Gkhodeli said:
And once the hall sensors got damaged and the motor aquired constant drag and vibration when turning the technician wouldn't believe the motor was faulty and kept asking for further tests under load. So from what I understand, what I need is to replace hall sensors with better quality ones if possible (higher heat resistance) and add statorade tot he motor when tested as reparied. Are the ones you suggested same or better than what is usually installed on these motors in China? Is there one best make of the halls I can use?
Even the halls that came in it can take a lot of heat; you won't find parts that are much better at that part. If the motor gets hot enough to cause a problem with them, it's too hot because the system is not working right, or the motor is being used too hard for it's capabilities.
The problem causing the heat needs to be found and fixed to prevent it from causing other, even worse damage (burning motor windings, demagnetizing magnets, etc).
If the scenario of wrong phase/hall combo is the cause, it's easy to fix, once the controller is working or replaced. Right now, don't worry about that becuase you can't test for it. :/
If you get genuine SS41 or SS411 halls from a reputable supplier (farnell, digikey, mouser, etc), they'll work fine (assuming ESD precautions are used during all handling and repair of all parts involved).
But before ordering / replacing any sensors, test them. They might not be the problem, and it would kinda suck to have opened the motor and done all that work to not have fixed anything.
Regarding the mosfets, I found very little literature but so far what I have inquired is that the sabvoton 7280 uses IRFB4115PBF (TO-220 150V 104A).
To be certain of what's in there, you'd have to actually open your controller to find out what FETs it really has--it's very common for all sorts of devices to not have what they say they do, either because the manufacturer cheaped out and went with whatever was available that cost less, or because the parts they bought were counterfeit (marked as something they aren't; it's also a really common problem and a good reason to only buy from well-known reputable suppliers, vs ebay, aliexpress, etc--you just can't know what you are going to get otherwise).
If you're replacing them all, it doesn't really matter what's in there, though.
Here the voltage is more than double I need (150v as opposed to 72v) and amperage is 104a (as opposed tot he 80a controller). I did think to install stronger fets, but was afraid that in case of future issues something else, more problematic and expensive to replace would blow if the fets let the current though.
I definitely recommend putting FETs at least as good as what should be in there. The reason for higher voltage rating is because there can be spikes of voltage back from the motor during some usages and events, and if they are not able to handle that voltage, they fail.
Also, system voltages are more complicated than they seem: your system is not really "72v". If you have a "72v" 20s (20 cell groups in series) lithium battery, then it is about 84v fully charged, and about 60-66v empty, depending on the BMS LVC.
The current is also more complicated--80A is the battery current rating; this is what most controllers are rated by. (A very few, like Kelly, rate by peak maximum motor phase current, everybody else rates by continuous max battery current, because that is much easier to determine and measure under various conditions, even though the more advanced of these does actually measure phase current internally to do what it needs to do).
The FETs don't see battery current, they see motor phase current, which because of the way the controller switches voltage and current to the motor to drive it, can be much higher, so the FETs need to be able to handle that without heating up too much. The more there are in parallel, the easier that is (which is why you see 6FET, 12FET, 18FET, etc for bigger and bigger controllers), but they still have to have a sufficient per-FET rating. Safer to go higher than lower, and if there is a rating already known, go with at least that much. Might be overkill...but that's better than the ragged edge that could fail at the worst possible moment.
When searching online i see a wide range of price difference. These mosfets cots about 4usd each on RS-components (which would amount to the total cost of new controller if I was to replace all mostfets) which is a european site, but the same can be purchased for 50cents per pc on alibaba/aliexpresss. There is a high likelihood that the euro or US sellers that have these mosfets come from the same exact chinese factories. I would greatly apprciate if you have a link for quality mosfets with realistic prices.
As noted above, counterfeit parts (that cant' do the job they claim, if they even work at all) are common on the cheap sites, even if they are not priced cheaply. The big parts companies need to vet their suppliers and buy from the actual manufacturers, because if they contaminate their supply chain with counterfeit parts, they open themselves up for serious problems with the large companies they sell to. So you're much more likely to get parts that will do the job you need them to from them.
If you look around at some recently-posted-to threads about repairing devices, there's posts by I think "whatever" that talk about the bad parts received from aliexpress/etc. that didn't work, and there are others around over the years. Sometimes you get lucky and the parts you get work well enough for the purpose, so you can try it if it's cheap enough for you to risk that money and time. I think one set of the parts he got did fix his charger; that's luck.
It is unfortunate but common that a new device will be cheaper than fixing a broken one; this is partly because of bulk pricing vs single-part pricing, etc.
Even if you buy the more expensive FETs, it's easily possible the controller still wont' work because of blown gate drivers (which you might be able to fix if you do enough electronics troubleshooting) or even a damaged MCU (which you can't fix).
If you do have to replace the controller, you might consider a sensorless-capable (that can still use hall sensors if the motor has them) controller so that you can use it whether or not your motor's sensors work, and save the trouble of opening the motor up for that part.