72V Electric Motorcycle Battery Build: 23S LiFePO4 50Ah with JK Smart BMS (Advice & Feedback)

[Phantom_KNA]

Hi everyone,

I’m planning a custom battery DIY project for my electric motorcycle and wanted to share my setup to get your feedback, advice, or any tips before I start ordering the parts.

Currently, here in Mexico, commercial 72V 20Ah Lithium-Ion packs are available for my budget, but I’ve decided it’s much better to import high-quality cells and build a custom pack with more capacity and better cycle life.

Project Goals & Bike Specs:

• Vehicle: Electric motorcycle with a stock 72V Lead-Acid controller.
• Target Capacity: 50Ah.
• Chemistry: LiFePO4 (looking at prismatic cells like EVE LF50K or similar, Grado A).

The Setup & Technical Decisions:

1. Cell Configuration (23S instead of 24S): Since the stock lead-acid controller handles a maximum float voltage of around 86.4V, a standard 24S LiFePO4 pack charged at 87.6V ($24 \times 3.65\text{V}$) might sit too close to the controller’s Overvoltage Protection (OVP) limit. To play it safe and protect the electronics, I am choosing a 23S configuration. This gives me a nominal voltage of 73.6V and a safe peak fully-charged voltage of 83.95V.
2. BMS: I will be using a JK Smart BMS (8S-24S). I chose this because of its integrated active balancing (0.6A/1A/2A), which is essential for managing large 50Ah cells efficiently. I will program it via the app specifically for the 23S cell count and fine-tune the cut-off voltages.
3. Discharge Rate: The 50Ah cells are rated for 3C continuous discharge (150A), while my stock controller rarely pulls more than 30A–45A on peak acceleration. The cells should run very cool and relaxed.

A few questions for the community:

• For a motorcycle application subject to vibrations, what is your preferred method for compression and cell insulation (acrylic sheets, fiber tape, etc.)?
• Do you foresee any issues with the stock lead-acid controller low-voltage cutoff? (It usually cuts off around 63V, which means it will stop the bike at around 2.73V per cell—acting as an extra safety margin before the BMS triggers LVC).
• Any specific recommendations for a reliable charger matching this 23S configuration (~84V max)?

I would love to hear your thoughts, experiences, or any red flags you might spot in this blueprint.

Thanks in advance!

 

[Pmkr]

My knowledge is very limeted, but 2 thing I can tell you.

1. If you don't planning hard offroad driving, then the vibration won't be a really serious issue, because the basic structure of the bike provides some proper shockabsirption.

2. From lead-acid to LiFePo the charging controll what will not working reliably, minimum that's what the manufacturer told me, when I palnned to mix up my system between the 2 types of batteries.

 

[Phantom_KNA]

Thanks for the feedback. I’m currently gathering information on how to configure it for 23S, since the BMS comes set for 24S—though I assume it can be reconfigured.
I could use 24S, but I’d first need to check if the controller supports the ~87V that LiFePO4 reaches.

My knowledge is very limeted, but 2 thing I can tell you.

1. If you don't planning hard offroad driving, then the vibration won't be a really serious issue, because the basic structure of the bike provides some proper shockabsirption.

2. From lead-acid to LiFePo the charging controll what will not working reliably, minimum that's what the manufacturer told me, when I palnned to mix up my system between the 2 types of batteries.

 

[freesty]

go with 24s. Charge it to 3.55 or 3.6V per cell, it's 99% SoC and in better voltage range of the controller, more fun to drive.