My DIY LiFePO4 Build Experience

Woody

Solar Addict
My DIY LiFePO4 Battery Build Experience - Part 1

Summary
: Was is worth it…yes from a learning experience but no because I thought I only would have to assemble and go. Who knew I had to become a battery manufacture? I just wanted affordable high capacity batteries.
=====================================================================
Background:
Around the fall of 2020 I started my search once again for a battery for emergency backup system. I always like the amount of available energy big Flooded Lead Acid (FLA) forklift battery could provide, and the used market wasn’t too bad on these reconditioned batteries. Used forklift batteries was the way to go over the years if you had the means to move them about. However, the price was still rather high for a battery that would be left in a standby state. As times were becoming more dynamic and unstable, it was time to start looking again for something. In reviewing the available FLA batteries there was a couple ways to go. Banked style where the cells are contained in a steel bin and all connected or modular aka single cell that you have to connect together. I favored the single cell approach since you could move one piece at a time verse one massive battery. Price was rather high for the available amp hours. In my searches, going back a little over a year ago is when I found online these amazing videos talking about LiFePO4 batteries. There was this very excited guy talking about solar energy, his experience with it, and more. Yeah it was Will! Will’s videos on LiFePO4 batteries got me very interested in them. Seemed oh so easy to do it yourself that after a few months I decided to try to assemble one. After all I’m an EE doing solar for ages and I have the fabrication equipment and skills, so piece of cake.

Here’s what I’ve built.
Build 1: (12v 4S) 200Ahr LiFePO4 cells, 4 of them, purchased online via a dealer who had stock in the USA and would deliver in a few days. Big dollars for get these batteries NOW vs pay and hope the came in from China. The batteries that came were very nice. Had the laser welded bolt stud for attaching the cable. Ordered the BMS Will’s recommended via OBS. This was a 12v setup so a simple 4S configuration. --- Overkill BMS 120Amp

Build 2: (24v 2P8S) 280Ahr LiFePO4 cells, 16 of them, purchased online via AliExpress. Boy that was a big concern. Big dollars to me and I hoped and prayed all would go ok. After a long wait, the shipment did finally arrived. The protracted shipping time was not the seller’s issue but huge backlog in shipments going across the ocean. --- Overkill similar BMS Only 60amp but will use the BMS as a battery monitor and as a controller to enable/disable a power feed to the inverter via solid state relays.

Build 3: (12v 4S) 100Ahr LiFePO4 cells, 4 cells, purchased via AliExpress. Another 12v battery system --- Overkill similar BMS 120Amp

Build 4: (12v 4S) 200Ahr LiFePO4 cells, 4 cells, purchased via AliExpress. Another 12v battery system --- Overkill similar BMS 120Amp

Additional Tools/Materials:
For all the equipment and tools that I already had, I still need additional items to support these builds including:
  • Kapton and Double Stick Tape
  • 4 wire voltage / internal resistance meter YR 1035+
  • Bench Power Supply (old ones couldn’t support the high current low voltage)
  • Copper bus bar & Cables (needed more not enough on hand)
  • 6mm Stainless nuts, washers, studs, … (Nothing this small s had to order)
  • Clamp on DC amp meter (old ones OK but wanted a better one) UNI-T UT210D
  • Cables/Lugs/Heat Shrink (Needed more that what I had already)
  • Fuses / Breakers / Switches (Needed more than what I had already)
  • Panel Volt/Amp/WattHr Display
  • Plastic cutting boards
Lastly, I had to purchase a new LiFePo4 capable shore power chargers (PD9180ALV) and MPPT chargers. The older ones I have are all for lead acid. The only item that I choose not purchase to support the build process that many do, was an active or passive loads for capacity testing device. I choose not to perform discrete load/capacity testing on the cells. This process would require more of my time and money that I just didn’t want to consume.

DIY Battery Build Issues/Considerations:
Studs/Bolts/Nuts and Stripping:

Terminal holes on the 280Ahr cells were not drilled perpendicular. I had to customize bending each stud for holes. Then I used Loctite to secure the studs to the cell terminals. The bus bars that I fabricated have a center terminal stud so that I could tighten sensors/cables to it and not touch the nuts attached to the cell’s terminal studs again. The idea was to reduce the amount of tightening and loosening of the connections/nut at the cell terminals.

