Steps before powering off BMS...

[kolek]

I need to power off my BMS to install a LCD screen.
I'd like to avoid having to precharge my inverter again.
What's the best series of steps to power off the BMS?

I'm thinking:
1. Remove load from inverter
2. Do this at night, when PV input is virtually zero

Next steps I'm not sure.
3. Turn off charging and discharging in the BMS?
4. Switch off BMS?

Problem is the above steps will probably cause the inverter to discharge its capacitors and then shut down because it will have no source of power.
(Inverter is not yet connected to the grid)
Any other ideas for how to do this?

 

[upnorthandpersonal]

Temporarily bypass the BMS. Turn off the BMS, install screen, start BMS, remove bypass.

 

[Supervstech]

Turn off the inverter first, put jumper wire between b-&p-
Proceed with operation, reverse.

 

[kolek]

Turn offbthe inverter first, put jumper wire between b-&p-

I have a 200A DC breaker between my batteries and the inverter (separate from T-class fuses), if amperage is 1A or less, can I just throw that breaker instead of powering off the inverter?

Reason being, there's a green button on the Deye which appears to be power but it doesn't actually seem to do anything. Maybe I have to hold it down for it to work, not sure.

Also, if the inverter is off or disconnected, I'm curious why it's necessary to put a jumper between b- & p- before powering off the BMS?

 

[kolek]

I should add, I don't need to, or at least wasn't planning on physically disconnecting the BMS after powering it off. Just insert some plugs into it.

 

[upnorthandpersonal]

You can probably get away with 'hot plugging' the screen into the BMS. Just be careful and make sure the connector is the right way around, and you pick the right port. But a bypass is easy and safer.

 

[kolek]

You can probably get away with 'hot plugging' the screen into the BMS. Just be careful and make sure the connector is the right way around, and you pick the right port. But a bypass is easy and safer.

I think I'm going to try a hot plug. I like living dangerously. Let's see if I can Die Another Day. I mean anyway I have No Time to Die. Live and Let Die, is what I say.

 

[DIYrich]

I have a 200A DC breaker between my batteries and the inverter (separate from T-class fuses), if amperage is 1A or less, can I just throw that breaker instead of powering off the inverter?

The idea is to keep battery power at the battery connection of the inverter. Turning off the breaker doesn’t do that.

 

[SparkyJJO]

If you shut it down for only what 10 seconds to plug in the cable, are the capacitors going to discharge that quickly?

If they do, what's the harm in just precharging again?

 

[kolek]

I finally got the LCD battery monitor running. What a piece of junk.

Cost me $40 + 3 hours of my time.. The wiring comes as a complete sloppy mess, different wires hanging loosely all over the place. Trying to wire in a power button, find a suitable DC adapter and connect it, and then secure all the loose wires, and make it look reasonably nice took me 3 hours. JK-BMS and everything they make is for chumps. SoC says 59% and it should say 30%, and there's no place in the BMS to just calibrate the SoC. Have to force it to go to full state of charge just to calibrate it. Has zero documentation. I messaged them with a support question, of course they ignored my message. Andy of Andy's Garage goes into a lot of this nonsense, but JK-BMS is just weak, I don't care what the fanboys say.

I see @Will Prowse doing reviews of those slick SOK rackmount batteries with professional BMSs that have built-in inverter communications that are bug free and built-in precharging and I am envious.

If you love JK-BMS do me a favor please just refrain from responding and let me have my "opinion" on this. I get that you love JK and you love buying "DIY kits" like this from China with no documentation and soldering little wires together. Doesn't mean I have to.

 

[Supervstech]

I bought one of those...
It functions.
It could have been done FAR better for sure.

 

[upnorthandpersonal]

Doesn't mean I have to.

Maybe DIY isn't your thing, and that's fine. Plenty of products out there.

 

[kolek]

It could have been done FAR better for sure.

If there is one thing I've learned in my life, it's don't buy a "kit" from China.
It will never come with any documentation, and the things they will expect you to do to assemble their "kit" will just boggle your mind.
We once made the mistake of buying a 3d printer kit from China. LOL. Needless to say, it took about 38 hours to assemble, was missing 1/3 of the parts you needed to assemble it, and it didn't work when we were done.

I always imagine the dudes in China shipping this stuff laughing with their buddies about it, like "No way in hell are they gonna get this to work... hahaha"

 

[kolek]

Maybe DIY isn't your thing,

Generally I don't mind certain DIY projects. I've been trying to analyze what it is that I hate about these particular projects, and I think it's just that I hate sloppiness and kludging, and it's so difficult to take sloppy things and make them clean and elegant like this LCD wiring. Does that make sense?

 

[upnorthandpersonal]

I think it's just that I hate sloppiness and kludging, and it's so difficult to take sloppy things and make them clean and elegant

Yeah, possible. Personally I don't have an issue to get things to look clean and elegant as you put it, but I'm also someone who likes functionalism combined with minimalism. I wouldn't want an LCD screen on my batteries for instance. I don't even want to look at the BMS, and generally never do. I have a Grafana dashboard, true, but I rarely use it now - the system runs itself, the Grafana interface was just there to support the development process (automatic power diversion, decision making based on weather/available energy/...) which is the fun part for me.

 

[robbob2112]

If there is one thing I've learned in my life, it's don't buy a "kit" from China.
It will never come with any documentation, and the things they will expect you to do to assemble their "kit" will just boggle your mind.
We once made the mistake of buying a 3d printer kit from China. LOL. Needless to say, it took about 38 hours to assemble, was missing 1/3 of the parts you needed to assemble it, and it didn't work when we were done.

I always imagine the dudes in China shipping this stuff laughing with their buddies about it, like "No way in hell are they gonna get this to work... hahaha"

LOL,

I bought a 3d printer from china and it came with nothing but all the parts. Took me about 3 hours to assemble because I had to spend time filing the bottom of the uprights so they were perfectly flat and at a right angle to the rest. Made ok prints right off, then much better as I tweaked things and printed parts to improve it...



And besides - real men never read instructions - it says that in my instruction manual, or so I am told.

 

[kolek]

I wouldn't want an LCD screen on my batteries for instance.

Right I think I'd be the same way but I still am not 100% sure my inverter is going to charge/discharge my battery according to my settings because my system has only been running for a couple days, so I'm paranoid and checking the voltage every 4-5 hours. I already came close to overdischarging the battery because the inverter settings were wrong so I need to be careful until I verify it's running correctly.

I have a Grafana dashboard, true, but I rarely use it now - the system runs itself, the Grafana interface was just there to support the development process (automatic power diversion, decision making based on weather/available energy/...) which is the fun part for me.

Anything related to IT or systems development I can completely appreciate, I love that stuff too. Awesome that you can do that.

 

[kolek]

Made ok prints right off, then much better as I tweaked things and printed parts to improve it...

Yeah that sounds about right.

China: "Yes, you need to 3d print that part to assemble the 3d printer."
Customer: "But I don't have a 3d printer, that's why I bought this one from you"
<muffled laughter>