Victron 12v - 24v MPPT controller, investigating the FETs.
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- Опубліковано 22 тра 2024
- A Victron MPPT 100 -50 charge controller with a blown fuse, and I think a shorted FET, what do you think?
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I've had reasonable success repairing electronics, but I'm by no means an expert. I'd suggest remove the blown fet, then check the board for shorts where you've removed the fet, if no shorts then replace the fet with one from the other boards and re test with the power supply with a low current limit. When fets blow, they can often take out the driver chip and other components too, particularly diodes and low value resistors, so check round, particularly in the vicinity of the fet. Good luck.
Hi, thanks for this info, yes rob a FET out of another board, check it and install. I.m hoping because it's not actually let the smoke out that the rest will be OK. Test with a limited current is definitely the answer, cheers
@@TheInfoworks The bench power supply is, in my opinion the second most important piece of kit to get after a multimeter if you want to repair electronics, apply power, low voltage, low current, see what happens, if voltage stays near set limit and current is low then no shorts or significant power consumption, if current goes to limit and voltage drops significantly then you have a low resistance, you can calculate that from Ohm's law, it's exactly how a multimeter works, but you get to set the limits, so it actually tells you far more than the multimeter.
I sometimes temporarily replace a blown fuse by linking an ammeter across the fuse socket to see what current is flowing under test.
@@andypdq Very much like testing a circuit with a battery and a small load rather than a multimeter, tests the ability to carry current, or pull the voltage down and show a large load or short. Interesting experiments.
@@davidbrodie5044 It's a suite of analytical tests, each one hopefully tells us something, just like the first unit blue smoke showed the problem area, cheers
Hi Andy, seems like they're using the FETs as a double pole switch and using a pair on each to share the current. I don't know how the MPPT charge controllers work; Presumably they're a hefty buck converter which can taper the power delivered to the battery.
There is a capacitance between gate and source so when it's charged up the FET is ON, leakage is low so the FET will stay on until Gate is grounded. Can be troublesome when prototyping with loose cables!
Ian, yes I think they are variable buck converters, allowing current to rise until voltage drops, a balancing act. I'm thinking to replace the duff FET and see what happens, cheers
Done it..... clicked it....👍👍
N x
Hope so, time and experiments may reveal, cheers
Due to their low cost I'd replace all the FETs. It seems to be working OK, the variable volt and current on your power supply suggests the MPPT part is working. I'm wondering where the current surge comes from to blow the fuse. I'd expect the battery to be more capable of delivering the current needed than the charger to blow the fuse.
Ian, yes I'm wondering about that, there must have been a path to create a dead short across the battery, there may be a diode somewhere that has blow also, or maybe the FET also acted as a diode, hmmm
Ian, where's the best place to buy FETs? cheers
@@TheInfoworkshi Andy, they seem to be £5 each on the UK sites, clones to be had for £1 each, some say new and original.
Alternative I've found is Toshiba TK100E10N £3.86 each or £3.19 each if you buy 10 on Farnell. There's also Vishay SUP70042E which seems to tick the boxes except it's surge Amp rating is only 200A (continuous 135A at 75degC), it's surge rating is much lower than the Infineon but well over the devices rated 30A charge current. They're £2 each inc VAT from Farnell if you buy 10. You'd be safe replacing them all with the higher rating unit I'd bet. Victron themselves might populate with what they have in stock and may have bias or preferable purchasing price with Infineon brand FETs
@@TheInfoworksI usually pick a FET then shop around, end up on ebay or Aliexpress. I go off the photos to determine authenticity. Been OK so far.
I had a look for FETs over 100V. Seems odd that the device is a 100v 30A charger and then use 100v FET. Perhaps the FETs are in series rather than parallel, or the FETs are ran at battery voltage as they are on the output.
@@ianhelsbyservices Ian, thanks for the info, I think as a proof of concept I will rob one out of the duff unit, cheers
I rewatched the clip showing the power supply and whilst it stays for a moment at 1.2A it quickly drops (I'd expect stable). Was this you removing a supply and caps being discharged or likely a symptom or an unhappy machine? I suppose a PV panel would output variable current rather than voltage due to shade and clouds?
Ian, I'm thinking its a product of a duff gel battery charging up rapidly, The fact that things were happening and a FET got warm is promising, cheers
I'm no expert. In my experience fets starting to fail appear good not under load. As for interchangeable fets, check the data sheet for gate voltage and triggering current.
Hi, that's interesting, I'll rob some out of the duff unit and test them with a bulb and battery, cheers
Hi @Sim6699, do you have any theory as to why a seemingly well specified fet would fail?
@@ianhelsbyservices Ian, I'm thinking heat is the problem, either direct or by destroying capacitors that could maybe make it switch half on, and so get very hot, cheers
@@ianhelsbyservicesusually to much current creating heat, which in access breaks down the material between drain and source. At first they breakdown underload but eventually short or go open circuit.