Run CATL EVE cells to charge Ecoflow.. then charge EVE separately?

[beowulf]

Hi all,

Basically trying to do like some others have posted on various forums. Most of my day to day energy use is on my computer system at home.. WFH. I'd like to get one of the new EcoFlow Delta 2 units for $800 as it has the inverter in it, and I'd like to have one for portable use on drives. Given the long life of these batteries, during the day my energy use is .45c per KWh thanks to PGE passing on their fire/death bills on to us customers. Used to be half of this a couple years ago. Anyway, I thought.. can I run my PC (about 700 watts when gaming or 300 or so watts when surfing web, working, etc) and monitor with a handful of devices (usb audio, etc) on one of these 1000wh batteries for most of the day during peak times?

If my math works out, my monitor is about 100watts max, and most of the time computer is 600 or so. Assuming 750watts or so, I Assume this battery would last just about one hour.. give or take a little? Is that correct?

So I been looking at some DIY battery options, like the EG4, etc.. but the CATL EVE 3.2v cells are pretty affordable, about 1/2 that of other options, and from what I've read though they are from China, their Grade A Prismatic cells are top of the line. So 4 of them at 300ah work out to about $700 give or take when you get them. I've read that a 48v system is more efficient and better than running them at 12v as well. So I was thinking if I put them in parallel to have a 300ah 48v battery pack, that can charge the Ecoflow Delta 2.. it might give me a few hours of use total on my pc/monitor setup. Is this possible.. does it make any sense at all so that I can charge battery during offpeak hours and possibly with a long cable and solar panel in the back yard (about 20 feet away)? Or is it ridiculous/stupid to consider this.

The plan is to add more CATL even batteries to make it a bigger pack altogether. I assume I'll need a BMS for charging the EVE as well, and possibly some inverter or what not to convert solar panel and AC power to charge them?

Or is there a better way to go?

TL;DR want to run my PC/monitor that I work on 10 to 12 hours a day (for all purposes not just work) on battery power to reduce the cost I spend at day time energy costs.. aware that it will likely take a couple of years before "break even" with the cost of batteries/etc, but also want the ecoflow for portable use and power outage use situations.

Thanks.

 

[Brucey]

The biggest issue will be that the Delta 2 has a single mppt port with 500W max input. If your base load is 750W, the outboard 48V battery won't be able to keep up with the load and so your delta 2 battery level will drop down to empty (slower than if there wasn't an external battery but dropping regardless). With a 250W charging deficit you'd likely get three hours or so of runtime with 750W base load? Versus one hour without the external battery.

 

[Brucey]

Workaround if your budget permits is get a delta 2 max instead of Delta 2, as that has two 500W mppt inputs. Run two xt60i connectors to your 48V battery bank and then you can charge at 1000W, faster than your base load is draining.

 

[beowulf]

Hey..thanks for reply. So I ended up getting the River 2 Pro, 768wh battery. It can do 220watts input on solar, but I could pick up an MPTT external unit that can handle a lot more solar input.. in fact what I decided to do was buy one of Jehu's battery setups from Jag35. Its a 16 cell 74ah 48v battery pack, about 3.7Kwh of storage give or take. I am now trying to figure out what to use to charge THAT battery, and also how to then connect that one to my Ecoflow River 2 Pro.
After some testing (using the River 2 Pro that shows me how much energy its giving to the pc/monitor/etc), I am fluctuating between 220 to 280watts throughout the day when not gaming. I tested how long I could go on the battery and got right about 2.5 hours though I did set it up to not go below 20% so I can get about 2 hours of use before I have to charge it up. With the 3.7Kw battery (once I figure out the rest of what I need to use it as I hope to use it) charging the ecoflow during day use, I think I should be able to get 12 to 16 hours of use without solar charging the big battery.

