YOU found the problem with the QUCC BMS. Can we fix it?

We're having a closer look at the BMS issue of the QUCC BMS. Many of you made suggestions and left comments on what the problem could be caused by. I do some more testing and exploration and dig deep into this BMS.
Eventually I found what the issue is... all thanks to your help!
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[@Sylvan_dB]

Glad you took a meter and measured across the relay. All the assumptions and guessing were driving me crazy.

[@OffGridGarageAustralia]

You and me both!

[@jasondevine6014]

Ok as electronics technician I would do this next. Un-bolt the relay from the BMS, just from the BMS. With no power applied, measure resistance of both the relay and the small wire bypassing. This will confirm either relay or BMS board for certain. If it is BMS, trace the wire back to find the 2 MOSFETs that would be back to back. One or both could be shorted. I still think that the way this works is that over a certain current the relay kicks in. Under that it uses 2 MOSFETs in back to back configuration. That is the ones underneath the board. That is why you have power when you first turn it on and after you draw power it turns on the relay.

[@OffGridGarageAustralia]

Yes, I will do that...

[@TheNightstang]

You totally NEED to cut open that relay if they are welded together break them apart. Clean up the contacts a bit and hook it back up and see if it works lol!

[@Gnagnie]

Why cut ??? don't you thrust your multimeter?

[@shanebrowne2439]

Totally agree. Should be easy fix

[@kylegoldston]

Yep, and " it was only a split second current spike till the capacitors charged " you mean like a spot welder?

[@linpray]

how are u?are u interested in Seplos storage battery,battery bms? with active balancer

[@peterrock2838]

Try bypassing with another relay to see if the BMS works. I always have several lying around just for fun. I have bought so much solar crap in the past year I could open up a store... Thanks for another fun video!

[@adamsaiyad3959]

Thankyou for all the great videos . Sounds like you need the BMS that I've designed ... Test continuity on the relay when the relay is engaged and when it is disengaged. You need to use the continuity function . Secondly ..please can you also try and switch over the shunt place the load on the battery side and place the battery on the load side . Third thing ... This firmware and software was designed for a MOSFET controlled BMS . Using a lot of MOSFETs in parallel .

[@martinwragg8246]

I worked for many years on relay equipment, contacts welding together was a daily problem in telephone exchanges. Resistor/ capacitor networks called spark quench circuits were frequently used, which did help somewhat. The only sure way to stop contact welding is to only switch the current on and off via the contracts after the operate and release times of the relay, say 100 ms giving the contacts time to settle down.

[@williambuehler2784]

I agree, lets open up that relay and get a look as to what is going on.

[@wernerbecker4137]

Magh das relay öffnen 😜

[@crankydavesmylfs4787]

I’d try a hard reboot first. A size 9 steel cap usually works for me! Sure. It’s possible it may not work again but it always makes me feel better!!

[@donr416]

Back when I was in the USMC (1972) I worked on the AN/TYQ-2 air control system that had an issue. They flew me out to fix a field issue during a joint operation call FINGER if I remember correctly. I was "short" overseas so they'd left me behind when the operation started. I knew the system well. When I got on-site I looked at the symptoms and ran into the central computer group and kicked a certain card bay with my boot. I then ran back to the display unit and all was good. An Army captain observer had followed me through the "repair" and he just shook his head at the USMC repair method. What he did not know was that for 9 months I had searched for this intermittent fault and every time I tried to locate the fault the unit started working as I probed the THOUSANDS of connector terminals that connected each card bay to the rest of the system. (I was told in training that there was enough wire in the system to go to the moon and back, they never said how many pins were in each bay, but my estimate was 1200.) So when I disturbed the bay it would start working. The easiest disturbance was my boot. We completed the exercise.

[@diydan6045]

Good information I'm sure we'll all be waiting to see the inside of that relay. Make sure you use a light bulb or a resistor to pre-charge your inverter, so as not to get a spark.

[@robertkosovich1232]

been servicing electronics since tube days, retired now but lets cut open that relay and look inside, see what ya got? Good Video, thanks again!

[@michaelb.1192]

I also think the big 10 Watt resistor is for precharching the capacitors before the relay will close.

[@OffGridGarageAustralia]

Yes, it seems so and because the relay is faulty the resistor stays cold.

[@kevinmills5293]

If that were the case, wouldn’t the battery pack continue to be drained even if the relay was open?

[@aleks138]

I think they use a small mosfet to enable that

[@bobs8226]

You can see if something is short circuited with the Ohms setting of a DVM. If you disconnect the two power terminals to the relay, you can measure whether it is shorted(closed) or open. If the two disconnected power leads still measure shorted, then you have to figure out why.

[@yoking4925]

Nice video again of a person who has to figure out everything himself very recognizable. But connect a loose relay to the BMS to see if that's the problem. If so, there are enough alternatives for sale to be able to switch the correct load. good luck

[@paulbart3156]

Could you not measure the resistance across the relay points when the relay is in the open position to see if the relay contacts are fused?

