LiFePO4 DIY options

[tony.latham]

Dan from Freely Roaming...

I just watched his, Battery Upgrade Part 1 video.

There's a little man on my shoulder that just said, "I hope our AGM dies soon!" The little sh**.



Tony

[lfhoward]

The box is finished including the threaded rods.


It’s a very snug fit.


I’ll cut a vertical slot in the white plastic divider for the BMS’s temperature sensor.

[lfhoward]

Dan from Freely Roaming...

I just watched his, Battery Upgrade Part 1 video.

There's a little man on my shoulder that just said, "I hope our AGM dies soon!" The little sh**.



Tony

Dan has a great LiFePO4 series of videos actually. He is the one who inspired me to think this kind of battery was within reach.

I plan to Craigslist my lead acid deep cycles and the old lead acid chargers as soon as the new equipment is installed. You could take the plunge now!

[saltydawg]

Dan from Freely Roaming...

I just watched his, Battery Upgrade Part 1 video.

There's a little man on my shoulder that just said, "I hope our AGM dies soon!" The little sh**.



Tony

We are seeing a weakness in the force, its all going according to the plan.

[tony.latham]

We are seeing a weakness in the force, its all going according to the plan.

For sure.

Tony

[lfhoward]

Just an FYI:

Cutting and drilling copper bars makes them as hot as hades.
And since copper is such a good conductor, the other end gets super hot too.

Melted clamp, too close to drilling. Note burned wooden workbench.


One down.


The goal is to begin top balancing soon.

[Tom&Shelly]

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

Leads to an interesting thought: Many of us looked at homebuilt and kit teardrop designs from the 30's - 40's, but we wouldn't build one that way today (although we might capture the look) because safety is better understood and the materials today are better than what was available.

But, how much will things change in the future? Might someone in the 2060's (say) build a classic Latham teardrop using Tony's book? (Found among their grandfather's antique woodworking books, along with "How to use your jig saw," and "Draw knife techniques for the backwoods carpenter") I'll bet plywood will still be around (okay, at $500/sheet maybe), and one could essentially copy Tony's design. Can't imagine the propane design changing much--why would it?

But battery technology will be so different by then, anything written about it now would likely be totally out of date.

Tom

[lfhoward]

Battery bank assembled into an 8p, 3.28 volt 624 Ah pack for top balancing.


Top balancing commencing at 8:30 pm on 6/15/21. This is going to take a while.


It may take a week to go from 3.28 volts to 3.45 volts at 1.5 amps per hour. But, 3.45 volts should be a safe voltage that is on the flat part of the LiFePO4 voltage curve. After it reaches 0 amps transferring at 3.4 volts, it should only take an hour or two to make it to the target voltage of 3.65. At the 3.5+ volt stage I will have to be paying close attention so I can stop the charging when it gets to 3.65. The battery should hold 3.5+ volts for 30 minutes to an hour after being disconnected. If not, I can give it a little more juice and try again. I am following the top balancing directions here:
http://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank/
And here:
https://www.saildivefish.ca/lifepo4-batteries-part-four-top-balancing-pack/

[lfhoward]

The previous photo had the power supply set to 3.40 volts, but here is what it looks like at 3.45 volts:
(Note, disconnect the battery before adjusting the power supply setting, then hook it back up.)



Looks like we are getting 50% more amps, so it should take a little less time.

[bdosborn]

At the 3.5+ volt stage I will have to be paying close attention so I can stop the charging when it gets to 3.65.

You really have to watch it, once it's charged they spike up to 3.65V ( and over) in a minute or so.

Bruce

[lfhoward]

At the 3.5+ volt stage I will have to be paying close attention so I can stop the charging when it gets to 3.65.

You really have to watch it, once it's charged they spike up to 3.65V ( and over) in a minute or so.

Bruce

Thanks Bruce. I will watch it like a hawk at that point.

Is it safe to go to sleep with the power supply set to 3.45 volts constant voltage? I absolutely don’t want to ruin anything.

[bdosborn]

Yeah, that should be 60-75% charged or so.



Bruce

[lfhoward]

Yeah, that should be 60-75% charged or so.



Bruce

Thank you, that graph is helpful. Looks like the 3.28 volts I started at is below 10% capacity. Looks like I have about 80% capacity to fill (3.6 volts is at 90%). SO, 624 * 0.8 = 499.2 amp hours. Whoa. That will take 250 hours at the 2 amps the power supply is doing right now. A little over 10 days I estimate. Think it will really take until next Friday?

[tony.latham]

But, how much will things change in the future? Might someone in the 2060's (say) build a classic Latham teardrop using Tony's book?

Here's a curious fact about the book. They are done by what's called print on demand. When you order one, the printer pops one out. There is no inventory. In theory, it'll go on that way in the future as long as there's a demand.



Tony

[lfhoward]

After a night of charging at 3.45 volts (and about 2 amps), my pack is now up to 3.31 volts on my multimeter (from a starting voltage of 3.28 yesterday). I've found that the power supply I'm using drifts slightly even though it is set at constant voltage, but voltage only varies +/- 0.05 volts after a few hours. I'll keep an eye on it and make sure voltage stays within a healthy range.