What I am trying to figure out is if the EG4 3Kw inverter (about $750) can be used to provide solar when available, but if not, use AC from the wall to charge up the 3.7Kwh battery system. But I'd like it if there were a way to ALSO ensure charging occurs once the 3.7Kwh battery cells get down to 20% as well. I am not sure how accurate the whole "keep LFP batteries between 20% and 80% for longest life" is, but that is my goal. Charge battery off of AC (ideally during off peak hours if it can last that long) when battery drops to 20% during peak hours or at any point during off peak hours if its below 80%. If I can add solar at some point (can't right now.. have to figure out running the solar cables through a wall, or window screen, etc).. then during the day, charging the battery with solar unless it drops below 20%.. in which case, kick over to AC (or if it can do both great).

I am not sure if gear exists to handle that "logic" or not. I was also looking at Victron. As I want to add more battery to this system eventually, and even more so eventually add this to whatever house I end up living at (but in case I rent instead of own.. ability to easily add it and take it off without needing permits/construction/etc to attach it) have it powering the whole house. At that point I would have a much larger battery system and solar option hopefully. Hence, I am ok with spending $1K or so on a charge controller with MPTT inputs to handle several 400watt panels (e.g. the EG4 has 5000 watts if PV input max). If that's what it takes.

Anyway.. not sure what else I need yet, still learning how all this gets wired up.

 

[Brucey]

So the problem is going to be that the river 2 pros mppt input is:



And here's the range of voltages for a 48V nominal battery:

 

[Brucey]

I'm guessing you got the r2 pro during Amazon sale? They did drop the Delta 2 down to $679 as well, and the Delta 2s 11-60V mppt voltage range is perfect for your 48V nominal battery. Perhaps return the r2p if within return period.

 

[beowulf]

I got the river 2 pro + 220 solar for $850.. still about that price now. Figured it was not bad for what it gave.. especially being LFP.

So are you saying I can't charge my River 2 Pro from the 48v battery? I mean I could add a pure sinewave to the 48v and plug in the AC of the river 2 pro.. but I was hoping to avoid that extra conversion and loss of energy. Someone had shown me a downverter or whatever its called.. e.g. around 40 to 70v down to 35 or something like that.. forget now, but bumps the potentially full 48v (which may put out 50v or more) down to under 48v so it wont overload the river 2 pro.

Too late to return it all though.

 

[Brucey]

I got the river 2 pro + 220 solar for $850.. still about that price now. Figured it was not bad for what it gave.. especially being LFP.

So are you saying I can't charge my River 2 Pro from the 48v battery? I mean I could add a pure sinewave to the 48v and plug in the AC of the river 2 pro.. but I was hoping to avoid that extra conversion and loss of energy. Someone had shown me a downverter or whatever its called.. e.g. around 40 to 70v down to 35 or something like that.. forget now, but bumps the potentially full 48v (which may put out 50v or more) down to under 48v so it wont overload the river 2 pro.

Too late to return it all though.

I'm not sure what the actual mppt limit is for the r2p, says 50V max but maybe there's a bit of leeway. My understanding is there's a software limit which it will hit first. However there's always a risk that you'll let the magic smoke out if you give it too many volts, personally I wouldn't risk it.

Stepdown transformer would do the job not sure on efficiency losses but prob less than a DC->AC->DC conversion.

 

[beowulf]

Yah.. I will probably pick up the Victron 48v to 24v 12amp 280watt stepdown device. I am not entirely sure how to wire it up. The one thing I don't quite know is if the big red/black cables on my DIY batter are for output or input. I assume output, which I would assume then goes to this 48v/24v controller. My concern there though is from the video Jehu put up, it looks like he's got some pretty thick 0/1 gauge red/black wire, and the input on the victron is much smaller wire. So Not sure if the bigger wire in his video is JUST to be able to pull up to that 600a those batteries can put out, but you can use smaller cables and pull less.. or what.

But assuming those are output wires, not sure then where I connect whatever wires to charge the thing. There is a BMS, new to BMS so I am assuming there is inputs on the BMS where I would plug solar into or AC (hopefully both), which then attaches to the battery terminals, and then might also have batter outputs? I dont know. Still a lot to learn.