Range extender batteries

[TCS-14]

I have a 2020 Specialized turbo Levo with a 700w battery, and would like to add a second battery to extend my range. Looking at what's available online as pre-built decided I would rather build myself. Question is what's the best way to add a second battery safely without doing possible damage to the main battery. I have no idea what type batteries are in the main battery other than its a 36v @ 19Ah unit. I assume if I build a 36v @ ?Ah battery and parallel it with the main I should be okay, but what about protection such as back feeding into the main from the secondary battery? Do people use diodes to protect each battery or is this not a concern?

Dave

 

[amberwolf]

It depends on how the BMS is setup in the packs you use together as to what types of issues you might encounter, if any.

There's a number of threads in these lists that discuss the issues in detail; most are obvious by title (not every thread listed is relevant):

https://endless-sphere.com/forums/search.php?keywords=parallel*+pack*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=parallel*+batter*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=range*+extend*+batter*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

 

[TCS-14]

Well after reading through a few of those links

As long as the voltage between to packs are the same 36v-36v okay to parallel. One person mentioned as long as the packs are within .1v of each other. Never have built a battery pack before so not sure if this is realistic or not.

If each battery pack Ah rating is different its okay to parallel just make sure voltage is the same.

Separate BMS on each pack is okay as long as they're charged individually.

No mention of any blocking diodes to keep one pack from draining into the other so it seems this isn't an issue.