8s ESC powered by 10s battery - will it work?

mh, yeh 4.4ah is not the best to work with… but 3ah might be also okay…

I imagine you might be able to run it at 70-80% of max charge (if I follow the logic of what I posted in 1st thread)…

80% = ~3.5ah 70% = ~3.10 ah…

Still usable and will yield about 10km range at least, if battery is in good shape and if it it even works.

Might not give you the max output, as these are probably not highest output cells I believe.

So, not to burn it on 1st try, @TeknoAbu I would suggest you to do this:

If you got voltmeter (u should have one, if you work on esk8 lol)… plug it in parallel with battery terminals while charging, then, when you see 38-39v, stop the charge… the voltage will go back a volt or two but will later on remain stable.

If you really wanna use the board and dont want to burn the esc, you might as well charge till only 35-36v.

Just check in what condition / state / voltage the battery currently is… maybe it doesnt need any discharging or it is already too high.

You probably can charge / leave the battery at 34v but it wont give you a lot of range… basically at 3.4v battery is at ~25% or so… so in your case, maybe 1ah of capacity and would probably only work for about 3km or so.

Right, thank you kindly for the help! I’ll follow your instructions, and film it - for science! :smiley:. If the battery is totally unusable, I guess I just have to go and buy myself a battery that actually matches the ESC. :slight_smile: . If so, what battery should I go with then?

Yuup, @Okami is right and I stand corrected. The LiFeP04 is the 3.6v per cel. My $25 is still on the table. Partial charge is a great idea. No guts no glory.

You can exceed the max drain-to-source breakdown voltage of the mosfets on the board at which point you will get high current and magic smoke, so saying that voltage is no problem especially in upping the voltage on an 8S designed ESC is silly.

Why not up the battery voltage on the VESC from 12S to 14S? Voltage is no problem right?

I run two 4s 10000mah multistar in series from hobbyking . Easy cheap charging.

@SimosMCmuffin so is there a way to physically inspect and read values to determine how much ‘over-voltage’ can the mosfets /parts sustain?

I know that one of the limits is probably capacitors itself :smiley: but they usually should be at least a few volts higher right…(?)

@MoeStooge thanks for reminding of lifepo, but since he didnt mention it here and I dont believe he has one for escooter (for ebikes more popular) then i didnt even mention it here, yes with lifepo at 10s, it would work quite well actually because of lower voltage but lifepos usually are more expensive, bigger in size / less capacity.

The El.cap voltages are easy to determine of course as they’re written on them, but on the MOSFETs you would have to look at the model number on their package and find the datasheet and check what it says for maximum Vdss breakdown voltage.

Here’s a datasheet shot for the IRFS7530 MOSFET used in the VESC:

So even the though the VESC’s MOSFETs are rated for 60V, the recommended battery voltage is 50.4 V (12S) to give a little overhead.

There is a economic reason why they do use as low Vdss voltage MOSFET as they can, as their component price will quickly start rising the higher current and voltage you go and even then the hobby ESCs use many lower current MOSFET in parallel to raise the max current capability and spread the heat generation over larger area. So an 8S ESC is most likely rated very close to the particular battery voltage.

Trackstar manual says 33.6v max do not exceed. My $25. Is still good.

I said

Slight overvoltages are far less likely to burn anything than slight overcurrent. If you actually exceed any component rating you can obviously destroy them - that should be common sense. The used components are typically a little overspecced however so that they can handle abuse (with voltage spikes and so on). The caps are not rated to 25.2V on a 6S ESC but a little more and so on. I tried it myself with an 8S LifePo on a 6S ESC - no smoke but OV protection kicked in.

At what voltage was the Lifepo?

3.6 x 8 = 28.8v…

so about 4v more (25.2v - 28.8v = 3.6v precisely, if lifepo was at max or so)

That’s a 17% safety factor in the MOSFET. And would be pushing your ESC 20% over manufacturer limit. Sounds like fun.

@SimosMCmuffin besides mosfets, are there any other parts which might be ‘regulated’ and need to be operated in specific voltage?

Then @TeknoAbu could take a photo of his mosfets inside esc after or before he burns it :smiley: though it might as well also give just over voltage error and not run properly, if it is smart enough :slight_smile:

I think someone had posted inside pics of dis-assembled FVT120… might as well go there and see if mosfet number can be seen there.

Here’s the manual for the OP’s ESC:

They stress not to use more then 8S voltages.

There are basically 4 parts that might break from the voltage. El.caps, MOSFETs, MOSFET gate drivers or voltage regulator for MCU. There might also be a TVS protection diode to protect from voltage surges/spikes and if you cross that diode’s breakdown voltage it will basically short-circuit the battery terminals together and atomize the diode into the atmosphere in a couple milliseconds probably.

Of course the only certain way is to test and see if it works :wink:, but the voltage limits are there for a reason…

1 Like

Mh, Thanks for clarifying things! TVS diode vaporization sounds fun! :smiley:

Well… If you saw my first post here, im a bit amazed at castle creations (talon?) esc, that it can still work a few volts higher and just beeps when in overvoltage then again, it is a completely different price group so we cannot be really sure that the esc @TeknoAbu used has any circuits which check the voltage.

I do know some of them check for voltage automatically so maybe they have a setting to sense over-voltage and not drive the mosfets, if the scenario is such… this is why i recommend him to start slowly and see how the esc responds and not slam it with 8v higher voltage which might be too much in my opinion, otherwise they would rate it to 9s or something.

@SimosMCmuffin from what you said, it sounds like mosfet driver might also be quite prone to this, if it is close to the limit… we see what happens with vesc and Drv quite a lot… :smiley:

@TeknoAbu Smoke, Fire, Cold feet?

Alright everyone, I have been super-busy with the massive amount of exams just until now, so I’m very sorry that I haven’t been able to do something in the recent days… anyways - update is here!

Just to summarize it all once again, I now tried to connect a 36V Li-Ion battery into my 34V max ESC. Quite simple of a result though. The fact is, that the ESC won’t use the battery’s power to run the motor. Compared to when I did a quick 14V setup with some old batteries this same day, the motor was running as intended.

When I plugged the 36V battery in the following happened: 8 light beeps indicating 8 cells, one long deep beep indicating that the transmitter was connected succesfully, and then just the ESC rapidly flashing a red led. No magic smoke or anything (thank god), no hot wires, no hot battery and no power to the motor at all. The ESC just kept on flashing this red color.

What has happened? Can the ESC actually detect if it’s getting overvoltage? If possible, what to do now?

Over Voltage Protection. I was rooting for you. Some of your better equipped ESC have this feature.

Right, I knew it…

Do I have any possibilities by this time other than buying a new battery, or can I somehow remove the protection?

If not, could you suggest a battery (or batteries) that would fit my skateboard then?

I run two 10000mah 4s in series on my trackstar. You could take apart your battery and re configure your cells if your up for a challenge. My battery cost was around 130usd. Some batt soul searching.