DIY LiFePO4 100 Amp-Hr battery Build

[posplayr]

If anybody decides to go this way using the basically high capacity naked (thin aluminum shell) cells, you have to realize that their packaging of these cells is pretty critical as ignorance of this in a mobile application can result in cell shorting and fire.

If you are only looking for 100-200 amp hr of capacity, then I would probably suggest just buying from one of these options.

https://www.mobile-solarpower.com/li...batteries.html

If you want to be more adventurous then go for these reinforced cells that are going to be easier to package. Realise that in a price comparison total to the door all in (with shipping)price for the 280 amp-Hr grade A matched cells is $147/280 ampHr (290 actual) while these Fortune 100 amp hr cells are 126 + tax and shipping conus.

So they are approaching 2.5x to 3X more expensive.

https://www.electriccarpartscompany....ncased-Battery

If you go with the EVE cells then be prepared for doing some research and design work. A 32 cell 48V battery is going to be a lot of energy and you want to make sure you have some protection in the event of a fire. It is rare, but it can happen and it best not to have to say "..Whoops burned the house down"

As I start to build my enclosure for the 200 Amp-hr van battery I will document the process or at least the design.

[posplayr]

I just posted this thread at the DIY Solar Forum. It is an update to my original plans in this thread. The original plan was to do a 100 Amp-hr replacement for dual frame-mounted lead-acid battery boxes.

After going through the implications of Lithium to electrical connections, DC-DC chargers and alternator upgrade options I basically changed direction and created a single 200 Amp-Hr battery that was going to go inside the Van.

To extend longevity for my already moderately bloated batteries, I went with an optimized 12 psi compression approach and thermal controls for cooling and heating.

This is pretty involved DIY (unless you are good at fab which I try but with a lot of effort) so I can't really recommend it unless you are committed. I am trying to get a reasonable 5-10 years of useful life out of these LifePO4 batteries despite the brutal (for Lithium) weather conditions in AZ.

https://diysolarforum.com/threads/di...thermal.31764/

[Scalf77]

Nice work.

-greg

[posplayr]

Originally Posted by Scalf77

Nice work.

-greg

Thanks, Greg

For those of you wonder what all the fuss about compression is all about. There has been a change in the manufacturer's specification where the charge-discharge cycles for the EVE LiFePO cells go from 2500 to 3500 cycles when using compression which is nominally 12 psi on the sides of the cells.

To be clear there do not seem to be any commercially available batteries that use some form of cell compression. At best they use packing tape but as you will see they also leave space between cells. Apparently the compromise between the detrimental effects of high temperature out weight the detrimental effects of not compressing. Or alternatively, the complexity of generating a relatively constant 12 psi is not warranted in the price-competitive solar battery market.

The overall impact is that the reduced capacity at the specified cycle count.

This subject has been widely discussed in the DIY channels. Specifically how to simply get the specified compression levels. You can see this Youtuber expressing some level of frustration on finding the best approach.

https://youtu.be/uZe6BDvWPfI