Swytch Pro/Max yellow battery connector secrets revealed?

[Cisco-man]

Disclaimer - you mess around with these battery packs at your own risk - what follows are my own observations that may or may not be fact!

On the yellow connector on the battery: - the two centre connections (O and D shaped) are charging input only. There is circuitry before the actual battery beyond these two pins (measured voltages here don’t reflect the full voltage of the battery pack), so don’t ever try to take output from these, and measuring here with a voltmeter will not give you a true reading of the battery voltage.
In its stand-alone state, the battery will not give any power to the remaining four flat-shaped connections without doing either one of two things. First thing, is pressing the button on the battery itself. The battery charge-state lights will light up, and full battery potential will be presented at the two outermost flat connections of the yellow connector. The second way, is two form a connection between the inner two flat pins. Shorting these two flat pins on the battery will turn the pack on too (I have done this with a wire with a 500mA fuse in it, and it turns the pack on - proven).
So on the bike half of this connector, thats why there are only a red and a black wire coming out of the yellow connector inside the controller box, these wires only connect to the outer two flat pins to feed power to the controller, and the inner two flat pins form a short to turn the battery pack on.
with regard to this shorting link, I tested continuity of the bike connector in both directions to ensure that it wasn’t a diode doing the shorting. There was absolutely no resistance in either direction.

 

[saneagle]

Disclaimer - you mess around with these battery packs at your own risk - what follows are my own observations that may or may not be fact!

On the yellow connector on the battery: - the two centre connections (O and D shaped) are charging input only. There is circuitry before the actual battery beyond these two pins (measured voltages here don’t reflect the full voltage of the battery pack), so don’t ever try to take output from these, and measuring here with a voltmeter will not give you a true reading of the battery voltage.
In its stand-alone state, the battery will not give any power to the remaining four flat-shaped connections without doing either one of two things. First thing, is pressing the button on the battery itself. The battery charge-state lights will light up, and full battery potential will be presented at the two outermost flat connections of the yellow connector. The second way, is two form a connection between the inner two flat pins. Shorting these two flat pins on the battery will turn the pack on too (I have done this with a wire with a 500mA fuse in it, and it turns the pack on - proven).
So on the bike half of this connector, thats why there are only a red and a black wire coming out of the yellow connector inside the controller box, these wires only connect to the outer two flat pins to feed power to the controller, and the inner two flat pins form a short to turn the battery pack on.
with regard to this shorting link, I tested continuity of the bike connector in both directions to ensure that it wasn’t a diode doing the shorting. There was absolutely no resistance in either direction.

Thanks a lot. You're a star. Do you have to press the button on the battery to enable charging? If so, it's a simple BMS switch that many batteries have.

All that sort of makes sense. It's a portable battery that's designed to be carried around in a bag or whatever when you're off the bike. There's always a danger that something in the bag could short the connector, so you need a way of disabling the connector as soon as you remove the battery. The inner pins are a simple BMS on switch. The problem then would be charging, so they added a parallel switch to re-enable the BMS.

 

[Cisco-man]

Thanks a lot. You're a star. Do you have to press the button on the battery to enable charging? If so, it's a simple BMS switch that many batteries have.

All that sort of makes sense. It's a portable battery that's designed to be carried around in a bag or whatever when you're off the bike. There's always a danger that something in the bag could short the connector, so you need a way of disabling the connector as soon as you remove the battery. The inner pins are a simple BMS on switch. The problem then would be charging, so they added a parallel switch to re-enable the BMS.

Hi Saneagle.

No, there’s no switch on the battery to enable charging. You just plug in the charger without pressing anything.

 

[Cisco-man]

Hi Saneagle.

No, there’s no switch on the battery to enable charging. You just plug in the charger without pressing anything.

The switch on the battery is non-latching. It’s only on when you’re pressing it. Just there to show battery state I’m guessing.

 

[saneagle]

The switch on the battery is non-latching. It’s only on when you’re pressing it. Just there to show battery state I’m guessing.

It must have separate charge and discharge MOSFETS in the BMS. To me it sounds like they've wasted their efforts. if the charge socket is live, why switch off the output connectors. It doesn't make sense.

 

[Sturmey]

It must have separate charge and discharge MOSFETS in the BMS. To me it sounds like they've wasted their efforts. if the charge socket is live, why switch off the output connectors. It doesn't make sense.

