Post your Lithium/LiFePo4 DIY battery projects

[boywonder]

After some chatter over on this thread:

https://www.sportsmobileforum.com/fo...tml#post317700

....I'm starting this thread to post/document DIY Lithium battery builds.....

Hopefully questions can be asked by those thinking about building a battery, and those of us who have built packs can discuss their builds and design choices.

Resources:

There are some good DIY builds on Youtube, and also there is a DIY battery sub-forum on diysolarforum.com

https://diysolarforum.com/forums/diy...tery-banks.22/

Also Andy/Offgridgarage on youtube has done a fair bit of testing of various BMS's and lots of Victron stuff.

..and of course Will Prowse youtubes/reviews are quite informative as well.

If you are interested in building a pack, I suggest spending lots of time on the DIY battery bank subforum of diysolarforum.com

[boywonder]

Design Considerations:

Besides sizing the pack, you'll need to size the BMS depending on what you expect your max load to be; BMSs for 12V systems typically max out around 200A.

BMS's are available with with or without Bluetooth. The bluetooth versions are a few dollars more and are totally worth it IMO.

Most all of the cells available for packs are made in China and they are graded either A or B grade. However, most all of the Grade A packs available online are packs originally manufactured for the EV market but they do not meet the specs (typically C rate and or ability to balance) for electric vehicles.

So flunky EV cells get graded as A grade for other uses......and they will work fine for van house batteries. B grade cells are also available; these typically can be challenging to get balanced but they are cheaper than A grade. Many also are also bloated a bit. Many A grade cells are slightly bloated; this is considered normal.

One issue that can be a challenge is knowing what cells will actually show up after you hand over your cash. Many vendors ship from China so those cells (depending on the vendor) can be a crapshoot and are obviously difficult to return. These also take weeks to get to the US since they ship in large lots. There are a few vendors that have warehouses in the states and have good reputations.

One more design consideration is cell compression. The manufacturers publish data showing that if you squeeze/compress the cells you can get more life from the pack. The exact force/pressure that you compress the pack can be somewhat fuzzy and some builders compress and others don't.

[posplayr]

Since my 1997 E-350 was totaled, this project has been back burnered.

Write up on my 200 amp-hr RV battery.

https://diysolarforum.com/threads/di...4/#post-437407

FYI some basic work on balancing that works very well for cheap cells

https://diysolarforum.com/threads/pa...ocedure.26301/


The solar batteries for the house.
https://diysolarforum.com/threads/or...-5#post-395278

[boywonder]

My design criteria was that the pack has to fit in the space where my old AGMs are located, and that space is 7" wide. Off the shelf batteries are wider than 7", so that's one reason why I decided o build a battery.

Here is my home-brewed pack.....Eve 280ah cells and a JBD 200A BMS in a 1/2" aluminum compression enclosure. Compression is provided by belleville spring washers as shown.

The Eve cells are the long life (6000 cycle) part number.

Battery terminals are blue sea parts, really nice (as expected) but a bit pricey. I was attempting to fabricate terminals but ended up with the Blue Sea parts; they work great.

When the cells arrived they were at 3.29V each; I wired them up in series and charged them to 13.6V (3.4V/cell) with a 60A intellepower charger, then wired them in parallel and topped them up to 3.65V with a 5A bench top power supply.

The BMS is mounted under the top plate and is electrically isolated from the chassis, but I'm not sure that makes any difference.

I also added a small cooling fan that is controlled by a $12 amazon thermostat; it's presently set to turn on at 105F.

[boywonder]

Originally Posted by posplayr

Since my 1997 E-350 was totaled, this project has been back burnered.

Wow......that's unfortunate.....do you still have the van? ..or at least the battery pack?

..I was hoping you might chime in, I remember that you built a pack.

I just read your thread....impressive build!

[posplayr]

Originally Posted by boywonder

Wow......that's unfortunate.....do you still have the van? ..or at least the battery pack?

..I was hoping you might chime in, I remember that you built a pack.

I just read your thread....impressive build!

Yes, I have the van. As it turned out I had a lot of stuff that was not even installed in the van but had been purchased already. I'm an aerospace systems engineer and I had to redo work So I preplan for all contingencies and growth options (which can be complicated). I don't have a 3D drawing program but do use PowerPoint and multipage Schematics in KiCAD to maintain some sanity.

