Whats it takes to burn up a vesc 4.12?

Hey there, new to the esk8 world and I have some uncertainties on how exactly I should set up my current/amperage parameters for my specific build. Building a mountain board on a slimmer budget so the last thing I want to do is burn something up when I could have easily prevented it. Build components:

-FS vesc 4.12 50a cont. 240a peak

-7s4p li-ion 8ah (2 hoverboard battery packs in parallel, not ideal but dirt cheap with a built in bms and will be upgrading later)

-180kv 6354 1920w 80a max sensrd unbranded Chinese (figured I could get away with running way under the max amps to greatly reduce risk of burning up my cheap motor)

-16t pinion pulley

-72t drive pulley

200mm (7.9 inch) off road pneumatics

I know its not the greatest set up and definitely not a performance set up but its all that budget will allow for the time being. I do have a second identical vesc and motor in the mail on its way so will be doing a dual drive set up mainly for off road traction purposes. But the main thing I want to know is how many amps can the vesc safely handle? Im just unsure because the advertised 240a peak really throws me off. Im more familiar with the RC world that has advertises esc’s with burst current ratings for a set amount of second of burst at that current that the escs can handle but they are never 5 times the max continuous like with the 4.12. I dont want to limit my vesc to 50a if it can handle way more than that. Aslo, is that 50a rating referring to the battery in current or the motor out current?

Ive done some flat ground testing with what I think is a conservative set up but I want to know very clearly what the line is so that I never cross it. Here is the setting for my initial tests with only 1 motor and vesc:

Motor max 50a

brake max 30a

absolute max 130a

battery max 35a

regen max 15a

I just left temp settings at default, I think 80c start 100c off for mosfet

*recommended settings for all would be greatly appreciated.

I was surprise at the performance considering my settings so I believe with another motor and vesc and also with turning up the power to what it can really handle, I wont need much more performance for a long time to come other than a different battery. I got up to 18 mph, which I dont think I’ll want much more speed with an off road board anyways, brakes were slow but I know I can turn up a bit, just didnt want to go flying for the first ride. And nothing got even remotely hot.

Last question for this thread, Has anybody played with installing heat sinks to their mosfets and could that greatly improve performance and lower the risk of burning something up? If you have heat sinks can you over amp your vesc a bit more as long as the temperature settings are correctly set and catch it before anything gets hot? Just thought it was crazy that nearly every RC esc comes with a heat sink and fan but these 4.12 vescs dont initially need them and they are moving much heavier objects.

Thanks in advanced. I hope this is not too much information on one post at one time.

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On 7S you should be pretty safe with a 4.12. I wouldn’t bother bursting to 130, just leave it at 50 and if it feels underwhelming then slowly move it up. Your regen max is way, way too high if thats per side then -30 amps into a 4P battery will destroy it. You want about -6A per side or if you only have 1WD then -12.

Again if you’re using hoverboard batteries they’ll be a massive bottleneck, you can only use about 20 battery amps per side.

Given that a 4.12 ESC is only about $40, its not worth trying to overclock them for better performance, it just creates a potentially unsafe scenario and will cost enough that you should have just gotten a better one. RC ESCs run at about 4S, 150 amps, and its amps that causes the heating. At 50 amps its not as much of an issue

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@Anubis No I currently have the 2 hover board batteries with a parallel connector going to 1 vesc. So it was only feeding -15 amps to both, -7.5 each. I’ll bump it down to 12 though, thanks for letting me know that. I didnt ride hard so I doubt I hurt anything. And if I understood correctly, I can pull 20 amps off each 2p battery pack? So 40a total since I have 2 2p in parallel? Or just 20amps off a 4p pack?

And yeah Im going to upgrade batteries as soon as possible, I purchased the entire hoverboards for 25 dollars each “needing new batteries”, I knew they were just over discharged from sitting unused too long so I just by passed bms to just high enough voltage so that the bms would take back over and do the rest of the balancing.

Btw, Is that 40$ usd for a 4.12? if so whats your source?? I spent 60 usd on mine from china!

In the UK we get super cheap 4.12s, they’re as low as £36 on ebay which depending on the status of brexit fluctuates between 42-46$, and that’s shipped from the UK and taxed :smiley: 20 amps per pack so if you’re only using single drive then yea 40 amps max, some of those hoverboards use a 12 amp bms though so better to check maybe. And yea, max 2~3 amps regen per p group, so no more than 12 amps back into a 4p pack. Remember, max regen doesn’t effect how hard you can brake, only the energy the vesc will recover.

Ok cool! thanks for the help man. I just discovered batteryhookup.com and will probably be making a battery purchase from them pretty soon. Stupid cheap resale fully tested cells and packs! And yeah Ill check on that bms



I have a $260 order halfway here pending delivery estimate. I also got a KWeld to begin serious battery construction.

Also I burnt my VESC 4.12 PCB on 6S due to a high KV+A motor, so watch out for that. It was perfectly fine with the same motor on 12S, lower V = more A = not good.

@Fosterqc Oh sweet! What will the specs be on your battery?

Do you by chance know the best way to figure out how many amps my bms is rated for on these packs? No specs online have said a thing about that. Its a jettech 25.2v

Beware on the battery hookups 9s ATL packs. I got 21 of them and 14 arrived completely DOA with no good cells. (Of the good cells I’ve tested all are 2850-3050mah). They are replacing 6 of them though, and the cases and BMS’s are legit.

