You're right, i don't have any experience. The cells are grade A and they are well matched, but i guess you can't be 100% sure about that when they come from China.
So just to be clear,
"(2) verifiable quality well-matched grade A cells" refers to something quite different than the grey market 280Ah cells, I believe you have. All indications are that they are decent quality cells, but we can't know the cell grade (every reseller I've communicated with claims new, matched, A grade), and can't know the reason they are being sold at such a steep discount relative to
verified grade A cells
sold through official channels. And they will probably not be matched and binned to the same standard either (though again, can't say for sure).
This is not to say that its not possible that they are grade A or A- (more likely) or that they won't perform to expectation (they probably will). But I think its important to be realistic about expectations and unknownables, and be realistic about price (at least two resellers who sell A and B grade cells have said they could not sell a true A grade cell at this price point). If you are realistic and cautious about expectations, its much more likely your expectations will be met or exceeded
This was a long winded way of warning that an unofficial/grey market reseller claiming cells are A grade and well matched, is very different from cells actually being A grade and well matched (hence the huge cost savings we get).
By conservative limits you mean depth of discharge? I intend on having a 80% DoD (10%-90%), or even less, like 70%.
Yes conservative voltage limits / depth of discharge. Basically stay safely in the flat part of the curve. I would probably go more conservative than 10-90 without a BMS 20-80, maybe even more conservative to start, but then I wouldn't go without a BMS, and have no experience on that front, so I might not be the best to listen to on this. The point being, the margin you leave needs to be a large enough safety cushion that any imbalance between cells is covered by that cushion and no cell strays into dangerous/harmful territory. In reality the best way to go about this would be through testing your specific pack and seeing how the individual cells charge/discharge and how well matched they are, and basing your limits on the observed characteristics. This is outside my experience, outside my comfort zone, and beyond my limited scope of knowledge, so I'll leave it at that.
My idea was to use the Victron BMV to monitor the voltage and trigger a relay or a battery protect wich will disconect all loads when it reaches 10% or 20% SoC. Sorry i wasn't clear about that.
That's a good idea. I'm not sure it fills the same role as a BMS, but it seems like a sensible way to limit bandwidth / depth of discharge. Particularly since your system has a lot of Victron components.
That's true, the EasySolar 24/3000 it's more than i need in some areas. The MPPT is twice more powerfull than i need, and i also don't need the power assist feature. The inverter runs at 2400W continuous, and i only need 2000W at most. But i'll be traveling in Africa in high temperatures, and the inverter output power will drop to 2200W at 40C.
Internet conectivity for VRM is nice to have, and the fact that i can monitor and control the sistem at a distance was also behind my initial idea on not adding a BMS.
Does the easysolar have a GX device built in?
Plus 5 years warranty is good peace of mind. I don't like the 1-2 years warranty on most other brands. It's expensive but it will last longer, hopefully
)
I think all Victron components besides batteries carry a 5 year warranty now.
Buying the individual, appropriately sized components from Victron, would've cost me even more than the Easysolar.
Out of curiosity what does an easysolar 24/3000 cost? I'm from the US, we don't get the easysolar here..
Considering all your advice, i will be adding a BMS
I think this is the prudent and sensible path to take.
and i'm leaning towards Overkill Solar, but is the 100A limit enough?
One of the better quality commodity BMS' I think. The other commodity BMS worth considering is the Daly BMS. I would also take a look at the SBMS0, its more of a niche product but its top quality and works very well with most Victron components. Best of all its not current limited at all (since current doesn't flow through it). There is a steeper learning curve though and more to consider.
I don't think i'll actually draw more that 100A even with all my DC loads on and the inverter running a 2000W load at the same time, but is pushing the BMS limit. Would that be ok?
Another option i was thinking about is to wire the Easysolar independent of the BMS since it will never run without me in the van. It will only be on when i'm cooking, and i can monitor it myself, plus it can turn itself off at a 20% SoC. That leaves the BMS with an easy job of taking care of the DC loads and balance the cells.
Not a good idea in my opinion. What you may be able to do however is have the BMS trigger the remote on/off port on the Victron inverter/charger/scc. However I'm not sure how workable that would be with an all-in-one.
is it ok running the BMS close to it's limits, but not for long, realistically it will only run close to the max for 1 hour a day?
Thank you again for your answers and advice, very helpful.
Probably not advisable, especially not in high heat. I don't have personal experience here, most people like to leave oversize by anywhere from 20-100%. I believe
@OverkillSolar may have stated that he has tested the BMS at its continuous rating with no ill effect (or maybe I'm misremembering), in either case, running at or near 100% often will at the very least create heat and shorten the lifespan of the BMS.
Because you will have very good first layer protection (via all your victron components) I would consider just getting a ~200-250A Daly BMS that will just sit in the background doing not much of anything beyond monitoring and balancing until there is a problem.
