12V 280Ah LiFePo4 battery Build and Test
- Thread starter Haugen
- Start date
That's interesting. So what happens if you charge all the way to 14.6 volts after the cells are caught up. Are they balanced?
Circling back to the QR codes / serial numbers.
Anyone find a way to decipher any of this?
Particularly of interest:
1. Production date code (code 2, position 1-3)
2. Specification code (code 1, position 6-7)
3. Tracking code (code 1, position 8-14)
I have these same cells ordered from Alibaba ,I think some people will be shocked what i paid for them ,I hunt and hunted for the best price ,I got 4- 3.2 280 amp cells with shipping included i paid 440.00 .If anyone interested i can give you the link ,You will not find a better price ,I got my cells they were in perfect shape and all was well balanced all read 3.25 volts .I have 8 cells 3,2 280 amp ,I was going to do a solar setup with them on some land .Mom got sick she came to live with me so now i am making 2 -12 volt 280 amp mobile power stations using these cell for each 12 volt 280 amps with solar hookup ,charging power A.C. source i have a blue tooth best BMS out there right now i can monitor my cells via my kindle fire and the temp sensors work great as well .I am also hooking up USB ,Type C ,a MPPT Controller for solar charging also A.C. power charging for a hellva lot less then solar generators anywhere with 4 times the power of any that i have seen ,I figure cost me around between 700.00 and 800.00 dollars to build ,Anyone wants the link email me here bobbytriplett643@msn.com and in the subject line in CAPS for Lifepo4 cells so i do not over look you .
Cells charged back up with no issues. Full 280Ah. I haven't been able to take time to compile the data. It took about 4 days with the pathetic charge current.
The balance was acceptable at less than 100mV between high and low. Leaving then on charge balanced them back to within a couple mV.
The balance was acceptable at less than 100mV between high and low. Leaving then on charge balanced them back to within a couple mV.
curiouscarbon
Science Penguin
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Thanks for the update. Glad the cells settled to close voltage range ? Good job
Ampster
Renewable Energy Hobbyist
The good news about a slow low Amp charge is that if there is any need for the BMS to shunt some cells as they approach the knee of the curve there is time for the BMS to do its thing. The last charger I purchased for my EV conversion had the ability to program 4 different charge profiles. One of the ones I used was a slow low Amp charge to let the BMS balance the cells. I think Tesla does that when you charge at home at a slow rate. Certainly that does not happen when I get a quick charge at a Supercharger.
Thanks for the update. Glad it is working out for you.
Bob B
Emperor Of Solar
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That's how I balanced my 380 AH pack with a Chargery BMS. I crept up on full charge after reaching the start of the knee and let the BMS balance.
Tesla's management system measures cell imbalance at top of charge, calculates the excess energy in the cell, and tasks a bleeder circuit with burning the determined amount off of that cell over time during quiet periods.
It still requires the cells to go into the upper knee to make the determination, but the (perhaps substantial) time required to bleed the energy is independent of the time spent charging at high SOC.
Ampster
Renewable Energy Hobbyist
Some Tesla owners have reported small increases in range after what they describe as a balancing charge. I regard that as anectdotal but your description helps in understanding how it works. The part I don't know is what is defined as quiet time. I am sure it does not include going down the Interstate at 80 MPH after fully charging at a Supercharger.
At the top of charge, when the computer can see the imbalance most clearly, it calculates an amount of energy to bleed off for the cell. The bleeder is just a small, fixed resistance, so the energy burn goal can be turned into a time goal. The time goal is latched into a bleed controller on the cell. I actually can't come up with a reason why the bleeders couldn't run continuously once latched, but apparently they prefer to do it when the pack is at rest.
I'm sure the bleed power vastly exceeds the rate at which a healthy cell can come out of balance, so it probably doesn't matter too much. The amount of re-balancing is likely small relative to the balance capacity.
As for range increase, it is hard to say, but I know that the range estimators (not the actual range, mind you) were pretty prone to getting skewed if the pack stayed in partial SOC for long periods. At least, that's how it was on my Roadster. Presumably they have the same energy-counting error accumulation that we all do; Tesla doesn't have a way to defy the physics. Yet.
