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Success! Building my own secondary TC battery - and it works!  

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socobelfast
Posts: 42
(@socobelfast)
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Joined: 1 year ago

OK, so a quick update. The batteries worked perfectly well in parallel above 85%. It was awesome being able to run sport mode 3 for so long without worrying about a fall in voltage robbing the bike of power. The additional weight also helped with the grip of the bike, making it much more reliable when leaning over into corners.

Then we run into problems!

The regen issue that @flyingelectric highlighted struck. Initially, it wasn't too bad, just very brief and momentary. However, it got so bad that no matter how many times I switched the bike on and off, I couldn't get the regen symbol to stop flashing. Eventually, I just unplugged the spare and completed my shift on the original battery alone.

When I got home, I tested the two batteries with the multimeter. The new battery is supplying power, the voltage had dropped about 3V from fully charged. But obviously the original battery is supplying more power and the two batteries are becoming unbalanced.

I have decided that the solution is to use the two batteries separately. I won't get a power reading on the new battery, but that's OK. I can use it until the power noticeably drops, then switch manually to the original battery and carry on from there.

If I can maybe find a bluetooth battery meter to get the voltage displayed on my phone, that might be an idea. And I still plan on hooking up a third battery in parallel with my second one. Hopefully that won't create any imbalance because I'll be using the same cells in the same configuration.

Disappointed, but not too disheartened.

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alexaraducristian
(@alexaraducristian)
Joined: 2 months ago

Eminent Member
Posts: 38

@socobelfast

Congratulations on your work and glad to see you did it in the end, in your first post I felt a lot of enthuziasm.

Now you explain such issues... what if you don't use the regen at all (which is anyway bullshit)? Simply make sure to release the throttle if your bike has enough speed (I mean equal or higher) than your current gear can reach. Will you still have the same problem?

 

Or apply what @flyingelectric suggests.

Anyway keep us posted.

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flyingelectric
Posts: 81
(@flyingelectric)
Trusted Member
Joined: 9 months ago

@socobelfast

A solution can be to 1) disconnect the 4-pin connector on the original battery. That'll removes the battery status to a blinking 0%. That may solve the regen issue . If that don't work there is also option to 2) remove the bms for your new battery for discharge so that the bms is only used for charging your battery(because there may be issues between the two bmses while discharging).

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flyingelectric
Posts: 81
(@flyingelectric)
Trusted Member
Joined: 9 months ago

Some info and thoughts that I have:

Why does your bike regen at 85%. At this level the newly build battery transfers energy to the original Super Soco battery. As this happens the original bms activates "regen" and as such terminates throttle input as a software programmed phenomenon.

https://secondlifestorage.com/showthread.php?tid=641

What it explains on the website above is that at certain voltage levels there is more energy and it may not be the same levels at the same voltage for these two paralleled batteries. Some cells have more energy stored in 3,3-3,5 voltage level spectrum and others between voltage levels 3,65-3,85 etcetera (calculating the square area for specific energy at each voltage level).

The second attribut is the power of a cell or a battery. If you would have had a less powerful battery that you had build you mightn't have any regen issues is one of my theories.

These graphs below shows what happens with the voltage level if you drain more power from a cell or battery:
https://www.richtek.com/Design%20Support/Technical%20Document/AN024

 

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alexaraducristian
Posts: 38
(@alexaraducristian)
Eminent Member
Joined: 2 months ago

@socobelfast

Did you buy the original BMS? Or just a generic 17s one?

What is the size compared with original? I think it's not really half, but more like 2/3 from original. Right?

What is the final price? 

 

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socomods
Posts: 71
(@socomods)
Trusted Member
Joined: 2 months ago

have you tested the bike with just the DIY battery?

i am assuming that the cells in the original soco battery are also 10A cells, not higher? baring in mind the original battery is supposed to be able to provide 100A, but the controller limits it to 40/50/60A (depending on model and drive mode) (those figures are only what i have gleaned from here and some basic power calcs)

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flyingelectric
(@flyingelectric)
Joined: 9 months ago

Trusted Member
Posts: 81

@socomods

Original battery does not give more than 50A max output.

Yes you are right, they are 10A specified 18650 cells. LGGBMH11865 3200mah light blue cells.

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socomods
(@socomods)
Joined: 2 months ago

Trusted Member
Posts: 71

@flyingelectric

i think that is just down to the controller though? it wouldn't be sensible for the battery to be run at max current, some headroom is always a good idea - but as the batteries cells are only 6 in parallel that suggests 60A max available current, rather than the 100A someone else quoted here

 

 

 

 

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