12V 280Ah LiFePo4 battery Build and Test

[Haugen]

Just to add from the back page about dissimilar metal corrosion. I usually use this chart or another I can't find right now to see if I am going to have a problem. I've seen some of this corrosion happen so fast that I always check now.

View attachment 18685

That's a pretty good noble metal chart. Usually of you are within one step in the table, there is not a lot of risk.
The reason I harp on it is because aluminum and copper are so far separated on the table and the lithium batteries have such a long life cycle. It's a perfect recipe for neglected terminals to slowly corrode if not maintained.
I know that I get complacent sometimes, so I'm building mine to be free of corrosion long term. Aluminum bolts, and oversized aluminum bus bars on aluminum terminals with lubricant. The transition to copper will be the lugs going to the BMS and battery.
Easy to spot degradation there.

 

[Pi3.14]

Just got this message about Daly 250ah smart Bms, I didn't think parameters where adjustable for 4s, but he affirmed it has been changed and now can be adjustable for 5s and below,

 

[Haugen]

Just got this message about Daly 250ah smart Bms, I didn't think parameters where adjustable for 4s, but he affirmed it has been changed and now can be adjustable for 5s and below, View attachment 18709

I only bought the 120A version because I wanted margin above my intended use. If the draw on my camper battery is more than 50A, it will be a really bad day. Just LED lights, fan, charge phone, and 12V fridge. Maybe play some music on the radio, but the purpose is for hunting trips to get away from it all.

 

[Haugen]

Back on topic, I hooked up the BMS last night and it came on and the Bluetooth module connected right up. The app I got from the Play Store was the same as from the seller.

I found a newer version of the app on a different thread in the forum that works better and has more options.

I'll go find the link and post it here.
I tried several other apps in the Play Store, but none of them would connect.

 

[Haugen]

Go to post 18 of this thread for the link.
Great information about the BMS there

Finally found a LiFePO4 BMS with Low-temp Charging Protection

Spent the last few days and tonight testing BMS: 1. The "new" daly LiFePO4 BMS (that states in the data sheet that it has low temp charging protection) does not have low temp charging protection. And yes, it has a temp sensor attached. This disappointed me big time. Video to come. 2. Next, I...

diysolarforum.com

 

[childcarepro]

Just ordered an 8-pack of those 280Ah cells; very excited. Should be here sometime "before September 1," supposedly.

Keep us posted on your progress!

 

[Haugen]

First discharge of the battery using the BMS.
I'm using an old 1500W inverter running a ceramic heater. On low, it draws about 45A and on high, it will peak around 90A.
I ran it around 3 hours (mostly on low because I didn't want to stand watching it baking in the test room)
It's just a preliminary rig to prove that it is working and will handle my real life loads.
Next step is to combine the 3 cables on either side of the BMS into one each way and crimp on the big lug. (crimper arrives Friday) also cut the bus bars to size and shape to replace the cheapo ones that came with the cells.
Stay tuned!

 

[Haugen]

Decided to stay up later and see if I can get past the knee while I work to get my datalogger to talk to my computer.
Software is being difficult and it's always a pain to get the serial port talking to the device.
Windows decided it needs an update, so watching the voltage slowly sink as it reboots.
Everything staying balanced as we sink towards 12V.

 

[Haugen]

Got it to shut down for under voltage!
That works!
Reconfiguring for charging.
Only 10A is going to take all night and most of tomorrow

 

[Haugen]

Used some screenshots with and without the load on to do the math for internal resistance.
Voltage drop with a 71A load was only about 40-50mV. That's about 5mOhms.

 

[Haugen]

Great progress today! Things are finally coming together. I got home from work and, as expected, the battery was still charging. Was at 67%.
Getting the laptop to see the datalogger has been a struggle. I finally just ran every installer I could find on the disk then started running all the apps. The device finally showed up and within minutes, I configured the Voltage, current, and temperature and lit off a scan. I noticed that I had my sense leads to the shunt backward, so I stopped, reversed them and set up some scaling so that it displays the current accurately when reading across the 0.5mOhm shunt.
Charge is almost done.
This weekend I'll rework the BMS wires and post some pics.
After adding voltage monitoring wires to each cell, hopefully I can discharge and recharge before the hurricane gets here.

 

[Haugen]

Alright, I took the BMS off the system to work on the wires. It really bothers me to have 3 separate wires to carry the current into and out of the BMS. Thus far, I was using just one wire and was able to pull 40A constantly and the wire was just warm.
I got into a little debate with someone on another thread about this. He insisted that when you change the gage of the wire you should always have a fuse. He insisted that each of the 6 lines should get a fuse because any one could fail and leave higher currents on the remaining wires. He's not wrong, but the fuses and fuse holders add so much complexity, cost, and failure opportunity that it's not really worth discussing.
Anyway, that's a long introduction to how I'm dealing with this issue. The rest I'll say with pictures.
Enjoy!

 

[Pi3.14]

the 6m screw terminal on 280ah battery is small, have you noticed the neg terminal screw gets real hot at 66amps, I wonder if the small terminal limits amp discharge amount as it gets real hot.

 

[Luthj]

Your ring terminals are stacked wrong. Highest current ones go on the bottom.

 

[Pi3.14]

Gotcha, the blue from BMS is on bottom, but the TR16(black on top). Also checking cell resistance. One of my cells seems to discharge faster. Got to 2.79 others were at 3.14 .3.22,3.22. Cleaned and switch 2 busbars (process of elimination). Charging up now and will balance and discharge again, hopefully didn't get a bad cell???

 

[Haugen]

What gage is the wire to your BMS?
What is the current rating for the BMS?
You shouldn't run it at max capacity for very long.

 

[Haugen]

What gage is the wire to your BMS?
What is the current rating for the BMS?
You shouldn't run it at max capacity for very long.

 

[Pi3.14]

6Awg bms, 150a daly, ran at 120a for about 10 secs, but normaly not above 66a i think for small 6m terminal screws. 3.31/3.32/3.23/3.32, right now resting so I'll balance and do a discharge at 44amp to check resistance on cell #3.

 

[Haugen]

6Awg bms, 150a daly, ran at 120a for about 10 secs, but normaly not above 66a i think for small 6m terminal screws

6AWG wire is only good for an absolute maximum of 101A. Anything over 50A will likely produce a temperature increase.
My 120A BMS has 3 10AWG Wires. That is an equivalent to 5AWG with 118A capacity, but I bought it knowing I would seldom exceed 60A. Anything more, I expect heat.

 

[Pi3.14]

Yep, I wont be pushing it past 66amps or 750 watts. The 6awg from BMS didn't get hot, but the TR16 -Bat cable and top -terminal did at 110amps, I had a hard bend in it, so changed to longer smoother curve and helped. Checking all wires for heat, looks much better, I have a Daly 250a smart BMS(configured at 2.7 and 3.7 disconnect, they say I can configure myself thru BT) coming so I'll prob be selling the 150a Daly separate, not sure how many amps the 6m terminal screws can handle. Checking resistance on #3 cell just to make sure they stay within .5v when discharging. Mines portable so its part of the craftsman versa modular rolling tool chest, got rubber cushion on bottom and sides to keep bat nice and cushy, bottom will hold inverter, 40A MPPT, cables, and other 180a Lipo, 460Ah is lotsa electrons.