LiFePO4 Battery Build

First order of business is to make sure the BMS are correct and workable as I ordered what I believe to be the OEM version of the Overkill Solar/Radio B BMS. These were JBD 4s 200A version that were about $100 each delivered.

Connected up, and The Bluetooth connected right up to my iPad. I can’t get the Android version to work.

Next up, input all the correct parameters and download to the BMS, and then I need build a fixture to hold all 8 and top balance..

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I will compress for the initial top balance. All cells came in @3.295 (6) and 3.296 (2)

I have to tighten up a little and measure the 4 corners. One of the issues is how to measure “compression”. There is a specification, but not easy to tell how much is “enough”:).

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dtfeld said:
I will compress for the initial top balance. All cells came in @3.295 (6) and 3.296 (2)

I have to tighten up a little and measure the 4 corners. One of the issues is how to measure “compression”. There is a specification, but not easy to tell how much is “enough”:).

View attachment 114604
Click to expand...
Looks great so far! Are there spacers between the cells in that pic? I'll be adding some on my build, I think it's especially important in a dynamic marine environment to prevent chafing through the OEM cell cases.

One note - I always kind of cringe when I see bare wrenches hanging around these batteries, one slip of the wrench across the posts and BOOM. I've seen a lot of folks wrap them in electrical tape to insulate them in case of a fumble.
 
GnrlPatton said:
Looks great so far! Are there spacers between the cells in that pic? I'll be adding some on my build, I think it's especially important in a dynamic marine environment to prevent chafing through the OEM cell cases.

One note - I always kind of cringe when I see bare wrenches hanging around these batteries, one slip of the wrench across the posts and BOOM. I've seen a lot of folks wrap them in electrical tape to insulate them in case of a fumble.
Click to expand...

Great point! I have a set of wrenches wrapped in tape for working "in the box", or in or on top of the cells...this was an addition for tightening the threaded rods and they hang out abou 12" on either side, so a dropped tool is captive.

I also remove wedding band and watch while doing this...

There isn't any spacer in this at this point. Probably should consider it...

For the actual build, insulation is a must and also making sure no stress riser/pressure points to punch through the case or any other component.

Just getting some of the major components on hand and start making some decisions on how this goes together as space is limited.

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dtfeld said:
I will compress for the initial top balance. All cells came in @3.295 (6) and 3.296 (2)

I have to tighten up a little and measure the 4 corners. One of the issues is how to measure “compression”. There is a specification, but not easy to tell how much is “enough”:).

View attachment 114604
Click to expand...
I don't think tight at all; It's simply to keep the cells from changing shape which obviously can alter their lifecycle.
The cells can also deform under shock loading and vibration; ie boat in rough water.....
 
Top balance underway…estimate this will take about 2 days if uninterrupted. I’ll be keeping an eye on this while charging…

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Life expectancy stipulates a 300 Kgf fixture... I think a little compression will be fine. If I cycled 2 times a weekend every weekend of the year, lets call it 100 time a year, that's a 35 year life expectancy @ 25C, or about half that at 45C.

I'm expecting these to provide a lot of juice for a long long time, probably outlive my ownership.

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dtfeld said:
I have to tighten up a little and measure the 4 corners. One of the issues is how to measure “compression”. There is a specification, but not easy to tell how much is “enough”:).
Click to expand...
Seeing your progress has really gotten my juices flowing! As for the compression, if it's either a value in pounds/kilos of "crush", or purely a width measurement, it's be easy enough to figure based on the pitch of your all-thread.
On a side-note, I have an electric motorcycle on order. 80 mph top speed, 80 mile range. I figure it'd look good parked on my swim platform for use when we dock. https://sondorsx.com/pages/metacycle
iu
 
If you buy one of these power supply’s, expect to upgrade the charge leads, the included are pretty wimpy. I used some 10ga wire and I doubled my output.

Still gonna take a while…

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Nater Potater said:
Seeing your progress has really gotten my juices flowing! As for the compression, if it's either a value in pounds/kilos of "crush", or purely a width measurement, it's be easy enough to figure based on the pitch of your all-thread.
On a side-note, I have an electric motorcycle on order. 80 mph top speed, 80 mile range. I figure it'd look good parked on my swim platform for use when we dock. https://sondorsx.com/pages/metacycle
iu
Click to expand...
Very cool!
 
Nater Potater said:
Seeing your progress has really gotten my juices flowing! As for the compression, if it's either a value in pounds/kilos of "crush", or purely a width measurement, it's be easy enough to figure based on the pitch of your all-thread.
On a side-note, I have an electric motorcycle on order. 80 mph top speed, 80 mile range. I figure it'd look good parked on my swim platform for use when we dock. https://sondorsx.com/pages/metacycle
iu
Click to expand...
Wow! That bike is so cool Nater! You have to post a pic of that on the platform! How much does that weigh? Sharp looking bike man.
 
