16 cells or 32 cells best for a 24v System?

[Johannlog]

Okay, thanks for all the advice and sharing your knowledge....
I've been doing more research and reading as suggested; I think I better understand the components now.


Here is my plan, let me know if you think it will work or if I should make changes.... I'm more concerned about making a solid system than saving a few $.


Here's what I'm planning to make.
2x 40Amp Renogy SCCs (already have these)


I'll connect these to a DCC-300HB Chargery.


I'll connect my 4,000w 24V Giandel (6,000w surge) Inverter to the DCC as well. The inverter will power my 100A house panel.


The DCC will be connected to the Chargery BMS8T-300 which will be connected to16x 280AH (Amy's EVE) Matched cells, (with 300A fuses). (2P8S configuration of the cells)
My understanding is that I can connect 16 cells to this BMS


My understanding is that using 2x 40A SCCs I should not exceed 100A charging input.

My understanding is that using 2x 40A SCCs I should not exceed 100A charging input.
But I might be wrong on this.
Planning to use 8x 315W panels (4 panels per 40v SCC). 8x315w = 2520w ÷24v = 105A
I think I'm calculating this right.

 

[Steve_S]

You can do 2p8s with Matched cells ut connections and the BMS leads must be "perfect".
Each battery pack goes to DCC then to Common DC Busbar (if multiple packs.) which can take the SCC's & Inverter/Charger.
NB: Scc's & Inverter/Charger must be fused or have breakers as appropriate. SCC's 40A output breaker/fuse, Inverter/Charger 300A Fuse/Breaker.
2x 40A SCC's will not overrun the battery charging. You must adhere to the requirements for each SCC. The configurations much all match as well, I don't know if those can have a Parallel link (I doubt it).

The system MUST be Voltage Calibrated & Corrected ! Every piece of equipment MUST have an accurate read on Battery Voltage, even 1/2V can result in issues (Big ones no less). LFP like all Lithium is very sensitive, we are dealing with Millivolts after all. Line loss through the wires & lugs adds up quite quickly and will affect the accuracy of the voltage & IR readings the BMS uses. See link in my Signature on Calibration.

BTW: The Chargery DCC can be installed on the Negative Side but it can also work on the Positive Side (more efficient) BUT you MUST have the ISO Board that goes between the BMS & the DCC. It is also Much Better to take the power from the Battery Pack terminals and power the BMS via the Ext. Power plug, this has less "flutter" and is more stable as opposed to powering the BMS via the sense leads. Do ensure you get the ISO Board & the External Power adapter.

Good Luck

 

[Simi 60]

the capacity of the batteries and the capacity of the BMS are two totally different measurements. a 100 Amp BMS means that it can handle 100 Amps of current through it. the 280 A/H you are referring to is the capacity of the batteries. different animals. so yes you can use a 100 amp BMS on your 280 A/H batteries that is assuming that your inverter is never goiing to draw more than 100 amps.... what by chance is the maximum draw for your inverter??? thats what will determine the size of a BMS you need. Same goes for your charging source.. if solar, does your system put out more than 100 amps? if so you you need to go into your SCC and set a maximum charge current of less than 100 amps.

Now by paralleling 2 or 4 battery packs each would have its own BMS and as such they could shut off at different times Example given, you have four (4) 24VDC 280 A/H packs, each is giving lets say 50 amps to the inverter... (total load of 200 amps) one BMS shuts down for whatever reason....lets say undercharge protection for GP. when it does the other battery packs now have to put out additional amps to keep the inverters output the same so now instead of each pack giving 50 amps you have 3 packs giving 66.6 amps one more shuts down and now you have two packs each giving 100 amps to continue the load. you simply need t follow the math and the train of thought when you do this. just make sure that if you are pulling a large load that the shut down of one or two battery packs will not cause any issues. most 4Kw inverters can pull a maximum of abut 250 amps at full blast. so in other words in order to run that inverter at its full capacity you would need 3 battery packs that have 100 amp BMS's obviously 4 would be better. if you are not running the inverter at its max capacity then obviously less is OK. just a thought to think about.

*Max draw is what is listed for a magnum 4024 which is a 24 volt 4KW inverter... YMMV

Thanks for that info
Seems I should be very much in the ballpark with my victron multiplus
Or have I read it wrong?

Victron MultiPlus 230-volt AC, 24-volt 5000-VA inverter charger with 120-amp battery charging and 100-amp AC transfer capability compatible with all batteries including Lithium. https://www.outbackmarine.com.au/multiplus-24-5000-120-100-inverter-charger-victron

I'll be doing 3 X 8s 24v packs with a JBD 200amp BMS and a MRBF on each

 

[Daddy Tanuki]

Thanks for that info
Seems I should be very much in the ballpark with my victron multiplus
Or have I read it wrong?


I'll be doing 3 X 8s 24v packs with a JBD 200amp BMS and a MRBF on each

Not overly familiar with them but yes if running multiple BMS's to share the load. Most folks advise that you derate the BMS by at least 25% if it is a mosfet based system vice a contactor type. its just the nature of the beast with an all electronic BMS.

 

[lekeola]

I'm planning to order either 16 or 32 Eve cells (280AH) from @Amy Wan (Luyuan) to build a 24v system to be charged with Solar.
Would it be okay to go with the 32 cells, or is that too many parallels/series connections?
I heard @Will Prowse say something about a recommended max number of parallel connections.
I'm thinking I would use the 24v 8s BMS from Over kill, I would need 4 of them I think? (Unless there are better options)

What a coincidence, am paying for 32cells from @Amy wan today too,

 

[lekeola]

I'm planning to order either 16 or 32 Eve cells (280AH) from @Amy Wan (Luyuan) to build a 24v system to be charged with Solar.
Would it be okay to go with the 32 cells, or is that too many parallels/series connections?
I heard @Will Prowse say something about a recommended max number of parallel connections.
I'm thinking I would use the 24v 8s BMS from Over kill, I would need 4 of them I think? (Unless there are better options)

I want to buy from Amy too, I'm paying today, do you mind sharing your experience about the EVE cells u bought