LiFePO4 DIY options

[Tom&Shelly]

<snip> I think DIYing a lithium is still a bit over the top for most folks

Yeah, the learning curve is pretty steep and unless you like messing with electrical stuff, lead acid is the way to go for folks who just want to run some lights and a fan.

Bruce

That's the conclusion I came to when we started our build.

But these threads do look interesting. If I have time in a few years and my brain is sharp enough by then, I may take it on. (Does a brain get sharper after age 59?)

Until then, these are fun reading!

Tom

[tony.latham]

That's the conclusion I came to when we started our build.

In a sense, I didn't have a lotta choice. Remember, I was writing a book that didn't need: Chapter 24, Building the Lithium Battery

Tony

[lfhoward]

I’m glad you all are enjoying the thread!

I have always loved projects and challenges. I was the kid who could spend days building a Lego creation, and visualized it in my head for days before. I am enjoying being able to research and build a LiFePO4 battery bank, and document it along the way. Hopefully this thread will be a good resource for someone someday. (To that person: Please do your own research— I’m documenting what I did, not necessarily what you should do!)

Today I foraged for parts at the local home store. I got plywood for building the battery box, along with threaded rods, washers, and lock nuts. For the battery terminals themselves I found M8, 12 mm flange bolts. I also located and bought some ring terminals for the BMS balance leads. All of this was not too expensive, but then I ordered a Victron BMV212 battery monitor (with shunt & Bluetooth), a temperature sensor, and a 75/15 MPPT controller from Continuous Resources. That was a little pricey! But Continuous Resources has a 5% discount code which helped a little. PM me if you would like to know what it is. There are other items at Continuous Resources that I have my eye on and will probably get at some point, but what I got today will allow me to run a capacity test and recharge the batteries, which is what I need to do next after top balancing.

The 75/15 MPPT charge controller will eventually go in the trailer, but for now on my workbench it will double as a charger.



The way this will work is I have a bench DC power supply that I can set up to 30 volts and 10 amps. 25 volts x 8 amps = 200 watts, which is like a solar panel at noon and within the capacity of the MPPT controller. I thought about getting a plug in Victron charger, and may get one eventually for charging with shore power, but I know I’m going to need the MPPT charge controller more! I’ll report in on how well this works. The 200 watts of input power should convert to a 15 amp charge at about 13.3 volts to the battery, or something thereabouts.

[bdosborn]

I put my batteries together in two blocks, just so I could still lift them. Even though they don't have lead in them four larger LiFePO4 cells still weighs around 40#. I used some baltic birch plywood that was laying around the garage to put them in compression, with the current price of lumber I wish I'd used something cheaper! I'm top balancing eight 180 a-hr cells in this pic:

Bruce

[lfhoward]

<snip> I think DIYing a lithium is still a bit over the top for most folks

Yeah, the learning curve is pretty steep and unless you like messing with electrical stuff, lead acid is the way to go for folks who just want to run some lights and a fan.

Bruce

That's the conclusion I came to when we started our build.

But these threads do look interesting. If I have time in a few years and my brain is sharp enough by then, I may take it on. (Does a brain get sharper after age 59?)

Until then, these are fun reading!

Tom

Back in 2015 when I started my trailer project and designed the electrical system, I didn’t have the extra funds or the mental bandwidth (with the rest of the build to do) to attempt a lithium battery system. It looks like the prices have come down since then and there are more good options now for cells and BMS’s. There are definitely more resources out there on the internet in terms of people who have done it and documented their progress. I don’t have Tony’s book, but maybe I should!

[lfhoward]

I put my batteries together in two blocks, just so I could still lift them. Even though they don't have lead in them four larger LiFePO4 cells still weighs around 40#. I used some baltic birch plywood that was laying around the garage to put them in compression, with the current price of lumber I wish I'd used something cheaper! I'm top balancing eight 180 a-hr cells in this pic:

Bruce

Looks like a good plan for you to make 2 separate modules. How many Ah are those cells? They look much bigger than the ones I got. All 8 of mine together are about 40 lbs.

I won’t be able to parallel and top balance mine inside the box I’m making because of the battery arrangement. I’ll need to put all 8 cells in a row on the benchtop for that. But starting with the first capacity test discharge, they will be compressed inside the box.

