EM3ev E-Bike Battery Replacement After 4 Months of Daily Riding

[Cr777707]

Hey everyone,
After four months of daily use, I wanted to share some honest feedback on my e-bike battery replacement from EM3EV. I commute and run errands around Los Angeles — averaging over 100 miles a week — so reliability is a big deal for me.

My Setup​

• Motor: Bafang BBS02 750W
• Old Battery: 48V 14Ah (failing)
• New Battery: 48V 20Ah from EM3EV

Performance​

• Range: Increased from roughly 35 miles to just over 60 miles per charge
• Charging Time: About 4.5 hours using a 4A charger
• Heat: Runs noticeably cooler even on longer rides
• Build Quality: Clean welds, solid construction, and neat wiring layout

What stood out most to me is the consistent voltage output — there’s no power sag even on steep climbs, which makes the bike feel smoother and more responsive.


I’d recommend anyone considering an upgrade or replacement to focus on quality packs that use smart BMS systems and properly balanced cells. That’s where EM3EV really seems to stand out.


If you’ve ever wondered how to safely remove your battery or install a new one, EM3EV also offers easy-to-follow tutorials — great for riders who aren’t super technical but want to handle basic maintenance themselves.

 

[Gionnirocket]

EM3EV is a solid battery with a good reputation.
But much of what you are experiencing (range, voltage drop, heat) is because of the increase in Ah. . .
Yes some can be attributed to cell quality as well.

 

[PCeBiker]

I checked out the website and it appears that there's a difference in cell type too.

Some batteries had a higher amp output (28 amps) with a lower Ah rating than what appears to be another similar battery (13s4p) with a 20 amp BMS but a higher Ah rating.

So different watt hour ratings for the same number of cells.
(I kinda got lost in the math though. You might wanna check my homework. )

 

[Gionnirocket]

Sure.
When building a small battery I had them use Sanyo cells rated at a continuous 10a instead of the Samsung 8a. Since the battery was only 3 in parallel with a 750w motor, it became more important.
But if you had a smaller motor you might not need to or even notice the difference.

 

[PCeBiker]

Sure.
When building a small battery I had them use Sanyo cells rated at a continuous 10a instead of the Samsung 8a. Since the battery was only 3 in parallel with a 750w motor, it became more important.
But if you had a smaller motor you might not need to or even notice the difference.

Was there a Watt hour difference between the Sanyo cells and the Samsung cells? (capacity of individual cells?)

 

[Gionnirocket]

It was a few years ago but I believe they were both rated @3500mAh
Nominally both were 10Ah

 

[PCeBiker]

It was a few years ago but I believe they were both rated @3500mAh
Nominally both were 10Ah

Ohh, so kind of a no brainer picking the Sanyo cells then if they can put out more current?
As long as the quality is there and they aren't fudging their numbers??

 

[Gionnirocket]

I recently temp connected it to my 1000w with an 85% charge and it easily took me on a 25mi ride with plenty to spare.

V_Sag was more noticeable than when using my 21ah battery, but that's to be expected. It performed more than well enough and the weight difference was very noticeable and welcomed.
I'm looking into buying an empty battery case and thoughtfully placing it inside so I can start using it again.

I don't ride my BBS02B much at all now and doubt I will in the future.

 

[Slaphappygamer]

Sounds like the old battery was 13s4p of 18650 cells and the new one is 13s4p of 21700 cells.

Like Gionnirocket said, the increased capacity (ah) is why voltage sag is much lower.

I’m sure, with the 48v 14ah, voltage sag was about 3-4 volts. Which is what you typically get when running at about 1000w.

EM3EV has a great rep! I was also introduced to this place, by another user. That particular battery will fit inside my Ride1Up 700 frame. I’d just have to strap it in to secure it.

Usually, when selecting a battery, youd have 2 types. High discharge packs or high capacity packs. It’s a trade off. Some Molicels seem to be the best of both worlds. Which is why they are more expensive.

Cheap no name batteries usually are the worst of both worlds, but they are cheap. So, what’s more important?

 

[PCeBiker]

Sounds like the old battery was 13s4p of 18650 cells and the new one is 13s4p of 21700 cells.

I found this ??,..

 

[Slaphappygamer]

Yep. 35e and 28a are both 18650 cells.

Also notice the higher capacity battery has lower discharge and the lower capacity battery has higher discharge.

 

[Gionnirocket]

Only one problem with this entire discussion....
The O P seems to be a EM3EV troll.

 

[PCeBiker]

Only one problem with this entire discussion....
The O P seems to be a EM3EV troll.

Yeah, he's probably a robot working for EM3EV ??

 

[PCeBiker]

Also notice the higher capacity battery has lower discharge and the lower capacity battery has higher discharge.

Yeah, that's the part that I find interesting.

I guess there's a tradeoff for a higher current discharge battery?

I wonder how the would compare if they were both putting something like 2 amps continuous?

 

[Gionnirocket]

Bot or twat... Seems he only has one thing to say... Twice.

 

[Old-tool-guy]

I recently temp connected it to my 1000w with an 85% charge and it easily took me on a 25mi ride with plenty to spare.

Very classy installation.

 

[Gionnirocket]

Well it was only a one test ride install and the battery is half the size of the stock battery case. Under the cardboard it was tightly packed with neoprene padding and was exactly as installed after a no holds barred ride. The adapter to plug into the bikes battery port was a thing of beauty... but that information is classified.
In the end it got a 10 on functionality

 

[Slaphappygamer]

I wonder how the would compare if they were both putting something like 2 amps continuous?

That would be less than 1C for each cell. The 35E would be able to sustain that for longer time than the 28A. Though, I believe the 35E will heat up faster, also at higher current, than the 28A would.

If you normally ride in a cooler place, like Canada, then the ambient temp (considering airflow) may help reduce the heat of the battery at the higher current.

 

[harryS]

I didn't think EM3EV needed to use trolls to extoll their products. They have lots of satisfied customers. Disclaimer .. not a customer.

I wonder how the would compare if they were both putting something like 2 amps continuous?

The P28A is 2800 mah vs 3500 mah for the 35E. At a 2A draw, you get more life out of the 35E. Battery designers make tradeoffs between capacity and max current and factor in healthy derating factors for heat and longevity,

The P28 might get selected if the rider had a motor pulling 40A. With a 13x4 array, that's 10A per cell, less than hall of its rated capacity, Plenty of headroom. At that kind of current, you're at the upper limit of the 35E. But either way, if it's only 4 cells in parallel, that's 11.2AH with a P28 and you'll be lucky if you can draw 40a for even 10 minutes. Probably less with the 35E.