An Electric Scooter Community on a Mission to Stamp out Transportation Mediocrity.

Discuss the Xiaomi mijia mi M365 original and pro versions in this forum. Topics include hardware, software, hacking, riding, and everything in between.
By danyro
Posts
#17526
Hi folks,

i just finished the upgrade of an external battery pack to my m365.
Now comes the question that i did not find an answer even high level to it.

How should be charged the external and the internal batteries in order to be fully charged an in the same time balanced across all cells?

i am using the Y method.

any advice is extremely appreciated.

thanks

By Caidyn
Posts
#17534
If it’s wired up properly I believe you should be using the same charge port used to charge the internal battery. The batteries should be wired in parallel to add the capacities together. If it’s wired in series it would add the voltages together which you don’t want.

By danyro
Posts
#17610
They are set in paralel through Y method.
But the external battery shouldnt be charged via charging port in order to benefit of an even charging via BMS?
Will make a difference if the charging port of external battery is soldered to the factory charging port? Im this.way both packs.will be loaded via their BMS

Any thoughts?

By IamPurple
Posts
#17612
Dont quote me on this, but I think the best, right after charging separately, is to charge via the second batteries charging port, that way the external will charge trough BMS and the internal, even though charging trough the wrong port, will still have some protections and balancing going on because it has more fancy BMS.

By IamPurple
Posts
#17613
This is what Rollerplausch has to say (translated from German): ABSOLUTELY IMPORTANT!
It becomes dangerous when trying to brake electrically with 42V and more! The scooter with all eventualities denied any electric brake assistance and one is forced to come to a halt with the one weak disc brake, which is intended only for slow holding! The voltage buffer between 41.5V and 42.25V is thus mentioned for a good reason so sharp and is ALWAYS up! At the beginning, regenerative braking (= KERS or electric braking) is possible downhill for at least a certain amount of time!

Separate charging - charging time 4-6 hours (RECOMMENDED)
In the meantime, the balances for both batteries may occur and the voltages need only be checked shortly before the journey in order to assemble both batteries. This at best only shortly before the journey, so that balancing flows or losses are saved - which can arise due to the different voltages (between 41.5 and 42.2V). Still harmless compared to coming!

Charging by additional battery charger - 8-12 hours (possibly OK)
Charging via the additional battery charging port would be the second safest method for the additional battery, but also charges the internal battery to 42V. This is determined by the other power supply or its set charge end voltage - therefore, the voltage should be guarded to save the M365 battery!

Charging via Xiaomi charger - charging time 8-12 hours (not recommended)
This charges both batteries to the power supply end set voltage of 41.5V. It should be noted that the additional battery is charged via the discharge port and the BMS of the additional battery in the case of an out of control cell NOT turn off nor can properly balances , since the cell voltages just never reach 4.2V or even exceed!

The following exception has already been explained for the BMS ports : The BMS unloading port (-P) was re-soldered to the loading port (-C) of the BMS. Then, of course, this method seems ideal for lazy people ... Attention, the additional battery will not balance itself!

Charging by both chargers - charging time 4-6 hours (negligent)
Here the BMS can not work as intended! Depending on the combination of the batteries , the following occurs in addition to an uncertain final voltage :

Y-Method : The BMS of the auxiliary battery can not switch off due to the Xiaomi charger, which contributes via the discharge port!
Parallel soldering to the internal battery : Both BMS can not shut down properly or work !!!

By danyro
Posts
#17654
thanks for explanations and reference.

so the best method without too much hassle, would be the 2nd option.

But maybe someone with electricity skills/know how can say if charging port of external battery would be connected to the original internal battery port charging and in the same time, it will charge both batteries via their designated charging port, at the same voltage...

dont know if this would be a feasible scenario ..


By IamPurple
Posts
#17681
danyro wrote:
Mon Nov 25, 2019 12:02 pm
thanks for explanations and reference.

so the best method without too much hassle, would be the 2nd option.

But maybe someone with electricity skills/know how can say if charging port of external battery would be connected to the original internal battery port charging and in the same time, it will charge both batteries via their designated charging port, at the same voltage...

dont know if this would be a feasible scenario ..
That setup you describe sounds like the worst scenario mentioned by Rollerplaush:
"Charging by both chargers - charging time 4-6 hours (negligent)
Here the BMS can not work as intended! Depending on the combination of the batteries , the following occurs in addition to an uncertain final voltage :

Y-Method : The BMS of the auxiliary battery can not switch off due to the Xiaomi charger, which contributes via the discharge port! "

And it doesnt accomplish anything that charging via the second batteries charging port wouldnt, it just adds extra danger. Both batteries will still charge to 42V, because they are connected in parallel and will equalize no matter what. If you dont want them to charge to 42V to prolong charge cycles, you can limit the charger to 41.5V or 41.0V, but that might be problematic: if you use the cheep aliexpress batteries, they will require to charge to close to 42V for cell balancing.
I woulnt worry much about reduced charge cycles, because you will have two batteries and each battery will be used less, equalizing the loss. Might be even better because the batteries wont heat up as much as less current is drawn from each one, prolonging their charge cycles/ life.

The part about regen braking not working when battery is at 42V is omething you want to test - does it really not work and how much you have to drain the battery for it to start working again. Shouldnt be a big deal once you know it.

TURNING VOI INTO PERSONAL SCOOTER

Hey guys, there is a solution for the VOI ES-100D[…]

thank you very much I will try after work

COVERT A WHEELS BIKE?

I have fully converted 2 of them and I am very g[…]

Where are you located? I need es4 dash :D