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DIY Battery dilemma: (Build vs Buy)

R

RScupper

New Member
Joined
Oct 4, 2024
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1
Location
Seattle, WA
Greetings compatriots,

Need a sanity check on considering a "build" option for a simple 48v16s battery using prebuilt box and EVE 280 cells. Reading the threads here, this looks very standard although sourcing the battery box and cells seems dicey with reports of counterfeit or used cells, bloated cells, etc. Some quick online searching on the costs of the box, bms, and cells together for roughly $2800 with shipping. Some cheaper and some more expensive options, but this gets me a 48v16s battery with roughly 14kWh of capacity. On the "buy" side, the Signature Solar battery racks look solid, have extended features, UL certification, and a warranty. Two racks gets me around 10kWh for $3k.

Seems like I could get more capacity for a little less money with a reliable DIY battery.

Thanks!
-RS
 

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Where are you at in the world? $2800 for a box and 16 cells sounds overly expensive. Every time I look at doing one it comes out to about $2000 if I round up with sales tax.

As to the question, you've got a Victron setup there so I'm assuming you're going to want to overcomplicate things with comms and such that are compatible which makes a build kit more difficult. If you don't need the UL and certs and stuff, you can save some. If it's really going to be $2800 for a Victron compatible BMS kit build or $3000 for a pre-built Victron compatible, the cost savings really don't justify the extra work.
 
If you do not have all the needed tools and extra parts that the kits do not include, then if added up, this will increase the cost of a DIY kit and may not make 1 kit a better value, vs more or many DIY kits, which nearly always have more capacity for usually lower cost, if not similar cost to server racks.

Good and seldom used tools can add up quickly, especially if one doesn't know what to get, doesn't shop for sales or is impatient to learn and so buys 2 or more of a tool while learning what is good or bad. Eg: Lugs and crimpers.

Also, DIY is a helpful learning process for just future troubleshooting or repairs. Server racks seem to more often have non user (welded cells and bus bars) and so are difficultto repair or void warranties if self repairs are attempted. If return shipping isn't included in a warranty claim, then the warranty claim could be really expensive. Check if warranty shipping both ways is paid by you or the seller? DIY is similar but most by an extra cell or two to insurance against time lost to single cell returns. That adds cost to DIY, but I just gambled and on 2 packs had all great cells, so skipped the insurance cells.

In my remote case, with poor delivery access, warranties are pretty much useless, as it is a 6+ hour return trip to a city to ship anything.

Check the really long Luyuan battery case thread, for info on decent, lower priced metal cases and that allow for some customization. You MUST contact them to get an accurate shipping price on your order estimate vs the extremely inaccurate and expensive Alibaba shopping cart estimate. Lots of satisfied users and the cases keep improving.
 
Having said that, 50% more capacity for less money is really hard to beat.

Personally, I always choose the DIY option because it's significantly cheaper per watt-hour at the higher capacities and it's a lot more fun. Cell fails? You know how to find and replace it because you put it there. BMS gets wonky? You know how to find and replace it because you put it there. Solar forum clout and bragging rights to your friends? Can't buy that from Sig Solar. 😜

Whole thing fails and becomes an "Up In Smoke" thread? You know who's ass to kick for the shoddy craftsmanship.

Granted, I've been known to go deep down the DIY battery build rabbit hole. 😁
 
I answered my thoughts on this question here...
SeaGal

Post in thread 'Your preference, DIY or rack?'

Ronnie B said:
If you were to buy batteries today for your system, which would you buy and why?
Click to expand...
DIY every time for me, even if it cost $1000 more per 15kWh. I like the control of my DIY BMS to Inverter software and knowledge of how it all works.

millsan1 said:
More expensive, but in theory, if warranty is needed, someone else is holding the bag.
Click to expand...
Disagree. My DIY batteries come with a 5 minute SLA response time, 24/7, 365 days per year. If something ain't working, I would want to resolve it now, even if it's me in my pyjamas :).... I hate trying to convince some spotty teenager that something is...
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I am a very DIY guy, but in '21 when building out my van, I installed all Victron products, including 2 of their 200ah batteries. There are just too many folks here with issues with their DIY batteries - BMS, compression, bus bars, balancing issues, etc. Now, of course there are many DIY battery builds that work great and save tons of money, but this battery thing is just one item I won't DIY. Last year I replaced my home PV system Concorde lead acid battery bank with 2 Trophy 220ah lithiums. No isssues or problems, they just work. I guess I just don't want to take a chance on getting bad (counterfeit) cells, bad advice or other issues.
 
I DIY'd 5 280AH 48V batteries. It was amusing and everything works.
But I would recommend buying prebuilt. There are a lot of dangerous lessons that need to be learned.
Plus you can buy prebuilt with closed loop communication. UL certified. You get warranty and tech support from the battery seller and the inverter company. And it passes permit requirements.
 
@RScupper UL listing or meeting ABYC standards is important for insurance purposes.
Up in smoke without it could mean total loss with no recourse.
 
