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alaskannoob avatar image
alaskannoob asked

SmartSolar 450/200 & Blown Fuse in Lynx DC Distributor -- What Happens with Current?

setup.jpgGot all my equipment from UPS and am trying to design it. In my design I have two 450/200s in parallel that can provide 400A to my 48V battery bank. My battery bank consists of 4 Pylontech US5000 lithium in parallel, in parallel through the Lynx with another bank of four batteries. Had to do it this way cuz Pylontech cables only support 100A of current.

What happens if a lightning strike or something makes a fuse pop or a C/B pop and half the batteries are then isolated? Do the MPPTs know to not charge the bank with 400A and to cut it in half? Or can they be programmed to do that since the system talks with the Pylontech batteries?

Or will 400A on a sunny day still get pumped through the Lynx and then blow the other fuse or pop the other C/B so that all the batteries become isolated from the system?

Many thanks for the help!

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Alexandra answered ·

@AlaskanNoob

If you fuse the outputs of the mppts through the lynx then the mppts will have a blown fuse and then that is no longer an issue?

And in theory if you have a GX device the Pylontec connected, will have limted charge current from the mppts using DVCC so overcharging should not be an issue.

Or at least that is my understanding here?

You can also have SPDs on the pv input so the surge hopefully is diverted before the equipment as well.

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alaskannoob avatar image alaskannoob commented ·

The MPPTs will in fact have a fuse in the Lynx. And it will be the same rating as the fuse in the Lynx that goes to the two battery banks (250A). So that makes sense to me that if a lightning strike were to blow one of the Lynx battery paths, it would blow them both and the fuses to both MPPTs and it would not be an issue. I'm not sure if it would be possible to blow one 250A fuse in a Lynx and yet not blow the other 250A fuses in there.


But there are also C/Bs that could isolate one of the battery circuits and not the other I think. If one set of batteries provided too much current and it tripped the breaker. Hopefully again in that case the battery fault would be communicate to the Victron MPPTs so it would limit 400A to 200A.

The issue in my setup wouldn't be overcharging as the 4 remaining batteries could actually take the 400A of charging. The issue in my setup is the Pylontech cables (which wouldn't be an issue if I had wired very single battery directly to the battery bus with longer cables). Because I only ran 4 cables to the bus instead of all 8 (for four batteries), were I to try to charge them with 400A I would be putting 200A into cables that are only rated for 100A. That's what I'm trying to avoid and am wondering if I can do that in the software with Victron somehow. I would think the Victron software would monitor how many batteries are powered on (assuming the BMS provides that info) so I'd like to program it to limit charge to 200A if only four batteries are on to ensure I don't overheat wires.

I do have a Cerbo GX in the system too. I just don't know anything about the Victron software and settings yet though (along with many other things about this process).

Thanks for telling me about DVCC, I'm going to look into that.


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Alexandra avatar image Alexandra ♦ alaskannoob commented ·

You will need some kind of GX in the system. And yes the software in the GX will connect to the Pylontec batteries and know how many there are (if connected correctly.) And it will control the charging from there if the system is set up as described in the linked page.

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