question

Is there a reason you don’t want to build a 48V system which would be more efficient.

1. Yes

2. What are your batteries specs how do you plan to manage it? For your larger load that is over 100A, can they deliver that? Also consider the cost of wiring rated for those loads vs half that with 48V.

3. Get a pro to help you who can crunch all the numbers accurately for you. This isn't really what this community is for.

4. You can't compensate for bad weather/low light conditions by over-speccing panels, you would need a football field and a huge budget. But more is more, you need to do a cost-benefit analysis to work out if the returns are worthwhile, based on question 3. 252AH is not a lot for the loads you are talking about, especially not at 24V

5. If you plan to grow, go 48V rather. You can scale charge controllers. Most Multis and quattros can be paralleled, just plan for it upfront. Rather use an external cerbo than an integrated GX if you plan to expand. For 2500W a 5kVA MP2 (4kW) or similar would suffice.

thanks for your response Nick. I will try to get an expert to help with build, and the calculations to ensure that it works, and more importantly that it's safe, I know the internet can sometimes set people off on the wrong track.

0, 24 volts, mainly because it seems to be common amongst other power wall builders, no reason other than that, I'll probably be using twisted solid copper core for the bus bars, so it'll be dirt cheap anyway, connecting the cells will be with fuse wire. Tell me, would there be a difference in wiring from the solar controller towards the panels ? that's the biggest run obviously

1, well, at least I got something right ? lol

2, Sony VTC4 and 5, although used, they're testing ok, and are high discharge 18650's. again, my maths fail me, but of the total load, I think it's supplied on a module level, split by those 144 separate cells (the rest of the modules just increasing the voltage of the system ?) can you help me with maths to work it to amps per cell ?

3, I will get help, but for now, I'm well ahead of myself, and learning I can do is part of the process, part of the enjoyment of this project, which is really a hobby rather than being financially economical. It certainly isn't time economic, it'll take a long time just to earn back what I've spent in plasters whilst shelling battery packs for the old cells :(

4, Agreed, I know I have 6.5kWh, remains to be seen if I can fill the battery bank with energy in a reasonable period, I fear the cost of panels to do so may be a shock to me,

5, I can go 48v, I'm not at that stage yet, can you decipher the following for me :-

Multi

Quattro

Cerbo

GX

MP2

thanks so much, you're a great help :)

Paul, I am going to suggest some light reading/viewing for you which will get you up to speed.

First signup here and hit the tutorials

https://professional.victronenergy.com/online-training/

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

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/index-en.html

The battery and battery management can make or break a system, if the googled specs are right, you should be ok but these types of packs are outside my comfort zone and hopefully someone help can steer you right. Used cells can be a bit hit and miss, so good luck :)

How are you planning to manage the packs, to prevent imbalances and for safety? In the absence of sense data, you need to consider a shunt.

Multi/MP2/Multiplus 2 is the victron inverter/charger with 1 AC input, the Quattro has 2, specs all online on the site.

Cerbo/GX is the brains that brings the parts together, provides the connectivity and coordinates all the disparate devices - providing remote access and access to VRM cloud portal. So a necessity.

thank you, looking at those links now

Paul

I had a quick look at BMS, I've obviously a lot to learn ! It came as a shock, the prices of these BMS for the 'storage size' battery packs, Batrium jumps out, but the cost is 2.5 time that of my cells ! prohibitively expensive ! I'll dive onto a more specific forum to see if people have any suggestions on cost economic ways to solve the BMS, failing that, it's small battery projects from now on