Charging laptop Li ion pack with bench supply

[bd139]

Just got my hands on a new, well 2014 NOS Lenovo 68+ pack. This is a 6 cell pack (3 series 2 parallel) li-ion pack made of 3300mAh 18650s. Unfortunately it's dead and zero volts because it's been sitting there for 5 years. Seller is sending another one out (tested) but before I throw it in the trash, I thought I'd do a post mortem. Looks like the low voltage disconnect has kicked in. Hmm, wonder if I can give it a kick?

I cracked open the edge of it (it is just clipped together and have access to the battery contacts. Each parallel pair is reading 2.78V, total 8.35V which is perfectly balanced and not totally FUBAR but under voltage so I assume the BMS has kicked in and disconnected the cells.

I don't have a suitable dedicated charger for this and have no li-ion charging experience. Two questions:

1. Is it ok to stuff a bench supply across it set to 3.8V per cell (total 9V) set to 500mA to charge it?
2. What's the chance the BMS on the pack will come back to life at X volts and start working again?

I'm going to monitor it carefully while I'm doing this.

If it doesn't work I'll probably recycle the cells which appear to be good and build a pack for my FT-818ND

[bd139]

Ignore this. RTFM'ed. Set CV=4.2*Ncells, CC=0.1C. Leave it for an hour and pray.

[shakalnokturn]

I used to bring the older packs back with this method, haven't had much luck with the newer ones.
Leave it for an hour, keep a finger on the temperature if you can.
You could also consider getting to something like 3.8V with your lab power supply, then see if the laptop will take over from there.

[amyk]

There will be something that looks like a 3-terminal fuse ( https://www.usbid.com/assets/datasheets/96/sc%20protector.pdf ) on the board. If that is still intact then the BMS should be OK, but probably not wanting to let the cells discharge any further. If it's blown then the BMS has decided to enter the "permanent fail" state and might be impossible to reset. The BMS should be accessible via I2C, there's software to work with them.

[Specmaster]

How did it go? I had occasion to get my old Acer laptop out, running Windoze XP and of course the battery is dead flat and not accepting a charge. Over the weekend I ordered replacement battery for it and it arrived yesterday and seems to be working OK. I'm wondering if I could coax the old battery back to life in a similar fashion? [emoji848]

[bd139]

Unfortunately it was still dead after the charge process was complete. I got the voltage back up to the rated 10.6V and the BMS was still cut off. I tried jumping it by connecting battery plus to out+ on it. No banana. I didn't open it fully as I didn't want to trash the pack and actually use it afterwards so I just levered the edge up and clipped onto the strips.



However the thing has 6 decent quality Panasonic 18650 3.3Ah cells in it which appear to be well balanced and healthy now so I'll recycle them. I've ordered some spacers, nickel strip, BMS, heatshrink and will make myself a nice 3s2p radio pack. That'll give me 6.6Ah for around 250g of mass compared to the 7Ah out of my 1.4Kg SLA at the moment!

@specmaster: you might be lucky with the Acer one but if the cells are totally dead or EOL then it's probably worth scrapping it

[Specmaster]

Already tossed it in the scrap, the cells are years old anyway, must be at least 8 or 9 years old so not really worth doing anything with the cells.

[bd139]

Ah yeah that's definitely had it. You can possible re-cell it but it's a PITA and the new clone ones are relatively cheap.

This one was new in box sealed so I figure the cells are probably still good. Looks like they are!

[Kilrah]

A lot of these stupid BMSs don't reset when the error condition disappears but permanently disable themselves so they're only good for the trash, all you can do is salvage the cells for something else.

[bd139]

When I get around to taking the cells out I'll document what is in it and see if I can see what the BMS is. I did wonder if it was possible to reprogram it or reset it but I'm not sure I can be arsed.

This is all serendipitous because I was about to spend on some 18650s to build a radio pack so I'm actually happy this failed as it saved me some ££££ 

[CJay]

A lot of these stupid BMSs don't reset when the error condition disappears but permanently disable themselves so they're only good for the trash, all you can do is salvage the cells for something else.

I have some HP packs here which have been disabled because the users didn't charge their machines. Fortunately under warranty and we buy enough from HP for them to honour it but...

[RoGeorge]

Apart from the hardware BMS (hardware as in charge and load ballancing between the series and/or parallel cells) many new battery packs can talk a serial protocol with the laptop (don't know if that is the case for your pack model).  If so, some BMSs can be reset externally using some service commands over that serial protocol.

There are faults/errors that can not be reset at all.  A faulty battery can become a fire hazard, so no manufacturer wants to reset such an error once it was triggered, not even in service mode.

[amyk]

I did wonder if it was possible to reprogram it or reset it but I'm not sure I can be arsed.

Some of them can be, yes. Shops that offer re-celling services will know for sure. There's this (paid) software to do it too: http://be2works.com/

[bd139]

@amyk / @RoGeorge ... on what you have said I think I'll skip even playing with this and just recycle the cells.

I have some HP packs here which have been disabled because the users didn't charge their machines. Fortunately under warranty and we buy enough from HP for them to honour it but...