I'm sure the bleed power vastly exceeds the rate at which a healthy cell can come out of balance, so it probably doesn't matter too much. The amount of re-balancing is likely small relative to the balance capacity.
As for range increase, it is hard to say, but I know that the range estimators (not the actual range, mind you) were pretty prone to getting skewed if the pack stayed in partial SOC for long periods. At least, that's how it was on my Roadster. Presumably they have the same energy-counting error accumulation that we all do; Tesla doesn't have a way to defy the physics. Yet.
Ampster
Renewable Energy Hobbyist
LOL
But I do appreciate from what I have heard from a few Engineers at SpaceX and Tesla. They have told me when problem solving Elon insists on a clear understanding of the limits of physics and a very thorough understanding of the technology that allows them to overcome any limitations that physics may impose.
ArthurEld
Solar Wizard
Elon will probably become the most powerful human. He's got self driving electric cars, spaceships, solar panels, tunnel machine, his own satellite internet, hyperloop. and batteries. I'm sure there's more. He created PayPal too.
Ampster
Renewable Energy Hobbyist
I hope it doesn't go to his head. I also wish he would focus on a few of the great things he is working on. So far, he does seem to be able to multitask pretty well. I have not complaints with the value of the vehicles I have purchased from them and the constant over the air upgrades that I receive.
curiouscarbon
Science Penguin
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Elon Musk's Tesla Inc was founded by others and he was credited as co-founder through a lawsuit settlement
Martin Eberhard and Marc Tarpenning originally started the company in 2003 after Eberhard came up with the idea for electric vehicles
meaww.com
Hi Haugen,
Thank you for sharing all your work. Much appriciated for us new onces.
I also have orderd 280 cells for a 4S Unit. Do you mind sharing the BMS details you ended up using? I am very much in doubt of what BMS to buy?
Thank you for all your efforts.
Thank you for sharing all your work. Much appriciated for us new onces.
I also have orderd 280 cells for a 4S Unit. Do you mind sharing the BMS details you ended up using? I am very much in doubt of what BMS to buy?
Thank you for all your efforts.
@RunSim, I am using the SmartBMS from AliExpress.
US $7.47 13%OFF | smart BMS 4S 12V 60A 80A 100A 120A Li-ion LifePo4 Lithium Protection Board W balance High Current Bluetooth APP PC software GPRS
7.73US $ 10% OFF|smart BMS 4S 12V 60A 80A 100A 120A Li ion LifePo4 Lithium Protection Board W balance High Current Bluetooth APP PC software GPRS|Battery Accessories| - AliExpress
Smarter Shopping, Better Living! Aliexpress.com
a.aliexpress.com
My next project is a 16S of the 280Ah cells for backup power to my home. It will be installed with my SolArk and PV panels.
Going with the Heltec BMS for that one. I wanted the active balancing, so I spent a little more.
Ampster
Renewable Energy Hobbyist
That article doesn't mention JB Straubel who made the introduction to Musk. He is listed as a co founder. It is common for founders to not suvive several rounds of venture funding.Elon Musk's Tesla Inc was founded by others and he was credited as co-founder through a lawsuit settlement
Martin Eberhard and Marc Tarpenning originally started the company in 2003 after Eberhard came up with the idea for electric vehicles
Colonel.lp
New Member
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- Jun 8, 2020
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- 135
So, I have my 4 cells on the way from xuba. They sent the usual video measuring the voltage and IR. All the voltages are very close, within 3mv, but three cells have an IR of 12m.ohms and one is 14m.ohm. should this be cause for concern?
No, plus IR varies with soc.
Haugen. thank you for posting all this information on your experiences. I finally came back to read the rest of the thread. I have thoughts on corrosion. Copper oxide is conductive, aluminum oxide is insulator. Tin plating on copper will help prevent galvanic activity between aluminum and the copper. Of course it will do nothing to prevent oxidation of the aluminum.
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