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meh

joet12345 wrote: Fri Jun 04, 2021 11:55 pm

@joet12345 Excuse the rant but,

Lithium Ion cells are interesting beasts indeed with a supposed cut off top voltage of 4.2v and a low cut off voltage of 2.2v.

However notice in phones /laptops/cordless tools etc , they are not lasting.

Why ? Well reading a lot of scientific papers put out by uni students and profs there are many causes and different faults.

If you charge them to 4.2v they will not last long because the SEI layer (Solid Electrolyte Interface) clogs with ions ,reducing available ions in the system and they cannot be gotten back out. So...cut the charge earlier .4.1 if possible.

If you over discharge or overcharge then copper dendrites form and pierce the insulator .

The electrolyte has been found to be responsible for the formation of carbon based dendrites which again pierce the insulator..

A better cell from a safety aspect is LiFePo4. (LFP) These cells are top of 3.65v and low of 2.5v ,so you charge these to 3.4v only and discharge them no lower than 3v. Then they will last 10 TO 15 YEARS on a daily cycle basis. Well that's the theory anyhow.
I have boating friends who are into their 8th year now but most are on their second or third set of cells quoting charging mistakes and large discharges as the damaging factors.
One has the original set still going.

I have sets going for 4 years now ,with some problems caused by inappropriate lead acid chargers dropping into equalisation mode and pulsing the battery with over-voltage which then cuts the BMS off. in 10 seconds the BMS turns back on and the charger immediately tries again . End result is it stuffs the Mosfets and they short closed allowing passage of current . That allows the charger to push much too much current into the cells and they swell up with gases expanding.

Here is a page on FB to join and learn more about if you wish. https://www.facebook.com/groups/271980786862023/

When swollen for whatever reason they are NOT dead. Careful recharge and charge routines will see them recover and I have one cell that came to me at .6v and over a couple of years of gradual use its capacity and voltage have come back up to match its siblings.(I use two or 3 half second pulses of 30 volts with current as high as I can get to burn the dendrites )
If soft cells you can prick them with a pin at the top to release the gas but immediately seal them again with superglue or 704 or something that stops air getting in. The air oxidises the alloy tabs on alloy plates in 24 hours and that's the end of your cell.

More importantly for me , I run my farm basher on a LiFePo4 dropin . Its a Mitsubishi Pajero petrol and I just dropped it in ,put a battery cut off switch in , put a cheap round plastic voltmeter in the dash and its been going for 18 months without a problem . The BMS is 40 amp cut off max current . It wont start a diesel motor because the starter needs more current ,but petrol , no problem. Cost $410 delivered from Melbourne and 135 Ah .Steel case with screws so I can get in and look . Lead acid is dead for me . They want more than that for AGM's of N70Z size.

Li Ion cells...

Yes April, I can comfirm at candlepowerforums. They also recommend 4.1 max voltage, 3.2 minimum.
The Li-Fe-PO4 cells 3.50 to 2.9 Volts there.

The real problem is the batt. charger. Some go the Arduino route and program their own, most of the cheap stuff is NG.
I do find that celphone chargers in the phone are quite good. I have a Li-Ion batt in an older phone (3G 6YO) still going strong.

Regards
8Geee

The ebike (and other electric vehicles) forum run by http://ebikes.ca has a lot of battery info.

https://endless-sphere.com/forums/

A lot of them are making batteries from individual cells and getting (or making) programmable controllers and chargers running things up to small car in size.

An interesting piece of information dropped into my lap the other day .
I cant vouch for its veracity but it does fit the scenario I have watched over the past 4 years with Ali-express ,ebay etc.

There is supposed to be a law in place in China that prohibits the sale of LFP (LiFePo4) cells outside China.
This agrees with the practice I have seen of cells coming out of China are all second hand.
Even Ali-express will admit this if you push back at them on a purchase and an extra discount will be given.

Its a general opinion that the cells are firstly issued to the Military/Government then at a set useage time or capacity loss point they are refurbished and cleaned up and sold via small sellers on Ali and others. Those sellers tell you anything and pretend to be manufacturers but they are just padding up the site to fool you.

I don't know if Li Ion cells are the same . New can be sourced from Japan I think but the Chinese have some sort of patent on LFP that is protecting their market.
Its a bit late to be discovering this now as their patent is due to run out shortly but thats why electric car makers are having such difficulty with batteries.

April wrote: Sun Aug 08, 2021 2:11 am

An interesting piece of information dropped into my lap the other day .

Mind sharing the source?

April wrote: Sun Aug 08, 2021 2:11 am

I don't know if Li Ion cells are the same . New can be sourced from Japan I think

I was buying a 9-cells battery for my 17-inch Acer monster on Ali. The seller swore that the cells were Japanese and new, and that the battery itself was assembled in China. In terms of the time of discharge, it seems like the truth, but who knows. Although there is nowhere to go, only the Chinese are helping out. In my country, batteries are now made only for space satellites.

joet12345 wrote: Sun Aug 08, 2021 3:28 am

April wrote: Sun Aug 08, 2021 2:11 am

An interesting piece of information dropped into my lap the other day .

Mind sharing the source?

Yes go to https://www.facebook.com/groups/271980786862023/
and join then its in the recent posts . I'd post it more direct but I don't think it will work if you are not a member sorry.

April wrote: Mon Aug 09, 2021 12:04 pm

joet12345 wrote: Sun Aug 08, 2021 3:28 am

April wrote: Sun Aug 08, 2021 2:11 am

An interesting piece of information dropped into my lap the other day .

Mind sharing the source?

Yes go to https://www.facebook.com/groups/271980786862023/
and join then its in the recent posts . I'd post it more direct but I don't think it will work if you are not a member sorry.

I don't use facebook...hmmm

Can't you just pull out the link to the researchers site and post it here?

If not, no big deal....I am a battery enthusiast.

I have been thinking of playing with some portable power stations like this one:

[h]ttps://www.amazon.com/dp/B07D29QNMJ/ref=emc_b_5_t

and then take them apart to see the battery they use... but also understand that the circuitry is very very very important as well...

Only because you are a battery enthusiast though .! I think this might work . There is a lot more good technical stuff on that facebook page though.

https://l.facebook.com/l.php?u=https%3A ... Be18cjiBFQ

Jackery Portable Power Station Explorer 240,.......200 watts = less than an amp at 240v.

Personally I would buy a 135Ah 12 volt LFP battery (for $450 delivered ebay) and a 12volt inverter of $170 for an output of about 1000 watts or about 4 amps. Dont buy the cheaper $130 inverters thay are crap .
Put a house panel on your wagon (s/h $50 lots about now 250 watts) and your good.
Done it and it works good.
Battery can also be used as a starter battery in small petrol cars but need to change the BMS for diesels that draw more.Don't need to worry about the alternator ,that's bunkum these days ,too many diodes in it now .
Just replace the car battery when you want to or run a switch and 2 circuits I did.
Charge from car or solar.
The battery will outlast the car.