BMS and blown HY1807 (LIM12030A8S-PCBA)

Hello all,

Does anyone know why the HY1807 burn?

Have tested a few and they have around 7mOhm in Rds(ON)@8Vgs...

Sorry if i am hijacking, but have not found anything on the HY1807 fet elsewhere.. Maybe i should move to a new thread?



Best Regards
StuartStardust, another victim of burned HY1807 in a BMS.

7mohm when fully on.

what is it when partiallly on, and does that ever happen in your bms?

how much heat is generated within the fet at that resistance with the current flow thru it, and is it trapped within a wrapped up battery with no ventilation?

is it really the fet it says it is? lots of fake parts out there, marked as one thing but not really that, or they are rejects supposedly destroyed but isntead resold so they dont' meet their specs.

what's max voltage it oculd possibly have across it in your setup? what's max voltage it can handle? if you have regen braking that outputs a higher voltage than the fet can take, and the bms detects a condition from reverse current flow (charging) where it turns the fets off, then you could get a condition where there's more voltage across the fet than it can handle, and it could breakdown and start current flow in it's off state, where failure cna be pretty dramatic.



lots of possible reasons fets could die--probably a lot more thn i could think of in two minutes.

if you need to make a box for a hot bms, a good material is PCB board or polycarbonate. probaby drill some vent holes in it and fix the corners with bolts and insulate the bolts. polycarb is ok till over 140 degrees. pcb is ok till 200'C. you'd have to get the copper off the pcb use the other side.

This is a spin-off topic, did not know people was so nice to help, so moved it to here, hope thats the correct way.

From my first post in (http://endless-sphere.com/forums/viewtopic.php?f=14&t=64091) has been moved to here.


Now to the extra info:

Nominal to 24V/250W motor is 10,4A.

Motor Controller can handle 36V, and bms will cut voltage at 34 volts.

I am however running 8S LiPo, so a bit higher voltage on engine

But BMS is said to handle 15A discharge. (LIM12030A8S-PCBA)

They are not wrapped with batteries, and have enough air flow.
Also, on BMS i measured the gate voltage to 8V.
I do not think the BMS will be partially on, it will cut at low and high voltage.

It should be able to handle the back current, as the BMS will go into charging, until voltage is high enough of cause.

But at trottle cut-off, the charge will go trough the diodes i guess, will have to verify that later.
Vf on diode in Hy1807 is 0.315 at zero load, and 0.660Volts @ 1.000Amp.
- So this could be the problem i guess, as the high voltage over the diode will give a nice (too nice) warm HY1807.

- Also the over voltage is still a possibility.

Solution?
still in progress...

Trick:
Always overspec when buying a BMS.

Kind regards,
StuartStardust

that does not make sense. what diode does the current flow through? if you have no way to measure current you have no idea how much current flowed through the output mosfets.

The diode in the mosfet when current is reversed.
Soldered the one that was not blown from PCB, and tested it to find specs, as i could not find any datasheet on the HY 1807.

There are 4 mosfets on the BMS. They are paired, 2 for charging on/off and 2 for discharge on/off. These pairs are connected in series (Drain to Drain), so i guess there will always be a pair of mosfets in reverse, using diode an conductor. Source in one end goes to Power- and Charge-, and source in the other end goes to Battery-. This way the BMS can cut current in discharge when voltage is low, and cut charge when voltage is too high.

So the hottest mosfets will be the ones in reverse, due to higher voltage across them.

if you have no way to measure current you have no idea how much current flowed through the output mosfets

Click to expand...

Correct, whit no measurent, i do not know how much current.
I am trying to do post-mortem analysis on this blown BMS/HY1807 and find the likely place of failure.

Then i can find upgrade mosfet, or add a better bypass diode.

My guess for now is a fet with lower Vf/better cooling will help, as it is not the Ron that makes them hot, but maybe i am wrong.. :?

Thanks

Kind Regards