[jayson2]

hi to all!

i'm trying to build a DIY 18650 battery pack out of the samsung INR 3500mahs and my configuration is 23 in parallel and 30 in series = 100Ah 96V. my confusion is on charging this beast. what is a good charger that doesn't blow up the battery pack but can charge it quickly.

Any inputs on this set up would be much appreciated!

Cheers,

jay

 

[jayson2]

Thanks for the reply! I'm actually planning on using no BMS. There are 690 18650 cells and in 23 paralel(23x30).. i cant find a bms matching this configuration so im planning on doing the resistor to copper situation build. The chargers you suggested are a bit pricey. Question.. does the voltage of the charger have to match with the battery pack?

 

[jayson2]

haha. i literally started researching about the setup yesterday and i did see some DIY chargers but im not thinking of suicide yet .

and for the numbers.. i just realized they are other way around (oopss). so 30cells in parallel and 23cells in series.

so its:
23x4.2V=96.6V
30x3.3ah=99.9Ah

I found this on the web which a few people suggested to me.
https://goo.gl/r2CioJ

i contacted the seller and the seller told me that he can customize it to do 96V while pushing max of 15A so the battery would be charged in about 6.6hours.

Do you think this charger could do it if it was optimized properly? Any other suggestions/ inputs are very much appreciated!

 

[jayson2]

wow i have a lot to learn. i think this splitting 1 to 4 modules would be a really good idea but im concerned about a few things.

First. The idea of using BMS (4 of them) could be a little too much limiting.. you say you can only draw out 17a from every module so that means a motor that peaks current at 65ah-70ah would barely have enough current. 17ah x 4 = 68ah? im not sure if this is right or wrong.

Second. There will be more batteries (exactly 780cells..13x15=195 x 4 =780) used which means more weight that can be moved around (not much room on a bike in the first place).

Third. The idea behind charging 4 modules and then reconnecting them back would be a troublesome thing to do and im not an expert on this so by all means correct me if im wrong. But if they are charged even slightly differently ( one has less or more than the other ), connecting them back together would throw off the controller (or something else) as the batteries are not synced.

But i love the idea and im not sure if anybody else has done this before. Anyone has any experience with this kind of setup? any inputs on my concerns and what have you would be great!

 

[jayson2]

Thanks for the info! really loving this setup now. I have more questions though.

1) So for charging them, do you make a charging port for every module or just do 2 modules per charging port and then do parallel charging? which is better?

2) how do you eyeball calculate the range for a 26s30p? as you said the range depends on the Watt hour of the battery and the motor. In my case the motor peaks power at 4200w and peaks current at 65A..top speed 74.5 miles an hour (with load). i found this formula on the web and did it based on this setup:

watt hour per mile= 96Vx (65ah/74.5mph)= 83.75.

96v x 100ah=9600w

so, 9600/83.75= 114.6 miles.

Is this an approximate measure or even correct?

many thanks!

 

[jayson2]

Perhaps the 4200 watts is output power and the motor is only 4200/6240 = 67% efficient when producing this peak output?

YES. Thats what i was thinking but i wasn't sure so i did double check with the seller and turns out output power is 4200 and input is 6240.

heres the link to the motor i was going for: https://goo.gl/s1DEHf

i wanted to something to go 100km/h easy but the efficiency seems pretty terrible at high speed...

what motors do you suggest based on the 100km/h preference?

 

[jayson2]

im thinking of sticking with the 4 modules with separate charging ports and chargers. right now im looking at the batteries to do this job.. what do you suggest? i found these which are relatively cheap and hold high capacity ( https://goo.gl/kfDWSR ). i want to have a high range but also use a motor that can push to 100km/h or so without paddling. as always, open to more suggestions and advice. thanks!

 

[jayson2]

theres enough space on the bike, its a pretty big 28' xl frame but 1000km?!!! I think i messed up the math by alot then lol.

i did this:
65A peak current
96V motor
so, 65A x 96V = 6240w --> peak motor input. the output power is 4200w (based on what i was told by the seller)

my battery is 96V x 100ah =9600wh
9600wh/6240w= 1.54 hours of riding 120km/h

which means 120km/h x 1.54 = 184.6 km at max speed.

i live pretty far from the city ( about 30km ) so it would be nice to do 120km/h on the highway with a heavy bike .

Correct the math if im wrong (which i think is 100% wrong at this point )

 

[jayson2]

This 600km range setup seems PERFECT! im a range anxious person and i dont mind the extra weight and space taken by the batteries (i have enough space in the bike frame). so if i were to build 2 chargers to push 25A for each 2 pairs(13s14p).. what do i need?

i found thess 2 power supplies on ali :
https://goo.gl/UMuLaH
https://goo.gl/8BFt4G

and this charger module:
https://goo.gl/zx5TDC

Do you use an AC plug wired to the power supply and power supply wired to the charger module ? How does this work? what else do i need ? Thanks!