[@granite-headgold1038]

This is EXACTLY what I would do first. Even just a continuity test would tell you if they are fused or not.

[@martinwarriner7570]

Just measure the volt drop across the power terminals of the relay will tell you if it is functioning without having to reach for the hacksaw.

[@martinwarriner7570]

Oh you just did Andy! I'll go away and sit in my dark corner again now.

[@andylambertz4364]

Really like the Weather forecast: only 5 Ampere Solar - all i need to know 😅

[@KD2HJP]

This hacksaw zoom in deserves 1.5x speed playback

[@MachielIedema]

You should use Ohm over the relay contacts, not voltage. You don't to open the relay to figure out if it's good or bad.

[@OffGridGarageAustralia]

I can test the resistance but need to open it to see if it's fixable.

[@granite-headgold1038]

@@OffGridGarageAustralia check continuity across the terminals while the relay is open. I also commented elsewhere on these comments that perhaps there are really two relays within the relay case, both sharing the same common terminals; one for charging and one for discharging, so that could present a problem with accuracy of that test. I suggest disabling discharge within the app before performing the continuity test, just to rule that out, then try the same test with it enabled as well.

[@ricardomarcelino8388]

We need to see those melted parts ,😁😁😁. Great job and thank you! Even more interested now, since my 4 x 50ah have arrived to Madrid... Being busy. You have inspired me to go forward. Keep up the good work, your videos make me run to see them.

[@Adlay_Eetswah]

The relay may have fused together when you connected your inverter without a pre-charge 🤷🏽‍♂️

[@Adlay_Eetswah]

Whoops I wrote that comment before you mentioned it at the end of the video 😬 I agree with opening it up but maybe after you get a replacement 😂

[@edwardvanhazendonk]

Hi Andy, check the current through the small black wire with your power clamp, als check the voltage accross the poles of the relais, if the relais is broken there should be no voltage accross the poles (but the black wire might trick you if the current flows through it)

[@OffGridGarageAustralia]

I checked the voltage across the terminals... The wire is definitely too small to cope with high current. It's a voltage sense...

[@edwardvanhazendonk]

If you can find a new DC relay, you can opt to replace it with a new one, that way you have a spare BMS for an additional accupack

[@habana7638]

@@OffGridGarageAustralia Why not use your UNI-T meter's Ampere clamp, measure the amperes going in and out, switch on the relay and measure again...

[@Swannking]

Voltage across the relay should be zero. It is just a switch. You should do a continuity test instead. Discconect the wires before u do that.

[@Sanwizard1]

This. If its shorted, you should be able to see that instantly.

[@offgridtruckerdude7133]

If the relay was open, one contact would be positive the other negative and you would get a voltage reading, closed contacts give no reading as there would be no voltage differential

[@Swannking]

@@offgridtruckerdude7133 that’s true. It’s an indirect test for the relay. If there is something wrong with the voltage supply, u will read 0 whether the switch is on or off. Continuity test is a much direct test in this situation.

[@OffGridGarageAustralia]

Never measure continuity in a life system. You could fry your multimeter.

[@Swannking]

@@OffGridGarageAustralia thats why I mentioned to disconnect your wires .

[@Tony-Elliott]

Would be nice to see what's happened to the relay contacts. Great video

[@linpray]

how are u?are u interested in Seplos storage battery,battery bms? with active balancer

[@richardowens9061]

The large resistor is probably a pre-charge resistor to protect the capacitors in your inverter.

[@OffGridGarageAustralia]

Yes, that is correct.

[@khalilullahyosufi9379]

As per this video in 12:41, I may understand that there is two relay inside one relay-package for controlling charge and discharge current and every relay has a/its high current diode installed as series inside the called relay-package. the high current diode of discharge relay has already been damaged/shorted due to over current or ... as Andy said. So, the charge current goes through this discharge shorted diode when the discharge relay is ON. PROPBLEM FOUND.

[@loganv0410]

I thought it might be a different frog at 22:21 Another great vid. Keep 'em coming!

[@nigelcharles511]

I would be very interested to find out what the actual problem is so please continue with the diagnosis. However to ensure longterm reliable operation I would change to an alternative product. I seem to remember you saying that you chose this one because it had higher balancing current (200mA I think?). I see that the higher current Daly BMS (200A and higher) also has a 200mA balancing current.

[@FutureSystem738]

Great stuff Andy. Any BMS overvoltage or undervoltage situation which would deactivate the relay would surely create a huge spark- so I think it’s therefore pretty likely that a relay just won’t be reliable enough IMHO. It’s the opening of the relay, under load, which can create a MONSTER arc with DC, not the closing of the relay. Maybe the relay is not even rated for DC- AC is much kinder on relay contacts.

[@OffGridGarageAustralia]

It's a 300A relay from an EV, so should be totally fine with that.

