Adding a Key to battery pack ?

I was just wondering on what you guys use if you've ever added a key to a battery pack?

https://imgur.com/IppF0pL

thanks!

These work pretty well for 50V and below.
https://www.amazon.com/Battery-Disconnect-Isolator-Removable-Waterproof/dp/B07MTYX5Z5

I use the grin Tech key switch with my 57 Volt (initial) packs.

https://www.ebikes.ca/keyswitch.html

Do you want the key to switch the pack on and off completely? Or are you looking for a key to turn the BMS on and off?

The former requires a switch that can handle the inrush current of charging the caps in the controller, at the voltage the battery is fully charged at, without welding the contacts shut or burning them, as well as the peak and continuous currents the controller will draw while in use. That's a fairly large switch for an ebike.

I use a harbor freight battery cutoff switch, with a big red plastic handle key, on SB Cruiser, and it's been working fine for a couple of years of this so far (peaks of over 120A under some circumstances in various experiments, continous of 18-20A).

On previous bikes, I tried an ignition switch just like the Grin one, but with large enough gauge wire to handle 40-50A, and the switch failed from arcing during turn on, and heating during the peak loads eventually deforming plastic bits of the switch casing.

I also tried a Briggs&Straton keyswitch, all metal casing, etc., for the early version of SB Cruiser when it only had about 30A peak and 15A continuous or so. That one failed similarly, though it didn't have any deformed plastic bits, the contacts were destroyed.

The latter only needs a regular keyswitch, as it doesn't handle any significant current, just switches the BMS enable/disable line on and off. If there's no place on the BMS to hook up a switch, you can cut the trace to the BMS's FETs' gates, and put the switch between one side of the cut and the other. If the siwtch is on, the BMS can enable input and output. If it's off, it can't, and the battery inside is disconnected from the outside. The FETs handle all the current and switching, just liek normal.

amberwolf said:

Do you want the key to switch the pack on and off completely? Or are you looking for a key to turn the BMS on and off?

The former requires a switch that can handle the inrush current of charging the caps in the controller, at the voltage the battery is fully charged at, without welding the contacts shut or burning them, as well as the peak and continuous currents the controller will draw while in use. That's a fairly large switch for an ebike.

I use a harbor freight battery cutoff switch, with a big red plastic handle key, on SB Cruiser, and it's been working fine for a couple of years of this so far (peaks of over 120A under some circumstances in various experiments, continous of 18-20A).
snip

Click to expand...

Thanks for all the great info def learned alot just in this post....

so this is what i'm now thinking... ordering this (i know it's another point of failure

https://www.amazon.com/dp/B07MTLV55T/?coliid=I1MGKWLEEBLMYF&colid=34YXCY3URVAUR&psc=1&ref_=lv_ov_lig_dp_it

then switching the button for a key... basically i want a key lol

what do you think of this?

Note that it says it's for up to 12s. If your battery pack is more cells than that in series, results are unknown (might work, might blow up).

The Luna SSR is rated up to 60 volts (14S) and 120 amps. Comes with a locking LED lit push button. But you can use the inner two connections with a key.

See it here...
https://lunacycle.com/remote-on-off-solid-state-switch/

Handles controller inrush up to 1500uF total capacitance.


Lit up switch to the right of the displays on the cockpit panel... (I like lights :wink: )




Shoe horned it into the back of a 52 volt nominal bottle battery cradle.




Regards,
T.C.

One more thing to consider.
I would check with the controller maker that it can handle the power being switched on and off.
I have experienced 2 controllers break doing this and now use a precharge resistor before switching on. (In fact it is recommended by Kelly controllers).
For switching I use a Gigavac relay with a bypass resistor added. The miniature relay I use can handle up to 800v dc and 400A.
Just a thought.

Tommycat ....are you actually using the Lunacycle remote switch? And all is well with it? I just tried one of the Flippy switches like this and it failed under load immediately after switching a 7S pack on.

Hi Headrc,

Yes, I've been using it for over a year and a half with no problems. 52 volt Li-Ion system with 1500 watt peak hub motor. (Magic Pie V5) But for full disclosure I've reduced capacity to 750 watts, and 20 MPH top speed. (Bike laws) It makes and breaks the negative line. No trouble with my system's regen...



What's a Flippy switch

I mentioned it wrong ...it is a Flipsky switch ...similar to the Luna switch. Here is a link to one:

https://www.amazon.com/Cigooxm-Flipsky-Electric-Skateboard-Scooter/dp/B07V5Y6NZ2

I wired it up yesterday and tested it just for battery on/off for a 7S battery and it worked fine. But as soon as I put a load to it, the Flipsky switch failed.

In which way Flisky switch failed?
contacts burned?
Connecting battery to controller require beefy switch , because capacitors in controller - spark.

No sign of contacts burning ...and since the electronics are enclosed with black heat shrink I cannot see if there is visible evidence of a failed component. Obviously the switch is now closed, permanently passing voltage from the battery. And of course I am trying to get a response from the seller and get a refund so I do not want to tamper with the heat shrink. The specs stae the Flipsky can handle 280A continuous and 800A burst ...there is no way that I subjected anything like that to it. Actually, my meter stated 25A on initial start up and then 5A continuous.

I just purchased one of these and tested it under load today:

https://www.amazon.com/gp/product/B07MTLV55T/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

All went well under load....so obviously the Flisky was not up to the task and did not meet its specifications.

Switch from Grin,
it has AWG 16 tiny wirs soldered to it?
I and majority here use AWG10 size.

miro13car said:

Switch from Grin,
it has AWG 16 tiny wirs soldered to it?
I and majority here use AWG10 size.

Click to expand...

On the Grin switch page, it says to remove the 16 AWG and install larger wires for higher loads. I soldered on 10 AWG cables and have had no issues since about 2014/15.

Grin page quote "Okay for higher current controllers if you upgrade the wire gauge".