Cell Insulation:
To insulate between cells or is the blue plastic covering enough? I followed the suggestion of another DIY forum member who recommended the thin Dollar Store plastic cutting board as an affordable way to add additional electrical isolation between the cells.

Battery Box HVAC?
Do you include a heating pad and controls with cells or keep the battery in a heated environment? How about cooling if located in a high temperature location? I skipped all of this and will keep them in an temperature controlled space instead.

To Compression or Not To Compress, That tis the question:
I choose to use Kapton tape the cells together and then structural constrain them to keep them from moving about. So, the cells are constrained but no additional compression applied.

Bus Bars:
Copper or Aluminum, Rigid or Flex – I went with solid copper bus bars but time will tell if I should have used flexible cable instead. This cell bloating is a concern since this can cause a lot of stress on the terminal studs when using solid bus bars. Properly managing the charge/discharge process along with a conservative depth of charge / discharge (10-20% off low/max values) should help reduce any bloating and extend battery life.
 

Woody

Solar Addict
(Part - 2)

So was it worth it after all of this?
Yes
because I learned a lot about these batteries. What makes a good vs bad one. What component vendors are high quality vs low quality. I believe one can save a good 1/3 of the price implementing a DIY battery vs an off the shelf one if you have the DIY skills and resources available to build one. Just keep in mind that there’s a fair amount of time you have to put in to make this a successful build.

No because initially I calculated the savings of a DIY battery would be at least ½ price compared to an off the shelf battery for the same capacity. In fact, I was under the misconception that could get more than double the capacity for less than the price of an off the shelf battery. Oops I needed a lot of miscellaneous items in addition to the cells, BMS, and bus bars. Additional savings are realized on future battery builds once you have all of the equipment/parts. I also way under estimated the time I had to put in to making this batteries!

More importantly I tend to agree with FHORST regarding the DIY vs off the shelf battery process. I realize now that as a DIY LiFePO4 battery builder/assembler you ARE the manufacture. As such, every consideration/issue is on you! You can’t expect to just slap the components together and wham bam your done.

As a battery manufacturer, you have to find a quality battery cell manufactured. Then an honest / reliable vendor to purchase them from. Once the cells/products arrive you are the incoming receiving department and the QA for receipt of the product. Assuming all is physically good, the product then needs to be tested to verify that they are functional and as specified in the purchase agreement. Assuming no issues, else you play the vendor return game, you get to charge them up for top balancing. Once all are fully topped off, you can proceed to the assemble phase. Hopefully nothing failed or bloated else you have a return and a replacement process to do. Assuming all the items are good, you now need to fabricate a compression structure for the cells. Would that be just tape, compression springs/washers, some sort of 3D printed box, ammo box, milk crate, … that’s all up to you to put together. Once assembled you need to put on the bus bars. Use the thin ones they sent, purchase new ones, or fabricate some. Then wire in your BMS that you selected and ordered for your build. Finally, you have completed your manufacturing of a working battery!

How’s that bad boy holding up? All good, well that process wasn’t so bad was it. Oh NO something isn’t working. Do you have any cell voltage/charge/discharge variation issues? BMS tripping out? Hot spots on the battery connectors? Hopefully no catastrophic failure but they can happen. So, if something failed now you play forensic engineer to identify what failed and how it failed so you can take corrective action. Once that’s done you get to order replacement part(s) and repeat the build process. That’s the good/bad in being your own DIY battery manufacture.

Would I do another DIY LiFePo4 battery build? Maybe, but not anytime soon.