[@FutureSystem738]

@@OffGridGarageAustralia Yeah, “SHOULD” being the important word. Have you decided to cut it open?

[@mondotv4216]

If you have a look at your video why I didn't buy a Daly (might be regretting that decision now) at around 8.00, I'm pretty sure you can use the RS485 port to connect to your Victron MPPT and it will instruct the Victron to turn itself off in over charge situation. I'm not sure what happens to the contact on the SW port but I suspect that is just for a switch to manually turn the BMS on and off. I agree having relooked at that video that the BMS is not working correctly.

[@OffGridGarageAustralia]

In theory that would work and would be ideal, but Victron RS85 is not talking to other RS485 devices from what I read. Only a few BMSs are able to connect to Victron and they also need t special firmware to do that. Also, the Victron 150/35 does not have a RS485 port.

[@stupidmonkeykev]

Do you need a charge relay, a 2nd relay, because how can a single relay BMS allow discharge while stopping charge. Only 'FET based BMS's can do that on a common port - assume its a single relay BMS ?

[@stupidmonkeykev]

you said exactly this later in the video :)

[@kirovoleg]

Yeah. I find it weird that the same relay is being activated separately for charge and discharge. It is using the same conductor. So i think the problem is that the firmware is probably designed for a dual relay one. For this case it should disengage charge and discharge simultaneously to protect the baterry and prevent current from entering it. But that is a bit pointless as you cant discharge it also.

[@granite-headgold1038]

Perhaps there are really two relays inside the case, both sharing the same common external terminals.

[@kirovoleg]

@@granite-headgold1038 mm. If that is so then it is a bad software implementation. It should disengage charging and discharging simultaneously if the cells go too high or too low. Otherwise if any of those are still active the connection wil still be mantained.

[@granite-headgold1038]

@@kirovoleg depends on the circuit design I guess. It would certainly help us figure it out if a schematic were available... Think about a FET based common port BMS; they both share the same port, but charging and discharging can be disabled or enabled independently of one another. I have an 8S Overkill Solar BMS, which is a common port FET based design. Interestingly enough, it uses the same app for management. Though I have yet to install it, as I am still in the process of top balancing my cells, and awaiting the arrival of some properly sized ring terminals for the balance leads. Also waiting on some power resistors to show up, for my 1.8kW load bank, so I can do a capacity test using a Victron Smart Shunt to monitor/data log.

[@Mr.X3D]

The smart shunt... is that connected to ground and + on the charger side of the bms? Might ground directly to battery through that... ok, looked further in the video, it is pulling through the smart shunt, that is the only possible reason to me

[@tracysmith7318]

Your getting a free replacement BMS. . Pull the old relay apart. . Nothing lost. . .

[@dayleedwards3521]

OK, lets try this. The 10 ohm resistor is wired ACROSS the relay contacts. You can see this if you look closely at the PCB. One end connects to the black fly lead to battery, the other to the output terminal, after the relay contacts. This allows a limited current both in and out of the battery bank when the contacts open. Ohms law tells us this will supply a maximum output current of I =E/R, or 56/10, or roughly 5.6 amps. Charging current will be limited to PVv - V batt, or say 75-56=21v across the same 10 ohm gives a max charging current of roughly 2 amps. Just why your figures differ is hard to fathom with limited information and real figures to work with,,, do you have a good multimeter?.. The battery is never completely disconnected from the charge controller and this is normal. The requirement here is for the 10 ohm "leakage " current will be similar to any balancing current, This is not an active balancer, the deign connects those SMD resistors across the high cells, the more cells that are loaded, the less excess current available. The DC pulse current when connecting the inverter CANNOT weld the contacts.... these are closed and therefore cannot arc. The only way for contacts to weld shut is when they attempt to open with an inductive load, never the case with a large capacitive load which an inverter is upon its initial connection.. AC relays have the added advantage of the mains going through zero 50 times a second to extinguish any arc, DC contact are made much beefier for this reason. More disinformation hopefully corrected. To test that relay, short the main contacts when charging with the relay off. You should see an increase in charging current. OR, simply power up your inverter with a load then turn the relay off. Put away that hacksaw.....

[@OffGridGarageAustralia]

Yes, that is correct. Hence if the relay is off we still can supply the Shunt with power.

[@henvern]

When the relay is off, the irrigation pump should not have received 15 amps. Also the MPPT puts out only a fraction of a volt higher than battery voltage so could not have pushed the approx 2 amps we saw if through 10 ohms. Contacts can certainly weld when closed. Think spot welder. MOSFETs are more robust than relays in this respect, but less robust to voltage spikes.