Could it be some kind of anti-spark arrangement to prevent the main connectors from burning when connecting the battery or charger?
(or possibly for BMS to latch out the charger)

 

[saneagle]

Could it be some kind of anti-spark arrangement to prevent the main connectors from burning when connecting the battery or charger?
(or possibly for BMS to latch out the charger)

Could be. I didn't think of that, though it would be easier and better to make the other switch a latching on/off switch for the BMS.

 

[Cisco-man]

Could be. I didn't think of that, though it would be easier and better to make the other switch a latching on/off switch for the BMS.

I had to look up what BMS stood for. Something else to read up about. I’m enjoying this e-bike stuff, it’s perfect for a retired techy like me, to keep boredom away!

 

[AntonyC]

I imagine that for anti-spark the BMS is turned on slowly by the inner flat pins. For charging the anti-spark circuit leaks enough to show on a voltmeter but effectively isolates the charge pins. A cheap way to do that would be to skip a charging MOSFET and use a low Vf diode, they tend to be leaky.

What continuity is there between the charge pins and outer pins? Does the voltage on the charge pins vary with battery on/off? On charge how much of the charging voltage appears on the outer pins?

 

[Greenrun]

Does anyone know what the yellow battery connectors are called and/or if they are commercially available. Id like to build / adapt a higher capacity battery that I could carry in the front bag for longer rides.

 

[saneagle]

Does anyone know what the yellow battery connectors are called and/or if they are commercially available. Id like to build / adapt a higher capacity battery that I could carry in the front bag for longer rides.

You don't need that connector. Just run the controller's battery wires outside the box and put on your favourite connector, then you can run wires to any battery you want and put it wherever you want.

 

[StuartsProjects]

Does anyone know what the yellow battery connectors are called and/or if they are commercially available.

Which ones do you mean ?

There are lots of yellow connectors that could be used for batteries.

Might be helpful if you provided an image or a link to the connector you had in mind ?

 

[AGS]

He is talking about the Swytch yellow connector. No chance of finding that anywhere. It’s proprietary to Swytch.

 

[lenny]

https://www.amazon.co.uk/LinsyRC-Anti-Spark-Connector-Sheathed-Housing/dp/B09946S6LH/

 

[StuartsProjects]

He is talking about the Swytch yellow connector.

He\she could be, but that would be a guess.

 

[Cisco-man]

He\she could be, but that would be a guess.

Saneagle’s suggestion gets my vote. Bring the red and the black from the actual controller into the outside world and you can connect any 36v battery to there. My addition to that would be to Make it a break plug/socket connector and send the red and the black back into the battery holder and up to the proprietary Swytch yellow connector. That way you use the Swytch set up as normal, but you can separate the break connector to connect your external battery. The last thing you want to do Is connect both a Swytch battery and an external one at the same time!

 

[Cisco-man]

In answer to one of AnthonyC’s questions: -
Taking a fully charged pack measuring 41.6v on the outer flat pins when you press the test switch on the pack, if the pack in not under charge (no charger connected) I get 0v across the outer flat pins and 35.3v across the two charger pins (O and D). With the battery on charge I still see 0v on the outer flat pins.

 

[Cisco-man]

Measuring at the charging pins, there is no change to the voltage whether the pack is turned off, or turned on using the test button. A reading of 36v this time for both pack on and pack off.

 

[AntonyC]

Hm, inconclusive but I guess it's a regular two port BMS and doesn't rely on a proprietary charger.

IIUC there might be a hack to indicate battery condition. If at random times you stop charging the battery reading should drop a LED about one time in four...? When the battery resistance triples this would become three out of four etc. The only use I can think of for this is when the ride is weak to help rule out other faults like PAS or controller.

 

[Solarbake]

1. Saneagle’s suggestion gets my vote. Bring the red and the black from the actual controller into the outside world and you can connect any 36v battery to there. My addition to that would be to Make it a break plug/socket connector and send the red and the black back into the battery holder and up to the proprietary Swytch yellow connector. That way you use the Swytch set up as normal, but you can separate the break connector to connect your external battery. The last thing you want to do Is connect both a Swytch battery and an external one at the same time!

   It doesn’t matter if both battery’s are connected at the same time not good practice but your still only supplying 36v as they in parellel and not series