Adding second battery to BionX system.

[Andy1234]

Hi guys. Few weeks ago I bought a used bike Trek T700+ 250W BionX motor and battery works only for 30km with 3 of 4 assist level. Honestly, I'm very disappointed with this range but the bike itself is in very good condition.

The original battery is a 48V Trek/BionX R320 RIDE+ G2 (6.6Ah 320Wh not sure) 13s3p package.
https://www.fietsaccuwinkel.nl/product/trek-r320-ride-g2-accu-6-6-ah-320wh/
Apparently it's hard to replace cells and you can damage the electronics so inspired by this post:

The easy way is to go to the battery - motor high power connector (the two pin BAAS connector near the rear axle) and just add another 13s battery there.
BionX original battery and extender battery need to have a similar voltage when you connect them. First add the BionX battery, than the range extender. When disconecting vice versa.
Battery meter on the console will work fine. Capacity is not limited, you my add as much extender capacity as you like.
[...]
For starters I suggest the extender solution. Make a nice BAAS y-cable (they can easily be connected the wrong way, be aware not to mix + and - !!!!) and add your 13s extender battery there. They need to have a similar voltage (+/- 1V) when connecting.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=75785&p=1453529#p1144659

I decided to build my own 13s6p battery using NCR18650BF Sanyo 3500mAh 4.9A cells:
https://www.nkon.nl/rechargeable/18650-size/sony-ncr18650bf.html
Now I am waiting for delivery:
Spot welding machinehttps://www.aliexpress.com/item/SUN...?spm=a2g17.10010108.1000001.12.724c7aa2ka3eeC
Separate charger (8A) https://www.aliexpress.com/item/54-...?spm=a2g17.10010108.1000001.12.26483fc1qH274H
Battery meter https://www.aliexpress.com/item/10S...?spm=a2g17.10010108.1000001.12.5b9f3defNnPcn2
and BMS (60A) https://www.aliexpress.com/item/13S...?spm=a2g17.10010108.1000001.12.27991781VrdiBy.

If I understand correctly after building the battery, I need to plug directly into the power supply at the motor?
Here:

Do I still have to remember something? Is it necessary to turn off the energy recovery during braking?
Thanks for your help, I will upload photos of progress and I hope that the whole operation will succeed.

 

[d8veh]

You can't connect directly to the power connector. You must leave the original battery connected and use your new battery as a range extender by connecting it in parallel. The two batteries must be the same voltage when you connect them and you must disconnect the range extender when you charge either battery.

 

[Andy1234]

Thank's for answer.
I want to cut this original cable from the previous post and make 2 connectors.
In one of them I will connect the original battery, in the second range extender. So it will be fine?

Example:

 

[d8veh]

That's how to do it. Don't forget to disconnect for charging otherwise the battery you charge will charge the other through the discharge terminals, which bypasses all the charge safety controls.

 

[guelao78]

I might be wrong but: in your second battery, the BMS won't allow the battery to be charged during regeneration. Then you might end up with the main battery (the only one receiving energy from the regeneration) at a higher voltage than the second battery. I don't know what might be the consequences of this situation. Maybe someone else could comment on that?
Cheers