[@dayleedwards3521]

@@henvern The battery voltage will drop when the relay opens, as the current drops because of that 10 ohm resistor. Therefore the MPPT controller will raise its output voltage to compensate for that voltage loss in an attempt to increase the current. THIS is exactly why I suggested to Andy to dispense with this BMS, it is unnecessary and complicates things. Look up NO BMS on youtube..... Just why the pump can drag 15 amps is beyond me at this point..... is that 15 amps at 56 volts, or an unlikely 15 amps at 240 volts? There is no logical or methodical measuring going on here, causing silly guesswork. That relay would have been closed to allow this. The inrush current cannot weld those contacts. I have the exact same inverter here for repairs, the input side capacitors are 3x 220 mfd at 64 volts. Given copper and inductive wiring losses, the maximum inrush current will not exceed 200 amps for less than 10 microseconds , rapidly and exponentially decreasing as the capacitors charge, or around ..8 joules of energy. This current, or indeed even the time will not allow any heating to the degree required to weld contacts. This is why you only get a spark at the wire, but not a weld when connecting an inverter. To Andy.... if you dont want a spark, just connect your inverter with the relay turned off, this will place 10 ohms in series.......

[@dayleedwards3521]

I see Andy has belatedly admitted to shorting his pack off camera........ which side of the relay was this short, was it a big dramatic short with hot and smoking wiring or just a wee spark???? This may change the outcome too.... But, this aside, I stand by my above statement.

[@StarJackerSRL]

I think it works only if you stop charge and discharge from the app because there is only one relay.

[@jstaffordii]

This was my thought also. App software is designed for non common port BMS control ie it needs 2 separate relays. One for charge and one for discharge to seperate the power flow. Or get CANbus system so all devices communication is functioning as a system. SMA, Victron, Schneider, Outback, Magnum to name a few. Cobbled together Chinese parts that don't communicate will cause headaches.

[@jeremyolney]

Just take the new BMS and replace the faulty relay with a new solid state relay. Then in theory you will have 2 working BMS.

[@andresgodinho]

I understand what you Said but a solid State relay doesn't allow current to flow when you only want to cut charging... It just cuts charging and loads and everything.

[@robertgrant5895]

SSR tend to die shorted when they do fail. Kills your battery unless you happen to be there and notice the problem.

[@infinitygreenpower]

I sometimes have the same problems with RELAY so before you open RELAY you can just hit hard with a small hammer on the relay body and it will return to work if there is adhesion between its poles.

[@OffGridGarageAustralia]

That could probably help....

[@BischesseHunting]

@@ursodermatt8809 to be sure let the Hammer test run for 5 minutes and repeat it 3 times

[@ebenwaterman5858]

What a "White Knuckle" event. A 300 amp relay welding contacts? !!! I bought one and immediately took it apart. No way it could weld itself together. Gotta see inside. Your Wife and Kids are fortunate. :)

[@OffGridGarageAustralia]

These BYD relays are for 300A and used in EVs. I can hardly imaging it would weld from just a spark (where the caps where also precharged).

[@NackDSP]

The cell balancing is a simple circuit on each cell independent of the others. When a cell goes above 3.35V, a resistor load is switched on to that cell to draw 165 mA from it. Each cell has it's own resistor and switch. No power is transferred between cells by the balancer. The high cell does not send current to the low cell as you explained. The balancing only happens when any cell is above 3.35 Volts. The balancing current of 0.165 Amps is so low, it will take hours to actually move the cell voltage. So you can easily observe which cells are out of balance with it connected. All this information is in the balancer specification sheet. You should study it carefully before making more statements about how it functions. You pack seems to be working perfectly. The goal of the balancer is top balancing, so when the battery is fully charged, no cell is pushed to a higher voltage than the others, as that would cause it to degrade faster than the others. With the cells below 3.35V, the balancer isn't doing anything other than measuring the voltage of the cells.

[@OffGridGarageAustralia]

This is for passive balancers, similar to the ones in the BMS. Active balancer will transfer energy from higher cells to lower cells.

[@NackDSP]

@@OffGridGarageAustralia I just read the specifications for the balancer that you are using in this video. Maybe you were talking about something else. Maybe you could share the source of your information.

[@OffGridGarageAustralia]

@@NackDSP It's a BMS with balancing function, not a balancer.

[@beilkos]

You are amazing. I've watch all vids, never get bored.

[@OffGridGarageAustralia]

Wow, thank you!

[@bboyda4399]

It might be time to make a test jig for connecting batteries to auxiliaries, to eliminate spark and short potentials automatically without having to rely on always completing a perfect hook-up each time.

[@sydscrace9046]

Hi Andy, as the BMS switches on the negative side of the battery, it’s not the case that your negative connection of the current shunt monitor is back feeding through the BMS. It’s just that normally the BMS is BEFORE the current shunt? Just a thought?

[@fathergratwick]

I believe that bms software is designed for a bms with mosfets and or 2 relays. (one for charging and one for discharging.)

[@solargarage]

Lets get some eyes on the inside of that relay.

[@corybodiker6243]

I’ve had relays that the springs for the contact broke and it sounds like it was working but it wasn’t.