I wish HP were that good to us. We buy a metric ton of their kit but get bugger all. Mind you it depends on the HPE rep you end up with.

[CJay]

@amyk / @RoGeorge ... on what you have said I think I'll skip even playing with this and just recycle the cells.

I have some HP packs here which have been disabled because the users didn't charge their machines. Fortunately under warranty and we buy enough from HP for them to honour it but...

I wish HP were that good to us. We buy a metric ton of their kit but get bugger all. Mind you it depends on the HPE rep you end up with.

We buy a *lot* of kit, if mine is representative of all the offices across the UK it's at least a couple of million a year just on laptops.

But, all HP laptops should have at least a year battery warranty, extendable up to three I think?

[Inverted18650]

I have a large collection of 18650 cells, BMS units for almost every battery pack out there, many drill packs, and I have spun a few of my own. If you need anything let me know. Depending on your devices current draw, may I recommend a handheld drill battery, one from a cordless vacuum or cordless lawn mower, to move the added current safely as the cut-offs are in ten's of Amp's.

[bd139]

We buy a *lot* of kit, if mine is representative of all the offices across the UK it's at least a couple of million a year just on laptops.

But, all HP laptops should have at least a year battery warranty, extendable up to three I think?

Similar expenditure on server kit here. I think they just hate us because we buy Lenovo laptops mostly

I have a large collection of 18650 cells, BMS units for almost every battery pack out there, many drill packs, and I have spun a few of my own. If you need anything let me know. Depending on your devices current draw, may I recommend a handheld drill battery, one from a cordless vacuum or cordless lawn mower, to move the added current safely as the cut-offs are in ten's of Amp's.

Thanks for the offer however I've just bought half of Aliexpress!  Got spacers, nickel strips, heatshrink and BMS boards arriving in a couple of weeks.

WRT current I'm pulling max 5A out of these.

I'm also going to attempt to obtain more dead ones. Did some reasearch and it turns out you can pick up 50-100 of these packs for literally pocket change at auctions. That would make a decent storage bank!

[RoGeorge]

If you are looking for powerful yet cheap storage packs, look for the battery packs used in electric vehicles, at the scrapyards.  Tesla ones looks very capable power packs, and have integrated BMS.  Scroll at about one hour in the video, to see the inside of the pack:



Coupled with solar panels and inverters, it can easily power a house.

[bd139]

Cool stuff. Will watch that now.

Need to move somewhere I can have a safe outbuilding first 

[Specmaster]

Fecking hell, those cars must have a really low centre of gravity with those massive battery packs mounted on the floor. Certainly would not want to replace a set of batteries on the model S, mega $ I reckon right there.

[bd139]

They're about £10k a go I think. That's not a bad deal over the lifespan including energy usage compared to suitably equipped mid-range saloon.

I work with someone who has a 2014 model S (LHD) at the moment and it's pretty nice and hasn't lost much range yet. I think he's done about 60k in it.

[Specmaster]

I think £10K is about right but at what point would you need to replace the batteries compared to a conventional engine, given that many properly maintained engines are well into the 200K miles bracket and still going strong?

[bd139]

I'm not sure it's possible to compare that because the entire cost metrics for running a Tesla are completely different. I will try.

For example a full charge costs £6 to £9 approx depending on battery size. The battery is warrantied for 70% capacity at 100k miles.

Lots of rounding here.... Tesla battery has about 450 miles in it so that's about 200 charges so £1200 total plus say new battery at 100k miles. £11200 = 11.2p/mile

My Citroen C3 1.0L ... averages about 50mpg because I drive terribly in London ... 100k miles costs £10744 in just fuel = 10.7p/mile.

BUT and a big one, at the end of that 100k miles I have to pay out £10744 for the next 100k miles, not £1200...

So Teslas are pretty cheap to run, but factor the battery cost into the TCO if you get one!

Note: this excludes maintenance and running costs which I haven't even looked at.

Edit: plus this! https://electrek.co/2018/04/14/tesla-battery-degradation-data/

[Specmaster]

Hmm, thats actually quite impressive and interesting but I notice that they also only recommend charging to a maximum daily of 70% giving a theoretical range of 315 miles maximum under just the right conditions and we all know that those just don't exist in the real world.

I can see how such a car might well be appealing and a perfectly plausible mode of transport both economically and in the green sense (doubts about the total green credentials of the car and batteries manufacture process), for the city driver and those who daily drive sits comfortably well under the maximum of 315 miles daily.

There are still many vehicles in daily use that would daily exceed that mileage, things like company cars used as rep transport, delivery vans, coaches and trucks so there is still a long way to go yet before we could in theory all make the switch.       

[bd139]

70% is pretty standard. My laptop does that if you set it to optimise for battery lifespan.

Superchargers only take 40 mins to fill up to 80%. Network is pretty good. I can drive from home to Milan stopping for 2h in total for charging and a shit and a pasty ... i stop more than that just having three kids in the car.

I see different problems at the moment. Firstly a lot of us can’t charge it at home. Secondly the capital cost is too high. Other than that I’m there. Hence why I bought the C3. Runs on farts and doesn’t eat up a lot of cash in the short run.