10

A lot of folks use something like this.

 

[e-beach]

Learn Ohm's law. It comes in handy with e-bikes.

So 1000w / 48v = 20.83 amps.

If you find a DC breaker that is rated for 48v and over and can handle 21 amps or over, you are good to go.

 

[E-HP]

Since you're only looking for a switch, and not current/short circuit protection, you can use a cheap AC breaker for that purpose. You won't be breaking current, so you don't need contacts that deal with that type of arc. I use one like this:
https://www.homedepot.com/p/Siemens-60-Amp-Single-Pole-Type-QP-Circuit-Breaker-Q160/206632137?source=shoppingads&locale=en-US&mtc=Shopping-B-F_D27E-G-D27E-27_8_CIRCUIT_PROTECT_DEVICES-NA-NA-Feed-PLA-NA-NA&cm_mmc=Shopping-B-F_D27E-G-D27E-27_8_CIRCUIT_PROTECT_DEVICES-NA-NA-Feed-PLA-NA-NA-71700000034238981-58700003943782709-92700050456676742&gclid=EAIaIQobChMIkOfOxuui7AIVPB-tBh3bvwAcEAQYAyABEgI4sfD_BwE&gclsrc=aw.ds

It won't open due to a fault, since it's AC, but mine has a few thousand actuations without any issues (voltages between 52V - 90V).

 

[john61ct]

There are also anti-spark connectors, rather than a switch just rig a quick-pull disconnect pigtail, in effect disables the electric components, fits in your pocket like a key.

https://endless-sphere.com/forums/viewtopic.php?t=72687