[@OffGridGarageAustralia]

Yep, I've got one, it seems :D

[@andinbriwel1092]

You heard the relay click, so you got the settings understood now. Disconnect the conductors from the relay, Measure across the relay, and see if it really is open. If it’s open, and you’re still getting 9A charging current, you’ve got something wired in a way that is allowing current to reach the battery from the charger even when the relay is open.

[@Sirslayer_X]

The 10 ohm resistor could be a shunt for the bms. The bms does display volts and current readings to your phone. Like the smart shunt . So you could be double shunted

[@jasondevine6014]

10 ohm is not a shunt, too much dissipation. It would be more like 0.001ohm for the shunt. But yes there is a shunt between the 2 bolts on the BMS board.

[@Sirslayer_X]

@@jasondevine6014 there are 10 ohm shunts in the market .. but I can't post any links

[@aleks138]

the bms is rated for 200A continuous and 800A spikes. you're not running that much current through the ceramic resistor

[@maxklinger6023]

Hi Andy, Would you consider disconnecting the input and output? Check it for continuity. That will tell you if the relay contacts are closed. I assume the contacts are normally open. Good Luck.

[@mkroach59]

Try using a resistor when chargng the capacitors in your inverter, your battery has a huge inrush of current, as you mentioned the large spark.

[@OffGridGarageAustralia]

The resistor is in the BMS: 10Ohm, 10W

[@longwhitecloud]

@@OffGridGarageAustralia I think what Michael Roach was saying (and I agree), the capacitors in the inverter will likely momentarily draw many hundreds, possibly thousands of amps to pre-charge the internal capacitors at the instant when the BMS relay closes and applies power to the inverter, which is a likely reason for the relay contacts to be 'welded' closed. In large systems, we pre-charge the capacitors with a shunt before we turn on the inverter.

[@rottweiler9535]

Please correct me if i am wrong , is that a separate port bms?, a mechanical rely can only be in 1 of 2 states, "open" or "closed" it can not differentiate charge or discharge current, if you can still discharge then they system can charge

[@neilpateman333]

It’s a common port bms so I agree how can it differentiate and control both discharge and charge separately. I think whether you choose discharge off or charge off it does the same thing , suppose to open the relay contacts. This bms software is generic, so a lot of the settings may not have any affect, it’s up to the bms manufacturer what features he is going to support.

[@BischesseHunting]

@@neilpateman333 exactly, this config does not make sense. The bms might Balance but but the Existenz protection options are very bad and some will never work as expected

[@jamesbsa6450]

I'm no EE, @Off-Grid Garage (Andy), but could the 10 Ohm resistor be for handling inrush current - e.g. a relay-shorted starting resistor?

[@OffGridGarageAustralia]

Yes, that is what is is for. And it stays cool because the relay is always on.

[@rickpalmer9518]

fantastic--As an aircraft mtce eng. never had welded contacts been a problem on relays in 30 years of working on aircraft dc or 400 cycles ac--usually UL Approval (underwriter laboratory) is found on many domestic products--which means this kind of failure and hence certification of this component would have not occured because UL approval is an insurance that surge currents can exceed contactor rating and not weld permanently as/construction--imagine if you had a fire caused by this contactor=the insurance would have reason not to pay---YOU are doing the UL work for the chinese--car starter solenoid relay would be a better substitute on 12 volt battery bank

[@FKZNL]

Do You have a separate small relay or contact in the BMS that goes high or low if there is an over or under voltage? If so you could use that that to stop the MPPT from charging as this is your only charge source? In case the MPPT fails and keeps charging a last safety is the large relay to disconnect the battery from loads or chargers. This would be a save solution since you use quality stuff as the Victron MPPT and the inverter which both can be programmed to accept a remote on/off signal.

[@OffGridGarageAustralia]

OK, I know what you mean. There is no other relay in the BMS and there is no remote input on the MPPT. The inverter has one though.

[@FKZNL]

@@OffGridGarageAustralia The MPPT has a on/off input via a non inverting VE direct cable. docs.victronenergy.com/ve.direct-non-inverting-remote-on-off-cable.html#purpose-and-function. if you google you also find diy solutions.

[@jeboldt1961]

Why don't you check the continuity between terminals before cutting up your relay? You shouldn't see voltage between terminals...but between terminals and opposite battery terminal

[@tullgutten]

Just put the multimeter over the contactor (relay) terminals and switch it on and off. When the contactor is off you should see around battery voltage over the terminals. And when the contactor is closed you should see close to 0 volts.

[@tullgutten]

And on car relays when they are stuck closed you can often just tap the housing with the handle of a screw driver and it releases

[@donr416]

"It's not what you don't know that is the most dangerous - it is what you "know" that is wrong that kills you. "

[@sousmangoosta]

Yes open it open it!!!

