What is the advantage of choosing for a BMS that can talk to your inverter? (Seplos)

drbytes

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Merde alors :)

But note that Seplos also doesn't support putting a 280ah and 304ah in parallel. At least that is what I was told by the Seplos rep. on Alibaba.
He did argue that the difference between the 304 and 280 isn't that large and it should work out fine.
 

HRTKD

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That makes me wonder once again, if I shouldn't just pair a 280 and a 304 and create a 16S of 584AH cells.

Something about this approach just seems wrong to me. If you were to do this then I wouldn't configure the Ah to anything more than 560 Ah. If you set it to 584 Ah then wouldn't the charge device try to push more into the 280 Ah cell than it should?
 

houseofancients

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That is an interesting proposition. I have not seen anyone do something like that but it may be the better way to parallel cells of different capacities (assuming the BMS can handle the capacity of the 'mega cell'). The problem you are likely to run into is that the cells will be of different physical dimensions and getting the Busbars to all line up might be a challenge.
andy @off grid garage is doing that right now
 

drbytes

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I debated that as well; but the 304 cell will sink current until it will reach 3.65 and then it'll shut down by means of the bms.
The parallel 280AH, which if full, will have too high a resistance and the current will go to the 304ah.
These pairs should also equalize themselves.
I don't really see how it is any different than having individual sections inside a cell contributing towards capacity vs actual physically separate cells contributing towards capacity.

Or I'm missing something obvious
 
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houseofancients

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I debated that as well; but the 304 cell will sink current until it will reach 3.65 and then it'll shut down by means of the bms.
The parallel 280AH, which if full, will have too high a resistance and the current will go to the 304ah.
when you top balance the voltages will equal out, sure the 304 will take a bit more load as it is keeping the 280 at the same voltage level, but give they arent far apart in ah, it shouldnt be too bad ( you would still be left with 292 ah between a 280 and a 304 cell)
 

FilterGuy

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( you would still be left with 292 ah between a 280 and a 304 cell)
I don't follow that logic.
If I build a 2P16S battery out of 280AH cells, I would have a 560AH battery.
If I build a 2P16S battery out of 304AH cells, I would have a 608AH battery.
How does mixing the cell size take it all the way down to 280AH?

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If I build a battery out of 280AH cells and a separate battery out of 304AH cells and then parallel them I will get ~584Ah.
How is putting the cells in parallel first and building a single battery going to be different? I argue that putting them in parallel first and using a single BMS is going to remove differences in the BMSs and actually work better to balance the load between the different size cells.

Note: As I said before, doing parallel first will introduce challenges in lining up the busbars.
 

houseofancients

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I don't follow that logic.
If I build a 2P16S battery out of 280AH cells, I would have a 560AH battery.
If I build a 2P16S battery out of 304AH cells, I would have a 608AH battery.
How does mixing the cell size take it all the way down to 280AH?

-----------------------------
If I build a battery out of 280AH cells and a separate battery out of 304AH cells and then parallel them I will get ~584Ah.
How is putting the cells in parallel first and building a single battery going to be different? I argue that putting them in parallel first and using a single BMS is going to remove differences in the BMSs and actually work better to balance the load between the different size cells.

Note: As I said before, doing parallel first will introduce challenges in lining up the busbars.
280 + 304 = av 292 ah.

i have never said to use either, way of paralelling but what indid mean to say is that these cells are so close apart, that when top balanced this wont be a big issue
 

toms

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It makes no difference if the parallel cells are different capacities. You don’t average out the capacities when in parallel - you add them together.

If you have a 100ah cell and a 10ah cell it’s no problem to parallel them, you will end up with a 110ah cell.

Charging is no different to any other cell, the parallel pair (no matter the capacities) can be treated as a single cell.

As has already been pointed out, you may need flexi bus bars.
 

Rossman

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Didn't see this mentioned elsewhere but my auto generator starter can be triggered by state of charge (reported by BMS) as well as other standard voltage triggers.
A proper closed loop communication will also allow the BMS to change the charging current supplied by telling the inverter/charger what it needs, versus it just getting what you hard code the inverter/charger to.
 

RikH

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It makes no difference if the parallel cells are different capacities. You don’t average out the capacities when in parallel - you add them together.

If you have a 100ah cell and a 10ah cell it’s no problem to parallel them, you will end up with a 110ah cell.

Charging is no different to any other cell, the parallel pair (no matter the capacities) can be treated as a single cell.

As has already been pointed out, you may need flexi bus bars.
Exactly. Keep in mind what the guys do with lots of different 18650's in one "cell". That's the same principle.
 

drbytes

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hmm, maybe that why there are so many fires with them ? ;)
Ok dude, respectfully, please stop. I don't shy contrarian POV but they have to be informed points, not just random stuff flung to the wall, I'm trying to weed out the nonsense and would love to keep this thread on point.
 

houseofancients

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Ok dude, respectfully, please stop. I don't shy contrarian POV but they have to be informed points, not just random stuff flung to the wall, I'm trying to weed out the nonsense and would love to keep this thread on point.
actually i was pretty serious.
many of those fires were caused by run away cells.

you want each cell monitored individually , and ideally bms's communicating with the inverter/charge controller.
1 ramp down amps when almost full
2 halt charging on error
3 provide a good SOC and voltage
4 prevent hard bms shutdowns

then again, just my 2 cents, do with it whatever you like
 

Andrea91a

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Vorrei capire se il bms seplos , in caso di spegnimento del bms, stacca il regolatore di carica per evitare di bruciarlo.. perche la tensione dei pannelli e molto alta
 

drbytes

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I think you need to set that in your charge controller. I mean, if it can not detect that the battery has been disconnected it's not a very good charge controller ;)
 
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