Going from 24V to 48V, some questions

[Tunnerus]

I have a 24V LiFePo4 battery bank with three parallel batteries, one Winston 100 Ah, one no-name Aliexpress “135 Ah”, and one Eve 280 Ah. Am thinking of swapping my MPP Solar PIP GK 3024 to something 48V-based to allow bigger storage and more output than the current 3kW.

What options seem the smartest to upgrade this battery bank to 48V? I am pondering putting the 100 Ah and 135 Ah in series, and buying another Eve 280 Ah to expand the current one. If I understand things correctly, I may not need to change the BMSs. The 100&135 Ah may lose a little capacity as the 100 Ah cells are likely to be the constraining factor.

Is this possible, or should I try to sell the 100 & 135 and acquire new for the 48V system?

Any help highly appreciated, including pointers to previous posts here on the forum, as I cannot seem to get the search to function.

 

[12VoltInstalls]

should I try to sell the 100 & 135 and acquire new for the 48V system

That would be what I would do.

FWIW here’s partly why I have an aversion to 24V equipment: if you don’t need/want 12VDC - lighting, chargers, etc. - but need higher 120VAC capacity there’s a bit of a limit to 24V batteries being as “easy” as 48V to begin with, imho.

You ‘can’ mix and match parallel batteries (though not preferred or ideal aka “correct”) with LiFePo4, but then if you want to expand or upgrade and higher voltage is the practical solution, unequal series-grouped are disadvantageous at best. As you’ve stated.

But at $900-$1300 there’s a gazillion inexpensive ready made 48VDC commodity battery options, and lots of 48V equipment available from mid shelf to top tier.

Plus you probably want the headroom for 6000W (just guessing) and just plunking another 24V battery in is less cost up front but without some of the interactive capabilities of an assembled battery.

So either buy one ready-made or! buy another group of cells and build a 48V with a reconfigure your existing Eve 280 and carry on, selling the 100- and 135Ah to offset a bit. Alternatively, selling your whole existing system (less the Eve) might net you more cash.

 

[Tunnerus]

Plus you probably want the headroom for 6000W (just guessing) and just plunking another 24V battery in is less cost up front but without some of the interactive capabilities of an assembled battery.

Thanks for the advice! Correct, I am looking to go for 6kW or higher, and I understand that 48V will remain a suitable voltage for a long time.

 

[12VoltInstalls]

understand that 48V will remain a suitable voltage for a long time.

What you need to pay attention to is watt-hours and discharge capacity.

48V by itself doesn’t guarantee “suitable voltage“ - voltage is just the electrical “pressure.”

 

[Steve_S]

I would suggest a different approach to this conundrum. I have run LFP banks with different H packs.. Most "radical" was, 1x100AH, 2x175AH, 2x280AH in parallel. It works fine but there are a few quirks as you can imagine. In fact, after a couple of years I decided to cleanup & harmonize it out with 6x 280AH in all new cases with new JKBMS (Inverter edition).

My suggestion to get new cells that match what you have. The Wnstons are a bit "unique" compared to the others, so I would source 8 more of those to make a proper 16S. The EVE-280' are easy to get and likely whatever brand of 135AH cells you have are also still available (or very close ones) IF you provide the Brand/Model/Version of those cells, some of us may know where to get them...

Nor applying KISS for the longterm, I would very strongly suggest that each pack uses an identical SmartBMS which can be managed & controlled by 1 APP or better yet with a PC Application. Also depending on what AIO you choose to go with, the new Inverter Capable BMS' can directly interact with the AIO.

Now if adding 8 New Cells to 8 existing cells, I strongly suggest that the "lot" be Top Charged & Balanced in parallel and allowed to fully saturate till only 2-5A is taken by the cells prior to setting up the new 16S packs.

LFP Cell prices have been dropping radically and that will continue for a few more months till likely just the end of July. But also be aware that Politicos in EU & North America are starting to get stupid & want to start adding all sorts of duties, levies & fees along with supporting it with irrational fear-mongering. Because I see you are in Finland I am PINGING @upnorthandpersonal as he is "local" to you and has darn good knowledge about the ongoing situations and a heck of a lot more... He's a Treasure Trove of Goodness.

Good Luck, Hope it helps.

 

[upnorthandpersonal]

or should I try to sell the 100 & 135 and acquire new for the 48V system?

Definitely what I would do. You can get 280Ah cells from NKON in The Netherlands for under 80 Euro. This saves the hassle we have right now getting stuff from China (and I say this as someone buying cells from China regularly). It also means you don't have the capacity mismatch and other potential issues. You could still use your existing batteries as well - just make a mobile cart or something for garden work or whatever if you can't get them sold.

Tervetuloa foorumille!

 

[12VoltInstalls]

would source 8 more of those to make a proper 16S. The EVE-280' are easy to get

looking to go for 6kW or higher

Steve - related situ here but unrelated. Same effective concerns.

Is that not going to be enough nominal discharge Amps capacity if maxed?

I’m reading this thread and the context is similar to a system I’m trying to design for my sister and b-i-l with an LV6548, but budget wise they want to limit themselves to one 5kWh/100Ah battery which is bms limited to 120A discharge (calculated 5760W discharge available at 48V nominal) and the supplier suggested that an LV6548 if amp-starved (watt starved?!) would let the factory smoke out (not switch to ‘grid’ and protect itself) if the 6548 was presented with a > ~5100W load (guessing at 90% conversion efficiency).

So would @Tunnerus find himself in that same scenario if the inverter got loaded heavy? Or maybe the bms with the Eve cells is higher amps (200A discharge)?

This was new info to me and since it’s wandering around my head and is relevant here I thought I’d mention it.

 

[Steve_S]

Steve - related situ here but unrelated. Same effective concerns.

Is that not going to be enough nominal discharge Amps capacity if maxed?

I’m reading this thread and the context is similar to a system I’m trying to design for my sister and b-i-l with an LV6548, but budget wise they want to limit themselves to one 5kWh/100Ah battery which is bms limited to 120A discharge (calculated 5760W discharge available at 48V nominal) and the supplier suggested that an LV6548 if amp-starved (watt starved?!) would let the factory smoke out (not switch to ‘grid’ and protect itself) if the 6548 was presented with a > ~5100W load (guessing at 90% conversion efficiency).

So would @Tunnerus find himself in that same scenario if the inverter got loaded heavy? Or maybe the bms with the Eve cells is higher amps (200A discharge)?

This was new info to me and since it’s wandering around my head and is relevant here I thought I’d mention it.

I cannot speak to any EG4 product. I do not & will not use an AIO type system.
Batteries in Parallel share/divide loads. As I setup my refreshed bank of 6x280AH packs each with 200A BMS, that can deliver 1200A combined without going over BMS rating. I've previously pushed things to extreme limits through the Thrash Testing I did a couple of years ago.

The part with having only 1 Pack capable of 100A / 120A at a push, is the limiter as to what any "inverter" will be able to deliver. 48V X 100A - 4800W. NOTE that I base that at 48V (3.0Vpc not 3.2 Nominal).

This likely doesn't answer your Q. Sorry