[@nickush7512]

When in doubt.... get the hacksaw out !! :)

[@oneeyedphotographer]

There's a fine German company, Fein, which has a product they call a Multitool. To me, they're expensive. However, it seems that by now just about everyone down to Ozito has a knockoff. One of its accessories is a saw blade, it vibrates back and forth at right angles to the device. It should do a neat job of decapitating that relay with no internal damage.

[@MrJramirex]

Fein's patent for the oscillating multitool expired some years ago, that is why everyone tool company sells their own multitool.

[@sidneygornall4564]

Hi another quick statement from the guy in England

[@kevinmills5293]

Compared to FLA batteries the LiFePo4 battery can deliver huge current surges due to very low internal resistance. Connecting them to the inverter, which has decoupling caps with very low ESR, the inrush current, with no pre charge, would be way more than the relay could handle. Think of it as a spot welder.

[@OffGridGarageAustralia]

I think it still worked afterwards... It's a while ago. And I had it precharged but waited to long to actually connect the cable. The spark wasn't like 🧨but larger than the one I captured on camera

[@kevinmills5293]

@@OffGridGarageAustralia it will be interesting to see inside if you should pull it apart at some point.

[@michaelb.1192]

Let's say the big spark you talked about melded the relay together. But what if the relay disconnects (after you replaced or fixed it) and connects again after the time the capacitors are discharged. There can be a spark inside the relay again and meld the contacts together again! The relay must handle that with no problem a several hundret times, if not, it is not the proper relay for that BMS or aplication.

[@OffGridGarageAustralia]

That's what the 10Ohm resistor is for...

[@michaelb.1192]

@@OffGridGarageAustralia That also means that it is important that the relay is open if you connect the first time - to give the 10 Watt resistor a chance to preload the capacitors thrue the thin black cable you showed going across the relay before the relay closes.

[@neliosamch3195]

No Andy. I think the relay is working ok. It cut off the power going in but not the power coming out. It has the charging and discharging cable conncted together but the magic happens inside the bms.

[@janosvarga962]

Yea. Dismantle it to pieces. Some more forensic work worth watch.

[@MrSqueegey]

Glad the problem,was found and solved.

[@OffGridGarageAustralia]

Well...

[@guntherbluml8069]

I also suspect welded contacts of the relay. This can happen when closing the relay with discharged capacitors connected to the output. Initially they act as a short circuit and the current is only limited by the resistor values in the circuit (internal resistor of cells, wiring, shunt, fuse,...). My guess is that the ceramic 10 Ohm resistor should provide a precharge function together with some Mosfets back to back (like a solid state relay). If this circuit fails the next time turning on the relay the contacts have a high chance of welding together. The plunger inside would still move as it is actuated by the coil but the bar connecting the studs and closing the circuit will stay in the closed position. A mechanical shock (e.g. knocking with a hammer) could break it loose again. But the chances of stucking again are high.

[@OffGridGarageAustralia]

But should the 10W resistor not prevent the high precharge current?

[@guntherbluml8069]

@@OffGridGarageAustralia it should but only if it is implemented correctly in the firmware and without a physical fault. I don't know the BMS and the internal design. Without a measurement of the voltage outside (after the contactor) it is not possible to diagnose a mail function of the precharge circuit or the main relay.

[@mondotv4216]

Also that resistor is a pre charge resistor for the relay

[@OffGridGarageAustralia]

Yes, most likely.

[@rljzathras]

High current DC breakers really should have a magnet to "blow" the arc away from the contacts. Otherwise, a nice spot welder you have.

[@jasondevine6014]

The 10ohm is more than likely for the power supply of the electronics. The balance resistors are next to the plug.

[@jukkapekkaylitalo]

Is nice that although i have yet to get my batteries i have beefy HEYO BMS basically Daly 24s 250A. 250A Should be RMS peak is over 400A.

[@Tom111060]

... makes it sense to measure the voltage across the two negative poles? Shouldn't it be done against a positive pole?

[@habana7638]

haha..I thought exactly the same, do you really think Andy realizes he's trying to measure a voltage across the same negative pole?, it's funny that he tries anyway...

[@offgridtruckerdude7133]

Bypass the relay with a starter silonoid, or a battery isolator relay so it will work for you while you wait for the new one.

[@linpray]

how are u?are u interested in Seplos storage battery,battery bms? with active balancer

[@offgridwanabe]

On my Ant BMS when the bms reaches a overvoltage it sends a message to Charge Controller and shut off the charger it seems your bms does not control the charger. The only way my charge controller can still send current is when I have a load to use the current.

[@offgridlivingstlucia8865]

The ant bms works very well the time i install my bms they was cell was going to high and the bms give a warning and it turn the charge controller off

[@offgridwanabe]

@@offgridlivingstlucia8865 yes it works as intended

[@shenn7332]

Thank you for the explanation. I was wondering how it can control charge and discharge with only one relay.

[@mondotv4216]

You measured voltage across the relay terminals, not the input voltage. You would expect to see 0V. You should have measured resistance across those terminals. When it's active you should be measuring 0 Ohms. When it disconnects you should be measuring open circuit.

