I built a custom 60V 34Ah Sur-Ron Battery for €400 to save my dead bike (Student budget / Design Validation Stage)

[qannerai]

Hey Endless-Sphere community,

I wanted to share my latest project. I am a 20-year-old student from Belgium, and my 2022 Sur-Ron Light Bee had been sitting idle for a while. When I wanted to revive it for my university commute because gas prices are insane, I found out the stock battery was completely dead. Too many cells were degraded beyond saving.

Looking online for a replacement OEM battery, specifically the older 2020-2023 60V stock versions, the absolute cheapest brand-new stock replacement I could find on the market was 1300 euros. Since I had a strict total budget of max 500 euros, buying a retail replacement was completely out of the question. I decided to leverage my previous DIY home-battery experience and design my own replacement pack instead.

I spent a solid month purely on R&D, 3D designing, and troubleshooting just to get everything to fit perfectly and function seamlessly. I have been in the middle of a brutal 3-week university exam period while finishing this up, so sleep has been completely optional, but it is finally alive and currently in the Design Validation Stage.

THE SPECS AND THE CELLS (NO ALIEXPRESS GARBAGE)​

When it came to the cells, I refused to gamble with sketchy webshops or AliExpress knock-offs because safety is my number one priority. I bought raw, bare A rated BAK 21700 5000mAh (15A continuous) cells directly from NKON, which is the most trusted supplier here in Europe, for around 1.45 euros per cell.

Before building, I ran capacity tests on these BAK cells. At a 1A discharge rate, they tested at a real 4850 mAh, which brings the total real-world pack capacity to a solid 34Ah. With a 7P configuration, these 15A BAK cells give me a combined 105A continuous discharge capability, which is perfect for the 90A demands of a stock Sur-Ron setup.



QUICK SPECS OVERVIEW:

• Configuration: 16S 7P (Modular design: can adapt to 16S 8P or 20S 6P)
• Real Capacity: 60V 34Ah (~2.04 kWh) - Tested at 4850mAh per cell
• Cells: Genuine A rated BAK 21700 5000mAh 15A From NKON
• BMS: 2 options of JK BMS "same PCB size" (Supports 100A-200A continuous / 200A-350A peaks)
• Busbars: Copper strips + steel strip sandwich structure for ultra-low resistance
• Total Raw Material Cost: ~480 euros (~160 euros for 112 cells, rest for BMS, copper, cables, case, etc)

THE BUILD PROCESS AND HEAVY-DUTY INTERNAL WIRING​

Building this pack was a massive test of patience. To keep internal resistance as low as humanly possible, I went with a 0.15mm copper + 0.2mm steel sandwich structure (10mm wide) for the busbars. To distribute the massive current load evenly across the pack, I split the series connections across 5 individual parallel strips.

For the main internal power leads, I used ultra-thick 8AWG wire for the positive terminal (+). For the negative terminal (-), I ran triple 12AWG wires (3x 12AWG in parallel). This gives me massive current capacity while allowing enough flexibility to route the wires safely inside the tight enclosure.

Because welding copper requires an insane amount of energy, my capacitor spot welder was pushed to its absolute limits:

• I had to wait 15 seconds between every single spot weld just for the capacitors to fully recharge.
• Every 15 minutes, the welder got so hot I had to stop and force-cool it under a fan.
• In total, the assembly and welding took me about 8 hours of non-stop, intensive labor, but the rock-solid connections were worth it.

REAL-WORLD TEST RESULTS​

I just finished the first real-world torture tests, taking it off-roading and trail riding. The results:

• Way Less Voltage Sag: The original stock 32Ah battery is notorious for dropping an insane 7V to 9V under full load, which kills your top speed. In my real-world tests, this custom pack showed a drop of only 0.3V per cell (from 3.6V down to 3.3V). Since it is a 16S configuration, that recalculates to a total pack sag of just 4.2-4.8V under load. Thanks to the BAK cells, copper/steel sandwich, and 5-strip series layout, we cut the original voltage sag nearly in half. The power delivery stays completely consistent even below 50 percent capacity.
• More Top Speed: I can still hit 70 km/h even when the battery is running low. On a full charge, it hits 80 km/h effortlessly, something my original battery never achieved.