I really need to see the quality of product improve. The existing physical terminal attachment design sucks. Poorly drilled/tapped shallow holes must stop. Consistent, quality built LiFePO4 cell must be the everyday standard and not “I go lucky, I got matched grade A extra capacity high quality cells super cheap…”. Additional improvements that I would like to see more of the heavy-duty bolt style terminal cell used on the Overkill Heavy Duty Terminal batteries. As for the leaking cells, that shouldn’t happen unless the product was damaged in shipping. Overheating, upside down cells, rough shipping… whatever the excuse the vendor gives needs to stop. Build a quality product and package it so that can handle the shipping process. Expansion/bloating issue must be addressed in the cell chemistry/design. The physical design of the battery cell structure should be implemented in a manner to constrain the internal materials without the need to apply external mechanical forces. The shipping / delivery times along with product availability must improve. Better return/refund process is badly needed. Hopefully these issues will improve as new manufactures come online. So, for me, my future LiFePo4 batteries will be off the shelf ones. This way the vendor takes all the design, reliability, and risk issues associated with building a quality product. I really don’t want to be a battery manufacture.
 

Ludrock

New Member
(Part - 2)

So was it worth it after all of this?
Yes
because I learned a lot about these batteries. What makes a good vs bad one. What component vendors are high quality vs low quality. I believe one can save a good 1/3 of the price implementing a DIY battery vs an off the shelf one if you have the DIY skills and resources available to build one. Just keep in mind that there’s a fair amount of time you have to put in to make this a successful build.

No because initially I calculated the savings of a DIY battery would be at least ½ price compared to an off the shelf battery for the same capacity. In fact, I was under the misconception that could get more than double the capacity for less than the price of an off the shelf battery. Oops I needed a lot of miscellaneous items in addition to the cells, BMS, and bus bars. Additional savings are realized on future battery builds once you have all of the equipment/parts. I also way under estimated the time I had to put in to making this batteries!

More importantly I tend to agree with FHORST regarding the DIY vs off the shelf battery process. I realize now that as a DIY LiFePO4 battery builder/assembler you ARE the manufacture. As such, every consideration/issue is on you! You can’t expect to just slap the components together and wham bam your done.

As a battery manufacturer, you have to find a quality battery cell manufactured. Then an honest / reliable vendor to purchase them from. Once the cells/products arrive you are the incoming receiving department and the QA for receipt of the product. Assuming all is physically good, the product then needs to be tested to verify that they are functional and as specified in the purchase agreement. Assuming no issues, else you play the vendor return game, you get to charge them up for top balancing. Once all are fully topped off, you can proceed to the assemble phase. Hopefully nothing failed or bloated else you have a return and a replacement process to do. Assuming all the items are good, you now need to fabricate a compression structure for the cells. Would that be just tape, compression springs/washers, some sort of 3D printed box, ammo box, milk crate, … that’s all up to you to put together. Once assembled you need to put on the bus bars. Use the thin ones they sent, purchase new ones, or fabricate some. Then wire in your BMS that you selected and ordered for your build. Finally, you have completed your manufacturing of a working battery!

How’s that bad boy holding up? All good, well that process wasn’t so bad was it. Oh NO something isn’t working. Do you have any cell voltage/charge/discharge variation issues? BMS tripping out? Hot spots on the battery connectors? Hopefully no catastrophic failure but they can happen. So, if something failed now you play forensic engineer to identify what failed and how it failed so you can take corrective action. Once that’s done you get to order replacement part(s) and repeat the build process. That’s the good/bad in being your own DIY battery manufacture.

Would I do another DIY LiFePo4 battery build? Maybe, but not anytime soon.