[@lornebonnell2007]

Maybe they use the same app/software for the relay and MOSFET versions of the BMS the MOSFET versions of the BMS have separate charge and discharge FET's so they can for example disable charging but still allow discharging, which I am not sure how you could do with just a single relay. That would explain why the app has a switch for chg and dischg?

[@dash8brj]

You have to pull that relay apart. I wanna see the state of the contacts :)

[@mondotv4216]

To measure voltage on the relay connect your negative probe to the negative side of the battery and your positive probe to the output side of the relay. Unfortunately I think this will make no difference the way you've wired it (by design) it's in parallel with both the load and the charger so if you have a common ground, you're still going to be measuring voltage from the charger and inverter. If the battery were a floating ground you should see the relay interrupt the circuit and the voltage drop to zero. I guess you could do it at night when the MPPT is not generating any voltage.

[@OffGridGarageAustralia]

That's not the case. I turned off the solar charger and the inverter will not provide any power on the battery side, it consumes power. I measured the voltage across the terminals of the relay. If the relay would have worked and opened I should have measured 50V.

[@immrnoidall]

lol. you got to love those chinglish translations.

[@Tex260Z]

Looks like you were trying to measure voltage from the two positive terminals, (in and out of the relay)?

[@philbrooke-little7082]

This could be just a stupid Idea but some two wire driven relays are latching and work by reversing the current to the coil. They have a magnetic latch. Also some BMS’ have the ability to drive these but it needs to be set up in the software. Maybe you have a setting that is incorrect for whatever relay you have.

[@OffGridGarageAustralia]

Which setting would that be?

[@philbrooke-little7082]

@@OffGridGarageAustralia It was just a thought as I know some BMS’ can drive these types of relay but it needs to be setup. I don’t know the sepecifics on yours. I would be tempted to unplug the relay driving wires, check the voltage it drives at, it may be 12v, and then try driving it both ways round with a separate supply to,see if it is one of those type relays.

[@BastelPichi]

Get a new relay and put it in there and always use a resistor to precharge the capacitors

[@OffGridGarageAustralia]

Apparently it has this 10Ohm resistor build in for exactly that reason.

[@BastelPichi]

@@OffGridGarageAustralia teh bms? Cant be

[@jamest.5001]

I'm hoping all works out because I'm planning on getting a similar bms,

[@OffGridGarageAustralia]

A brave plan...

[@RenaatG]

You could measure the voltage between the big relais contacts

[@jamest.5001]

The software and display make me think it should have two contactors, or it should be set up as a charger bms, or discharge BMS!

[@BischesseHunting]

Software is for multiple Hardware bms and does not Cover which functions are available on the connected Hardware. 2 more Tests: How far can it fly? How far can it dive? Follow the test sequence!

[@cncdavenz]

Will this inrush current always happen when the relay closes and the inverter is connected. Maybe the 10watt resister is across the relay contacts to charge the capacitors.

[@OffGridGarageAustralia]

That is a very good point! And that's why we have supply to the BMS even if the relay was off. Makes totally sense to me. Thanks for the tip!

[@GlaucusBlue]

Assuming you paid by MasterCard or visa you can try a charge back. Not guaranteed but worth a try, credit or debit card. Some banks are better than others, you may need to push. And alibaba and aliexpress have quite long windows to make a claim, so worth checking there as well.

[@OffGridGarageAustralia]

AliExpress have excellent customer service I found. So has the manufacturer. It's all sorted now...

[@muddy11111]

Andy..Your "voltage sense wire" looks rather large, try putting a clamp meter on it and see what current it is passing. I suspect you have a software problem on the charge side. Your bms may have mosfets handling low currents for charge and discharge with current sensing, the relay being brought on for large loads. (It does not make sense to run a high current relay for a small load.) The relay went off when you pump pulled a high current and came back on again when it went off. So the high current through the mosfet turned off the relay to try to protect it's self, which obviously did not work. I had an early version of the software downloaded from Will Prouse's site. With this I set the balance to work off line and it turned off the charging while balancing. With the new software this no longer works, the charging does not turn off. I suspect the software is not turning off the charging rather than the bms failing. I am running a different bms but the same software.