ENCLOSURE, SAFETY, AND FUTURE 52AH UPGRADES​

• Current Prototype: Printed in PETG-GF (Glass Fiber) with a 3mm wall thickness. It has survived heavy vibrations and rough terrain perfectly.
• Future Production Plan: If I bring this to market, I will transition to an aluminum extrusion housing for maximum structural safety and weatherproofing.
• Weatherproofing: Internal silicone seals, waterproof gaskets, and a dedicated internal compartment for a custom silica-gel packet to absorb any potential internal moisture.
• Aesthetics: The front will feature a clear tinted plexiglass window, allowing you to see the JK BMS status lights and check for moisture at a glance, while looking incredibly sci-fi.
• Future-Proof Modular Design: In the future, when the new BAK 65E (6500mAh) cells roll out, I designed this exact same enclosure to adapt perfectly to a 16S 8P configuration. This means you can build a massive 52Ah battery inside this exact same footprint with absolutely zero modifications to the bike. No battery lid extenders, no new bottom plates, nothing. You just slide it right in, connect it, and ride.

FUTURE PLANS: I NEED YOUR FEEDBACK​

My ultimate goal is to bring the 60V 34Ah pack to the European market for around 850 euros. I want to offer this with zero compromises on safety, which means taking a massive cut on my own profit margins. Honestly, I do not mind at all because this is my absolute passion and I want to make good batteries accessible.

A lot of people might wonder why I am not building a fully overpowered, high-voltage battery for Europe straight away. Since I live in Belgium, tuning laws here are incredibly strict. If the police catch you with a heavily modified, overpowered bike, they will immediately confiscate your bike on the spot and hit you with a massive fine. That is why for Europe, I prefer keeping the bike looking and acting stock, allowing you to rely on the secret handlebar brake code to easily toggle the limiter on and off when needed.

To make this stealth setup work flawlessly, I am currently developing the communication protocols and want to know what the community prefers. Which feature should I focus on first?

• Option A: A custom handlebar-mounted JK display screen showing real-time voltage, percentage, precise Amps in/out, and temp data.
• Option B: A custom protocol-translator module that talks directly to the stock Sur-Ron controller, keeping the OEM dashboard fully functional so the secret limiter code remains active.

However, for the American market and riders outside of Europe, if there is enough interest, I am highly motivated to build a high-power monster. Once I master the manufacturing techniques and scale up production with your help, I want to release a 72V battery capable of a massive 200A continuous and 350A peak (for 1 minute). My target price for this high-power 72V version would be around 1200 euros once mass production is scaled.

If there is serious interest in these batteries, I am planning to launch a crowdfunding campaign to make this a reality. Before I can legally sell or ship anything in Europe, the pack needs to be officially certified, which requires passing the strict UN38.3 testing standards. This certification process alone costs around 8,000 to 12,000 euros.

The crowdfunding will also allow me to invest in proper manufacturing machinery. I need a much better, high-end pneumatic spot welder to work way faster, and I want to transition to using pre-cut, custom-ordered copper busbars. Eliminating the manual cutting phase will save an insane amount of labor hours, which will ultimately reduce assembly time and drop the final cost for everyone.

I can only achieve this scale, certification, and pricing with your help and feedback. Let me know what you think of the design, the specs, and which direction I should take first.

Cheers from Belgium.

 

[lnanek]

Isn't that like $400 more expensive than common sellers like Amorge for a weaker battery that can handle less continuous amps?


I wouldn't try to start a business doing something other countries are already quite good at doing much cheaper. Just won't net any sales.

 

[thepronghorn]

Oof. New user, ai in the name, LLM generated post, post is kinda an ad so should probably be in the for sale section... Not a great start. If you're just telling a story, I would much prefer you wrote it in your own words.

Nice 3d printed case though. Can you show more pictures of that? Did you consider a hexagonal cell packing instead of square?

 

[neptronix]

Moved to the correct section. Please be honest with the premise of your posts going forward, and read our rules.

LLM output? i won't read it, let's hear it in your words. This is a community of humans communicating to humans

 

[qannerai]

Moved to the correct section. Please be honest with the premise of your posts going forward, and read our rules.

LLM output? i won't read it, let's hear it in your words. This is a community of humans communicating to humans

Sorry guys, English isn't my first language so I used an AI tool to help clean up my grammar and make it readable. I can see how it looks like an ad now, but I genuinely just wanted to share my DIY build! Thanks for the feedback.

 

[neptronix]

Yeah, it had an influencer spam vibe.. i'm not sure if you intended that.
We are typically insta-banning lots of accounts who use this exact same tactic. But you seem like a real person.. so i spare the axe

Most people here are happy to read broken english. it's okay to have AI translate for you; people won't notice. But to have it generate text from a small prompt... will usually end up looking like spam.


