Server Rack vs DIY Cells re: ah

[TheHappyNomads]

I came across a potential good deal on some EG4 LL Server rack batteries. They're 48v 100ah.

I've also been very tempted lately to go the DIY route and build a 2x system for the same price using 304ah cells in a 16s setup.

Obviously, the build out, BMS,etc is a determining factor but is the difference in ah or kWh produced the most important determining factor when considering battery systems?

 

[BentleyJ]

kWh per $ vs. your particular storage needs vs. your budget.

 

[TheHappyNomads]

I don't have a budget per se but I'm trying to be as budget friendly as possible. Panels will be (10) 400w in the SF Bay Area so around 8 hours a day of sunlight so what, around ~ 2400w / day production wise???

Am I calculating this correctly?

EG4 LL >>> 4.8 kWh per battery * 4 = 19.2 kWh = $275/kWh (~ $4400 purchase price for all 4 + rack from dif seller for total of $5260)

DIY >>> 14.64 kWh per battery * 2 = 29.28 kWh = $150/kWh (includes two BMS, wiring, bus bars, etc.)

I won't really have a ton of room to increase # of panels due to the size of our home. Our energy usage could really use the larger battery bank but it doesn't seem like my panel production would ever really keep up with/charge the larger bank as we draw power from it.

 

[BentleyJ]

In CA, I would say the minimum battery size to yield the highest benefit would be enough to carry the loads all the way through Peak ToU rates from approx 4 to 9pm. Having extra kWh is a bonus because it gives you extend run time in the event of a long outage. Even if solar doesn't produce 100% of what is consumed at peak times you can always use the charger at off peak to top them up.

Not sure what your PV azimuth and tilt is, we get 12 to 16kWh per typical day from a 3kW array in So. Cal. You should be able to average 20kWh per day with those 10 panels. Plus or minus depending on your roof.

 

[TheHappyNomads]

Yeah, I'm an idiot. That calc was only for one panel. For the entire array I should be producing that 20kWh average even with marine layer for a couple hours in the morning. Good catch. It's not necessarily the TOU window that messes us up. We have a PHEV that eats 16kWh every single day because we use the entire 30 mile range for commuting.

 

[OffGridForGood]

Yeah, I'm an idiot. That calc was only for one panel. For the entire array I should be producing that 20kWh average even with marine layer for a couple hours in the morning. Good catch. It's not necessarily the TOU window that messes us up. We have a PHEV that eats 16kWh every single day because we use the entire 30 mile range for commuting.

Unless your EV is parked while it is sunny out, you need a battery pack larger than the EV charging you want to do each evening.
I have two factory 100Ah server racks, and three DIY 14.3Ah packs. There are pluses for the comms available on the factory servers, and the fact you just slide them in and hook them up, compared with assembly of DIY packs. Costwise the Factory units are double (per kWh) of the cost of DIY in my experience. If budget allows, get a stack (or two) of EG4 100Ah 48v packs, that will be 30kWh of storage, cost will be about 9,000 plus the rack and wiring, a few things like breakers, fuses for servicablilty and safety. I find DIY batteries are a fun project. Aside from budget, it depends on if you are the type that wants to DIY or the type to plug and play I guess.

 

[hwy17]

Are they LL V1 or V2?.

 

[TheHappyNomads]

Are they LL V1 or V2?.

V2 I'm pretty sure

 

[TheHappyNomads]

Unless your EV is parked while it is sunny out, you need a battery pack larger than the EV charging you want to do each evening.
I have two factory 100Ah server racks, and three DIY 14.3Ah packs. There are pluses for the comms available on the factory servers, and the fact you just slide them in and hook them up, compared with assembly of DIY packs. Costwise the Factory units are double (per kWh) of the cost of DIY in my experience. If budget allows, get a stack (or two) of EG4 100Ah 48v packs, that will be 30kWh of storage, cost will be about 9,000 plus the rack and wiring, a few things like breakers, fuses for servicablilty and safety. I find DIY batteries are a fun project. Aside from budget, it depends on if you are the type that wants to DIY or the type to plug and play I guess.