Christo said:
Wow! That bike is so cool Nater! You have to post a pic of that on the platform! How much does that weigh? Sharp looking bike man.
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Okay, real quick so we don't derail this thread: 200 pounds, can carry up to 400 pounds, isn't scheduled for delivery until sometime in March. Fat chance, I'm thinking... Okay, back to the battery thread.
 
dtfeld said:
Top balance underway…estimate this will take about 2 days if uninterrupted. I’ll be keeping an eye on this while charging…

View attachment 114614
Click to expand...
Dave - not to be critical but to top balance (and to actually connect the leads on the boat) it is important to have one power supply lead on one end of one buss bar and the other lead on the opposite end of the other buss bar. That way all of the batteries are seeing the same voltage/current and the balancing is equal. In the setup you are showing the first battery in the stack will be overcharged before the last gets topped. The measurement connection in the middle of the pack is correct.
 
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To further that thought - for example, in high energy setups like what I'm doing the battery bank is connected in parallel using large buss bars on the positive and negative terminals then at both ends of each buss bar, equal length cables (4/0 in my case) route to master buss bars (one positive and one negative through a shunt). All of the loads and charging are managed through the master buss bars. The ensures all of the batteries are constantly equal in voltage which is ultra important in lithium battery life. Also, I sized my buss bars to support 1.5 X the demand/charge current.
 
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ttmott said:
Dave - not to be critical but to top balance (and to actually connect the leads on the boat) it is important to have one power supply lead on one end of one buss bar and the other lead on the opposite end of the other buss bar. That way all of the batteries are seeing the same voltage/current and the balancing is equal. In the setup you are showing the first battery in the stack will be overcharged before the last gets topped. The measurement connection in the middle of the pack is correct.
Click to expand...

Tom, Feel free to be critical. I spent a lot of time reading and planning this, but always room for improvement and other ideas ( and I’ve gotten good ideas and advice from you). And these ain’t cheap, and the price of failure high.

This is a good point. I have this setup as you described now that I have a proper set of charge cables. The cheap and cheesy ones shipped with the power supply were not long enough, or large enough wire.

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Since were talking critiquing and assembly ideas. Tom recommended Micarta or fiberglass sheets, but I have a roll of 1/16” neoprene rubber sheeting that I has going to use as separators/insulators, and also as a protector around corners and other stress/ pressure points. I’ve seen guys use all kinds of stuff, fiber paper, cutting boards…



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ttmott said:
To further that thought - for example, in high energy setups like what I'm doing the battery bank is connected in parallel using large buss bars on the positive and negative terminals then at both ends of each buss bar, equal length cables (4/0 in my case) route to master buss bars (one positive and one negative through a shunt). All of the loads and charging are managed through the master buss bars. The ensures all of the batteries are constantly equal in voltage which is ultra important in lithium battery life. Also, I sized my buss bars to support 1.5 X the demand/charge current.
Click to expand...

I looked at this. I actually purchased a Victron 24V inverter/charger with the intent of going with 1 large 8s 24V battery vs 2x12V with the current Magnum Energy. This make a lot of sense electrically on the DC for a 3000W inverter when it comes to current, cabling, ease of finding BMS, and as you point out cell maintenance.

However there are not a lot of good enclosures for a 8 cell, and while lighter, this cell would have approached 100 lbs.

The other deciding factor was the Magnum Energy transfer switch is capable of switching 2 30A legs, which may be something I want to use for a future upgrade. Being already installed, the cost just wasn't worth it in the end. And I REALLY wanted to go with Victron. They make really GREAT stuff.

Ah, the compromises we make...
 
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Same process in a dual setup like you are implementing. Build each battery (12V) in parallel like you are doing but use large buss bars to connect the cells. Then using a large cross section cable tie the two batteries in series. Then connect the load to the battery buss bars at the ends. The idea is to make the individual cells think they are one and when current is flowing it is equal across all of the cells and that is to essentially have zero impedance in the buss assembly. In this arrangement you will be relying more on the BMS to maintain cell balance. Regardless, however, you are right there is compromise...
 
Getting towards the end of the top balance. With only 10A @ 3.XX volts (about 35watts) it was going to take FOREVER as this is over 8000Wh (3.2V *304Ah/cell*8Cells)!!

I did 2 things to speed this process up. I reassembled the into 4s assembly with the BMS attached an RC battery charger capable of almost 400 watts to bulk charge. I then reassembled into parallel set up and ran both chargers at 3.65V with a total of about 100watts of output. Still took 2 days+.

RC Charger says its done, smaller power supply still pumping just a little bit more. I'll wait for the current to drop to 0 at 3.65V and let them sit over night and recheck the individual cells.

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