[saltydawg]

Maybe we ( the guys that know lifepo4 ) should write up a diy trailer diy lifepo4 battery how to post. To include things like temp sensors and heating pads for cold weather charging.

My issue is I am building a camper for a friend, who is not going to want to worry about cold weather issues with lifepo4 batteries. But I like them and for the cost of a diy battery, including a thermostat and heating pads I get more out of it than I can with agm for the same cost. Sure i could go fla, but then you have things like need to check the water level. I can get the 78 ah cells for the 165, plus a bms for 50, a thermostat for 20, heating pads for 20 and be cheaper than the 100ah agm that tony uses. And Have more usable power.

[bdosborn]

They look much bigger than the ones I got.

Yeah, I hear that all the time. They are 180 a-hr CALB cells.

Bruce

[lfhoward]

They look much bigger than the ones I got.

Yeah, I hear that all the time. They are 180 a-hr CALB cells.

Bruce

[lfhoward]

Maybe we ( the guys that know lifepo4 ) should write up a diy trailer diy lifepo4 battery how to post. To include things like temp sensors and heating pads for cold weather charging.

My issue is I am building a camper for a friend, who is not going to want to worry about cold weather issues with lifepo4 batteries. But I like them and for the cost of a diy battery, including a thermostat and heating pads I get more out of it than I can with agm for the same cost. Sure i could go fla, but then you have things like need to check the water level. I can get the 78 ah cells for the 165, plus a bms for 50, a thermostat for 20, heating pads for 20 and be cheaper than the 100ah agm that tony uses. And Have more usable power.

I like that idea. It would be helpful to have something like that. For instance, I am designing my battery box to have the beehive heaters. I was wondering, do I need an air gap beneath the cells, and above the heaters? What kind of “floor” would be good to use above the heaters and below the batteries? I was thinking a piece of aluminum because it would conduct/spread the heat around the bank more evenly, but then I thought not aluminum because it could lead to a short if the blue wrap on the batteries gets worn through by vibration. The cases under that wrap are continuous with +.

I made some 1/8” ABS plastic dividers for the parallel blocks of batteries.

[saltydawg]

I like that idea. It would be helpful to have something like that. For instance, I am designing my battery box to have the beehive heaters. I was wondering, do I need an air gap beneath the cells, and above the heaters? What kind of “floor” would be good to use above the heaters and below the batteries? I was thinking a piece of aluminum because it would conduct/spread the heat around the bank more evenly, but then I thought not aluminum because it could lead to a short if the blue wrap on the batteries gets worn through by vibration. The cases under that wrap are continuous with +.

I made some 1/8” ABS plastic dividers for the parallel blocks of batteries.

In an ideal world the al plate under the battery is a great idea, but as soon as you put in anything like a plastic spacer, your now blocking the heat. As for air gaps, i dont think they are needed. Personally I would do a layer of foam, the heater, then the batteries. But make sure the heater is as close as possible to the size of the batteries.

Maybe an ideal would be a piece of al with the heaters taped to it, the a thin layer of plastidip. But you should still surround the batteries with foam, dont let them lose the heat your giving them.

[lfhoward]

I just went back and rewatched the YouTube video where Dan from Freely Roaming puts the heater pads in his LiFePO4 box and I really like his solution. On the wood floor he placed silicone trivet pads to insulate the bottom of the box. Next came the beehive heaters, then an aluminum sheet. The aluminum sheet was wrapped in Kapton tape to make it non conductive of electricity but still allow it to disperse heat to the batteries above. The heater sandwich at the bottom was probably only about 1/4 to 3/8”tall. In addition, the floor my battery box will be sitting on and the compartment it will live in are both insulated.

For the lithium folks following this thread, has anyone ever had issues with excessive heat in the battery compartment that made a thermostatically controlled case fan a necessity? The thermostat I’m looking at has two relays, one for cold and one for hot. I live in the mid Atlantic for frame of reference. That’s plant hardiness zone 7 in case anyone is into botany.

[saltydawg]

I dont have a thermostat controlled fan, but I do have a 120 volt case fan hooked up to the transfer switch. If the inverter or the shore power is plugged in the fan is on. The idea is to vent the heat from the shore charger or the inverter. Not the battery.

[lfhoward]

Battery box constructed.

[lfhoward]

The box will fit where the bulky silver battery charger currently sits.



The tongue box that contains 3 lead acids will be converted to storage.