Good point. In general, I gravitate toward DIY whenever I can. Partially because I love DIY'ing all kinds of things. Partially because I can't afford to drop $9k on a dime like that. I don't have a specific budget but I know that's out of my budget ?

 

[OffGridForGood]

Good point. In general, I gravitate toward DIY whenever I can. Partially because I love DIY'ing all kinds of things. Partially because I can't afford to drop $9k on a dime like that. I don't have a specific budget but I know that's out of my budget ?

Yeah, there are always competing things to spend money on it seems.
I like learning a new skill, and the DIY batteries have been fun projects, and allow doing one at a time as funds/time/needs dictate. After the first two factory racks, I have been building one DIY 280Ah pack each spring, and each fall. By March 2024 my ESS will be a total of 84kW without dropping a big chunk of cash at any one point in time. In fact our entire solar experiment has been done this way, one step at a time, small investment at a time, expand-learn-dream-expand again.

 

[TheHappyNomads]

Yeah, there are always competing things to spend money on it seems.
I like learning a new skill, and the DIY batteries have been fun projects, and allow doing one at a time as funds/time/needs dictate. After the first two factory racks, I have been building one DIY 280Ah pack each spring, and each fall. By March 2024 my ESS will be a total of 84kW without dropping a big chunk of cash at any one point in time. In fact our entire solar experiment has been done this way, one step at a time, small investment at a time, expand-learn-dream-expand again.

I feel that! I've been doing a similar thing with picking up gear when I find a great deal. Patiently waiting. Stalking the marketplaces ? then grabbing stuff little by little. Batteries are the last piece outside of cables and stuff.

What BMS have you been using?

 

[OffGridForGood]

What BMS have you been using?

I will admit it, I started with Daly BMS's - I had experience with these from building E-bikes using 18-650 cells - but soon after the first DIY pack for the solar, I was disapointed with the Daly. I followed advice of others on the forum and changed to JK BMS - no issues with the JK's and much better balance control.

 

[StratRider]

I was about to ask a similar question but before I could this website guided me to these posts.
I was going to ask if Three Server Rack batteries @ 48v/100Ah's had an advantage over a DIY at 48v/16s using 304's
Saving almost $2k is sending me the DIY route. I suppose my next cost checking will be an All-In-One vs components.
Good thing I have plenty of time and this website to assist.

 

[OffGridForGood]

I was going to ask if Three Server Rack batteries @ 48v/100Ah's had an advantage over a DIY at 48v/16s using 304's

Do you need to move them ever?
I find a few high Ah packs are simple to keep in balance compared to 'many' lower (100Ah) packs.
A DIY 304Ah pack can easily weigh in at 200 lbs each.
effectively you have one BMS for 300Ah instead of three BMS's - and trying to keep them all in balance.
So... if you don't see any reason for moving them around a lot, I recommend the bigger cells.

 

[StratRider]

Do you need to move them ever?
I find a few high Ah packs are simple to keep in balance compared to 'many' lower (100Ah) packs.
A DIY 304Ah pack can easily weigh in at 200 lbs each.
effectively you have one BMS for 300Ah instead of three BMS's - and trying to keep them all in balance.
So... if you don't see any reason for moving them around a lot, I recommend the bigger cells.

The weight was my main concern as you are correct the batteries alone will be just under 200 lbs. but I believe I have a great spot where they wouldn't need to be moved.
So many combinations could be made though if I do go with components instead of an AIO.
Decisions, decisions this is not as easy as Will makes it look.

 

[goldserve]

I have three server rack batteries and 1 diy 200ah pack using jk bms. You have to be really confident and know what you are doing and if that is the case, diy will yield a much better value. Of course, you can diy your own panels and inverter and you would still get a substantial savings with server rack batteries. I diy my 200a service upgrade too but how far will you go without burning down your house right?

 

[OffGridForGood]

I don't worry about the LiFePO4 "burning down the house" - this chemistry is very safe.
I worry more about proper wire ga selections, good connections, checking terminals remain tight, lightning strikes, whole Provinces on fire upwind from me...other stuff, but not the batteries.