Inverter settings

[Raul]

Have you ever monitored the distribution of the charge/discharge currents across the individual batteries. If so, were they more or less in proportion to their relative capacities?

Ian

Yes I have, at loads on 600-700 and 1500w current is equal to their size within 1-3A.
At 70A discharge/ charge for example, each gets its equal share, the 304Ah battery gets 30-31A and the two 200Ah gets the reminder of the 70. I have the two 200Ah closer to the bussbar paralleled via a 35mm2, then the 304 Ah is 3m away under front settee via a 35mm2. Sometimes the 304 has a little lag to catch up, but it evens out within seconds.

So, matching batteries myth for me is busted.
As long as they have their own bms, they can be put together, and each will contribute accordingly to its size.

 

[bigtwin]

So, matching batteries myth for me is busted.
As long as they have their own bms, they can be put together, and each will contribute accordingly to its size.

That was always my understanding and all this fear mongering that is spread about is just nonsense.

Ian

 

[MichaelT]

Ok, I guess you are right. I understand there are air fryers out there @ 900w rather than the 1.400w that I have, so shopping on Monday it seems... Thank you Lenny HB for your input. I will let you all know how I get on. I need to sort this out before the 22nd of May as that is the date we leave the Island for our Irish Raid

Well just come via uk and pop into uncle lennys

 

[Barriesimpson]

Well just come via uk and pop into uncle lennys

Now there's an idea

 

[Barriesimpson]

I took these photos this morning so you can all see the setup and the parameters according to the app.

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[Barriesimpson]

I imagine that all the cables together on the battery posts is not optimal, but I was told that up to five cables was fine if they are not all large. Is that true or is there a better way? Bus bars maybe?

 

[headlight]

I took these photos this morning so you can all see the setup and the parameters according to the app.
View attachment 1048829View attachment 1048830View attachment 1048831View attachment 1048833View attachment 1048834View attachment 1048835View attachment 1048836View attachment 1048837View attachment 1048838View attachment 1048839

Those inverter cables look thin to me.

 

[Barriesimpson]

Those inverter cables look thin to me.

They are what came with the inverter and it was installed by the dealer from new. I would like to think they are fine.... but I understand what you are saying. Let´s see what the others think, thanks for your input headlight

 

[headlight]

They are what came with the inverter and it was installed by the dealer from new. I would like to think they are fine.... but I understand what you are saying. Let´s see what the others think, thanks for your input headlight

The positive and negative battery cables look to thin to me also.
Just because cables came with the inverter doesn't mean they are suitable as often the cables supplied are not.
Also just because a dealer has done the install doesn't mean it's good.
We've seen very poor dealer/professional installs often on here.
I must say that to me me that looks like a very poor install.
With the size of your cables my first thought is your problem is down to voltage sag.

 

[Barriesimpson]

The positive and negative battery cables look to thin to me also.
Just because cables came with the inverter doesn't mean they are suitable as often the cables supplied are not.
Also just because a dealer has done the install doesn't mean it's good.
We've seen very poor dealer/professional installs often on here.
I must say that to me me that looks like a very poor install.
With the size of your cables my first thought is your problem is down to voltage sag.

Ok, thanks. None of the cables get hot though so I assumed it was good. The installation is messy and I'm sure it could be a lot better, but I cannot find anyone here with sufficient knowledge/experience to sort it out.

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[headlight]

Ok, thanks. None of the cables get hot though so I assumed it was good. The installation is messy and I'm sure it could be a lot better, but I cannot find anyone here with sufficient knowledge/experience to sort it out.

Did you say previously that you are taking your van to Ireland ?
If so book it in to Vanbitz or Offgrid Power Solutions and have the set up installed properly.
That install looks poor for a DIY job let alone a dealer install, sorry.

 

[Barriesimpson]

Did you say previously that you are taking your van to Ireland ?
If so book it in to Vanbitz or Offgrid Power Solutions and have the set up installed properly.
That install looks poor for a DIY job let alone a dealer install, sorry.

