Quick update on the ownership experience of the Indian e-bike (that's with a close relative), around the battery replacement.
After around 4 years and 4000-odd km's, the battery started dying out. It was supposed to be a 60 km battery, started out with 70-80 km of range on pedal assist, gradually decreased to 30-40 kms and then suddenly dropped dead.
So these e-bikes are being built by small assemblers at low volumes from Chinese kits. The support/upgrade system is therefore ad-hoc, and one cannot just go to a shop and buy a replacement like a car/inverter battery.
As a reminder, these batteries are made up of 18650 li-ion cells. Ours was a 48V battery. I took it apart and found that it had a 13s4p configuration (13x4 cells arranged as 13-series, 4-parallel) for a voltage of 13 * 3.7 ~= 48V.
A 13s4p li-ion battery pack, credits: voltaplex.com
A sample BMS, credits: greenbikekit.com
In addition to the bank of cells, these batteries simply have a balance BMS (battery management system). It is a small controller that ensures that all 13 4-cell banks are charged to an equal voltage, and cuts off charging appropriately. Nothing particularly complicated.
The only catch is that these need to be spot-welded. Soldering irons are too hot and can degrade the cells during the assembly process. Spot welding, OTOH, supplies a high current for a couple of ms, forming a strong weld without heating up the cells.
Many designs for spot welders are available online, and you can build one using Arduinos etc for 10k-15k. Perfectly reasonable if you're doing 5 batteries, but a tad overkill for just one battery. I considered the DIY route briefly but then decided to seek "professional" options for convenience.
The first order of business is to decide on a cell. LG/Samsung cells cost around ₹250-₹350/piece. (So 52 cells is easily ₹15,000 in raw material). The BMS is another ₹1500 or so. This does not include the labour and misc. costs (tapes/connectors), so it's looking expensive.
The other problem is to find a custom assembler. I found a whole bunch of numbers (from Delhi/Pune/Mumbai etc) on Indiamart and called folks up. Turned out that most of them were wholesalers and wouldn't do one custom battery. I then stumbled upon a gent from Delhi who sounded technical, helpful, and interested over the phone.
I initially asked him for a quote with Samsung 26J batteries. He advised me against those, as those were designed for flashlights and all, and not high-discharge applications like electric vehicles. He recommended me a Chinese brand called "BAK".
I was skeptical about Chinese brands, and worked out some amperage math. (Since mine is a 250W motor, that's not a whole lot of current draw). So 26J could work, but he was right in that a 3C battery (higher discharge rating) would be ideal.
The next question was whether to go for a higher discharge branded cell or whether we could "wing it" with the Chinese option presented. Three things turned the decision in BAK's favour:
1. The older battery had no-name cells, and had served us well.
2. BAK is "premium Chinese", in that unlike questionable no-name brands, it is a solid large-scale operation. The weight etc. checked out, and it looked like a 80% of the job at 50% of the price kinda deal.
3. I found this Russian video of a dude putting the BAK cells through the paces. From what I could gather with auto-captioning and auto-translate (2021, really!

), it held up well against spec sheet claims of discharge rates/voltage drops etc.
So BAK it was. There are two BAK models in the 3C category - 2600 mAh and 2900 mAh. You can get the cells in the wholesale market for ₹70 and ₹100 (approx) respectively. Coupled with a new BMS, that's around ₹6500 in raw material for the 2600 mAh cell (2900 mAh was apparently having some stock issues). I was getting labour quotes of ₹30/cell from a dealer, but he did not carry BAK. All in all, ₹8000-₹8500 would've been a fair price for a new battery.
But apart from the Delhi gent described above, I had a hard time getting someone to do a custom job for me. Out of any other options, I reached out to him again, and he quoted me ₹9850 for the final battery. He was professional in that he recommended I send the full battery unit to him instead of him sending me a new inner "core" designed with pictures as a reference, so as to avoid any fit/compatibility issues later on. (Add ₹350/side in shipping to/from Punjab).
The new battery should be shipped back any day now, and since he'll repackage the entire thing himself, it should Just Work™ for a good 3-4 years, by which time the landscape would've evolved a lot more.
Bit of work, but it's all indiamart and calling and whatsapp-ing and paytm-ing (2021 I tell you!) and also gives you a nice peek into our nascent EV battery industry.
Quote:
Originally Posted by proton Any one can post about owner experience of this bike or equivalent available in India? |
My Bangalore e-bike experience is there in the first couple of posts. I hope that and the battery update give you the insights you were looking for!