[@berny8283]

Wie regelt das BMS laden /Entladen über "EIN" Relais? Wenn du entladen sperrst, was macht das Relais wenn Strom zum laden ansteht? PS:Sollte das Video erst zu Ende ansehen bevor ich fragen stelle! ;-)

[@OffGridGarageAustralia]

Hahaha, das war auch meine Frage ;)

[@kiello26]

I looks like the app shows delayed display. I think its best to use an ammeter to verify amp following

[@Zuikantyper]

With the relay non-energized, tap, smack, hit, the relay, on multiple axis (not sure what direction the contacts move). Measure continuity across it to see if it opens. With no connections to it, it should be open circuit. Should be able to break the "welded" contact loose with enough force. (look half way down this page, www.evpartner.com/news/detail-15665.html )

[@tonydickerson999]

Can't you replace the relay with a solid state relay

[@mrsunelectronics544]

Laderegler und Wechselrichter immer vorladen über Halogen Lampe, um den Strom der Elkos in den Geräten zu begrenzen ! Problem dabei es gibt Hersteller die Geräte bauen die sich selbständig immer gleich auf on setzen bei Akku Anschluss, und dadurch die Elkos gleich wieder entladen werden.... da fliegen wieder die Funken 💥😕 dann geht's nur mit Kabel und die Lampe (Vorwiderstand fix zwischen die offenen Anschlüsse) bis der Akku verbunden ist....

[@OffGridGarageAustralia]

Mach ich doch immer.

[@mrsunelectronics544]

@@OffGridGarageAustralia OK 👍 war mehr als Info gedacht, für Leute die noch nicht soviel Erfahrung haben 😉 Grüße zurück 😋

[@budmartin3344]

Great video. may be the relay has phony 300A rating or may be it is the factory rejected relay being used by the BMS maker to save money. BTW, I miss Kermit the Frog.

[@FutureSystem738]

Or maybe the relay rating is 300A AC- there is a huge difference when it comes to opening and closing the relay contacts.

[@budmartin3344]

@@FutureSystem738 Spec sheet of the BYD: EVR300CPES. Made to handle DC Voltage, use in BYD Electric cars. www.nbshenli.com/images/pic/file/20180830/20180830163959_27634.pdf Contact DC rating: DC 12V ~ 1000V

[@OffGridGarageAustralia]

I think that's why they have discontinued it and now the new BMS has an updated relay.

[@jamest.5001]

Can the polarity of the bms output be changed? Maybe it is designed for output or input only?

[@joshmo6454]

Why does your screen say “protection none”? Can you tap that and see if it changes? Time stamp 4:46 for example.

[@OffGridGarageAustralia]

That's just the message, there is no function to tap that

[@ArthurDentZaphodBeeb]

Hmmm, asking for a refund when you 'might' have 'accidentally' caused the relay to fail with a short seems a but odd. Open it up and see if the contacts are fried. If so, you should send QUCC payment for a new BMS as it seems it's user error...the honorable thing to do. I'd like to see you test how the relay withstands a blow from a 5kg hammer.

[@dayleedwards3521]

And, while Im at it, heres why the balancer works the way it does..... Lets set each cell to 3 volts max. Once the charge reaches this level the balancer will begin to load each cell. As this is only a few hundred mills, it wont do anything... yet. The charge controller will see an over voltaged pack and begin to shut down, this monitors the ABSOLUTE voltage of the pack. But, because you have a seperate duplicate high voltage shutoff, ,HVSO. we need to look at that one also. Your HVSO will now disconnect the main relay, as the pack is now around 38 volts. Now the charge current goes via the 10 ohm to limit the current to say 5 amps. This will continue to raise the voltage on each cell, and more and more balance shunt resistors will begin to divert current until the loss in heat will equal the current in. This takes TIME. The cells will EVENTUALLY float to the same level, your indicated charging current will continue.... it can NEVER shut off entirely until nightfall. The ONLY time your balancer will do anything is when the cells overvolt, over a period , and with big banks, can take HOURS An active balancer will monitor all cells IRRESPECTIVE of their absolute voltage, only looking for a 30mV difference between each, These work great and are my preferred choice. Passive loading also works well, but the cells need to slightly overvolt for this to work correctly. I suggest you ignore the 3rd decimal place on your phone, then these figures may make more sense

[@klausluchow7905]

Well why don`t you messure the relay.?

[@kevinmills5293]

I was getting very frustrated until Andy finally put a meter across the the relay terminals.

[@klausluchow7905]

@@kevinmills5293 If He would have measured the resistance, there is no need to open the relay. It's only a switch.

[@OffGridGarageAustralia]

I need to keep the tension in these videos...

[@kevinmills5293]

@@klausluchow7905 clearly the contacts are closed but it will interesting to see exactly what has happened. Welded contacts is the obvious answer but there may be some kind mechanical failure. We shall see - I hope!

[@DSmartLife]

Please open the relay!

[@PhilippeCJR]

you could use a temp camera, i can recommend the flir one or better/new variant with you mobile

[@OffGridGarageAustralia]

The relay gets warm when on...

[@PhilippeCJR]

@@OffGridGarageAustralia true, but i also remeber the fuse or some shunt was getting warm. I like my flir one. Very nice troubld shoot device. Deff will use it with my future solar lifepo setup😎👍

[@joelrosales6359]

Sir maybe the relay 12v/24v is not suited for your 48v battery set up.

[@musicinspire1745]

Good grief. Just put your multimeter across the relay input to output. If the voltage is zero, which it likely will be, then the relay or something else in the setup is shorted.