Here's my thoughts about this business..
- do you have any competitors in europe? if so, can they sell a battery cheaper than you?
- can your prospective customers order a battery for China cheaper than you can produce it?
- can you make at least a 25% profit margin?
- do you have some innovation that puts your product ahead of it's competition?

€400 for this big battery is awesome but..
If the answers to any of these questions look bad.. the possibility of failure is high.. and i would recommend doing some other business.
Make sure you spend good time to check your competition. This is key. The e-vehicle field is very competitive and has few survivors lately.

 

[bananu7]

I used ultra-thick 8AWG wire for the positive terminal (+). For the negative terminal (-), I ran triple 12AWG wires (3x 12AWG in parallel). This gives me massive current capacity

I think you might want to catch up with what the guys on modded light bees are up to these days before jumping to such adjectives 72v@40ah packs are pretty standard, and most are looking at larger capacity, with 300A peak battery power drawn - and that's the offroad low end, since the street-going specimen get way more powerful than that.

So at most, you've built a budget-spec battery. Can you scale it to be cheaper than other budget batteries on the market, especially from overseas?

 

[qannerai]

I think you might want to catch up with what the guys on modded light bees are up to these days before jumping to such adjectives 72v@40ah packs are pretty standard, and most are looking at larger capacity, with 300A peak battery power drawn - and that's the offroad low end, since the street-going specimen get way more powerful than that.

So at most, you've built a budget-spec battery. Can you scale it to be cheaper than other budget batteries on the market, especially from overseas?

there are already enough high end batteries with 72v and big capacity for people that want build crazy light bees. that market already exists.


i could also make a high power pack with high capacity and high dense honeycomb packing but i did not need it and i also dont need build it. same concept stays but everything just becomes more dense. doesnt matter if you make 60v 35-40ah or 72v 50ah you change the battery shape bms cables spot welds and the way you place the cells. if you want high density you can do it but then you have less cooling and stuff.


but sadly i cannot really do that here. i live in europe where laws are like 10x more strict than america. in some states in america people can ride a surron on the road without a plate and with way less problems, even when it is not limited. here in europe there are a lot of roller bank tests and they check if your surron does not go faster than 45kmh.


legally with a light moped you can only go 45kmh. yes it is boring but that is just the law here. if you go faster you can lose your bike, get a big fine, and they can make you put an off brand 2000w controller on it. this already happened to my friend.


the market in america and europe is very different. yes there are people here that still risk it but i dont want that and i know more people think same.


what i want make is more for people in europe that just want keep their bike stock but need a ready drop in replacement battery. like a 60v 40ah battery that fits normal without needing extender or changing half the bike.


there are a lot of surron riders that are not online posting builds or making their bike faster. they just ride it stock. and the 2020-2023 surron batteries are already getting harder to find, and drop in replacement batteries are also less available or very expensive. « in Europa=> belgium »


so i am building for a completely different market, more europe focused. my friends with stock surrons also all have batteries getting old now and after some time they need replace them. something like this would be perfect for them.


i know there are people like me that just want keep their surron as stock as possible. just drop a battery in and use everything normal and clean. i am now also working on the communication part so original display still works and battery percentage comes on the screen so everything stays stock.

« Sorry for my bad english »

 

[lnanek]

When I used to work for HTC, a mobile phone company, a decade ago the higher ups would always tell us only the premium models made money. The average models had to compete with hundreds of other generic models from other companies on price and made pretty much no profit or even lost money.

So it sounds like you are going to make average packs. Average packs compete on price, though. And labor is much, much cheaper in foreign countries. So your only profit margin is going to come from being able to raise your price slightly to account for cheaper shipping, which may not end up turning any profit due to the high cost of labor in your country.

Maybe you are saying you'll do all the labor yourself and pay yourself nothing, but that's not really a solid business decision. You can't replicate thar business model and make a lot of money doing that because you can't hire anyone additional for that rate. And it takes time away from building a successful career or business or getting higher education.

 

[qannerai]

When I used to work for HTC, a mobile phone company, a decade ago the higher ups would always tell us only the premium models made money. The average models had to compete with hundreds of other generic models from other companies on price and made pretty much no profit or even lost money.

So it sounds like you are going to make average packs. Average packs compete on price, though. And labor is much, much cheaper in foreign countries. So your only profit margin is going to come from being able to raise your price slightly to account for cheaper shipping, which may not end up turning any profit due to the high cost of labor in your country.

