Advice on Swytch kit bike additional battery

charge_moon_cruiser

Just Joined
Dec 2, 2023
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Hi everyone, I've recently purchased and installed a Swytch kit (new MAX Version) on my bike, it seems to work fine and I like the compact design - it works great for my short commute and easy to take battery off etc.

However for longer rides the range is not great at all - I can get about 12 miles out of it tops. (heavy bike and heavy me!)

I would like to be able to mount another battery (either rear rack or bottle cage mount) on the bike that I can take with me for longer rides.

I am thinking the way to do it is to tap into the wires on the front bracket where the battery mounts and then wire to a 3 way switch on the handlebars so I can switch between front battery/off/rear battery.

Just wondering has anyone done this or anything similar? New to ebikes so maybe there is a better way to do it

Will a 12v switch be OK to use?

Thanks :)
 

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saneagle

Esteemed Pedelecer
Oct 10, 2010
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Yoy can't use a switch like that because it'll melt. Even if you can find a switch that can handle the current, it won't last because the inrush current will burn the contacts. Easiest and safest is to splice in a connector and only connect one battery at a time. You can use any 36v battery you want and mount it how/where you want. You only need to get the two wires the right way round.

There's a long recent thread on this if you want to search for it, but all you need to do is splice into the two battery wires, like you suggested.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
20,274
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West Sx RH
Solder a pair of tails to a xt90 anti spark and then open the controller and solder them directly to the board.
 
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Cisco-man

Pedelecer
Sep 27, 2023
211
45
When you open up your handlebar battery holder, beware of the two very small rubber gromits that live on the two screws that hold the yellow plug to the case. You can see them in the attached photo. You might not need to remove the plug if you’re just tapping into it. Search for “swytch” and you should see a lot of posts on this as Saneagle says. Major point is, don’t connect two batteries at the same time unless they have the same voltage when connecting, or alternatively add schottky blocking diodes to protect the batteries
 

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Cisco-man

Pedelecer
Sep 27, 2023
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IF (and only if) you are electrical-savvy and don’t mind a bit of fettling, then adding a blocking diode to the mix would be a thought. That way, if you connect more than one battery at a time, then the diodes will prevent large (potentially damaging) current flows if the batteries have different voltages. There isn’t much room inside the swytch handlebar battery holder, but the case is a chunky aluminium casting that makes an ideal heatsink for the diodes. If I was doing this (I’ve gone a different way, and mounted the controller on the back of the bike), then my approach would be to fit a 30A double-schottky diode to the back(outside) of the case (see picture). When you cut the red lead inside the housing, the end that comes from the yellow plug would be soldered onto an outer pin of the double-diode, and the centre pin wired back to the red input of the controller inside the housing. The remaining outer pin on the double diode is where you connect the positive from your additional battery pack. I’ve measured my swytch controller and there is no apparent continuity between the case of the actual controller and its red and black feed wires, but I recommend that you isolate the diode from the housing with isolation screws and washer just in case.
 

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Cisco-man

Pedelecer
Sep 27, 2023
211
45
… but I still fully support Saneagle’s suggestion of using a simple connector as being the easiest way for most.