I have been stress testing them and they are very high quality cells. 10 amp charge, 20 amp discharge, 5 cycles Without puffing and only get warm on the discharge. Under 10 amp load 0.1v voltage drop observed and no noticeable warmth generated. Tried charging to 4.5v then draining completely and it and they puffed to 160% of the original size but no warmth or signs of failure. Did a capacity test and still at 1800 mah. Then when fully charged I punctured with a BB gun and they didn’t even smoke with a gaping hole in the pouch. And still was able to output 10amps shorted through my damn and held voltage at 3.85v for hours. So I think they are way safer then LiPo pouches and pretty cheap for a nice pack if you go that rout instead of 18650’s.

(Making a 12s 9p ebike battery with them. 1.2 kWh for under 250 all in).

Battery hookups is a good company, fast email reply’s and good shipping times.

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@JohnA Man I just found those flat packs and was blown away at the price of them! On sale for 4.99 each! I couldn’t find the discharge rate anywhere and that was the only thing worrying me so thanks for answering that for me! Is the bms rated for 20a dischage or just the cells?

If the shipping wasn’t as high I would have bought 6 of them already! I think a 9s4p would suit me quite nice for the time being.

Dude 12s9p!? What kind of range you think you’ll get with a 25+ah battery??

The BMS is only rated for 10 amps discharge. (And assume the cells are too, i did 20 amps to test the limits). It also uses a TI chipset in the bms that works for 6-9s packs do you could wire two in series for a 12s battery.

I’m hoping for a 40-50 mile range on my ebike without pedaling. But we will see. If you go this route too, look into closed cell polyurethane foam. Pouch batteries work best under some compression force and also can “breathe” 5-10% in normal charging and discharging use. so you wanna make sure your pack has room for this, and when the batteries eventually puff.

Pretty easy to disassembly cleanly, can give tips if you end up buying them.


Ok gotchya! Well thanks a bunch for the tips already! If I end up getting them I will defiantly holler at you if I have any questions! Seems that you’ve done your homework and know your stuff quite well!

That would be incredible to get that kind of range with no more than your battery cost you. Unbeatable dollar per mile. I hope to build a bike one day, I have the great palo duro canyon basically in my back yard and have always dreamed of rippin down the trails on a e-mountain bike.

Are you using the Included bms’s that the packs came with and doing a 6s in series +9p type set up or different bms all together?

Also, how thick is a single cell?

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No problem, I wasn’t able to find any info on them myself so I wanna do a full write up after i finish my pack with all of the tips and tricks I’ve discovered. Most of the research I’ve done has been on this forum or the other new one.

I’m currently planning on making two 6s9p batteries, each wired to one of the BMS’s. And then those packs in series. Im also thinking about modding two 24v chargers to be together in one case with one output so that I have a 4 prong cord that can charge each pack separately but at the same time. I also wanna have an extra balance plug wired in so I can connect my hobby charger to if I need to active balance the packs ever. Most bms’s on the market have like a 50-100mah balance current that barely does anything for high capacity packs, I just want it for the over charge cell protection.

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Single cells about 4.3-4.4mm thick from the ones I measured. Out of 10 cells the mean was 4.34mm thick.

The WxH dimensions are roughly 64mm by 89mm Or 2.5 by 3.5 inches.

Appreciate it!

Shame they had a lot of dead cells. I got two I was hoping to use as portable charger.

@Fosterqc I told them about the dead cells and they were happy to replace a couple. They said they weren’t aware some were completely dead, and that they have multiple pallets of them so it’s too many to go through. I had good luck “waking up” the dead cells, with low current from my lab supply. (I’ll run a capacity test on a few of the dead ones and reply back). I’m not sure how they will hold up long term, or how many cycles they can do before they puff though, being they say dead for so long.

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@JohnA Well I think it’s worth the risk since they’re so cheap. Glad they were willing to replace a few if them for ya!

When I revived my hover board packs they were about .3v per cell (i know, scary) and now I’m getting about 7 miles per charge on an inefficient mountain board. Original rated total ah would be 8ah but I have no idea how many amp hours I’m actually getting out of them since my hobby charger/discharger only goes to 6s. But I was surprised they are doing as well as they are with no dead cells so far!

I have a question for you though, have you experimented or ever heard of deep freezing over charged lipos to revive their capacities? I’ve watched a few YouTube videos but nobody that I can find has done a detailed experiment by physically measuring amp hours so idk if it’s legit or not. Definatly makes me want to do my own experiment.

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The ATL packs look well built.

I’m going to use them as CNR for my Onewheel. I wonder how much of a hit they could take

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@cskarke I haven’t really experimented with freezing the packs for capacity gain. But I did try freezing a puffed cell that I overcharged to 4.5v. Before the freeze the aluminum bag was fully inflated and after 24 hours it lost about 30% of its thickness. After the tests it went from 2879 mah to 1800 mah. I would be interested to see if it could help revive the capacity though.

If you plan to disassemble or remake a pack, keep in mind one of the electrodes is aluminum so you either need aluminum solder or to spot weld nickel strips to the battery to solder to. This solder from amazon works very well on soldering wires to the cells. Aluminum Solder Wire 96.5 Sn/3.5Ag .062 Flux Core https://www.amazon.com/dp/B00DC3102Y/ref=cm_sw_r_cp_api_i_pDC.DbYEEH6MY