Maybe you are saying you'll do all the labor yourself and pay yourself nothing, but that's not really a solid business decision. You can't replicate thar business model and make a lot of money doing that because you can't hire anyone additional for that rate. And it takes time away from building a successful career or business or getting higher education.

i understand what you mean and you are right if i was trying to make just another generic 60v battery based only on ah and price. then china wins every time because of labour cost and scale.
but that is not really what i am trying to make. i am not trying compete with 72v race packs or cheap generic upgrade packs. my target is more the older 2020-2024 european light bees with the old battery setup.
a lot of people here want keep the bike stock. original controller, original display, original battery percentage, no extender, no changing half the bike. you can still find original batteries sometimes, but not for a normal price and often they are not in stock.
my local official surron dealer in belgium "bornem" had the 60v 38ah battery for €1590, around $1814, and the newer 60v 40ah is €1749, around $1995. this is only for the battery. a 2020-2024 light bee here is often worth around €2200-€2400 second hand, around $2510-$2740. it is hard to tell someone to spend €1600-€1750 on a battery when that is already more than half the value of the bike.
yes there are Amorge packs i find online for my Sur-Ron on Alibaba around €1200, but the problem is i cannot even buy those batteries in my country because they are not available, so that is also not an option and cannot even get one shipped to belgium. a lot of them also do not have the stock communication protocol. the newer original batteries can fit physically but use different connectors and communication "RS485".
that communication part is very important for me. without it you can get flashing errors on the display and no proper battery percentage. i am working on making the JK BMS communicate properly with the original Sur-Ron system, so the bike still works like stock.
there are people who do not care about that and just want more power, and that is fine. but there are also a lot of people who just ride their Sur-Ron normally. they are not online posting builds, they do not want a 72v pack and controller, they just want drop in a battery and use the bike clean like before.
i already have people contacting me on Marktplaats because their original packs are getting old and they cannot find a normal replacement. after 4-5 years it is normal that batteries lose capacity or fail. more of these 2020-2024 packs will die in the coming years, while original replacements are getting harder to find.
i am not saying i can make a huge company tomorrow or that i can work for free forever. this is still a prototype and i am validating if there is enough demand. but if i can produce it safely and properly for under €1000, around $1140, or ideally close to €850, around $970, i would already be happy.
even if after warranty, shipping, taxes, failed packs, support and R&D there is only 5-7% profit left, i think that is fair. i do not need huge margins, i just want make a proper OEM-style replacement that people can actually afford. i know cells are not the only cost. you have enclosure, BMS, connectors, safety work, labour, warranty and transport. but sometimes replacement battery prices are still hard to justify. it happens with e-bikes, tools and cars too. a Bosch e-bike battery around 700wh can easily be €800, around $910, at a dealer. sometimes battery pricing feels a bit like printer ink. youtube video form bright "Netherland" a nissan leaf module was damage and only the price for an battery module of less than 4kw is 5000 € or 5600 $ thats just insane the price per kw for battery's are 120-80 euros per KW in bulk or even less and okey you have R&D and the case but not to justify 5000 euro for an battery module less than 4kw and without laybor
so no, i am not saying i will beat chinese factories on price for generic packs. i am trying fill a specific gap in europe: a fair and safe, stock fitting replacement for older Light Bees, with the original display and communication still working. maybe it is a small market now, but i think it will become bigger when more original batteries get old.

 

[BlueSwordM]

Yeah, it had an influencer spam vibe.. i'm not sure if you intended that.
We are typically insta-banning lots of accounts who use this exact same tactic. But you seem like a real person.. so i spare the axe

Most people here are happy to read broken english. it's okay to have AI translate for you; people won't notice. But to have it generate text from a small prompt... will usually end up looking like spam.


Here's my thoughts about this business..
- do you have any competitors in europe? if so, can they sell a battery cheaper than you?
- can your prospective customers order a battery for China cheaper than you can produce it?
- can you make at least a 25% profit margin?
- do you have some innovation that puts your product ahead of it's competition?

€400 for this big battery is awesome but..
If the answers to any of these questions look bad.. the possibility of failure is high.. and i would recommend doing some other business.
Make sure you spend good time to check your competition. This is key. The e-vehicle field is very competitive and has few survivors lately.

I'd say what matters most is #4 above all else.

If you're better than the others, you can charge significantly more.

Furthermore, they do have the advantage of local support, but they have to make sure their battery pack is practically bomb proof.

 

[The Toecutter]

20S would be a nice upgrade. I'm surprised people can get away with riding these in Belgium.