So basically after 6 months, I finally got a very nice settlement from the insurance company (it was 100% the other driver's fault). I was afraid they were going to offer $3500 but they started at $10K. I had a ton of receipts within the current year prior to the accident and then gave me 2/3 of that with most of the gig ticket stuff not even installed. So it was well over the $10k and I kept the vehicle and everything with it.

An unfortunate part of this accident (i was no hurt at all) was my mom ended up in the hospital and had a stroke although she was not in the van with me ; she was following in here car. So we ended up buying the 2000 E-350 XLT EB with the raised 16" top and Lift. So while I did have to start over, this will be a much more comfortable vehicle when done.

[boywonder]

Well.....kinda happy ending with the ins company anyway. I hope your mom is doing ok.

You've got another van project and boatload of stuff yet to be installed......do you have a build thread going?

I worked in aerospace in the late 80's.....for Bendix ( it was Allied Signal then, Honeywell now) in South bend In.

[posplayr]

Originally Posted by boywonder

Wow......that's unfortunate.....do you still have the van? ..or at least the battery pack?

..I was hoping you might chime in, I remember that you built a pack.

I just read your thread....impressive build!

So my main motivation for Lithium was I did not trust most of the commercial offerings that had none of the mechanical features for compression, cooling, and vibration. Additionally, I wanted to do a small project in anticipation of doing battery-backed-up solar for the house. I bought 32 of the 280 Amp-Hr EVE cells for a 560 Amp-Hr 48V battery.

You have a very clean design for that 7" tight space. Mine ended up being about a 10" width inside of the RB (over the driver's wheel well). In the pictures, you will see that i had a back bed area supported on 3/4" plywood frame going across the van vs length-wise.

As I progressed I realized It would save a lot of space if I could consolidate components directly on top of the battery. In the last picture, you can see I have all the power and ground distribution from copper bus bars going to all the external devices 9solart changer, DC-DC charger, inverter etc. This is not particularly modular from the battery standard point, but it is quite compact.

I think we discussed the issue of Load Dump and putting a LA battery in parallel with the Lithium. I explored in detail some electronics Load Dump protection, but in the end, the best solution was the LA battery. So the volt meter and red pushbutton you see are for voltage equalization when first connecting the LA to the lithium. The battery fits into the battery box although it is too tall. But adding a 2" spacer for the lid will work for this rear location. If you have these battery boxes mounted on the passenger side under the step there is not enough room for the extra 2".

The LA battery is for the 800 lbs Lift so it is an infrequent duty and a good match/secondary role for the load dump protection of the Lithium.

The van lift has a single battery box mounted in the rear. I ended up buying a high-quality used backup AGM battery that is a perfect solution for the lift and would work well with the lithium. I'm still not sure where they will go but i will try and consider having an option for adding a second of a similar form factor (albeit without the extra external components). For now, this is what you would call a "stretch goal" and only be necessary if I installed a chinee roof air unit.

The 200Amp-Hr battery consisted of 8 100 Amp-hr cells that were cheap and bloated and I got 30% off of that price. So in that previous post, I document a balancing process that pairs (parallel) cells to achieve might levels of cell pair matching. It is at least as good as Grade A selected cells.

[posplayr]

Originally Posted by boywonder

Wow......that's unfortunate.....do you still have the van? ..or at least the battery pack?

..I was hoping you might chime in, I remember that you built a pack.

I just read your thread....impressive build!

So I got the impression you used compression; I don't see where there are any springs. Maybe just compression but no springs? My 100 amp-hr cells came bloated so I wanted springs for sure.

My springs are sized for 12 psi over probably 1/2" of expansion. The 1"x3" steel rectangular stock added 1" on all sides. Other than that there is 3/16" vertical alum plate that is sandwiched between the cells to aid in heat flow from the center of the cell pack. So basically the cold plate is from welded stock (there is still the $75 ebay fluid cooling plate below this) and the spring compression frame is steel. They do not touch one another and are just a compression squeeze fit.

[arctictraveller]

Perhaps I missed it, but can you detail your plan for the van charging system? Upgraded alternator, DC to DC charger etc ?