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If anyone see's any problems or advice (need all the advice I can get) with this setup please let me know.  Hoping in this case a little knowledge (mine) is not dangerous.

I really enjoyed building this and learning about building this battery.  The sense of accomplishment is good for the soul and boredom!  A lot of people had input and know far more about this subject than I.  I was just following the breadcrumbs left by those before me.  Roger, Craneman and Pamella&Mike gave invaluable assistance and knowledge.

I did a lot of reading and watched a lot of video to try to get a general consensus on the best way to do this build for me.  I knew/know nothing about building a battery before I dove in head first.  Please do your own research and get comfortable with it.  It didn't seem hard at all (but there is conflicting info) to me and I saved quite a bit on the build compared to other retail options. 

I would start here for any guides for solar and LifePo4 battery information
 https://diysolarforum.com/resources/categories/beginners-resources.10/

Jack Lewis turned me on to Will Prowse and he has linked some solar articles in another post that are worthwhile, maybe he will chime in.

Also great information here
Assembling a Lithium Iron Phosphate Marine House Bank | Nordkyn Design


I think I will eventually have to install a residential fridge as others have—-so like Brad Metzger says about horsepower on the dunes "its better to have it and not need it rather than need it and not have it". 

So I ended up going with 8-3.2V 271AH CATL cells from Michael Caro from this thread Lishen 270ah-272ah cell group buy. | Page 96 | DIY Solar Power Forum  I ended up with 2 each of 4-3.2V batteries wired in series for 1-12V with a BMS. I paralleled these 2 batteries so I have 542AH of storage.

Yes, I read the whole thread (96 pgs as of today) and another to get somewhat comfortable with sending someone I didn't know 1 coach buck through PayPal.  I maybe could have bought the same cells for a little less money, from someone in China, but I could at least call or email this guy and get some response.  He seems to have done right for a lot of people on that forum.  He is trying to build a business doing this (being the middle man on batteries) so he has some accountability to try to do a good job and vetting his sources with those who've gone before.

Slow boat from China took a while, I ordered on 1/26/21 and received the batteries on 4/13/21.
One box of 3 were shipped with terminals down.  Michael said if they were bad he would replace.  No problem so far.

General premise of building the battery is as follows.  For me the BMS is the main thing to get right and you should purchase one that is reliable.  Will Prowse recommends Overkill Solar BMS and that is the one I used.

1. Charge batteries in Parallel to 3.6V to top balance (can takes days)
2. Break apart and assemble into 12v with BMS
3. Build a case for battery
4. Install

Need to adjust the following to make sure the charge profile of anything charging the batteries to a lithium setting—-Alternator, Solar, and DC charger on your inverter.

I have a Xantrex SW3000 inverter charger from 2010ish and I don't like the charge profiles they have available and there is no custom setting so have set it to AGM setting.  I will only use it to charge the LifePo4 when I can closely monitor. AGM=Bulk/Absorption@14.3V and float @13.45V.  A little higher than I want.


Components with Links. Total cost $1,350ish for 542AH

Batteries-$906
Lishen 270ah-272ah cell group buy. | Page 96 | DIY Solar Power Forum

2-Overkill Solar BMS with wires $264
12v BMS – Overkill Solar

2-cables used on each (+) post of each battery-$39
Amazon.com: Spartan Power 4/0 AWG 12 Inch Single Red Battery Cable: Automotive

2-fuse blocks and 2-60amp fuses $23
Amazon.com: TopstrongGear Solid Brass 0/2/4 Gauge 100Amp ANL Fuse Holder...
Amazon.com: Baomain ANL Fuse ANL-60 60 Amp 60A for Car Vehicles Audio System...

8- Bolts for battery case. $23
I used these and scrap 3/4" plywood for case.  Used foam from shipping to put on bottom and sides of battery
ONESTOCK 3/8" x 14" Fully Threaded Carriage Bolts with Nuts & Washers, 12...

1 pair- cable terminal $13
for connecting original Foretravel supplied cables to 2-BMS cables and 2 cables above
Amazon.com: UTSAUTO Battery Terminal 5/16" M8 8mm Stud Remote Battery...

1-Power supply $60
TUFFIOM DC Power Supply Variable 0-10A/0-30V| Portable Adjustable Switching...
Used to top balance batteries

Ended up using a few other things that I already had but not over $20 worth and I did buy a stand alone LIFEPO4 charger, just to have in case I need it.

I also installed a DCDC battery charger 12/12-30A to replace the Isolator and will attach pictures.  $220 with Foreforum discount from Bay Marine
https://baymarinesupply.com/victron-orion-tr-smart-non-isolated-dc-dc-charger.html
Lithium batteries will take a lot of charge at a high amperage and will possibly burn up your Alternator if OEM isolator is not replaced.

Isolator replacement


Shipped battery


Assembled battery


Installed battery


Some info BMS provides...maybe too much?



The attached PDF is where I tried to collect my thoughts and questions and the answers that I came to for my situation.  Some may not agree with the parameters I chose but these are what I came up with.

Just an update on my Battery Build.

Everything seems to be working great and I am very pleased with the batteries.  I have done more boondocking (but still not a lot compared to some) than usual.  Longest stint was 4 days and my solar has been more than adequate to recharge batteries every day.  The AGM batteries I had were good but I could not run the Microwave for long before the generator would automatically start
because of low voltage.

I did enjoy building and figuring out how to do this .  I did have some issues with my B2B, but it was user error.  I not only forgot to plug in the jumper that makes it work but my DW threw it out in the trash.  Justin at Bay Marine came to the rescue though.



But I think that the price of Stock lithium batteries has dropped so much it might not be worth the effort to do your own.  The battery that Craneman bought is now only $699 for a 200AH.  So for $1400-400AH you could probably have a system that would handle most peoples needs right off the self.
Amazon.com: Ampere Time 12V 200Ah Lithium Iron LiFePO4 Deep Cycle Battery,...