E. Cho said:
If you do not have all the needed tools and extra parts that the kits do not include, then if added up, this will increase the cost of a DIY kit and may not make 1 kit a better value, vs more or many DIY kits, which nearly always have more capacity for usually lower cost, if not similar cost to server racks.

Good and seldom used tools can add up quickly, especially if one doesn't know what to get, doesn't shop for sales or is impatient to learn and so buys 2 or more of a tool while learning what is good or bad. Eg: Lugs and crimpers.

Also, DIY is a helpful learning process for just future troubleshooting or repairs. Server racks seem to more often have non user (welded cells and bus bars) and so are difficultto repair or void warranties if self repairs are attempted. If return shipping isn't included in a warranty claim, then the warranty claim could be really expensive. Check if warranty shipping both ways is paid by you or the seller? DIY is similar but most by an extra cell or two to insurance against time lost to single cell returns. That adds cost to DIY, but I just gambled and on 2 packs had all great cells, so skipped the insurance cells.
Click to expand...
Good points and leads me to ask you're future plans. In my case, I grew my powerwall from the initial 5kwh to 121kwh over 5 years via DIY, background work. If 13kwh is all you're planning - then buy becomes more attractive in my mind. If you want to expand to 100kwh over the future years - then DIY can really start to pay off if you have the time as the tools and expertise are re-useable for battery #2, #3, ... the savings and knowledge start to pay off.
 
Do both?
Have to admit, I started out by buying two 100Ah 48v server racks to get going into solar...after realizing just what a solar set up was capable of, expanded with DIY packs to nearly 100kWh (and 30kWh on order).
It can be an interesting and fun project to DIY packs, and alllows a person to develop knowledge and skills, but that is not the goal for everyone; some just need an ESS that works and factory packs fit this very well.
Part of my own thought process on the DIY packs: future changes will be easy re-using the cells. Even if some new battery tech comes along next year, I know I have a lot of cells that can be re-purposed for other projects, a cabin, ICE-to-Electric conversions of equipment...lots of options & opportunities with DIY packs.
Current plan is ESS expansion to 200kWh over 3-years using DIY packs and the original two factory server racks together.
 
Brucey said:
They seem to have some issues as well:

www.18650batterystore.com

EVE MB31 Grade A Cells - 3.2V LiFePO4 314Ah Battery

Brand new Grade A EVE MB31 LiFePO4 cells with 314Ah capacity. 10+ years design life, 8,000 cycles. Get unmatched power and performance for your energy storage needs.
www.18650batterystore.com www.18650batterystore.com
View attachment 248354
Click to expand...
Aluminum alloys are very important to make a quality weld. Substituting the wrong alloy, accidentally or intentionally can lead to visually acceptable weld yet extremely brittle. Some alloys are better machining but a poor match to the other part to be joined. People trying to cut the terminal price unknowingly may have caused a huge problem. Even here on the west coast USA I have seen an increase metal suppliers delivering the wrong material. After I machine it a while I can tell if something’s off pretty quickly. A few years ago, a bar of “certified” material was way wrong. What I’m thinking is the battery’s post alloy probably hasn’t been changed but some venders have made many thousands of terminals wrong. They have better start tracking the root of the problem before they wreck the entire reputation of that design.
 
Being budget conscious, I have done research on DIY LiFePO4 battery kits with aims to potentially lower the battery cost and/or get more battery capacity for the money. Based on what I have learned thus far watching videos in YouTube, these kits can cut in half or more the cost of batteries with storage capacities between 14 Kwh and 16 Kwh per box, as they tend to go for 9 to 15 cents per watt hour of battery storage (perhaps cheaper, depending on the battery kit/cells brand, prices and/or deals). Specifically, I'm paying special attention to the Basen Green 48V 280A to 314A DIY kit (https://www.basengreen.com/product/diy-case-for-48v-battery-packenclosure-accessories-usa/). Why this kit? The BMS/controls come assembled from the factory with an equalizer unit and battery breaker, overall simplifying assembly and enhancing safety. A complete kit with 16 314A battery cells will go for $1,925 per box (11 cents per watt hour) and free shipping from a US distribution facility. The only thing this kit does bring is fire suppression capability. This option opens the possibility to be able to get three 16 Kwh batteries for the cost of two EG4 14 Kwh indoor wall-mounted batteries. However, it looks like these battery kits are more suitable for off-grid applications, and not so much to grid-tied setups (correct me if I'm wrong).
 
Last edited:
My new factor in DIY vs. prebuilt is I've been woken up to how broken some prebuilt's BMS balancing schemes are.

My DIY battery you can literally just hold at the balance voltage (55v/3.437vpc for me) and it will balance continuously until the entire pack is whipped into perfect balance (<.007). No need to cycle, just hold it there until it's done.

I couldn't believe a couple months ago when I discovered my prebuilt server rack battery cannot also do this, it identifies high cells on the way up and then applies a balancer to those until they're in line, but it does not then identify the next highest cells when held there. You would have to repeatedly cycle it to get it to re-identify the next highest cells. That's hot garbage to me.
 
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