Converting old 80486 laptop battery packs to lithium ion packs; I don't get it - Page 1
Forum section: electronics / beginners

author: Lex_Michdelectron
author_rank: Contributor
timestamp: April 02, 2016, 10:08:59 pm
content: This will be my first post on the forums, please go easy on me... I've got two old laptops running MSDOS that I want to convert to run on lithium ion cells, but I can't seem to understand how this charging stuff works. With this conversion project I would like to get to know more about this sorcery.The first laptop doesn't have a PSU anymore (and the connector on the laptop is really something special...), so my thought was to trash the internals of the battery pack (6-7v NiMh cells) and add a barrel connector to the plastics for something like a more common 12v or modern 19v PSU with a lithium-ion cell charging circuit (and a few cells) behind it. The old battery pack gave about 6v (according to the label), but when my lab supply was on 6v, it didn't get it up properly. 7v works best, so I want the pack to deliver 7v. On my lab supply it tells me it needs around 2.2 Amps when doing read/write stuff on a 3,5" floppy drive, so I'm guessing 3A is enough?I want the thing to function just like a normal (modern) laptop. I'm not afraid to use a soldering iron, I just cant seem to wrap my head around this charging (lithium ion) batteries stuff... I'm going to use the laptops for some packet radio projects (they'll mainly function as terminals for the TNC's), but for now I'm going to have my hands full on this first laptop. Who can help me understand what it takes to get this specific thing under control?The second laptop still has the original PSU and the original battery (still working good enough), but as I try to understand the charging magic on the first one, the second one will hopefully be easily done on my own

author: Audioguru
author_rank: Super Contributor
timestamp: April 02, 2016, 11:25:44 pm
content: Quote from: Lex_Michdelectron on April 02, 2016, 10:08:59 pmBut it has an antique 486 processor running MSdos and an old fashioned floppy drive. There is no way it will function like a normal (modern) laptop but instead you can make it function like a laptop did 22 years ago.An ordinary Li-Ion cell is 4.2V when fully charged so two in series give 8.4V that might fry the laptop designed for 6V. The 8.4V slowly drops to about 6.4V when the battery should be disconnected.

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 02, 2016, 11:45:23 pm
content: QuoteThen get some off the shelf battery charging/protection modules and use them to power the laptop through a suitable DC-DC converter.

author: Lex_Michdelectron
author_rank: Contributor
timestamp: April 03, 2016, 08:12:02 am
content: Quote from: Audioguru on April 02, 2016, 11:25:44 pm...As I said, they'll be used as terminals to communicate with the TNC's. I'm not a complete idiot, just when it comes to charging batteries and cooking.Quote from: jeroen79 on April 02, 2016, 11:45:23 pmIf I only knew what (and WHY these) off the shelf parts to use... That's why I was typing all these long sentences.

author: Brumby
author_rank: Unknown
timestamp: April 03, 2016, 08:35:07 am
content: I still have an old 486 running Windows 3.11 ....... and I still can't type faster than it can capture.

author: Kjelt
author_rank: Super Contributor
timestamp: April 03, 2016, 08:45:34 am
content: Can,t you find a replacement psu at ebay or with the dedicated replacement laptop psu companies?Then I personally would NOT switch to LiIon but stick with the original NiMH batteries because charging those is easy and safe while LiIon needs dedicated hardware and temperature sensors.charging the NiMH only requires a fixed charge current, the LiIon needs fixed voltage and current and sensing of voltage and temp. If NiMH charging goes wrong the batteries will vent steam, the LiIon can catch fire or explode.Unless you know what you are doing or use a pre fabricated charging unit dedicated for those cells do not use LiIon. I had 12 cells from an old laptop and finally all considered deposed of them, not worth the risk.

author: G7PSK
author_rank: Super Contributor
timestamp: April 03, 2016, 09:33:32 am
content: Try these, Ebay is a good place to look. They will have charging modules as well but I will let you look them up.http://www.ebay.co.uk/itm/2pcs-2-Cell-Lithium-Battery-Charging-Board-Charger-Module-Protection-DC-7-4V-3A-/191598861248?hash=item2c9c2e9bc0:g:Z2wAAOSwHjNWB69Ohttp://www.ebay.co.uk/itm/3-5-28V-to-1-25-26V-DC-DC-Converter-Boost-Buck-Step-Up-Step-Down-Voltage-Module-/351661935451?hash=item51e0af4b5b:g:7tUAAOxyBLBSCk6D