I really need to see the quality of product improve. The existing physical terminal attachment design sucks. Poorly drilled/tapped shallow holes must stop. Consistent, quality built LiFePO4 cell must be the everyday standard and not “I go lucky, I got matched grade A extra capacity high quality cells super cheap…”. Additional improvements that I would like to see more of the heavy-duty bolt style terminal cell used on the Overkill Heavy Duty Terminal batteries. As for the leaking cells, that shouldn’t happen unless the product was damaged in shipping. Overheating, upside down cells, rough shipping… whatever the excuse the vendor gives needs to stop. Build a quality product and package it so that can handle the shipping process. Expansion/bloating issue must be addressed in the cell chemistry/design. The physical design of the battery cell structure should be implemented in a manner to constrain the internal materials without the need to apply external mechanical forces. The shipping / delivery times along with product availability must improve. Better return/refund process is badly needed. Hopefully these issues will improve as new manufactures come online. So, for me, my future LiFePo4 batteries will be off the shelf ones. This way the vendor takes all the design, reliability, and risk issues associated with building a quality product. I really don’t want to be a battery manufacture.
Thanks for posting this. I live in Australia and had been considering building my own 200ah for my caravan but decided after weaving my way through the maze that is AliExpress, and being unsure of who was a reputable vendor or not, and the long wait and high cost of shipping to Australia, I decided to buy a drop in replacement battery from a reputable Australian company. A capacity test returned 206ah, so I was very happy with the result. The price of locally sourced lithium batteries has dropped considerably recently, and I recently purchased 2 x 100ah lithium batteries for an elderly friend, for his electric trolling motor. They come from a well established company and have a 3 year Australian warranty.
These cost $884 for the 2, with free shipping. The brand is Voltax, and after a comprehensive search online, I couldn't find any bad reviews. It's hard to justify building my own battery after seeing these prices.
Cheers
Dave.
 

K8MEJ

Solar Addict
For my own use in my RV, I'm glad I went with a DIY battery build. I was able to build an approximately 15KWh battery bank vs an approximately 4KWh battery bank if I had purchased Battle Born batteries for the same amount of money. And, I have BMS's I can communicate with and with a little open-source magic, eventually integrate into my Victron system for SoC sharing with the whole system via an open-source driver and my Victron Cerbo GX. One year later and with SOK and other cheaper battery options hitting the market, this calculus changes a little, but I'm still glad I did it. The savings on the batteries allowed me to go with Victron equipment for easy integration.

For even smaller systems, the calculus changes again. For a 100Ah or 200Ah system, it probably makes sense to buy something, especially if you don't need any communication with the batteries.

Eventually my home won't be grid-dependent and I will have a solar + ESS (energy storage system) that will power my house and use the grid for backup power or when we don't have enough solar. (I live in Ohio and we have a lot of gray skies, especially in the winter. If I were to build this system today, I'd absolutely build my own battery bank(s) but I'd spend extra on canbus capable BMS's and run a 48 volt bank. A few years from now when I get to it, lots will change and I'll have to make the decision to DIY or purchase at that time.

Great post, by the way. I don't mean to sound contradictory. I just wanted to share my experience. The learning and thinking process alone was worth it to me. If I were selling and installing systems, I wouldn't sell customers DIY batteries.
 

Sanwizard

Photon Sorcerer
(Part - 2)

So was it worth it after all of this?
Yes
because I learned a lot about these batteries. What makes a good vs bad one. What component vendors are high quality vs low quality. I believe one can save a good 1/3 of the price implementing a DIY battery vs an off the shelf one if you have the DIY skills and resources available to build one. Just keep in mind that there’s a fair amount of time you have to put in to make this a successful build.

No because initially I calculated the savings of a DIY battery would be at least ½ price compared to an off the shelf battery for the same capacity. In fact, I was under the misconception that could get more than double the capacity for less than the price of an off the shelf battery. Oops I needed a lot of miscellaneous items in addition to the cells, BMS, and bus bars. Additional savings are realized on future battery builds once you have all of the equipment/parts. I also way under estimated the time I had to put in to making this batteries!

More importantly I tend to agree with FHORST regarding the DIY vs off the shelf battery process. I realize now that as a DIY LiFePO4 battery builder/assembler you ARE the manufacture. As such, every consideration/issue is on you! You can’t expect to just slap the components together and wham bam your done.

As a battery manufacturer, you have to find a quality battery cell manufactured. Then an honest / reliable vendor to purchase them from. Once the cells/products arrive you are the incoming receiving department and the QA for receipt of the product. Assuming all is physically good, the product then needs to be tested to verify that they are functional and as specified in the purchase agreement. Assuming no issues, else you play the vendor return game, you get to charge them up for top balancing. Once all are fully topped off, you can proceed to the assemble phase. Hopefully nothing failed or bloated else you have a return and a replacement process to do. Assuming all the items are good, you now need to fabricate a compression structure for the cells. Would that be just tape, compression springs/washers, some sort of 3D printed box, ammo box, milk crate, … that’s all up to you to put together. Once assembled you need to put on the bus bars. Use the thin ones they sent, purchase new ones, or fabricate some. Then wire in your BMS that you selected and ordered for your build. Finally, you have completed your manufacturing of a working battery!

