Build a 12.8V 150Wh LiFePO4 Battery 4S2P

[@KuntalGhosh]

I bought 16 of them for 30$ because they were 4 year old cells made in 2017 and i bought them in 2021. I am using them on my ups and regularly test them they are holding full watt hour rated capacity. I am tracking the full cycles and run time every day to see how long these cells last and if they are any better than the leadacids i use for ups. These cells were cheaper than new lead acid in watt hour capacity. And they run longer than leadacid due to no pukert effect.

[@followthetrawler]

This gave me a great idea for building my own battery pack for astrophotography. The commercial power banks/tanks are so expensive, and perversely offer much more than I need in connectivity terms. Just a simple car lighter socket is fine. Looking forward to seeing how you build this out with balancers and chargers,

[@6kill6god68]

buying one of those batteries is my half month salary ... its nice to see you putting them together because i cant buy those kind of batteries ..

[@JulianIlett]

Really? The cells cost me £4 each, so eight cells is £32.

[@6kill6god68]

Yes the batteries are cheap but I live in south America and shipping alone to here is about srd 1500 to srd 2000 ..yes "srd" is my currency.. and I work about srd 4500 a month .. so yeah buying just one battery is already close to half my salary .. 😔 I have to stick to 18650 and lead acid batteries for now .. thanks for the video though 😁

[@mr.makeit4037]

I guess living in the US and UK, we don't realize the expense involved for electronics in other countries.

[@roidroid]

5:55 Venting is NOT SUS? Things have changed since the 2018 game _"Among Us"._ What a time to be alive. (Don't worry boomers i gotchu, consume thine above referenced material & thusly stay under the radar of later generations and their hunger)

[@-Graham]

1oz copper plane seems very thin for 10A let alone 20A. I know those boards are convenient but they seem vastly under spec for those discharge ratings. I would certainly be wanting something a lot beefier, especially as the bottom voltage seems to be around the 2v level for LiFePO4 cells.

[@JulianIlett]

There's a copper plane on both sides of the PCB, so I guess it's 2oz total. These PCBs are on my 8S4P pack which has been charged and discharged hundreds of times at about 10A.

[@-Graham]

@@JulianIlett I'm sure they work fine, but I have no doubt they do heat up a fair bit. It would be interesting to measure the resistance and see/calculate the voltage drop across one at 10/20A. I hate leaving extra capacity on the table. I am currently building a custom scooter from and old hoverboard and trying to use both 350w motors so I have been doing extensive testing of 37v lithium packs the last few weeks.

[@jameshancock]

@Jehugarcia does some great stuff with PCB bridging of batteries. You might want to take a look. 1000A on headway cells.

[@henniebecker2412]

Disappointing...!!! No mention of a Battery Management System that would be an essential part of such a system...??

[@hi-tech-guy-1823]

I would of added a Dubble Screw Terminal block to the PCB For the BMS & Bi Cell Equaliser "Suyep Screw Terminal Block Connector KF301-2P Blue Copper " or 3 ~ 4 Thermals so you can still poke a Multimeter Probes around

[@jamhough22]

I much prefer LiFePO4 chemistry, soo much safer than Li-on, and you can charge & discharge much harder too. There really isn’t much energy at the top and bottom of the curve, so i suggest cut-off voltages of about 2.9/3v and 3.5-3.55v. That should also extend the lifespan of the cells too.

[@JulianIlett]

On my 8S battery, I'm charging to 28V (3.5V per cell) and discharging to 23V (2.875V per cell). As you say, this is to minimise cell degradation.

[@himselfe]

Surprisingly affordable too for the capacity you get. Might have to get myself some of these!

[@brianhoskins1979]

I'm interested in such custom battery packs, but I am worried about safety. I know that you said these particular cells do not tend to catch fire, but I'd still be worried about it. With the setup you've got there, how do you intend to monitor them for problems such as one cell going bad and then that set of series cells getting continously charged from the other set of cells? Or do you not see this as a big concern?

[@RandomNoob]

Lithiun-Iron-Phosphate cells of any size are incerdibly difficult to get to burn, even if you drive a nail through them you will get a lot of smoke and a hot spot but very unlikely a flame. Even if you short them out they will generally just get hot and vent.

[@brianhoskins1979]

@@RandomNoob I might just have to try that to put my mind at rest. I have a project going on, which needs to use Lithium cells, and will go into the homes of friends and family. I can't have any possibility that they catch fire. So if this particular technology of lithium cells is safe, that is definitely a good thing.

[@RandomNoob]

@@brianhoskins1979 You can get them to burn but it takes some serious damage to the cells to start it unlike lithium-ion that will burn from minor damage or abuse.

[@ai6mk897]

I've used similar 6Ah cells in a 4s/1p configuration to power my satellite ground station using a small (100W) solar panel. I did lose 2 of the cells but after using an active balancer, the cells have been behaving perfectly. The balance across all cells is quite remarkable at 1-2mV using a Heltec capacitance based balancer.

[@JulianIlett]

Yes, I've found the active capacitor balancers work very well.

[@chenli3644]

14 minutes are too much time to show the required content

[@timhull8664]

Seem a bit big for only 6ah

[@MasterIvo]

Hi Jullian, I am amazed by how few active (series) capacitor balancers are on the market. Do you know how they are officially called, so I could better find them? Thanks!

[@JulianIlett]

Try these three links: www.aliexpress.com/item/1005005050192601.html www.aliexpress.com/item/1005005244785767.html www.aliexpress.com/item/1005005241453498.html

[@JulianIlett]

I just use the search term "active balancer"

[@MasterIvo]

​@@JulianIlett Thanks, but... I think I wasn't clear enough. Im looking to balance series super capacitors. so... not batteries. but to protect my super capacitors (skeleton)

[@JulianIlett]

Ah I see. I've only seen the passive top-balancing circuits (protection circuits really) that are fitted to the supercapacitor PCBs. I've not seen anything with BMS functionality for supercapacitors.

[@MasterIvo]

@@JulianIlett Isn't that weird? Maybe I would have to adjust an active BMS, for the right voltages... or... design one myself, using coils instead of caps to balance them.

[@abzaman77]

Do you have the PCB files for public usage?

[@101rotarypower]

Julian, is here a BMS that would operate in a “automotive like environment” for power sports vehicles, lawn tractors etc? Something that can tolerate variable alternator output to charge the cells back on the charge circuit, allow starter motor currents and both LVC/HVC? Really want to find a board that can do that and is affordable if possible!

[@JulianIlett]

You just need to check the cell data sheets for maximum charge current, maximum discharge current, low temperature limits, high temperature limits. Also, the cells must not be discharged below their minimum discharge voltage or charged beyond the maximum charge voltage.

[@magnets1000]

what are you going to use to charge it?

[@JulianIlett]

A 60- cell solar panel

[@leungyikwai]

is it suitable to use it as a car battery?

[@JulianIlett]

Not directly. The starter motor pulls a very large current which may exceed the cells discharge rating. Also, you'd need a BMS to prevent overcharge and overdischarge. Some sort of cell balancing is also needed.

[@321tryagain]

Charge management needs to be done very carefully below 0*C to prevent damage.