Yes we are on our way on the 22nd of May. That may well be the solution I need. Once again, thank you for your input headlight

 

[headlight]

Yes we are on our way on the 22nd of May. That may well be the solution I need. Once again, thank you for your input headlight

Proper cabling, bus bars , fuses and a shunt

 

[MichaelT]

Is the usb cable fully pushed into the BMS, looks like it's half out?

Book into off grid to get them to sort proper cables out or do them yourself as it's an easy job if you buy pre made ones.

 

[Barriesimpson]

Is the usb cable fully pushed into the BMS, looks like it's half out?

Yes, I thought that too, but it seems to be all the way in.

Book into off grid to get them to sort proper cables out or do them yourself as it's an easy job if you buy pre made ones.

What size of cable would you recommend MichaelT ?

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[MichaelT]

Yes, I thought that too, but it seems to be all the way in.

What size of cable would you recommend MichaelT ?

I fitted 50mm2 all round on mine. 2kw inverter 500mm long. I've got 2 batteries different makes and capacity connected with 50mm2 cables to bus bars (negative via a shunt) all 300mm long. Like Raul both batteries get drawn equally based on size. Got mine made up by sunshine solar, they even made the one from bus bar to shunt with 8mm one end and 10mm the other to fit the shunt. Maybe not an option for you unless you get them delivered to someone to pick up when in UK but there must be somewhere local who can make them for you.

 

[Raul]

I still can't see the bms, only the BT dongle with a USB cable coming from bms. I suspect is a Dally as mentioned before; the clue, that's a dally bms BT dongle.
There are few bad settings there, including mos temp.

Discharge protection should be set at -20C
Charge temp protection should be set at 5C
Mos temp should be 60C nor 45
Cell low voltage 2.8 is to high, under load can trip- I would have it at 2.6v
Sum voltage 2.6x4+0.1= 10.5V not 11.5v

Also I suspect your cables that came with the inverter may be ( chinese) aluminium copper clad. Lots of hammer crimp lugs are not helping either.
You can check by disconnecting one of the cables, and scrape with a blade knife at the lug end, after you expose the strands under the isolator. Also copper is quite heavy compared to ally clad.
That inverter needs minimum 35mm2 copper cables with hydraulic crimps, the hammer ones are for the bin, makes a rubbish high resistance connection.

Also I noticed you have quite high imbalance 93mV is allot, hence disconnection maybe a low cell hits the protection under load and cuts discharge.

 

[Raul]

To be fair, when it cuts out under load, it can be seen from bms, if is the culprit.

 

[Barriesimpson]

I still can't see the bms, only the BT dongle with a USB cable coming from bms. I suspect is a Dally as mentioned before; the clue, that's a dally bms BT dongle.
There are few bad settings there, including mos temp.

Discharge protection should be set at -20C
Charge temp protection should be set at 5C
Mos temp should be 60C nor 45
Cell low voltage 2.8 is to high, under load can trip- I would have it at 2.6v
Sum voltage 2.6x4+0.1= 10.5V not 11.5v

Also I suspect your cables that came with the inverter may be ( chinese) aluminium copper clad. Lots of hammer crimp lugs are not helping either.
You can check by disconnecting one of the cables, and scrape with a blade knife at the lug end, after you expose the strands under the isolator. Also copper is quite heavy compared to ally clad.
That inverter needs minimum 35mm2 copper cables with hydraulic crimps, the hammer ones are for the bin, makes a rubbish high resistance connection.

Also I noticed you have quite high imbalance 93mV is allot, hence disconnection maybe a low cell hits the protection under load and cuts discharge.

Interesting, thanks for the input Raul. Yes I see now that it is the BT dongle not the BMS, sorry for the confusion. As already mentioned, all the settings came like that from the manufacturer but I'm game to change them if that is going to help so long as I don't f**k it up by doing this.

 

[Peavy]

Interesting, thanks for the input Raul. Yes I see now that it is the BT dongle not the BMS, sorry for the confusion. As already mentioned, all the settings came like that from the manufacturer but I'm game to change them if that is going to help so long as I don't f**k it up by doing this.

