Birth of a new LiFePO4 DIY Battery

svsagres

Solar Enthusiast
Joined
Nov 14, 2021
Messages
191
Just thought I'd share my shiny new 460AHr, 2p4s LiFePO4 battery bank:

IMG_2289.jpg

Each pair of cells is paralleled using the bus bars that shipped with the cells, and each cell pair is chained to the next with two 2AWG jumpers. In turn, the class T fuse connects to the bank with equal length parallel wires, as will the BMS shunt.

Cells are in light compression, plywood battery box is fiberglassed into the hull. Battery is tied down by 3 webbing straps, plus the end fixtures are connected to the box. Picture was taken while setting up a REC ABMS, most of the time a plexiglass cover will be screwed down on top. The batteries themselves are sitting on plastic pool deck tile to allow any moisture that gets into the box to drain out the bottom.

Being a small boat (27' sailboat), it's a pain in the ass working on anything, but it's definitely going to be nice when it's all said and done.
 

svsagres

Solar Enthusiast
Joined
Nov 14, 2021
Messages
191
F7311457-8B3F-40EA-93C5-2EF17ED27533.jpeg

Thought I would share an updated photo now that all the high current wiring is complete.

Next up is the AC wiring (inverter chargers is just out of the picture) and control system. Probably a day’s work, but unfortunately I’m off on a business trip for a week.
 

Horsefly

Photon Sorcerer
Joined
Dec 12, 2020
Messages
1,497
Location
Denver, mostly
Don't you love that Victron Lynx Distributor? I'd never heard of it, but when I helped someone put together a LFP upgrade for his sailboat I realized just how great the Lynx Distributor is as a distribution bus bar.

I've got lots of respect for anyone taking on doing this stuff in a sailboat. No room to work. Good job.
 

svsagres

Solar Enthusiast
Joined
Nov 14, 2021
Messages
191
Don't you love that Victron Lynx Distributor? I'd never heard of it, but when I helped someone put together a LFP upgrade for his sailboat I realized just how great the Lynx Distributor is as a distribution bus bar.

I've got lots of respect for anyone taking on doing this stuff in a sailboat. No room to work. Good job.
Yeah. When I was planning this, I started adding up all the bits and bobs to do the same thing (300+A for both + and - plus fuse holders) and the Lynx quickly showed itself as the cheaper option.

The one thing I wish I could do is hook the fuse monitoring to my Cerbo, but I’m not using the Lynx BMS so no joy there.
 

Horsefly

Photon Sorcerer
Joined
Dec 12, 2020
Messages
1,497
Location
Denver, mostly
Yeah. When I was planning this, I started adding up all the bits and bobs to do the same thing (300+A for both + and - plus fuse holders) and the Lynx quickly showed itself as the cheaper option.

The one thing I wish I could do is hook the fuse monitoring to my Cerbo, but I’m not using the Lynx BMS so no joy there.
Not sure if it helps you, but there is a hack to make the LED's on the distributor show the status of the fuses. Otherwise, you have to take the cover off the distributor, remove the fuse, and check it with a multimeter. The LEDs normally require the Lynx Shunt or the Lynx BMS. The hack is pretty easy. I did it for my friend, and it works great. Here's the video explaining how to do it:
 

geolboy

New Member
Joined
Feb 24, 2021
Messages
29
View attachment 92385

Thought I would share an updated photo now that all the high current wiring is complete.

Next up is the AC wiring (inverter chargers is just out of the picture) and control system. Probably a day’s work, but unfortunately I’m off on a business trip for a week.
Hey @svsagres, how did you identify the Neg site of the shunt that mounted next to the battery? I have the same one and still trying to figure it out. Thanks!
 

svsagres

Solar Enthusiast
Joined
Nov 14, 2021
Messages
191
Hey @svsagres, how did you identify the Neg site of the shunt that mounted next to the battery? I have the same one and still trying to figure it out. Thanks!
I actually got it wrong initially. I was monitoring my BMS, and the values were all wonky (showing charging when it wasn’t, and so forth) so I flipped the sense lines from the BMS and all was well with the world. A closer examination of the BMS manual actually showed it had a good proper diagram.

Shunts themselves are bidirectional. What mattered was the connection to the sense wires.
 

geolboy

New Member
Joined
Feb 24, 2021
Messages
29
I actually got it wrong initially. I was monitoring my BMS, and the values were all wonky (showing charging when it wasn’t, and so forth) so I flipped the sense lines from the BMS and all was well with the world. A closer examination of the BMS manual actually showed it had a good proper diagram.

Shunts themselves are bidirectional. What mattered was the connection to the sense wires.
"Shunts themselves are bidirectional" - are you sure? Looking at bunch of youtube videos, those are usually mark with directions in vendor's installs - Barium, Victron.. In fact Batrium specifically talks about it and their software feature that allows to revers the flow reading if physically connected in reverse. Its here
5:30-6:00 segment. The shunt is looking exactly as ours. Sorry, just confirming, since I know little about shunts. In any case theirs and yours shunt position is identical, so I guess I have my answer and I'll do the same way.
Thanks again.
 
Last edited:

svsagres

Solar Enthusiast
Joined
Nov 14, 2021
Messages
191
"Shunts themselves are bidirectional" - are you sure? Looking at bunch of youtube videos, those are usually mark with directions in vendor's installs - Barium, Victron.. In fact Batrium specifically talks about it and their software feature that allows to revers the flow reading if physically connected in reverse. Its here
5:30-6:00 segment. The shunt is looking exactly as ours. Sorry, just confirming, since I know little about shunts.
Thanks again.
So both the Victron shunt and the Baterium shunts are different beasts as they have electronics permanently attached to the shunt itself. These do have a direction, but that is imposed by the attached monitoring electronics rather than the shunt resistor itself. The shunt mounted on my battery box is just a plain old naked shunt resistor. The monitoring is done by electronics embedded in the BMS, just to the right of it.

I just realized that you might be talking about the victron shunt on the left of the picture instead (there are two shunts in the picture). In that case it was from carefully reading the documentation and a bit of a lucky guess. In my case, I’m just using the Victron shunt as a DC Energy Meter rather than a batter monitoring shunt.
 

Horsefly

Photon Sorcerer
Joined
Dec 12, 2020
Messages
1,497
Location
Denver, mostly
A shunt is a piece of metal that current passes through, with connections to measure the voltage across the shunt, which infers the amount of current through the shunt. So with that simple definition, yes a shunt can be hooked up in either direction relative to the current flow through a battery system.

However, almost none of the devices discussed on this forum are just shunts. They are to one degree or another a "smart" shunt that processes the small voltage measurements into something more useful. Once all that stuff is hanging off a shunt, it probably has to be hooked up in the correct direction for the data to be meaningful.
 
Top