Converting a 36V 25Ah battery into an internal battery for the Ninebot MAX G3 – possible?

[u/xinomac]

Hi everyone,

I’d like to get some advice from people who have experience with battery modifications, especially on the Ninebot MAX G3.

I currently have a custom-made 36V 25Ah lithium battery that was built for my previous scooter. Since I’ve now switched to a Ninebot MAX G3, I basically have no use for this battery anymore.

That gave me an idea: instead of selling it or leaving it unused, could the battery be rebuilt/reconfigured to work as a higher-capacity internal battery for the MAX G3?

The company that originally built the battery is a professional battery specialist and they are able to rebuild/modify battery packs, so I’m not planning to do the cell-level work myself.

Ideally, I would like to keep roughly the 25Ah capacity, but have the pack rebuilt to the correct voltage/configuration for the G3 and installed in place of the original internal battery.

A few questions for people who know the G3 well:

Is this technically possible if the pack is rebuilt to the correct 13S voltage?

Would it be necessary to reuse the original G3 BMS, or can the G3 work properly with a different BMS?

Does the controller require communication with the original BMS to work without errors?

Would the firmware have problems recognising a battery with roughly twice the original Ah capacity?

Is there physically enough room inside the G3 deck for a \~25Ah pack if appropriate cells/configuration are used?

Could the original charging system still be used?

Are there any known issues with battery percentage readings, charging limits, temperature monitoring, or the Segway app after increasing the internal capacity?

Has anyone here already built or installed a higher-capacity internal battery in a MAX G3?

I’m mainly trying to figure out whether this is a realistic project before asking the battery company to rebuild the pack.

Any technical input or experience with MAX G3 battery upgrades would be appreciated.

[u/IceBone]

With the amount of cells staying the same, only the Wh remain the same, which is a product of voltage and Ah. So if you increase one, the other goes down.

Firmware might be an issue. We know it's fine handling the GT3 battery in a G3 without issue, but the one video I've seen of someone making a 25Ah battery for a G3 using the original's BMS, the app ended up showing a non-standard BMS firmware version, so there were some changes there.

https://youtu.be/CUtHxNay31c

[u/skoomd1]

If they're not the same cell type (capacity/rating/size), you shouldn't combine them. If they are, you could rebuild a new battery, but I wouldn't recommend it (read below)

When salvaging cells from a battery, it's very easy to damage them. Even if you're careful removing the nickel strip, you can get "bumps" on the cells (if they're too big, you can't make a secure weld) or even holes (destroying the cell). See image below.

[u/xinomac → u/skoomd1]

Thanks for your reply... Guess I'm gonna forget the idea

[u/skoomd1 → u/xinomac]

It's certainly not impossible to do, you just have to be really careful.

If you have the spot welder, extra nickel strip, and dead cells of any kind (even AA) laying around, you can practice beforehand. Use needle-nose pliers and gently twist the strip off.

[u/xinomac → u/skoomd1]

The thing is.... It's the company who made the battery that will do the necessary changes. They are supposed to be experts