Well lithium cells are relatively very small so can pack a few in series in less space to stack the voltage up, ultimately the values to look up are energy density (Wh per unit mass and per unit volume) since that is what matters for getting range and portability assuming those are the criteria.
Also different chemistry batteries have different number of max cycles and deep discharge cycles vs partial discharge, I imagine someone has tried I just donât think itâs normally a good idea.
More directly to what you asked we use 8-12 lithium cells in series that ends up roughly in the 40-50V range so would need something like 4 car batteries or motorcycle batteries to get to roughly the same voltage but I donât think youâd get the same range or Wh in the same volume or space.
Itâs been done, and it âworksâ, in that the esk8 will move under its own power. But your average car battery weighs about 40 lbs (~18Kg), and has a capacity of 40Ah.
Sounds like a lot, right? 40Ah at 12.6v (nominal voltage for a car battery) gives 504Wh, or the rough equivalent of a 12s4p lithium battery made of 30Q cells. (518Wh)
That 12s4p pack weighs just five pounds, though, compared to the ~40 for the car battery. That means the lithium battery has eight times the energy per pound.
But it gets even worse for the car battery. Lead acid batteries designed to start cars arenât built to be drained down low and then recharged. Theyâre designed to always be full, and only ever blast out a few percent of their energy to start the engine, then immediately be recharged again. If you treat a car battery like a regular esk8 battery, it wonât last long before its capacity starts to drastically degrade. To keep the best possible life, youâd have to treat it like itâs in a car: Always fully charged, and only use maybe the top 30% of its full capacity before recharging it.
If you take all that into account, the lithium battery has more like twenty-five times the energy per pound that a car battery has.
A 12v car battery is actually six individual 2v cells stacked together in series to get 12v. We do the same with our packs - The most common ones we use have between twenty and sixty individual cells inside, arranged into groups stacked together to give us the right voltage and current.
Our commonly used battery setups are usually 10 or 12 cells in series - 10x3.6=36v, 12x3.6=43.2v.
You can do the same thing with lead acid batteries, but as I mentioned before, they are just so, SO much worse than lithium batteries in terms of energy density.
there is this guy on the other forum that made a really nice vesc enclosure.
What is th easiest way to have leds inside like his? a single battery? or can you plug it right into the vesc?
There are several different ways, depending on exactly what kind of LEDs youâre using (bare LEDs that need a driver, or LEDs with their own current limiting such as the common LED strip), and how many LEDs you plan to use.
The vescs have their own internal power supply to run themselves, and they can supply up to 5V, 1A for external items such as receiver, hall sensors, and, yes, LEDs. Iâd stay well under that 1A limit though, donât want to risk stressing the vescâs power supply.
Using a dedicated switchmode regulator like Brian mentioned is a good option if youâve got 5v or 12v LED strip that requires no special current limits.
If youâre using bare high power LEDs (like for a headlight, or similar. âhigh powerâ means more than ~0.5w per individual LED) with no internal power circuitry, you can get dedicated constant-current LED driver modules that will run from the main battery just like the above. These are what I used for my headlight and tail/brake light.
If you donât want to screw with any of that, you can always just get a small USB power bank and some USB powered LED strip, and recharge the power bank regularly.
Keep in mind, this is only for bare, high power LEDs with no current regulation of their own, like what you find in headlights, flashlights (bright ones) and similar (The headlights, flashlights and etc all have something like this in them to drive the LEDs). This will not work properly with regular 12v led strip or whatever. For that, just use the DC-DC converter Brian posted. These still need some electrical knowhow to use properly - I recommend reading and digesting the datasheet.
Am I safe to set the max amps for the motor to 150a? this seems really high.
Using the esk8 calculator it says my max amps for the battery pack should be 80a is that correct? is there any advantage to setting it lower like 75a to give the battery a little bit of a breather?
Finally the deadband is to 15%, do I need it so high or at all? what do you set it too?
Thank you all in advance I would have just bought a boosted board like everyone else if it wasnt for you guys! I love your work.
Excellent question. This thread has heaps of great info, and heaps of missing info⌠but in a nutshell, battery amps and motor amps are not the same thing.
Basically, you can set your motor amps to whatever you like at the risk of melting your motor. Set it to 150 and see if it gets hot⌠it probably will on a single drive. But be aware that limiting your motor amps too low will drastically restrict your motor performance.
But your battery amps should definitely be set to within your batteryâs capability.
The motor pulls the amps. The amps donât just go to the motor because the battery is capable of outputting that much. How much you weigh/your throttle settings/how hard youâre throttling/grade of incline all go into it.
As @itsrow has said though, youâd need at least 2p groups to pull that.
Thank you both.
The full question is this;
I am 60kg, my board is a mtb, will be used as such going up steep hills off road.
2wd
12s6p 40t
Unity.
Imagine i max settings to the most reasonable it can go.
should i choose a
3510W 65A max 6374 170kv
or
-4100W 80A max 6380 170kv.
no point of having the extra weight of the 6380 is if i wonât even use the limits of the 6374.
the vesc does a voltage change depending on the speed of the motor (lowering the voltage but increasing the amps) between the battery and the motor⌠so you can safely set the motor max to 150a per motor, and the battery max to 80a per motor without exceeding the battery limit per motor.
unfortunately on a standard vesc 6, hidden in the firmware is a 120a motor current limit, so even if you enter a 150a motor current limit in the settings, this value will be lowered to 120a motor current limit without much indication this has happened.
if you set the battery limit less than the motor limit, youâll lose some throttle range at the higher speeds because sustaining 120a at those speeds requires more than 80a battery amps.
for that reason i recommend not exceeding 80a motor limit per motor and 80a battery limit per motor.
that said, 80a per motor will likely give a large amount of torque at full throttle, so you might want to try something lower like 50a bat and 50a motor at first, and if thatâs not enough torque for you, try increasing the settings while keeping them equal.
and remember, the battery limit setting is per motor
& the motor current limit setting basically determines how much torque you have at full throttle assuming the battery current limit setting allows that much power
Itâs a MTB, you already have a 12S6P of fucking 40T. Weight doesnât seem like the biggest concern⌠Get the 6380. Higher quality, longer lifespan. I believe higher efficiency as well.
Hey I know some electrical things! I think I only fried one Arduino Mega and cooked an alligator clip off a wire getting this test lift rig put together:
i @ ed the wrong person lol @whaddys we are in the same boat
Sorry @wafflejock!!!
I take the oputunity to ask another question though haha
i have 2 builds, 1 mtb, 1 street/at build both with gear drives
which vesc would you use for the mtb
