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Upgrading to a safer chemistry - LiFePO4 18650 cells


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Imagine you can trade off range for safety, which sounds good specially, if you commute a few miles per day.

Let´s take the case of a MTEN3 with a standard 67.2 V (16s2p) pack charging at 4.2 V per cell. Now using LiFePo4 cells, charging up to 3.6V per cell ,if we make a 18s2p pack we get 64.8 V, or maybe 19s2p (68.4 V).

The question is,...what would happen to the Control Board when it detects a voltage over 67.2V or maybe at the lower side, discharged at less than 57.6 V?

This will greatly reduce the risk of fires.

Any unicycle with LiFePo4 cells already?

Just a quick example of a 18650 LiFePO4 cell...

https://www.batteryspace.com/A123-System-Nanophosphate-LiFePO4-18650-Rechargeable-Cell-3.2V-1100mAh.aspx

 

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2 hours ago, Made_from_aliexpress said:

is,...what would happen to the Control Board when it detects a voltage over 67.2V or maybe at the lower side, discharged at less than 57.6 V?

It will beep, tilt back and after some time cut off.

One also has to consider charging by regenerative braking, which delivers a bit higher voltage than 67.2V...

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7 hours ago, FlyingWigs said:

I don't know how much the main board relies on the BMS to get battery status, so with the proper LiFepo4 BMS it might not communicate. A lot of research would be required to make a working conversion. 

MTEN3 disassembly videos show that the battery pack has already the BMS inside the heat shrink tube, and only the positive and negative to the Control Board and positive and negative to the charge port.

So at least regarding that it would be fine to change the batteries. But I believe that the low voltage detection could be a problem...

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