Barrie, to enter to parameter mode, you must have had the password. Did they give it to you, or did you found out trying? It may change warranty terms in case you want to change any parameters (I found the password googling). Just to be in the cautious side.

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[Barriesimpson]

Barrie, to enter to parameter mode, you must have had the password. Did they give it to you, or did you found out trying? It may change warranty terms in case you want to change any parameters (I found the password googling). Just to be in the cautious side.

Well I can enter into the parameters as shown on the screenshots, but have not tried to modify any yet, so I don't know if I need a password or not. We shall see.....

 

[Raul]

Its your call, but, as example those settings are half horrendous, for example low temperature charge protection -20C. Good lord the charge should stop by 5-4C celcius. At -20 charging, you already have done irreversible damage. Whoever set that bms must of done 100's of batches, then got mixed up with different chemistries. But ultimately the vendor should not send something like this out, I have seen it many times from so called manufacturers( importers) and don't have the man power to check them out, money is the prime interest.

 

[LostInSpace]

I find that devices without "settings" are the best, by far.

 

[Barriesimpson]

Its your call, but, as example those settings are half horrendous, for example low temperature charge protection -20C. Good lord the charge should stop by 5-4C celcius. At -20 charging, you already have done irreversible damage. Whoever set that bms must of done 100's of batches, then got mixed up with different chemistries. But ultimately the vendor should not send something like this out, I have seen it many times from so called manufacturers( importers) and don't have the man power to check them out, money is the prime interest.

Thanks Raul I shall be changing the parameters and see what happens.

 

[Barriesimpson]

So I spoke to the company who sold me the battery today and he is thinking it could be a problem with the BMS or the relay of the BMS. He wants me to recreate the problem and video the inverter cutting in and out and the app screens, so that is the next step. He also questioned the cable size to the inverter. I will keep you all informed, and once again, thank you all for your input.

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[Barriesimpson]

Latest update for those that are not bored to death with this thread.

I used the air fryer again, but this time at 195º rather than 200º and did not get the shutdown. The cables were warm but not hot and the errors on the app were these:

So the chap at the store suggested I increased the discharge temp high level from 50 (which is what it was set to) to 55 or 60. I have set it at 55 for now and will test again. He said he thinks the cable size is good for the current draw as it does not go above 92A, at least for now.

 

[bigtwin]

If your air fryer is 1400W then why is the current discharge only 90A (1.2kW)?

That suggests that your cables are current limiting (I.e. they’re too small).

Ian

 

[herald_400rl]

Just a thought, it may be bms overheating or bms connection. When is in a battery box, its hard to dissipate the heat. Next time you put a load on it to replicate fault, two things springs to mind to look for:
-monitor heat reading from bms, also feel for hot spots on the case, right at the moment of disconnection.
-second, have a multimeter to measure the voltage on the batt, and inverter terminals as it disconnects.

For reference, I take chinese Amps with caution, and make my own mind. As example JK bms comes with two 7awg cables soldered in, that you connect the battery negative. The bms is rated for 200A and it will do that for 30-40 mins as a test. No way I will let the bms settings on 200A, I knock that down to 110, as those two 7awg cables can't do 200A for to long.

Raul, as per other threads your wisdom is welcomed. Given I've just got one of these and there will be times I run an air fryer and so intend to draw 1500w+ occasionally, should I have bought the perhaps more robust 300a version?

 

[Barriesimpson]

If your air fryer is 1400W then why is the current discharge only 90A (1.2kW)?

That suggests that your cables are current limiting (I.e. they’re too small).

Ian

I have no idea, which is why I started this thread - I'm new to all this. While using the air fryer I am watching the app and the most I have seen is 91.5A and it drops to around 45A when cycling.

 

[bigtwin]

I have no idea, which is why I started this thread - I'm new to all this. While using the air fryer I am watching the app and the most I have seen is 91.5A and it drops to around 45A when cycling.

I think that it has been suggested more than once that your cables are suspect.

I would address that concern if I were you.

Ian

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