author: Lex_Michdelectron
author_rank: Contributor
timestamp: April 05, 2016, 06:40:30 pm
content: Quote from: Kjelt on April 03, 2016, 08:45:34 amUnfortunately there's no replacement of the PSU and the NiMH's are worn out. LiIon can be safe when I use the correct stuff to charge it etc. To be extra safe I came here to check what I need to fix this thing.Quote from: G7PSK on April 03, 2016, 09:33:32 amWhat I'm planning on doing now (as soon as China delivers) is a Step-Down DC-DC thingie and a barrel connecter in stead of the NiMH batteries in the battery compartment and leave the LiIon out for now. When I have more time I'll come back with better questions about this charging circuit.

author: Kjelt
author_rank: Super Contributor
timestamp: April 05, 2016, 08:11:01 pm
content: Quote from: Lex_Michdelectron on April 05, 2016, 06:40:30 pmThat is the major problem then. So then in circuit charging (charging the battery while using the laptop) is not an option anymore?QuoteBut can be replaced with the same type and probably higher capacitance with modern cells. I have done this numerous times with my powertools batteries, just replace them one on one and keep the safety electronics like the NTC or PTC and temperature fuse.QuoteThen also take a look at LiPo packs for racing cars, those might come in the correct voltage have large capacity and protection built inside the batterypack and can be directly charged with special chargers.I would not recommend building those yourself.

author: Lex_Michdelectron
author_rank: Contributor
timestamp: April 05, 2016, 08:17:15 pm
content: Quote from: Kjelt on April 05, 2016, 08:11:01 pmReplacing the NiMH with NiMH was something I didn't really think of, that might be an option. But then I still do not have a replacement for the PSU... The socket in the laptop is a really strange one and there is no voltage/amperage on the laptop. There was a sticker with that info, but the print on that sticker has worn completely.I'm going to take some pictures later, maybe others have some more info about it.

author: Kjelt
author_rank: Super Contributor
timestamp: April 05, 2016, 08:50:12 pm
content: Brand and modelnumber could help

author: Lex_Michdelectron
author_rank: Contributor
timestamp: April 05, 2016, 09:05:39 pm
content: I couldn't find much on this thing with the make and model, but here goes nothing:AcerNote 760iC, 486 DX4/75Some pictures:Laptop itself,the culprit,what's left of the sticker,the battery.

author: ade
author_rank: Unknown
timestamp: April 05, 2016, 09:45:40 pm
content: The AC adapter connector looks like a 3-pin DIN connector... you can still buy 3-pin DIN AC adapters, or just buy the connector and make your own? You'll have to figure out the proper voltage, wattage and pin requirements.NiMH is nominally 1.2V (maybe 1.45V fully charged) so at 6V that means your NiMH battery pack is likely 5 smaller battery cells inside it.You probably can refurbish the NiMH battery pack by throwing out the 5 old cells and putting in new ones. Often they are just AA-sized battery cells.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: April 05, 2016, 11:44:53 pm
content: https://www.pchub.com/uph/model/0--8198-1/AcerNote-760ic-parts.htmlAnd charger on eBay:http://m.ebay.co.uk/itm/Genuine-Original-DELTA-Power-Adapter-Charger-ADP-24BB-REV-A3-CHEAP-/251726984451

author: ade
author_rank: Unknown
timestamp: April 06, 2016, 01:37:56 am
content: Interesting, that is actually a dual-power connector, not DIN:Outputs 5.5V or 8.2-8.8V depending on if one of the pins is left floating or not.

author: Lex_Michdelectron
author_rank: Contributor
timestamp: April 06, 2016, 09:52:52 am
content: Quote from: ade on April 05, 2016, 09:45:40 pmThere were 10 cells inside, they were wired in 2 bundles of 5 in series. So you'd end up with 5 times 1.2v = 6 volts (nominal). So you got it almost, just double the capacity.Quote from: RGB255_0_0 on April 05, 2016, 11:44:53 pmThe Ebay ad doesn't ship to my country, and the other link is more than double what I paid for the whole thing. I have now officially decided the damn thing doesn't need a battery, so step-down DC-DC with a barrel connector on the outside of the housing it is. It will be connected through a dozen wires because of the TNC and the CB radio, so why bother making it portable again. I only wanted to do it to learn about the charging system on LiIon, but I guess that's out of my league for now. Time for a search through my parts bin for an old laptop charger that has enough amps.