Charging laptop Li ion pack with bench supply - Page 1
Forum section: electronics / repair

author: bd139
author_rank: Super Contributor
timestamp: January 14, 2019, 06:02:31 pm
content: 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

author: bd139
author_rank: Super Contributor
timestamp: January 14, 2019, 07:41:34 pm
content: Ignore this. RTFM'ed. Set CV=4.2*Ncells, CC=0.1C. Leave it for an hour and pray.

author: shakalnokturn
author_rank: Super Contributor
timestamp: January 14, 2019, 10:47:56 pm
content: 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.

author: amyk
author_rank: Super Contributor
timestamp: January 15, 2019, 03:09:55 am
content: 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.

author: Specmaster
author_rank: Super Contributor
timestamp: January 15, 2019, 07:48:58 am
content: 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?

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 09:35:47 am
content: 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

author: Specmaster
author_rank: Super Contributor
timestamp: January 15, 2019, 09:56:59 am
content: 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.

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 10:46:03 am
content: 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!

author: Kilrah
author_rank: Unknown
timestamp: January 15, 2019, 11:34:41 am
content: 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.

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 12:10:37 pm
content: 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 ££££

author: CJay
author_rank: Super Contributor
timestamp: January 15, 2019, 12:17:13 pm
content: Quote from: Kilrah on January 15, 2019, 11:34:41 amI 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...

author: RoGeorge
author_rank: Super Contributor
timestamp: January 15, 2019, 12:37:34 pm
content: 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.

author: amyk
author_rank: Super Contributor
timestamp: January 15, 2019, 12:38:14 pm
content: Quote from: bd139 on January 15, 2019, 12:10:37 pmSome 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/

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 04:22:25 pm
content: @amyk / @RoGeorge ... on what you have said I think I'll skip even playing with this and just recycle the cells.Quote from: CJay on January 15, 2019, 12:17:13 pmI 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.

author: CJay
author_rank: Super Contributor
timestamp: January 15, 2019, 06:25:11 pm
content: Quote from: bd139 on January 15, 2019, 04:22:25 pmWe 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?

author: Inverted18650
author_rank: Frequent Contributor
timestamp: January 15, 2019, 06:29:55 pm
content: 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.

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 07:10:43 pm
content: Quote from: CJay on January 15, 2019, 06:25:11 pmSimilar expenditure on server kit here. I think they just hate us because we buy Lenovo laptops mostlyQuote from: Inverted18650 on January 15, 2019, 06:29:55 pmThanks 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!

author: RoGeorge
author_rank: Super Contributor
timestamp: January 15, 2019, 07:58:26 pm
content: 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.

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 08:54:43 pm
content: Cool stuff. Will watch that now.Need to move somewhere I can have a safe outbuilding first

author: Specmaster
author_rank: Super Contributor
timestamp: January 15, 2019, 09:30:59 pm
content: 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.

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 09:37:52 pm
content: 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.

author: Specmaster
author_rank: Super Contributor
timestamp: January 15, 2019, 10:03:00 pm
content: 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?

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 10:17:40 pm
content: 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/mileMy 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/

author: Specmaster
author_rank: Super Contributor
timestamp: January 15, 2019, 10:46:18 pm
content: 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.

author: bd139
author_rank: Super Contributor
timestamp: January 15, 2019, 11:12:21 pm
content: 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.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: January 16, 2019, 12:07:41 am
content: Dumb question, but how do you get the cool " ? icon " in front of your thread to pop up in the thread description on the main page?Also, I will ship you a handful of cool BMS units to play with..I think you'll be hooked after you give them a spin. If interested let me know.

author: Kilrah
author_rank: Unknown
timestamp: January 16, 2019, 08:09:01 am
content: "Message icon" just below the title textbox when creating a new thread.

author: LapTop006
author_rank: Unknown
timestamp: January 18, 2019, 04:18:45 am
content: Quote from: Specmaster on January 15, 2019, 09:30:59 pmThe S & X have done really well on rollover tests for exactly that reason.https://carbuzz.com/news/watch-the-tesla-model-x-stubbornly-refuse-to-roll-over

author: bd139
author_rank: Super Contributor
timestamp: January 18, 2019, 08:07:03 pm
content: Back on the original point of the thread.Firstly, replacement battery arrived. So that's two new batteries in the machine for just shy of £80 and am going to order another one now. This is the projected battery life with dual batteries (100Wh) in the laptop. I expect about 10 hours realistically but you can hot swap these without turning it off so chucking another battery in the bag should get me 16 hours on the road without a charger.Secondly the duff pack has been disassembled. The BMS has actually committed suicide in this. There is no fuse I can find to replace. It's dead. RIP. The cells are all good and have been removed for safe storage until the pack components arrive.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 18, 2019, 08:58:02 pm
content: Quote from: bd139 on January 18, 2019, 08:07:03 pmNow that you wrote this, I remember I read about something similar on a cell replacement thread. The BMS might sense a battery disconnected, and disable itself. The purpose would be to avoid dodgy cell replacements and damage the company reputation. In order to avoid BMS disabling itself, people were talking about keeping the voltage while replacing an old cell: First put the new cell in parallel with extra wires, then disconnect the old cell, all done in such a way that the BMS can not detect an open circuit during the whole cell replacement operation. No idea if that is true, or just urban legend.

author: bd139
author_rank: Super Contributor
timestamp: January 18, 2019, 09:05:35 pm
content: I found some references to that on another forum and it makes sense to me.I actually tried to do the same thing last year on an HP 3478A multimeter cal battery replacement so I didn't lose the calibration data. I screwed that up and this resulted in a ful recal being required

author: Armadillo
author_rank: Super Contributor
timestamp: January 18, 2019, 09:42:27 pm
content: In most of the cases, People will only crack open the battery up when the battery has developed some kinds of faults, and the high probability that the BMS has disabled itself.In rear cases will People willing to crack the plastic casing open just to re-cell the battery, yes?Most will juice the batteries until it quit itself.Some BMS is secured with cryptographic protection Secure Hash Algorithm (SHA-1). So, Just not worth the time, IMO.

author: bd139
author_rank: Super Contributor
timestamp: January 18, 2019, 09:46:25 pm
content: Exactly. To be honest I'd rather they designed it with caution in mind and safe failure conditions than burn it and your house down.There is a large bin at my local tip which contains laptop and device batteries. There are hundreds dropped off every weekend. I wonder how many are reusable. In fact they probably end up in some Chinese recycling facility, rewrapped and sold for e-cigs in crappy markets