Very confused,
Wonder if someone could help me please, trying to make a battery pack out of 18650 batterys, I want to build a 24v battery pack for an electric skateboard.
Really don't know where to start as the battery ranges from 3.5 ish to 4.2 ish volts, I plan to use bms boards.
Could someone please help me design one?
Is there a calculattion? somewhere, I know how to achieve 24volts using batterys, just can't get my head round when the battery looses voltage and goes below 24v
Six 18650 batteries in series will give you approximately 24V. That's as close as you'll get with rechargeable batteries and that's generally all you need for running motors etc. They do not need an accurate fixed voltage.
As for BMS boards they vary greatly in the things they do and how well they do them. If you are planning on using some specific BMS board(s) please post a link to its specification/datasheet.
Steve
Thanks Steve
What I'm struggling with what happens when voltage goes under 24v, do you over supply the motor whith a higher voltage?
jonisonvespa:
What I'm struggling with what happens when voltage goes under 24v, do you over supply the motor whith a higher voltage?
You lost me...if the voltage goes under 24V why would the motor be getting a higher voltage?
Anyway the real point is that a "24V" motor will actually run on a wide voltage range. Lower voltage makes a little less power so you may need to open the throttle more, higher voltage a little more power so you close the throttle slightly. A 6S will be 25.2V immediately off charge and you need to recharge it when it gets no lower than about 20-21V. The motor will be fine with that range.
Steve
Yeah. What steve said.
I will add. Don't use super cheap 18650's they can't supply the amps needed. I built a 100watt led flashlight with 7s8p super cheap 18650's and a good bms. The ~8Amps the light draws at 32v with a cc-cv step up were too much for the batteries and they lasted about 8 cycles before they were trash.
jonisonvespa:
Very confused,Wonder if someone could help me please, trying to make a battery pack out of 18650 batterys, I want to build a 24v battery pack for an electric skateboard.
18650 is a size/shape only, doesn't indicate anything else. You need to say exactly what batteries. For instance I use 3.2V LiFePO4 cells and 8 of these in series will do 24V. LiPo will be different.
Really don't know where to start as the battery ranges from 3.5 ish to 4.2 ish volts, I plan to use bms boards.
Could someone please help me design one?
If you pay them the going rate someone might be into doing that. Have you tried locating an existing design to copy? This is something its probably worth buying for peace of mind if nothing else, LiPo especially.
Is there a calculattion? somewhere, I know how to achieve 24volts using batterys, just can't get my head round when the battery looses voltage and goes below 24v
cell_count = round(24 / batt_v)
Have you understood how one cell works? Then just multiply voltages by the number of cells for N cells in series, current/capacity unchanged.
Multiply current/capacity by M for M cells in parallel, voltage unchanged.