External battery switch - what works best?

[nickceouk]

I want to know what is the best solution for switching battery input to an ebike controller (BR v5 z9 but this should not be important).

As far as I could find by searching there is Option 1 an automotive/marine switch rated as 15A 250V AC or 20A at 125V AC ( left side in photos).
It's a dual pole dual throw switch - DPDT.

Option 2 Cam switch (right side on photos) which is rated at 20A 440V (AC-15) and 240V, 1A (DC-13)

1)Batteries I want to switch are OEM 13s with max draw of 20amps (case sticker)
2)14s with 80amps = 1C
3)14s with 20amps = 1C
4) potentially another 13s with 20amps= 1C

If I go by the rating the Cam switch has higher AC rating but I am also stumped by the 1A DC rating.

I also opened both to see which one has better(bigger) contacts inside the actual switch and upon inspection it's the automotive/marine switch which also looks much smaller overall compared to the Cam switch.

The batteries will feed the BR( set as 1000W ) through one switch that toggle internal OEM battery or external battery mounted under the seat post area and a second switch in a trailer will select which of the external batteries is used in the trailer.

I would use this setup for long trips ...so heating is an unknown and need help from more advanced users

 

[glennb]

I’ve destroyed switches in this way, and I’m sure I’m not alone in that. They also add resistance.

I’d use Anderson connectors for swapping between batteries.

And feed the battery supply into the three position rotary switch. This switch is perfect for implementing a pre-charge resistor.
- First position open (off, unconnected)
- Second position battery positive to controller with inline resistor
- Third position battery positive direct to controller.

You just need to pause long enough between moving from position two to position three for the pre-charge to occur. A couple of seconds ought to do it.

You can also loop a wire between positions two and three, so you needn’t run two separate wires from switch to controller.

 

[nickceouk]

He he - I have had this in the back of my mind that even if I ignore the added resistance (which I am unable to quantify as a battery capacity percentage) there is a decent chance of melting the switch since the DC ratings for them are very low.

If I use the Anderson connectors I don't know why I would need the rotary switch or any switch for that matter?
If it's for the spark when changing, I know there are xt90 or xt120 connectors with Antispark in built into them. I could perhaps use them instead of the Anderson...

The way I envisioned it is to route the OEM battery which resides in the bike frame to the outside under the seat. Have the 3 position switch there and return the cable to the controller compartment which is also inside the frame. That will leave the remaining one position of the switch for me to connect to the trailer via the hitch etc.

Provided overall efficiency loses are not really high I can live with that and trade for the convenience of not having to flip connectors but switch two buttons.

What switches other than the one I have listed are good for 60v DC with about 55amps max?
(I am running 10awg cables to the switch terminals)

 

[glennb]

It’s not so much about need. Any spark is a bad spark and reduces service life, so if they can be easily avoided it’s sensible to do so.

Anti-spark XT-90 might be the right tool for the job. I’ve seen them for sale, but never used them.

No doubt there’s switches that would survive your use case. Of all the heavy duty ones I’ve salvaged and tried out, none survived for long in my homemade lawnmower. And none made anything like the loud metallic clapping sound you can get from a beefy contactor.

I’d be thinking about whether you really need a switch in this setup … in terms of whether the inconvenience of having to plug/unplug is really much of an inconvenience.