Should I Make My Own or Buy Pre-Made?

[Devin82m]

Hey everyone, I've built 10 Ah LiFePO4 battery pack with BMS previously. I was thinking of either building or buying a 100 Ah battery. I was wondering if you suggest building it myself or buying a pre-made one? I was going to build my own, but started looking at prices for the components compared to pre-made packs that are fully serviceable like the SOK, and I don't see much point building one. Actually, it looks like building one would be more expensive.

Is my reasoning wrong?

 

[snoobler]

For the price of a 100Ah SOK, you can get a 280Ah DIY. Your call.

 

[Devin82m]

Are you using quality cells and BMS? I'm not being sarcastic, I don't know the brands and sites to buy those brands being a beginner. Honestly I go by reviews and what people on YouTube tell me to buy. :-D I just want everything to be durable and quality, I don't care to spend all my time swapping out components because I'm cheaping out on stuff.

But seriously, the Fortune cells I was looking at are $124 per cell. The Overkill BMS is $115. So that's $611 not including shipping or any other supplies I need. I have a quality solderer, Kepton tape, and other tools. The SOK 100 Ah battery is $570.

So please educate me.

 

[snoobler]

There are reliable suppliers used by forum members that provide quality cells. Some forum members (@Michael B Caro ) buy cells in bulk and re-sell at a very small mark-up.

4X 280Ah cells are about $550 shipped to your door (6-8 weeks). $115 Overkill = $665 for 2.8X the capacity.

 

[Bob B]

If you build your own battery, you can also put it together better than any of the pre-made batteries are. You can build it to handle the amount of current you need it to handle .... You can compress the cell to give the battery longer life. If you are in a hot climate, you can install ventilation ... If you are in a cold environment you can install insulation and heater ..... but to do it right requires a lot of research. There are dangers of shorting cells.

There will be additional expenses if you do it right and do a good top balance. There have been quite a few on here who have damaged their cells by this wrong.

I would suggest that if you are hesitant to do it yourself .... You probably shouldn't.

 

[Devin82m]

OK, yeah, true. Can you make specific suggestions though?

I built my 20 Ah pack last year, I didn't top balance them, I'm not sure how to do that. I also hooked a wire up wrong because the BMS wiring diagram was confusing, but I figured it out after it got hot, it works fine now, but I rarely touch it, it just sits on a shelf. It's supposed to be for off grid ham radio, like when camping.

Just because I'm afraid or could fry something doesn't mean I shouldn't try however, I'm up for learning.

One thing I did notice about those cheaper cells is that they have those pathetic looking bolt holes, unlike the more expensive Fortune cells with those nice lugs.

 

[snoobler]

Not everything will apply, but you may find some useful things here:

Beginners' Resources

New to the forum and building a solar power system? Start here

diysolarforum.com

along with this one:

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com