Battery capacity for Dengfu internal frame battery?

[hitman-chan]

Hi All.
I've just completed my dream dual suspension E-mtb. I assembled bike with Dengfu carbon E22 frame and painted it at home using 2 pack paint including a colour shift coat under 2k clear coat to jazz things up.

I used the Bafang Ultra motor but aquired it from Innotrace in Germany who mod the motor with their own controller which is more user friendly than Bafang's own controller.

All's working well but I have a curiosity about the battery capacity of the battery I got from Dengfu. It states it is 48v 17.5amp/h. Pretty much the highest capacity for an in-frame battery that I can see advertised on the Ali Express website. This gives a respectable 840wh of useable power.

However, I decided to get a spare empty battery box when I ordered the stock battery. I sent this to a well established UK e-bike battery builder to see what kind of capacity could be squeezed out, using genuine Japanese/Korean batteries. Low and behold, they came back and said that with limits of the case size, it was physical and scientific impossibility to get more than 48v 14amps. Even then, they did not recommend installing the highest capacity 18650 cells from Panasonic because the discharge rate might overwhelm my bikes current continuous 35amp/h wiring capacity and risk overheating. They strongly recommend instead some Sony 18650 cell which had a higher discharge capacity but would bring the overall capacity down to 48v 12amps.

I had a conversation.with a 2nd UK e-bike battery builder and they pretty much confirmed what the first firm said.

Therefore, either the Chinese battery makers are telling porkies or the UK firms have got it wrong, but they can't both be right.

Now I am left wondering whether to get a spare battery from China that may have exaggerated capacity but will at least work properly, and come in for around £350, or I go for a UK built battery that may last longer and have an accurate capacity (sound 600wh), but will cost over £500?

The second UK firm said they couldn't guarantee that all the bike's electrical functions would work due to the BMS (battery management system) they would install might not compliment the bikes other electrical components.

I wonder if anyone else has been thinking about this issue?

 

[Waynemarlow]

Therefore, either the Chinese battery makers are telling porkies or the UK firms have got it wrong, but they can't both be right.

Umm sort of. The Chinese battery uses genuine Sony 35E batterries Samsung INR18650-35E 3450mAh - 8A - 18650 - Li-ion - Rechargeable batteries | NKON which are about as good as you can get for this purpose in the 13S4P format getting maximum density at reasonable cost.

Your problem arises from you insisting on using the case, its designed principally to fit 18650 batteries in a 13S4P format. To get more energy you will have to fit another 13 batteries, obviously you cannot squeeze another 13 batteries in otherwise the original manufacturer would already be doing that.

You really have to think of making a battery outside the case. Have a look at Can you build your own battery for the E10 ? - EMTB Forums. One of the contributers to this thread has already been down this larger battery route using 21700 batteries outside of the original case, you may want to contact his supplier.