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.

 

[Zambam]

You will never see 3.65 V resting voltage of fully charged LFP cells. It will be around 3.40 V.

What's the name / model of your E-motorcycle? Isn't a Lithium battery option offered? If so, the controller should be the same.

 

[Phantom_KNA]

The problem is that importing lithium batteries into Mexico is complicated; I don't trust any Chinese manufacturers, and while there are domestic options, they are too expensive.
It is a e-bike generic brand chinesse, but good power, 72v 1500W motor, 40A 72v controller.
My experience with lead-acid batteries has been pretty bad; they don't even last 5 or 6 months.

 

[Phantom_KNA]

You will never see 3.65 V resting voltage of fully charged LFP cells. It will be around 3.40 V.

What's the name / model of your E-motorcycle? Isn't a Lithium battery option offered? If so, the controller should be the same.

Amazon.com.mx

These are the ones I'm thinking of buying.

 

[Zambam]

Amazon.com.mx

These are the ones I'm thinking of buying.

Will 24 fit in the battery space of your e-motorcycle? Over here, the same cells seem to be double the price.

 

[Phantom_KNA]

¿Cabrán 24 baterías en el compartimento de la batería de tu motocicleta eléctrica? Aquí, las mismas celdas parecen costar el doble .

TI have plenty of space, 360x240x180. The link you gave me isn't from the same seller.

 

[Zambam]

TI have plenty of space, 360x240x180. The link you gave me isn't from the same seller.

TI have plenty of space, 360x240x180. The link you gave me isn't from the same seller.

You have to be careful about "Grade A" cells. Not the same cells. You get what you pay for.

 

[Phantom_KNA]

Ok thanks

You have to be careful about "Grade A" cells. Not the same cells. You get what you pay for.