To be clear it depends on the VESC, and nosy are good to 12s… Now.
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ok that makes sense now, because you can set the ERPM limits safely with VESC right?
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Okay so with a 190 kv motor with 7 pole pairs and 12s battery at 4.2 volts per cell (50.4 volts). 50.4 * 190 * 7 = 67,032. But this assumes full battery (at top speed your battery will sag a little bit because of the power being pulled and as the battery depletes the voltage decreases. But Ben with a full battery you can never hit 100% efficiency. At 85% efficiency 12s 190 kv gets you 56,000 erpm which is safe. But many higher quality vescs can handle higher than 60,000. I’m not saying you should push the limit but the limit isn’t what 100% percent no load erpm would be.
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Yes, some VESCs, specifically the FocBox have been tested successfully to 80k ERPM. So 12s and 190kv are within safe limits.
*12s 
Is there way to limit ERPM? For my next build I have Flipsky VESC 4.14, Flipsky 6354 190KV motors and 12S pack. That means my build will go over ERPM limit.
EDIT: Just now I read discussion under the article and see that 12S and 190KV is hot topic. Anyway, is there way to protect my hardware and be sure I’m not hitting limits even at the cost of performance?
You can manually set the ERPM limit in the config, but you shouldn’t have too. With efficency figured in you shouldn’t reach 60k ERPM with 190kv on 12s, as explained by @Jacobee here…
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True you can’t really accelerate or reach top speed and also keep full battery voltage but there are also other things to consider.
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Often your 190kv isn’t actually exactly 190kv, maybe it is 193 or 188, you never know. For example, my old TB 190kv motors were “190” but they never reached over 58k rpm on a full charge bench load. My new ones are “190” but they reach 62k on a full charge bench load, so shrug, I have FOCBOX’s so I am not super worried about the erpm given that I never go that fast and they are pretty robust.
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Bench runs. When you are setting up your board you don’t want to worry about doing a full throttle without meaning do and ending up with a dead VESC, like I said I am not super worried about my FOCBOX, but with a cheaper VESC 12s like for example an Aliexpress Flier one or something, I might be more concerned with the components being able to take the high erpm. Easy to reach full speed when you are at bench load (basically free load).
All that being said I have run 12s “190kv” for 3 years and haven’t killed a VESC because of these aforementioned issues.
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Damn, good lesson:fire:
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I did not understand the Maximum Charge Rate
I am one of the guys who want the 12s8p battery that. I will built (first timer) to charge in 15mins !!! (hehe) safely and of course I cannot accept the idea that it needs 12hours of charging. So since I see big companies saying that with a fast charger you get in 30mins the 80% charged, HOW can I do it safely in a diy battery ? How can I calculate the optimal amps in order to buy the proper charger, the proper BMS or anything else related ??
Where are you getting these insane times
12s8p is quite large. Also, charge rate depends a lot on the cells, and then after that, on your BMS. It’s not a complicated calculation though.
Each cell’s “safe” charge rate is 1c usually, which for example, for a molicell p42a would be 4.2a since their mAh capacity is 4200mAh.
For a 12s8p of p42a you could theoretically “safely” charge it at 4.2x8 = 33amps. First of all, many BMS don’t let you charge that high in the first place, second, a 33 amp charger would be very bulky and expensive.
Anyways, I have no idea what the average charge time of people’s large battery boards is, but also, almost no one with a large board is charging with a puny 2.5a charger. I personally charge my 12s7p of 30q cells with a 6a charger and I wouldn’t say that it would take more than 2 hours from zero to full.
Again, no idea what the average charge time is, but I would be surprised if most people take more than 4 hours to charge their board. I don’t really feel like doing the calculation to see how many amps it would take to charge a 12s8p in 15 minutes, but the only cell I could possibly think of doing that with is a M1B or M1A (I forget the other names) LifePo4 cell. These have insane charging specs listed on their spec sheets…
Yet again though, it is highly impractical
In conclusion, I personally end up picking chargers based on how much money I want to pay. I make good money but my monthly esk8 budget is pretty small compared ot some people here. The most I’ve ever paid for a charger was like $45 on Aliexpress for my metal housing 6A charger from YZ power. It works great, charges my board in like two hours, and was a reasonable price.
You start getting into 15 or 20 amp chargers and the price goes out the roof from the view of reasonability in my opinion
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So I thought I’d be cheap and reuse my standard LiPo balance charger I use for all my small LiPos for my dual 6S 14Ah battery. Turns out that charging a single one of them takes 12 hours at 1.5A, and I can’t parallel them either because I only have one charger, so that’s 24 hours to fully charge my board. I’m half tempted to just spend the extra $100 and hook up an actual BMS and 6A charger, but given my current riding habits, the slow charging hasn’t been much of an issue. I just start charging it the day before I plan to ride.
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Good lord, that’s rough haha
Yeah 14ah at 1.5a is pretty bad.
Daly BMS for $30 bucks and a 6A charger for $45 isn’t too bad but you do then have to deal with the process of wiring up all the balance wires and what not
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With the right charger, one that is huge and costs a fortune (or lots of the right chargers in parallel), you could easily charge that quickly.
But it will not be safe and you will significantly shorten the life of the cells. EV’s have complex cooling setups that help manage the temperature of the cells during fast charging. Even then you are still damaging the cells every time you fast charge them.
Nothing with batteries is “free”. If you want higher capacity you typically have to accept a lower current rating or larger size. If you want a higher current rating you have to accept lower capacity or larger size. If you want fast charging then you have to accept shorter overall cell life. There will always be a tradeoff.
You might decide that the tradeoffs for fast charging are worth it. That’s perfectly okay. Each of us gets to choose how hard we want to use our packs.
I recommend staying below the fast/rapid charge rate for the cells you are using. Even this will be really bad for your cells since they are all bunched together and wrapped up so the heat will be trapped but at least it’s not, probably, going to set your pack on fire if you have a good BMS.
BTW, this is critical!
The faster you charge the more important the BMS becomes. This is due to the higher current level magnifying any differences between the cells and causing more of a voltage imbalance between the cells during charging.
Once you know the fast/rapid charge rate for the cells you are using then you can just multiply that by the number of cells in parallel to get the charger current rating you need.
To help reduce the risks and keep the cells from dying early I recommend staying at the standard charge rate or lower though unless you have some way to effectively cool the cells.
This does not mean just blowing air on the pack. 
In the middle of all those cells, wrapped in insulating tape, fishpaper, and shrink wrap, the cells are still heating up.
Which cells are you using?
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Ok the 15mins time was a figure of speech !!! I will use the p42A. I am still thinking of which BMS to use. I am thinking of the LLT 12s 20A charge only but again I am not sure.
What do you suggest
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The voltage numbers are off
The voltage that the motor sees is 1 / sqrt(3) times the battery voltage
This has to do with Space Vector Modulation and Three Phase Inverter properties.
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Wait this post confuses me. If I go 12s with my 190kv motors theyll fry the vesc? I’ve never heard of such a limitation. Using a vesc4
There is a nonzero chance, yes. It’s not guaranteed, but I certainly wouldn’t run a config like that. I am allergic to the taste of asphalt.
12S on a v4 vesc or vesc derivative is already pushing it a little depending on the exact hardware, and a fully charged 12s battery could spin a 190kv motor up to an unloaded speed of 67K ERPM. v4 vesc hardware is generally considered to have a safe upper limit of 60K, so that’s a bit spicy for my liking.
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I’ll never fully spin it unless it has no load and I’m testing it. This won’t really matter but I rarely pass 20mph, so I’m not too worried.
Can I just somehow cap.it so it’ll never fully spin up?
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