A Forum for Scooter Enthusiasts, Scooter Chargers, and Scooter Mechanics.

Discuss the Xiaomi mijia mi M365 original and pro versions in this forum. Topics include hardware, software, hacking, riding, and everything in between.
Ok so I built a 2p4s battery out of a old ES cells to overvolt a razor type scooter with a seat. It has a 16” 350 watt hub motor and I’m using a 36-48v controller.

I am using a M365 battery for the primary and made a splitter cable to hook both batteries into the controller.

So getting to my problem.... everything works fine when I just run the primary battery, voltage gauge reads 38.6. But once I connect the little battery I get nothing. Voltage gauge turns off and no power. Remove small battery and plug the primary battery in and everything works again.

Possible reasons for this:
1. The controller can’t handle over 52.3 volts ( seems very unlikely as it’s rated at 36-48v)

2. The controller thinks it should be operated at the 36v range and shuts down because the higher voltage.

3. Something wrong with my battery configuration. I know I can’t charge the little battery at the same time because it’s a different configuration.

Any ideas gang ?
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OK.... So a 2p4s battery pack will push 16.8 volts (4.2v x 4) when fully charged. A stock m365 battery will push around 42 volts when charged. Thats a total of 58.8 volts with both batteries at a full charge state.And you stated you were currently running at 52 something i think.. But check it your controller is a 36-42 volt controller. I think those numbers indicate voltage thresholds for the controller to operate within before high or low voltage shut off kicks in. So I think the answer is right in front of your face and youve actually answered your own question here. The controller SAYS: 36-42v (this happens to be the voltage of a typical 36v battey pack...42 when charged, 36 when discharged. Very common battery size, also) And youre running MORE than 42 volts and it doesn't work. And it SAYS 36-42 right on it...right? See where Im goin with this....

Remember that even on the m365 contoller, we have to modify firmware to over-volt the system. Otherwise it only really functions in he 36-42 volt range. Just like the one you have right now. And battery packs tend to be manufactured in increments of 12 volts. Probably because people are comfortable and familiar with 12v car batteries. So typical sizes we see are 12, 24, 36,48,60 volts etc. 42 volts is therefore probably not a size of battery you can use but rather the RANGE of voltage a typical 36v battery will produce. Dig?

Im happy that youve gotten out of you comfort zone and experimented with overvolting but I think youre overvolting a controller that wont run on anything over 42 volts. Just fully charge the m365 battery and it will be at 42 volts and I think thats as good as it gets with your particular controller. Add more capacity to keep that battery at 42 volts for a longer period of time and thats about as much performance as youre gonna get out of the controller you have.

(now in many generic controllers if you open them up there are empty places on the board that read different voltage increments and you can often move a resistor around or solder a new resistor into these spots to allow the controller to operate on higher voltage. The brainpower controller I used had this function. see photo. )

And FYI your wiring looks correct. I think you nailed it. Good work. I think the little bit of doubt you had in your wiring led you to over look and over think why your controller wasnt working. The answer was right there. If it was a snake, it would have bit you. But, hey, THIS is how we learn. Youre never gonna make that mistake again and you now have more knowledge than you did going into the project. So consider the endeavor a success. And so you know, it doesnt matter if you wire the second battery pack to the pos or neg side of the primary, its all the same shit. Only advice I would give you is to build your add on packs with the same "P" as your original pack. The m365 pack is a -3p-10s pack so I would build a -3p-4s additional pack. See what I mean? You dont have to do it like this...it will function fine how you have it, but as the batteries discharge having the same capacity on each cell will allow them to discharge more evenly increasing their lifespan and maintaining a more linear voltage discharge. And if youre overvolting, fully charge the damn batteries! If your primary was only at 38 volts, you left 4 volts on the table that could have been gained by just plugging it in! Haha..good shit tho man and its not in vain. Plug that extra pack into your m365 now instead and see how the power gain is. Its substantial. Plus, everyone who reads this now knows all this shit as well and our cumulative knowledge base is growing stronger day by day. Thats why were here in the first place.

Thanks LA,
My controller is 36-48v .. not 42.
That’s why I don’t think it’s pushing to much voltage to the controller.

I might open it up later and check the caps to see what there rated at.

I will update this when I figure it out. I might also ditch the generic controller and go with the 365 electronics as my girlfriend actually likes this sit down scooter To view images REGISTER or LOGIN for full access.
So swapped out the 350 watt with the 1000 and it’s running pretty fast at 54 volts. My battery charger only charges the small pack to 14.5 but at least it works well. I opened up the 1000 watt controller and it’s got 63v caps so I should be good. Assuming I have a controller that can handle the voltage, at what voltage do you think the motor would fry ? I’m looking at larger voltage controllers and can get one rated at 80 something.
And I’m taking about a 350 watt 36v hub motor for a bike or small scooter, not a 365 or zero motor.

Currently it’s got nice acceleration and a top speed of around 26.
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