How’s that bad boy holding up? All good, well that process wasn’t so bad was it. Oh NO something isn’t working. Do you have any cell voltage/charge/discharge variation issues? BMS tripping out? Hot spots on the battery connectors? Hopefully no catastrophic failure but they can happen. So, if something failed now you play forensic engineer to identify what failed and how it failed so you can take corrective action. Once that’s done you get to order replacement part(s) and repeat the build process. That’s the good/bad in being your own DIY battery manufacture.

Would I do another DIY LiFePo4 battery build? Maybe, but not anytime soon.

I really need to see the quality of product improve. The existing physical terminal attachment design sucks. Poorly drilled/tapped shallow holes must stop. Consistent, quality built LiFePO4 cell must be the everyday standard and not “I go lucky, I got matched grade A extra capacity high quality cells super cheap…”. Additional improvements that I would like to see more of the heavy-duty bolt style terminal cell used on the Overkill Heavy Duty Terminal batteries. As for the leaking cells, that shouldn’t happen unless the product was damaged in shipping. Overheating, upside down cells, rough shipping… whatever the excuse the vendor gives needs to stop. Build a quality product and package it so that can handle the shipping process. Expansion/bloating issue must be addressed in the cell chemistry/design. The physical design of the battery cell structure should be implemented in a manner to constrain the internal materials without the need to apply external mechanical forces. The shipping / delivery times along with product availability must improve. Better return/refund process is badly needed. Hopefully these issues will improve as new manufactures come online. So, for me, my future LiFePo4 batteries will be off the shelf ones. This way the vendor takes all the design, reliability, and risk issues associated with building a quality product. I really don’t want to be a battery manufacture.
If you have deep pockets, commercial is the way to go. But if your poor like me, I have found that cost per KW of energy is MUCH less with diy banks.
As an example, my DIY 48V banks cost between $120 and $150 per KW, based on when the cells were purchased (prices are going up!). To do the same size in Pylontech, based on a recent search, its about $2000 for 3.5KW, or $571 per KW.
 

Stiffmeister

Solar Enthusiast
Why are cell prices going up? What was the cost of a 280ah a year ago compared to now? I originally bought SHUNBIN off of Amazon two years ago because LiFePO4 plug and play was (and still is ) expensive.
 

Sanwizard

Photon Sorcerer
Why are cell prices going up? What was the cost of a 280ah a year ago compared to now? I originally bought SHUNBIN off of Amazon two years ago because LiFePO4 plug and play was (and still is ) expensive.
My Lishen 280ah cells were $78 each in Feb 2020, and shipping was $180. They now cost $95 each, and shipping is $440.
Its really the crazy worldwide logistics nightmare, and drunken sailor government spending that is inflating everything. And it will be getting MUCH worse, so hang on tight.
 

mininut2

New Member
Is that shipping charge from automated shipping estimated or from the sale rep?
The whole quote was from a rep, I don't think that they sell through Aliexpress. I got a couple of quotes from companies and requested a price match. They did !!
 

Brett V

Solar Addict
I’d love to see some details on how you used the BMS to control a solid state relay and which relay you used.
 

RV10flyer

Solar Enthusiast
$
If you have deep pockets, commercial is the way to go. But if your poor like me, I have found that cost per KW of energy is MUCH less with diy banks.
As an example, my DIY 48V banks cost between $120 and $150 per KW, based on when the cells were purchased (prices are going up!). To do the same size in Pylontech, based on a recent search, its about $2000 for 3.5KW, or $571 per KW.
On my 107 kWh of batteries (mostly grade A), it was more like $211/kWh, including 7-9 weeks of shipping from China, transaction fees, BMS, miscellaneous materials. This doesn’t include proper high cost 1000v insulated tools, test equipment, chargers, etc.
 
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