Is this layout proper?

[Nevadablue]

I’ve read and searched and still don’t understand everything about what I want to do.

I have six 100 amp 12 volt lithium batteries. I need 24 volts for my system. I found this layout, the website is in the pic…



That appears to be exactly what I need, except I have 6 batteries instead of 4.

This is what I propose to do. Is it OK?



The green line (wire) would have a connector in it. I have a 12 volt lithium battery charger that will be my backup charger. The new inverter doesn’t have a charger. By uncoupling the connector in the green wire, I can charge each 12 volt string independently if needed.

 

[acdoctor]

Looks correct except I can’t identify the red mark on the top right battery near the neg terminal.
That configuration would be called 3p2s. 3 parallel first then 2 series.
I would advise against 12 volt charging. You would need to charge both half to full capacity before reconnect.

 

[robby]

I am not a DIY battery pack builder but I see some issues with this. Do these batteries have a built in BMS and how much current can each BMS handle. Better yet just link the Specification sheet for these batteries. This is 24V at 300 Amps, I would be really worried about charging this even as two separate sections and then there needs to be fuses.
Somone like @Steve_S might be able to advise you better.
BTW when you say Lithium you do mean LifePO4 right?

 

[Nevadablue]

Thank you @acdoctor . I don’t know what that red mark is either. LOL I must have marked while making the “wires”.

Yes on the charging both ‘halves’. I intend to keep this battery bank charged with the solar panels, but needed a way to charge, just in case.

 

[Nevadablue]

I am not a DIY battery pack builder but I see some issues with this. Do these batteries have a built in BMS and how much current can each BMS handle. Better yet just link the Specification sheet for these batteries. This is 24V at 300 Amps, I would be really worried about charging this even as two separate sections and then there needs to be fuses.
Somone like @Steve_S might be able to advise you better.

They are Chins 100 amp 12 volt batteries with BMS. They told me it was OK to connect up to 6 in parallel. I had originally intended a 12 volt system, but changed after recommendations I got here.



This system is designed and intended to provide power to a pellet stove (heat) and evaporative cooler (cooling) and will probably never see even a 1000 watt discharge rate through the inverter. (It is a 3000 watt inverter) I may also connect a high efficiency refrigerator, but even the fridge and one of the other units running together would not pull over 1000 watts worst case (fridge Defrost and pellet stove startup).

 

[robby]

It seems like it would work but you have to first make sure all the batteries are fully charged and resting at roughly the same voltage before connecting them up. I would also wait for someone like Steve or @sunshine_eggo to give you some advice on the best way to charge the bank and also tell you if multiple fuses should be put in.

 

[Steve_S]

Will's Tests / Teardowns on CHINS Batteries.

https://www.youtube.com/c/WillProwse/search?query=Chins

The best way to connect these is:
Refer to the Victron Guide, section 3.3 3.3 Parallel battery bank wiring Page 18 onwards to page 21.

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

Suggested Charge Profile for 24V which keeps the batteries within the "Working Voltage Range (3.000-3.400Vpc)" and not pushing into the "Allowable Voltage Range (2.500-3.650Vpc)".
LFP is designed to work between 3.000-3.400, the Allowable range is the Voltage Range in which the batteries will not suffer harm.






Absorb: 27.6 for 45 minutes (3.45vpc) (some call this boost)
Equalize: OFF
Float 27.5V (3.437vpc)
MIn Volts: 21.2 (2.650vpc)
Max Volts: 28.6 (3.575vpc)
Rebulk Voltage: 25.6 (3.200vpc)
End Amps: 5.0A (*1) ( ! Allows for full Saturation at set Float Voltage)
(*1): End Amps is calculated from the LOWEST AH Battery Pack in a Bank. IE: (100AH X 0.05 = 5A
NB, not all charging systems have settings for EndAmps/Tailcurrent.

 

[Nevadablue]

Thanks for that! Now to digest it.

 

[TomC4306]

Float 27.5V (3.437vpc)

I prefer 54v (3.375)

Everything else totally agree.

 

[robby]

Float is best at 3.40 to 3.43V think 3.375 is being a bit to conservative.

 

[TomC4306]

That is where both packs rest disconnected. 3.375 - 3.38.
I actually only see float on those two days per month that are perfectly clear.

Edit. Remember, float only comes after a full charge and absorption.

I can't tell you how many times I thought we were going to hit float but didn't make it through absorption before the sun set.

 

[Nevadablue]

Ok, digestion complete. I still need help though. My visualizer isn’t what it used to be.

Does this look correct now?
(All cables to busbars and between batteries will be the same length)

 

[TomC4306]

I like it

 

[Nevadablue]

Thanks! I ended up moving the busbars to a board between the batteries so I could keep all the connections to the 18” cables I have.

 

[Steve_S]

Thanks! I ended up moving the buss bars to a board between the batteries so I could keep all the connections to the 18” cables I have.

That is far more appropriate, do not forget the fuses !
FYI, the busbars you are using are NOT 200A Capable regardless of the marketing shpeel, they'll warm by 125A and by 150 be toasty. We just went though that merry-go-round in a thread a couple of weeks ago. I "HAD" some of those earlier on and quickly learned, also you can end up spinning the terminals in the cheap craplastic. (especially after they've warmed up a few times.)
Check out David Poz' vid on them and ponder it.

RE FLOAT: Most days (sunny of course) I am in float by noon at which point the Active Balancing by the JKBMS's are busy levelling up the cells that only take another hour or so. IF you float & saturate 3.425-3.450 and charge ends, you'll see the cells quickly settle to around 3.400 - 3.405. NB I am quite North of most of you, near Algonquin Park Ontario Canada. Now in Mid October the daylight is shortening and I do not get to float everyday unless clear & sunny then by 15:00 hrs or so but by Mid November I won't be seeing float with my current Panel setup, which will be getting an upgrade next spring after the thaws... My Battery Bank has grown to the point that more & Panel & another SCC are required. 1190AH/30.4kWh).

BTW: As I use JKBMS' I start the active balancing @ 3.370 because it just happens to be the point were the cells start to diverge, to that point they are all basically within the 0.010

See this link, start at the top for more info but a Picture is worth a 1000 words eh.

Steve_S-Tech: My Final Config for Midnite Classic SCC & JKBMS' w/ Large Bank (works amazingly well) Includes Charge Profile & BMS Config

INTRO: I have debated posting this for a while until I got everything tweaked in and working as best as possible. The End Result is Gobsmackingly Good ! I cannot speak for other SCC and such as each is different & unique in their own ways BUT this may likely be a Good Reference. Civility &...

diysolarforum.com

 

[Nevadablue]

Well, that’s a shame. 40 bucks down the drain. Fooey
Anyway, I will look for better busbars and consider this layout. I think it will be the one. My cables fit better this way.

 

[Steve_S]

I actually have sets of those Pike Industries Busbars and damn they are quite the thing. There are other ones from Blue Sea & Victron etc there was some discussion in a few threads just recently. May be worth poking about.